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1
Chen, Tianyu [Verfasser]. "The geochemical cycling and paleoceanographic application of combined oceanic Nd-Hf isotopes / Tianyu Chen." Kiel : Universitätsbibliothek Kiel, 2013. http://d-nb.info/1044891807/34.
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Chu, Nan-Chin. "An investigation into Hf and Fe isotopes in ferromanganese deposits and their applications to paleoceanography." Thesis, University of Southampton, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402228.
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Guitreau, Martin. "Les isotopes de l'hafnium dans les TTG et leurs zircons : témoins de la croissance des premiers continents." Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2012. http://tel.archives-ouvertes.fr/tel-00713096.
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Ce travail de thèse présente des analyses isotopiques Lu-Hf par MC-ICP-MS combinées de zircons ignés et de roches totales d'une importante collection de granitoïdes archéens appartenant à la suite des Tonalite-Trondhjémite-Granodiorite (TTG) afin d'apporter un regard nouveau sur la croissance de la croûte continentale et tout particulièrement dans le début de l'histoire de la Terre. Nos données indiquent un bon accord général entre les zircons ignés, mesurés par ablation-laser et par solution, avec leurs roche-hôtes. Nous démontrons que le rapport Lu/Hf intégré dans le temps de la source mantellique des TTG est près de la valeur chondritique et n'a pas significativement changée au cours des 4 derniers milliards d'années. Par conséquent, les continents se sont formés à partir d'un matériel primitif non fractionné extrait du manteau profond par l'intermédiaire de panaches qui après fusion partielle ont laissés un résidu appauvri dans le manteau supérieur. Les cristaux de zircon extraits des TTG ont des compositions isotopiques en Hf cohérentes au sein d'une même population alors que le système U-Pb, dans les mêmes grains, est souvent perturbé résultant ainsi en l'obtention de valeurs d'εHf initial erronées. Ce problème est endémique aux cristaux de zircon détritiques archéens et en accord avec des résultats expérimentaux sur la mobilité préférentielle de l'Hf en fonction de celle de l'U et du Pb au sein du zircon. Nous suggérons que ce problème biaise l'enregistrement détritique archéen en faveur de valeurs d'εHf initial négatives qui contrastent avec les valeurs obtenues pour les TTG mais peuvent être expliquées par l'utilisation d'âges 207Pb/206Pb non-magmatiques. Si l'on considère les cristaux de zircon de Jack Hills au vu de ces résultats, la source des continents serait restée inchangée depuis 4,3 Ga.
4
Yu, Huimin. "Li, Hf and Os Isotope Systematics of Azores Basalts and A New Microwave Digestion Method for Os Isotopic Analysis." Miami University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=miami1322847998.
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Salters, Vincent J. M. "The use of Hf-isotopes and high field strength elements to constrain magmatic processes and magma sources." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/58018.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1989.Includes bibliographical references.
by Vincentius Johannes Maria Salters.
Ph.D.
6
Dausmann, Veit [Verfasser]. "Present and past changes in continental weathering and ocean circulation from radiogenic Nd, Hf and Pb isotopes / Veit Dausmann." Kiel : Universitätsbibliothek Kiel, 2018. http://d-nb.info/1153401193/34.
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Morisset, Caroline-Emmanuelle. "Origin of rutile-bearing ilmenite Fe-Ti deposits in Proterozoic anorthosite massifs of the Grenville Province." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/2842.
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The Saint-Urbain and Big Island rutile-bearing ilmenite Fe-Ti oxide deposits are located
in the composite 450 km² Saint-Urbain anorthosite (1055-1046 Ma, U-Pb zircon) and in
the Lac Allard intrusion (1057-1062 Ma, U-Pb zircon) of the 11,000 km² Havre-Saint
Pierre anorthosite suite, respectively, in the Grenville Province of Eastern Canada. Slow
cooling rates of 3-4°C/m.y. are estimated for both anorthosites, based on combined U-Pb
zircon/rutile/apatite and ⁴⁰Ar/³⁹ Ar biotite/plagioclase geochronology, and resulted from
emplacement during the active Ottawan Orogeny. Slow cooling facilitated (1) diffusion
of Zr from ilmenite and rutile, producing thin (10-100 microns) zircon rims on these
minerals, and (2) formation of sapphirine via sub-so lidus reactions of the type: spinel +
orthopyroxene + rutile ± corundum → sapphirine + ilmenite. New chemical and
analytical methods were developed to determine the trace element concentrations and Hf
isotopic compositions of Ti-based oxides. Rutile is a magmatic phase in the deposits
with minimum crystallization temperatures of 781°C to 1016°C, calculated by Zr-in
rutile thermometry. Ilmenite present in rutile-free samples has higher Xhem (hematite
proportion in ilmenite), higher high field strength element concentrations (Xhem = 30-17;
Nb = 16.1-30.5 ppm; Ta 1.28-1.70 ppm), and crystallized at higher temperatures than
ilmenite with more fractionated compositions (Xhem = 21-11; Nb = 1.36-3.11 ppm; Ta =
<0.18 ppm) from rutile-bearing rocks. The oxide deposits formed by density segregation
and accumulation at the bottom of magma reservoirs, in conditions closed to oxygen,
from magmas enriched in Fe and Ti. The initial ¹⁷⁶Hf/¹⁷⁷ Hf of rutile and ilmenite (Saint
Urbain [SU] = 0.28219-0.28227, Big Island [BI] = 0.28218-0.28222), and the initial Pb
isotopic ratios (e.g.²⁰⁶Pb/²⁰⁴ Pb: SU = 17.134-17.164, BI = 17.012-17.036) and ⁸⁷Sr/⁸⁶ Sr
(SU = 0.70399-0.70532, BI = 0.70412-0.70427) of plagioclase from the deposits overlap
with the initial isotopic ratios of ilmenite and plagioclase from each host anorthosite,
which indicates that they have common parent magmas and sources. The parent magmas
were derived from a relatively depleted mantle reservoir that appears to be the primary
source of all Grenvillian anorthosite massifs and existed for --600 m.y. along the margin
of Laurentia during the Proterozoic.
8
Liu, Chaohui, and 刘超辉. "Paleoproterozoic basins in the Trans-North China Orogen: stratigraphic sequences, U-PB ages and HF isotopes of detritalzircons and tectonic implications." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47163902.
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The Trans-North China Orogen (TNCO) has been recognized as a continent-continent collisional belt along which the Eastern and Western Blocks amalgamated to form the North China Craton. However, controversy has surrounded the timing and tectonic processes involved in the collision between the two blocks, ranging from the westward-directed subduction with final collision at ~2.5 Ga, through the west-dipping subduction with two collisional events at ~2.1 Ga and ~1.85 Ga, to the eastward-directed subduction with final collision at ~1.85 Ga. This project aims to present detailed lithostratigraphic, geochronological and isotopic data for the low-grade supracrustal successions in the TNCO to examine current models and to establish a reasonable scenario for the tectonic evolution of the TNCO in the Paleoproterozoic.
The low-grade supracrustal successions include the Hutuo and Yejishan Groups in the middle sector of the TNCO and the Songjiashan, Lower Zhongtiao, Upper Zhongtiao, Danshanshi and Songshan Groups in the southern sector. Lithostratigraphic data indicate that the Songjiashan, Lower Zhongtiao Groups and lower parts of the Hutuo and Yejishan Groups are composed of metaclastic rocks, carbonates and metavolcanic rocks, interpreted as back-arc basin deposits, whereas the Upper Zhongtiao, Danshanshi, Songshan Groups and the upper parts of the Hutuo and Yejishan Groups consist only of metaconglomerates and metasandstones, interpreted as foreland basin deposits.
To constrain the provenance and maximum depositional ages for these low-grade supracrustal successions, the LA-MC-ICP-MS technique was applied to analyze U-Pb and Hf isotopic compositions for detrital zircons from them. For the Hutuo and Yejishan Groups, we found major age peaks at ~2.5 and ~2.2 Ga and minor amounts of 2.8-2.6 Ga detrital zircons, which are consistent with ages of the lithological units in the middle sector of the TNCO. On the other hand, for the Songjiashan, Lower Zhongtiao, Upper Zhongtiao, Danshanshi and Songshan Groups, detrital zircons from them have the major age population of 2.85-1.95 Ma and the minor age population of 3.6-3.1 Ga, of which the former is comparable with ages of the lithological units in the southern sector of the TNCO and the latter was derived from the Paleoarchean and Mesoarchean crust of the Eastern Block. The maximum depositional ages of the low-grade supracrustal successions have also been well constrained in this study. For the back-arc basin deposits, their maximum depositional ages were constrained between ~2.15 and ~2.10 Ga. For the foreland basin deposits, the presence of ~1.85 Ga detrital zircons indicates that they were deposited after this time.
Taken together, we present a brief scenario for the evolution of the sedimentary basins in the TNCO. At 2.15-2.10 Ga, a series of back-arc basins developed behind an “Andean-type” arc that were subsequently incorporated into the TNCO during the collision of the Eastern and Western Blocks. At ~1.85 Ga, the two blocks collided along the TNCO, resulting in the crustal thickening followed by rapid exhumation/uplift, which shifted the back-arc basins to foreland basins. Such a shift in the late Paleoproterozoic supports the model that the collision between the Eastern and Western Blocks occurred at ~1.85 Ga.published_or_final_version
Earth Sciences
Doctoral
Doctor of Philosophy
9
Green, Michael Godfrey. "Early Archaean crustal evolution: evidence from ~3.5million year old greenstone successions in the Pilgangoora Belt, Pilbara Craton, Australia." University of Sydney. Geosciences, 2001. http://hdl.handle.net/2123/505.
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In the Pilgangoora Belt of the Pilbara Craton, Australia, the 3517 Ma Coonterunah Group and 3484-3468 Ma Carlindi granitoids underlie the 3458 Ma Warrawoona Group beneath an erosional unconformity, thus providing evidence for ancient emergent continental crust. The basalts either side of the unconformity are remarkably similar, with N-MORB-normalised enrichment factors for LILE, Th, U and LREE greater than those for Ta, Nb, P, Zr, Ti, Y and M-HREE, and initial e(Nd, Hf) compositions which systematically vary with Sm/Nd, Nb/U and Nb/La ratios. Geological and geochemical evidence shows that the Warrawoona Group was erupted onto continental basement, and that these basalts assimilated small amounts of Carlindi granitoid. As the Coonterunah basalts have similar compositions, they probably formed likewise, although they were deposited >60 myr before. Indeed, such a model may be applicable to most other early Pilbara greenstone successions, and so an older continental basement was probably critical for early Pilbara evolution. The geochemical, geological and geophysical characteristics of the Pilbara greenstone successions can be best explained as flood basalt successions deposited onto thin, submerged continental basement. This magmatism was induced by thermal upwelling in the mantle, although the basalts themselves do not have compositions which reflect derivation from an anomalously hot mantle. The Carlindi granitoids probably formed by fusion of young garnet-hornblende-rich sialic crust induced by basaltic volcanism. Early Archaean rocks have Nd-Hf isotope compositions which indicate that the young mantle had differentiated into distinct isotopic domains before 4.0 Ga. Such ancient depletion was associated with an increase of mantle Nb/U ratios to modern values, and hence this event probably reflects the extraction of an amount of continental crust equivalent to its modern mass from the primitive mantle before 3.5 Ga. Thus, a steady-state model of crustal growth is favoured whereby post ~4.0 Ga continental additions have been balanced by recycling back into the mantle, with no net global flux of continental crust at modern subduction zones. It is also proposed that the decoupling of initial e(Nd) and e(Hf) from its typical covariant behaviour was related to the formation of continental crust, perhaps by widespread formation of TTG magmas.
10
Pepper, Martin Bailey. "Magmatic History and Crustal Genesis of South America: Constraints from U-Pb Ages and Hf Isotopes of Detrital Zircons in Modern Rivers." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/347220.
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South America provides an outstanding laboratory for studies of magmatism and crustal evolution because it contains older Archean-Paleoproterozoic cratons that amalgamated during Mesoproterozoic and Neoproterozoic supercontinent assembly, as well as a long history of Andean magmatism that records crustal growth and reworking in an accretionary orogen. We have attempted to reconstruct the growth and evolution of South America through U-Pb geochronology and Hf isotope analyses of detrital zircons from 59 samples of sand from modern rivers and shorelines. Results from 5,524 new U-Pb ages and 1,199 new Hf isotope determinations are reported. We have also integrated our data into a compilation of all previously published zircon geochronologic and Hf isotopic information, yielding a record that includes>42,000 ages and>1,600 Hf isotope analyses. These data yield five main conclusions: (1) South America has an age distribution that is similar to most other continents, presumably reflecting the supercontinent cycle, with maxima at 2.2-1.8 Ga, 1.6-0.9 Ga, 700-400 Ma, and 360-200 Ma; (2)<200 Ma magmatism along the western margin of South America has age maxima at 183 Ma (191-175 Ma), 151 Ma (159-143 Ma), 126 Ma (131-121 Ma), 109 Ma (114-105 Ma), 87 Ma (95-79 Ma), 62 Ma (71-53 Ma), 39 Ma (43-35 Ma), 19 Ma (23-15 Ma), and 6 Ma (10-2 Ma); (3) for the past 200 Ma, there appears to be a positive correlation between magmatism and the velocity of convergence between central South America and Pacific oceanic plates; (4) Hf isotopes record reworking of older crustal materials during most time periods, with incorporation of juvenile crustal materials at ~1.6-1.0 Ga, 500-400 Ma and ~200-100 Ma; and (5) the Hf isotopic signature of<200 Ma magmatism is apparently controlled by the generation of juvenile magmas during extensional tectonism and reworking of juvenile versus evolved crustal materials during crustal thickening and arc migration.
11
Labanieh, Shasa. "Géochimie de l'île de la Martinique aux Petites Antilles." Phd thesis, Université Joseph Fourier (Grenoble), 2009. http://tel.archives-ouvertes.fr/tel-00467762.
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L'île de la Martinique a connu l'histoire volcanique la plus complète de l'arc des Petites Antilles, de 25 Ma à l'actuel. L'hétérogénéité chimique et isotopique des laves de l'île est très importante non seulement par rapport aux autres îles de l'arc mais aussi par rapport aux autres arcs intra-océaniques. L'objectif de ces travaux est d'expliquer la variabilité géochimique des laves de la Martinique et de caractériser les processus de genèse des produits volcaniques émis sur l'île. Pour cela, nous avons effectué une étude géochimique approfondie (éléments majeurs, éléments traces, rapports isotopiques du Pb, Sr, Nd et Hf) sur des échantillons de laves représentatifs de toute l'histoire volcanique de la Martinique. Grâce à une collaboration avec Aurélie Germa et Xavier Quidelleur de l'université Orsay - Paris XI, l'étude géochimique a été couplée à une datation des laves par méthode K-Ar. Les laves martiniquaises forment des droites et hyperboles de mélanges entre pôles appauvris mantelliques et pôle enrichis crustaux. Il apparaît que deux mélanges distincts sont visibles, un premier mélange est formé par les laves « anciennes » (entre 25 et 7 Ma) et un deuxième mélange est formé par les laves « récentes » (entre 5 Ma et l'actuel). Les pôles mantelliques et les pôles crustaux impliqués dans les sources des magmas ne sont pas les mêmes avant et après 6 Ma. Ce changement de source est probablement lié au passage de la ride asismique qui a décalé la moitié nord de l'arc des Petites Antilles. L'origine de la signature crustale des laves martiniquaises est testée en comparant un modèle de mélange à la source entre des sédiments de la plaque plongeante et le coin mantellique et un modèle d'assimilation de la croûte de l'arc par les magmas mantelliques ascendants. Le modèle d'assimilation intra-crustale ne peut pas reproduire les tendances décrites par les laves alors que le modèle de mélange à la source le fait parfaitement. La comparaison entre les pôles crustaux impliqués dans les mélanges et les sédiments entrants dans la subduction indique qu'il n'y a pas de fractionnement entre le Pb, le Sr, le Nd et l'Hf ce qui implique que les sédiments sont probablement ajoutés à la source par fusion partielle et non par déshydratation. Le rapport La/Yb des laves martiniquaises apparait comme un proxy de la proportion de sédiments dans la source des magmas et non du taux de fusion partielle ou de la nature de la phase alumineuse du manteau bien que la fusion, de l'ordre de 10%, ait lieu dans la zone de stabilité du grenat. Le gradient géographique du rapport La/Yb au sein de l'île traduit donc un gradient géographique de la proportion de sédiments, et montre que la proportion de sédiments dans la source augmente avec l'éloignement à la fosse.
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Gudelius, Dominik [Verfasser], and A. [Akademischer Betreuer] Zeh. "Petrogenetic Significance of Zircon in Mafic and Felsic Rocks of the Bushveld Complex: Melt Inclusions, Physicochemical Conditions and Hf Isotopes / Dominik Gudelius ; Betreuer: A. Zeh." Karlsruhe : KIT-Bibliothek, 2020. http://d-nb.info/1223027945/34.
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Couzinié, Simon. "Evolution of the continental crust and significance of the zircon record, a case study from the French Massif Central." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSES035.
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La formation de la croute continentale est une des conséquences majeures de la différenciation de la Terre. Les avancées récentes dans la compréhension de ce phénomène résultent de l’amélioration des techniques analytiques permettant la mesure in situ des compositions isotopiques en U-Pb-Hf-O de grains de zircon, minéral abondant dans les roches crustales. Cette étude reconstitue l’histoire du segment de croute affleurant dans l’est du Massif Central français (MCF), portion de la chaine Varisque d’Europe de l’Ouest, dans le but d’évaluer les limites d’utilisation des zircons pour retracer l’évolution crustale. L’origine et la signification géodynamique des principales unités lithologiques du MCF ont été étudiées en combinant les approches classiques de la pétrologie avec des données isotopiques U-Pb-Hf-O acquises sur zircon. Deux incohérences majeures existent entre nos résultats et les conclusions tirées de l’étude des zircons considérés hors de leur contexte pétrologique, approche généralement suivie pour analyser l’évolution crustale. Les âges modèles calculés à partir des données Hf suggèrent une importante croissance crustale au Mésoproterozoique dans le MCF, en contradiction avec le fait que 60% de la croute locale soit d’âge Néoproterozoïque. De plus, 5 à 10% de la croute du MCF a été formée durant l’orogènese Varisque sans que cela ne soit enregistré par le zircon. Dans les deux cas, ces incohérences résultent du caractère hybride des signatures isotopiques portées par les zircons. Celles-ci ne peuvent être correctement détectées et interprétées qu’en disposant de données pétrologiques complémentaires sur les roches contenant les grains analysésThe formation of the continental crust is a major consequence of Earth differentiation. Understanding how the crust formed and evolved through time is paramount to locate the vast mineral deposits hosted therein and address its influence on the global climate, ultimately affecting the development of terrestrial life. Recent advances on the topic of continental crust evolution benefited from improvements of analytical techniques enabling in situ measurements of U-Pb- Hf-O isotope compositions in zircon, a widespread accessory mineral of continental igneous rocks. The time constrains derived from the U-Pb chronometer coupled with the petrogenetic information retrieved from Hf-O isotope signatures are currently used to unravel the diversity and succession of magmatic events affecting the continental crust at the regional and global scales. This study reconstructs the evolutionary path followed by the crust segment today exposed in the eastern part of the French Massif Central (FMC), a portion of the Variscan belt of Western Europe, with the aim to investigate the potential flaws of the zircon record of crust evolution. In this scope, the origin and geodynamic significance of the constituent FMC lithological units are tackled by combining conventional petrological observations with zircon U-Pb-Hf-O isotope data. The results obtained following this integrated approach are then confronted to the conclusions that would have been drawn solely from zircon isotopic signatures, taken out of their petrological context, as is commonly performed in studies investigating crust evolution. The oldest rocks of the FMC correspond to Ediacaran (590_550 Ma) meta-sediments deposited in back-arc basins along the northern Gondwana margin. Such basins were fed by a mixed detritus originating from the adjacent Cadomian magmatic arc and a distal Gondwana source, presumably the Sahara Metacraton. Partial melting of these meta-sediments at the Ediacaran/Cambrian boundary led to voluminous S-type granitic magmatism, pinpointing a first major crust reworking event in the FMC. The origin of anatexis likely stems from the transient thickening of the hot, back-arc crust caused by the flattening of the Cadomian subduction. Subordinate melting of the depleted backarc mantle at that time is also documented. During the Lower Paleozoic, rifting of the northern Gondwana provoked coeval crust and (limited) mantle melting. Mantle-derived igneous rocks show markedly diverse trace element and isotopic signatures, consistent with a very heterogeneous mantle source pervasively modi_ed by the Cadomian subduction. Finally, the Variscan collision resulted in crustal melting as evidenced by the emplacement of S-type granites and the formation of migmatite domes, the spatial distribution of which being partly controlled by the crustal architecture inherited from pre-orogenic events. Synchronous intrusion of mafic mantle-derived magmas and their differentiates testify for Variscan post-collisional new continental crust production in the FMC. Two major inconsistencies exist between these results and the zircon record. First, zircon Hf model ages would point to substantial Mesoproterozoic crust formation in the FMC whereas more than 60% of the crust is actually Neoproterozoic in age. Second, new additions to the continental crust volume during the Variscan orogeny are not recorded even though 5 to 10% of the exposed crust formed at that time. The origin of both discrepancies inherently lies in the mixed isotopic signature carried by many zircon grains. Such equivocal information can only be detected when additional petrological constrains on the zircon host rocks are available and provide guidance in interpreting the zircon record of crust evolution
14
Green, Michael Godfrey. "Early Archaean crustal evolution: evidence from ~3.5million year old greenstone successions in the Pilgangoora Belt, Pilbara Craton, Australia." Thesis, The University of Sydney, 2001. http://hdl.handle.net/2123/505.
Full textAbstract:
In the Pilgangoora Belt of the Pilbara Craton, Australia, the 3517 Ma Coonterunah Group and 3484-3468 Ma Carlindi granitoids underlie the 3458 Ma Warrawoona Group beneath an erosional unconformity, thus providing evidence for ancient emergent continental crust. The basalts either side of the unconformity are remarkably similar, with N-MORB-normalised enrichment factors for LILE, Th, U and LREE greater than those for Ta, Nb, P, Zr, Ti, Y and M-HREE, and initial e(Nd, Hf) compositions which systematically vary with Sm/Nd, Nb/U and Nb/La ratios. Geological and geochemical evidence shows that the Warrawoona Group was erupted onto continental basement, and that these basalts assimilated small amounts of Carlindi granitoid. As the Coonterunah basalts have similar compositions, they probably formed likewise, although they were deposited >60 myr before. Indeed, such a model may be applicable to most other early Pilbara greenstone successions, and so an older continental basement was probably critical for early Pilbara evolution. The geochemical, geological and geophysical characteristics of the Pilbara greenstone successions can be best explained as flood basalt successions deposited onto thin, submerged continental basement. This magmatism was induced by thermal upwelling in the mantle, although the basalts themselves do not have compositions which reflect derivation from an anomalously hot mantle. The Carlindi granitoids probably formed by fusion of young garnet-hornblende-rich sialic crust induced by basaltic volcanism. Early Archaean rocks have Nd-Hf isotope compositions which indicate that the young mantle had differentiated into distinct isotopic domains before 4.0 Ga. Such ancient depletion was associated with an increase of mantle Nb/U ratios to modern values, and hence this event probably reflects the extraction of an amount of continental crust equivalent to its modern mass from the primitive mantle before 3.5 Ga. Thus, a steady-state model of crustal growth is favoured whereby post ~4.0 Ga continental additions have been balanced by recycling back into the mantle, with no net global flux of continental crust at modern subduction zones. It is also proposed that the decoupling of initial e(Nd) and e(Hf) from its typical covariant behaviour was related to the formation of continental crust, perhaps by widespread formation of TTG magmas.
15
Bouchet, Bert Manoz Romain. "Structure de la lithosphère continentale de l'Ouest USA : contribution des isotopes du Plomb,du Néodyme, et de l'Hafnium." Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2014. http://tel.archives-ouvertes.fr/tel-01066021.
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La lithosphère continentale est physiquement et chimiquement segmentée. La cartographie des isotopes radiogéniques de roches plutoniques acides, représentatives de la croûte continentale, et de laves basiques, représentatives du manteau, possède des similarités avec la cartographie sismique de la lithosphère sous-jacente. Ces similitudes permettent d'interpréter les observations sismiques en étudiant leurs caractéristiques chimiques et leur âge. Les isotopes du plomb permettent de dater et d'identifier l'empilement de segments crustaux qui forment la croûte. L'écart des âges modèles du plomb avec d'autres systèmes identifie le recyclage crustal et le réchauffement de la croûte au dessus de la température du système plomb-plomb. Le système plomb-plomb donne également accès au sous-étudié rapport Th/U qui contraint la profondeur de la source des roches continentales. Certains échantillons de l'ouest U.S.A. proviennent de la croute inférieure, et se sont formés par l'extension crustale ou par un flux de matériel au sein de la croûte. Les isotopes du néodyme et de l'hafnium marquent la fusion du manteau lithosphérique enrichis sous le Colorado Plateau, une région où est observée le détachement du manteau lithosphérique sub-continental. Ce manteau fond par décompression adiabatique, par extension localisée ou remontée asthénosphérique engendrée par la convection locale. Au final, l'association des systèmes isotopiques du plomb, du néodyme, et de l'hafnium avec la sismologie est une approche puissante pour étudier la formation et la déformation de la lithosphère continentale.
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Reid, Mattie Morgan. "Forearc basin detrital zircon provenance of Mesozoic terrane accretion and translation, Talkeetna Mountains-Matanuska Valley, south-central Alaska." Thesis, University of Iowa, 2017. https://ir.uiowa.edu/etd/5611.
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The Wrangellia composite terrane is one of the largest fragments of juvenile crust added to the North American continent since Mesozoic time, and refining its accretionary history has important implications for understanding how continents grow. New U-Pb geochronology and Hf isotopes of detrital zircons from Late Jurassic-Late Cretaceous strata from the forearc of the Wrangellia composite terrane allows more insight on the tectonic and paleogeographic history of the terrane.
Our stratigraphically oldest samples from the Late Jurassic Naknek Formation have a detrital zircon U-Pb signature dominated by Early and Late Jurassic grains (195-190 Ma; 153-147 Ma). Hf isotopic compositions of these grains are juvenile to intermediate (εHf(t)=4.5-14.7). Disconformably above the Naknek Formation are two poorly understood units Ks and Kc. The Ks unit is dominated by Early to Late Jurassic grains (159-154 Ma) with a few Paleozoic grains (347-340 Ma). Hf isotopic compositions of Carboniferous-Jurassic grains are juvenile to intermediate (εHf(t)=6.0-18.8). The overlying Kc unit has Late to Early Jurassic zircons (198-161 Ma), and an increase in Paleozoic ages (374-323 Ma). Hf isotopic compositions of these grains are juvenile to intermediate (εHf(t)=4.5-14.7). Samples from the Matanuska Formation have major Late Cretaceous grains (90-71 Ma), and minor Early Cretaceous (137-106 Ma), Late to Early Jurassic (200-153 Ma), Paleozoic (367-277 Ma), and Precambrian grains (2597-1037 Ma). Hf compositions have a wider range from both the Late Cretaceous grains (εHf(t)=-1.5-14.9) and Paleozoic-Precambrian grains (εHf(t)=-23.7-16.3).
Our results suggest an evolving provenance from Late Jurassic to Late Cretaceous time for the Wrangellia composite terrane forearc basin. The Late Jurassic Naknek Formation samples were dominantly derived from a juvenile to intermediate Jurassic igneous sediment source. During Early Cretaceous time, there is a slight increase in the number of Paleozoic grains in the Ks and Kc unit samples. The Early Cretaceous sediments have a mostly positive Hf isotopic compositions suggesting exhumation of Jurassic and Paleozoic juvenile igneous sediment sources. By Late Cretaceous time, our data illustrates another increase in Paleozoic grain abundances, in addition to the introduction of Precambrian grains, all with widely variable Hf isotopic compositions. We interpret this to reflect a larger sediment flux from the interior of Alaska where more evolved igneous rocks of that age are found.
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王冰媚 and Ping-mei Jean Wong. "Geochemistry, U-Pb and Sr-Nd-Hf isotopes of the Baijuhuajian A-type granites in Zhejiang Province: evidence for acontinuous extensional regime in the mid and late mesozoic." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39557297.
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Wong, Ping-mei Jean. "Geochemistry, U-Pb and Sr-Nd-Hf isotopes of the Baijuhuajian A-type granites in Zhejiang Province evidence for a continuous extensional regime in the mid and late mesozoic /." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/HKUTO/record/B39557297.
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Justino, Dayvisson. "Geocronologia das sub-bacias triássicas Rincón Blanco e Cerro Pontudo, Argentina: combinação de metodologia U-Pb e Lu-Hf em zircão." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/158330.
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As sub-bacias Rincón Blanco e Cerro Puntudo são depocentros pertencente à parte norte da Bacia de Cuyo, que está exposta em um terreno alóctone da Pre- Cordilheira, Andes Centrais, Argentina. Este terreno é descrito como parte do Supercontinente Laurentia, que foi adicionado ao protomargin Gondwana durante o Oroviciano. A bacia, que é um rifte Triássico, foi preenchida predominantemente de sedimentos clásticos e material vulcânico, vulcanclástico e piroclástico em ambiente continental, e é composta de vários meio-grabens assimétricos conectados por zonas de acomodação. Análises isotópicas de UPb e Lu-Hf em zircão foram realizadas nas unidades do embasamento, rochas vulcanoclásticas rochas e tufos de ambas as sub-bacias triássicas. O embasamento, representado por rochas vulcânicas andesíticas, foi datado em 269,9 ± 2,9 Ma com idades modelo de Hf de 1,34 a 1,60 bilhões de anos (Ga). As rochas vulcanoclásticas são compostas por zircões com idades de 238 a 1433 milhões de anos (Ma), com moda principal no Permiano-Triássico e Esteniano (1,0 a 1,2 Ga). Riolito e tufos triássicos formaram-se entre 246 e 230 Ma e têm idades modelo Hf variando de 1,02 a 1,50 Ga. Assim, as rochas vulcanoclásticas presentes apresentam dominantemente idades mesoproterozóicas, as quais são correlacionados ao Evento Grenviliano. Alguns grãos de zircão mostram idades modelo Hf paleoproterozóicas, que são interpretadas como sugestiva proveniência do Supercontinente Gondwana. A presença de idades mesoproterozoica dominante sugere que o magmatismo ácido associado a Bacia do Cuyo e o próprio Terreno Alóctono Cuyano tenha um embasamente Grenviliano.The sub-basins Rincón Blanco and Cerro Puntudo are depocenter belonging to the northern part of the Cuyo Basin, exposed in an allochthonous terrane of Laurentia that was added to the Gondwana protomargin and now exposed in the Precordillera Argentina. The rift basin was filled predominantly of pyroclastic and continental clastic sediments, and is composed of many asymmetric grabens half-linked by accommodation zones. U-Pb and Lu-Hf zircon isotope analyses were carried out in the basement units and volcanoclastic rocks and tuffs of both Triassic sub-basins. Basement rocks were dated at 269.9±2.9 Ma with Hf model ages 1.34 to 1.60 Ga. The volcanoclastic rocks contain zircons crystallized from 238 Ma to 1433 Ma with main peak at Permian-Triassic and Stenian (1.0 to 1.2 Ga). The Triassic rhyolite and tuffs formed between 246 and 230 Ma and have Hf model ages ranging from 1.02 to 1.50 Ga. Indeed, the volcanoclastic rocks present dominant Mesoproterozoic ages, mostly correlated to the Grenvillian. Some zircon grains show Hf Paleoproterozoic model ages which are interpreted to be part of Gondwana cratonic areas. The presence of dominant Mesoproteorzoic favored the hypotheses of a Grevillian basement for the related acid magmatism of the Cuyo Basin and allocthonous Cuyan Terrane.
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Demouy, Sophie. "La naissance des Andes au Crétacé supérieur : origine et construction du Batholite côtier sud-péruvien (région d'Arequipa)." Toulouse 3, 2012. http://thesesups.ups-tlse.fr/2201/.
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Durant le Crétacé supérieur-Paléocène, une intense activité magmatique localisée le long de l'arc Toquepala a entraîné la création d'un relief important le long de la marge sud-péruvienne. La croissance de cet arc coïncide avec le seul soulèvement connu le long de la marge, ce qui permet de proposer qu'il en est un moteur principal. Notre étude se concentre sur une section du Batholite Côtier péruvien qui s'étend sur 80x60 km pour une épaisseur supérieure à 7 km. Les données structurales décrivent un objet complexe, constitué d'unités plutoniques dont certaines ont subi des épisodes de déformation extensive syn à post mise en place. De grandes failles normales structurent le batholite en réponse à des contraintes tectoniques et à la croissance exagérée de l'arc. L'étude géochronologique souligne la construction discontinue du batholite, au Jurassique (200-175 Ma) et au Crétacé-Paléocène (90-60 Ma). L'exploitation des données géochimiques et isotopiques (Hf, Sr, Nd) permet d'identifier un premier stade dans l'activité de l'arc, caractérisé par une prédominance des processus de mélange et de cristallisation fractionnée, et un second stade durant lequel les magmas homogénéisés évoluent seulement par cristallisation fractionnée pour se mettre en place au niveau du batholite sous la forme d'unités très volumineuses. La maturité du système s'exprime par un phénomène de flare-up entre 70-60 Ma durant lequel plus de 70% du batholite est mis en place. Ce phénomène de haut flux magmatique est caractérisé par des signatures juvéniles des magmas et constitue un apport non négligeable à la croûte continentaleDuring the Late Cretaceous and Paleocene, intense magmatic arc activity resulted in the building of a continuous relief along the Peruvian margin. This arc growth coincided with the only known significant uplift along the coastal southern Peru. Our study has focused in the Arequipa area, on a batholith segment extending 80x60 km for a thickness bigger than 7 km. The structural study describes an object that is complex and consists of different plutonic units, that for some underwent extensive deformation syn to post emplacement. Major faults affect the batholith as a consequence of tectonic strains and exaggerate growth of the arc. The geochronological study indicates a discontinuous construction of the batholith, during the Jurassic (200-175 Ma) and the Late Cretaceous-Paleocene (90-60 Ma). Exploitation of the geochemistry and isotopic data (Hf, Sr, Nd) allows to identify an initiation stage of the arc during which fractional crystallization and mixing are predominant, and a thermal maturation stage during which magmas are homogenized in the deep crust, and evolve by fractional crystallization until the batholith level. This period leads to the construction of more than 70 % of the batholith and can thus be considered as a flare-up event. This event is characterized by juvenile signatures and also contributes significantly to the growth of the continental crust
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Smietana, Magali. "Pétrologie, géochronologie (K-Ar) et géochimie élémentaire et isotopique (Sr, Nd, Hf, Pb) de laves anciennes de la Réunion : Implications sur la construction de l’édifice volcanique." Thesis, La Réunion, 2011. http://www.theses.fr/2011LARE0012/document.
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Le système volcanique de La Réunion est formé de la coalescence des massifs du Piton des Neiges et du Piton de la Fournaise. Son édification, liée à l’activité d’un panache mantellique, est caractérisée par une phase de croissance sous-marine, puis subaérienne, suivie d’une période de dégénérescence, comme proposé classiquement pour les volcans boucliers océaniques d’Hawaii. De précédentes études ont montré que l’activité subaérienne de La Réunion aurait débuté il y a environ 2,2 Ma. Les analyses géochimiques menées jusqu’alors sur les produits associés à cette activité volcanique (subaérienne et sous-marine) ont montré un caractère chimique transitionnel avec une composition isotopique (87Sr/86Sr, 143Nd/144Nd et 176Hf/177Hf) particulièrement homogène pour un volcanisme de point chaud. Dans cette étude, nous montrons que des laves sous-marines récemment identifiées sous la série basique du Piton de la Fournaise (au sein de la sur Rift Zone Nord-Est) ainsi que des laves subaériennes affleurant à la base de canyons incisés dans le massif (Série Différenciée de la Rivière des Remparts), présentent des caractéristiques ne s’inscrivant pas dans le modèle d’évolution proposé précédemment pour ce volcan. Se pose donc la question de la nature et de l’origine de ces laves, ainsi que de leur place et appartenance dans l’édification du système volcanique réunionnais. De nouvelles investigations pétro-géochimiques et géochronologiques ont été menées sur la partie sous-marine de l’édifice de La Réunion. Elles révèlent l’existence d’un groupe de laves exceptionnel. Leur composition se distingue clairement de celle des échantillons communément analysés à La Réunion et montre (1) un enrichissement en éléments incompatibles couplé isotopiquement à (2) un rapprochement vers un pôle mantellique enrichi de type EM. Ces particularités géochimiques démontrent que le panache mantellique possède (1) une source hétérogène affectée par (2) des taux de fusion variables. De plus, deux échantillons de ce nouveau groupe datés à 3,77 (0,08) et à 3,34 (0,07) Ma étendent considérablement la période d’activité connue de l’édifice. Ces âges remarquables font de ces laves les plus anciennes jamais datées à La Réunion. La nature géochimique ainsi que la position stratigraphique des laves de cette étude (échantillons subaériens et sous-marins des massifs du Piton des Neiges et du Piton de la Fournaise) impliquent une réinterprétation du schéma d’évolution global de l’île. Contrairement aux études précédentes, nos résultats sur ces laves montrent que : (1) Les laves différenciées de la Rivière des Remparts, qui sont des laves subaériennes, de part leur position stratigraphique et géographique sous-jacente au Piton de la Fournaise et par analogie avec le Piton des Neiges, ne peuvent être reliées à l’activité de la Fournaise, (2) Le signal isotopique du groupe de laves sous-marines de la Rift Zone Nord-Est de la Fournaise, révèlent l’hétérogénéité de la source du panache mantellique sous La Réunion, source que nous identifions comme des enclaves d’éclogite contenues dans une lherzolite à spinelle, (3) L’âge plus ancien de ces laves sous-marines et leur localisation sous le flanc Est de la Fournaise remet en questions le schéma jusqu’alors admis pour l’édification de l’île de La Réunion reposant sur la construction du Piton des Neiges puis celle, adjacente, du Piton de la Fournaise. En conséquence, nos données géochimiques et géochronologiques sont de nouveaux arguments en faveur de l’élaboration d’un modèle d’évolution plus complexe, suggérant l’existence d’un troisième massif volcanique. Il est en accord avec les précédents travaux de pétrologie et de géophysique suggérant l’existence d’un troisième édifice à l’Est de La Réunion, communément appelé le Volcan des AlizésThe volcanic system of La Reunion is made of the coalescent Piton des Neiges and Piton de la Fournaise edifices. Its formation, associated with the activity of a mantle plume, is characterized by phases of submarine and subaerial growth, followed by a period of destruction, as described in the classical model proposed for Hawaiian Island volcanoes. Previous studies showed that the subaerial activity of La Reunion would have started around 2.2 Ma ago. Geochemical analyses carried out on the products associated with subaerial and submarine volcanism revealed their transitional chemical nature and their peculiar homogeneous isotopic compositions (87Sr/86Sr, 143Nd/144Nd et 176Hf/177Hf) for a hotspot derived magmatism. In this study, we show that some unusual submarine lavas were recently identified below the basal series of Piton de la Fournaise volcano (dredged on the North-East Rift Zone of la Fournaise) and below the subaerial lavas outcropping at the base of the differentiated series of Rivière des Remparts, indicate that the evolution of La Reunion system is probably more complex than previously suggested. The question of the nature and origin of these lavas, together with their implication on the formation of La Reunion, is an issue of major interest in order to better constrain the global evolution of the volcanic system. As a consequence, new petrological, geochemical and geochronological investigations were conducted on the submarine part of La Reunion edifice. They revealed the existence of a geochemically exceptional group of lavas. Its composition is clearly different from common samples of La Reunion and presents (1) an enrichment in incompatible elements and (2) tends toward an enriched EM endmember. These chemical specificities reveal that the source of La Reunion magmatic products is (1) an heterogeneous source affected by (2) variable melting degrees. Moreover, two samples of this new group dated at 3.77 (0,08) and 3.34 (0,07) Ma extend considerably the period of activity of the island. These rocks are the oldest samples ever dated at La Reunion. The nature and stratigraphical location of subaerial and submarine samples from Piton des Neiges and Piton de la Fournaise imply a new interpretation of the global evolution of the island. Unlike previous studies, our results indicate that :(1) The differentiated subaerial lavas from Rivière des Remparts, due to their stratigraphical and geographical location underlying Piton de la Fournaise, and by analogy with the Piton des Neiges, cannot be linked to the activity of Piton de la Fournaise. (2) The isotope signature of the submarine lava group from the North-East Rift Zone of Piton de la Fournaise, reveals the heterogeneous character of the mantle source under La Reunion Island, that can be modelled as embedded eclogite in a matrix of spinel lherzolite, (3) The age of this submarine group and its location under the eastern flank of Piton de la Fournaise, imply a more complex model of evolution of La Reunion. Therefore, our geochemical and geochronological data are new arguments suggesting the existence of a third volcanic center on the island. This assumption confirms the previous petrological and geophysical evidence supporting the existence of this volcano at the East of La Reunion, commonly called Les Alizés volcano
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Höfig, Tobias Walter [Verfasser]. "Geochemical (major and trace elements and Sr-Nd-Hf-Pb isotopes) characterization of the upper oceanic crust (sediments to gabbros) at ODP/IODP Site 1256 in the eastern Central Pacific / Tobias Walter Höfig." Kiel : Universitätsbibliothek Kiel, 2017. http://d-nb.info/1138979562/34.
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Höfig, Tobias [Verfasser]. "Geochemical (major and trace elements and Sr-Nd-Hf-Pb isotopes) characterization of the upper oceanic crust (sediments to gabbros) at ODP/IODP Site 1256 in the eastern Central Pacific / Tobias Walter Höfig." Kiel : Universitätsbibliothek Kiel, 2017. http://nbn-resolving.de/urn:nbn:de:gbv:8-diss-153979.
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Smietana, Magali. "Pétrologie, géochronologie (K-Ar) et géochimie élémentaire et isotopique (Sr, Nd, Hf, Pb) de laves anciennes de la Réunion : Implications sur la construction de l'édifice volcanique." Phd thesis, Université de la Réunion, 2011. http://tel.archives-ouvertes.fr/tel-00716829.
Full textAbstract:
Le système volcanique de La Réunion est formé de la coalescence des massifs du Piton des Neiges et du Piton de la Fournaise. Son édification, liée à l'activité d'un panache mantellique, est caractérisée par une phase de croissance sous-marine, puis subaérienne, suivie d'une période de dégénérescence, comme proposé classiquement pour les volcans boucliers océaniques d'Hawaii. De précédentes études ont montré que l'activité subaérienne de La Réunion aurait débuté il y a environ 2,2 Ma. Les analyses géochimiques menées jusqu'alors sur les produits associés à cette activité volcanique (subaérienne et sous-marine) ont montré un caractère chimique transitionnel avec une composition isotopique (87Sr/86Sr, 143Nd/144Nd et 176Hf/177Hf) particulièrement homogène pour un volcanisme de point chaud. Dans cette étude, nous montrons que des laves sous-marines récemment identifiées sous la série basique du Piton de la Fournaise (au sein de la sur Rift Zone Nord-Est) ainsi que des laves subaériennes affleurant à la base de canyons incisés dans le massif (Série Différenciée de la Rivière des Remparts), présentent des caractéristiques ne s'inscrivant pas dans le modèle d'évolution proposé précédemment pour ce volcan. Se pose donc la question de la nature et de l'origine de ces laves, ainsi que de leur place et appartenance dans l'édification du système volcanique réunionnais. De nouvelles investigations pétro-géochimiques et géochronologiques ont été menées sur la partie sous-marine de l'édifice de La Réunion. Elles révèlent l'existence d'un groupe de laves exceptionnel. Leur composition se distingue clairement de celle des échantillons communément analysés à La Réunion et montre (1) un enrichissement en éléments incompatibles couplé isotopiquement à (2) un rapprochement vers un pôle mantellique enrichi de type EM. Ces particularités géochimiques démontrent que le panache mantellique possède (1) une source hétérogène affectée par (2) des taux de fusion variables. De plus, deux échantillons de ce nouveau groupe datés à 3,77 (0,08) et à 3,34 (0,07) Ma étendent considérablement la période d'activité connue de l'édifice. Ces âges remarquables font de ces laves les plus anciennes jamais datées à La Réunion. La nature géochimique ainsi que la position stratigraphique des laves de cette étude (échantillons subaériens et sous-marins des massifs du Piton des Neiges et du Piton de la Fournaise) impliquent une réinterprétation du schéma d'évolution global de l'île. Contrairement aux études précédentes, nos résultats sur ces laves montrent que : (1) Les laves différenciées de la Rivière des Remparts, qui sont des laves subaériennes, de part leur position stratigraphique et géographique sous-jacente au Piton de la Fournaise et par analogie avec le Piton des Neiges, ne peuvent être reliées à l'activité de la Fournaise, (2) Le signal isotopique du groupe de laves sous-marines de la Rift Zone Nord-Est de la Fournaise, révèlent l'hétérogénéité de la source du panache mantellique sous La Réunion, source que nous identifions comme des enclaves d'éclogite contenues dans une lherzolite à spinelle, (3) L'âge plus ancien de ces laves sous-marines et leur localisation sous le flanc Est de la Fournaise remet en questions le schéma jusqu'alors admis pour l'édification de l'île de La Réunion reposant sur la construction du Piton des Neiges puis celle, adjacente, du Piton de la Fournaise. En conséquence, nos données géochimiques et géochronologiques sont de nouveaux arguments en faveur de l'élaboration d'un modèle d'évolution plus complexe, suggérant l'existence d'un troisième massif volcanique. Il est en accord avec les précédents travaux de pétrologie et de géophysique suggérant l'existence d'un troisième édifice à l'Est de La Réunion, communément appelé le Volcan des Alizés.
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Canile, Fernanda Maciel. "Geologia isotópica em zircões detríticos (U-Pb, Hf e O) e em rocha total (Sm-Nd e Pb-Pb) das rochas da Bacia do Paraná em Santa Catarina." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/44/44141/tde-24022016-140417/.
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Dados isotópicos U-Pb, Hf e de O foram obtidos em zircões detríticos das unidades do final do Paleozoico e início do Mesozoico da Bacia do Paraná, sudeste do Brasil, com o objetivo de determinar a proveniência dos sedimentos, assim como contribuir para o entendimento da evolução tectônica da bacia. Assinaturas isotópicas Sm-Nd e Pb-Pb em amostras de rocha-total também foram obtidas com o intuito de auxiliar na interpretação sobre as áreas fontes. A seção estudada, Coluna White em Santa Catarina, inclui rochas de 11 unidades estratigráficas (da base para o topo): Formação Rio do Sul, Formação Rio Bonito, incluindo os membros Triunfo, Paraguaçu e Siderópolis, Formação Palermo, Formação Irati, Formação Serra Alta, Formação Teresina, Formação Rio do Rasto, subdividida nos membros Serrinha e Morro Pelado, e Formação Botucatu, Idades U-Pb foram obtidas em 1941 grãos de zircão detrítico e variam de 242 Ma a 3,4 Ga. Todas as unidades sedimentares apresentam quatro grupos principais de zircões detríticos, Neoarqueano (2,7-2.5 Ga), Paleoproterozoico Médio (2,0-1,8 Ga), Grenviliano (1,1-0,9 Ga) e Brasiliano (850-490 Ma), refletindo a importância do embasamento Pr-e-Cambriano que bordeja a parte leste da bacia como áreas fontes, tais como as Faixas Dom Feliciano, Kaoko e Namaqua-Natal, incluindo o embasamento local datado em 584 Ma. O Membro Siderópolis apresenta uma importante mudança nas fontes dos sedimentos que preencheram a Bacia do Paraná, pois é a partir dessa unidade que o pico de idade permiana (266 a 290 Ma) é observado. Esse pico persiste até o topo da seção, a Formação Botucatu. As assinaturas isotópicas de O e Hf dos zircões detríticos mostram que parte dos grãos do Paleoproterozoico Médio é provavelmente de rochas do embasamento atualmente recoberto, que estava exposto até a deposição da Formação Rio Bonito. Os isotópos de Hf e O também mostram que parte dos zircões com idade grenviliana é proveniente de rochas argentinas, o que implica em longas distâncias de transporte. As assinaturas isotópicas de parte dos grãos permianos os ligam a fontes da Argentina e Chile, sendo que parte desses grãos possui forma mais arredondada, o que sugere que eles alcançaram a bacia pelo transporte em ambientes subaquáticos e não somente pelo ar (quedas de cinzas vulcânicas) como é comumente apontado. Outros picos de idade mais jovens (Ordoviciano ao Carbonífero), observados a partir da Formação Palermo e nas unidades superiores, também são provenientes de fontes argentinas e chilenas, mostrando a importância dos detritos de fontes distantes durante o preenchimento da bacia. Os dados Sm-Nd e Pb-Pb em rocha total mostram que os sedimentos da Bacia do Paraná apresentam predominância de fontes de origem crustal. As assinaturas são semelhantes aos granitoides de Santa Catarina, rochas da Faixa Ribeira, do Escufo Brasileiro, das Faixas Namaqua-Natal e Kaoko, Terreno Arequipa-Antofalla (embasamento dos Andes) e granitoides do Norte da Patagônia. Esses dados corroboram os padrões de zircões detríticos observados, que apontam para áreas fontes tanto proximais quanto distais. Além disso, as idades modelo Sm-Nd (\'T IND. DM\') obtidas são mais antigas que 1,4 Ga e mais negativas (-10 a -15) nas unidades inferiores (Formação Rio do Sul até o Membro Paraguaçu), enquanto que as unidades superiores apresentam valores de \'\'épsilon\' IND.Nd(0) entre -6 a -12 e idades modelo \'T IND.DM\' mais jovens que 1,5 Ga, sugerindo a participação de uma fonte mais jovem a partir da deposição do Membro Siderópolis, conforme foi observado pelos dados de zircão detrítico (pico de idade permiana)U-Pb, Hf and O isotope data were obtained from detrital zircons from late Paleozoic-early Mesozoic units from Paraná Basin, southeastern Brazil, in order to constain the provenance of the sediments, as well as to contribute to the understanding of the tectonic evolution of the basin. Whole rock Sm-Nd and Pb-Pb isotopic signatures were also taken in order to help the interpretation. The studied section, White Column in Santa Catarina state, includes rocks from 11 stratigraphic units (from base to top): Rio do Sul Formation, Rio Bonito Formation (Triunfo, Paraguaçu and Siderópolis members), Palermo Formation, Irati Formation, Serra Alta Formation, Teresina Formation, and Rio do Rasto Formation (Serrinha and Morro Pelado members) and Botucatu Formation. U-Pb ages were obtained on 1941 detrital zircons and range from 242 Ma to 3400 Ma. All sedimentary units show four main detrital age groups, Neoarchean (2700-2500 Ma), mid-Paleoproterozoic (2000-1800 Ma), Grenvillian (1100-900 Ma) and Brasiliano (850-490 Ma), reflecting the importance of the Precambrian basement bordering the east side of the basin, such as Dom Feliciano, Kaoko and Namaque-Natal Belts as source areas, including the local basement that was dated at 584 Ma. The Siderópolis Member shows an important change in the source of sediments with a Permian age-peak (266 to 290 Ma). This age-peak persists towards the top of the section until the Botucatu Formation. O and Hf isotopic signatures from the detrital zircons show that a portion of the mid-Paleoproterozoic grains is probably from rocks of the presently covered basement, which was exposed until the deposition of the Rio Bonito Formation. O and Hf isotopes also show that some Grenvillian aged zircons are from Argentinian rocks, which implies a long transport distance. Isotopic signatures of part of the Permian grains also link them to sources from Argentina and Chile, and part of these grains has more rounded shapes, suggesting that they reached the basin after long distance traveling on subaquatic environment and nor only through the air (ash falls) as it is commonly accepted. Other younger age peaks (Ordovician to Carboniferous) found from Palermo Formation upsection are also linked to Argentinian and Chilean sources, showing the importance of distant sources during the filling of the basin. The Sm-Nd and Pb-Pb data on whole rocks show that the sediments from the Paraná Basin present predominance of sources with crustal origin. Osotopic signatures are similar to granitoid rocks from Santa Catarina, Ribeira Belt, Brazilian Shield, Namaqua-Natal and Kaoko Belts, as well as the Arequipa-Antofalla terranes (Andes basement) and granitoids from North Patagonia. These data corroborate the observed detrital zircon patterns thar point to both proximal and distal source areas. \'T IND.DM\' model ages older than 1.4 Ga and more negative (-10 to -15) epsilon values were observed in the lower units (Rio do Sul Formation to Paraguaçu Member), while the upper units show \'\'épsilos\' IND.Nd(0)\' values ranging from -6 to -12 and \'T IND. DM\' model ages younger than 1.5 Ga, corroborating the addition of a younger source starting from the Siderópolis Member deposition upwards, as noted by detrital zircon data (Permian age-peak).
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Janin, Myriam. "Le plateau Amsterdam-St. Paul : caractérisation du point chaud éponyme et évolution de son interaction avec la dorsale Sud-est Indienne." Brest, 2010. https://tel.archives-ouvertes.fr/tel-00592036.
Full textAbstract:
Le plateau Amsterdam-St. Paul (ASP) est issu de l’interaction entre le point chaud éponyme et la dorsale sud-est Indienne. Il est prolongé au nord-est par la chaîne des Poètes Disparus, une chaîne volcanique liée à l’activité intraplaque du point chaud, Leur étude révèle que la composition du point chaud nécessite la présence dans le manteau source de croûte océanique chargée de sédiments pélagiques recyclée via subduction il y a 1,5Ga. Le panache ASP s’exprime en surface de manière discontinue et à la faveur de zone de faiblesses. La construction de la chaîne est ainsi directement liée (1) aux pulses du panache et (2) à la déformation diffuse liée au mouvement des plaques Capricorne et Australie. Des datations K-Ar révèlent que cette chaîne de volcans est constituée de: (1) une ancienne génération datée à ~9Ma et constituée d’édifices imposants, ayant probablement eu une phase émergée et (2) une jeune génération, âgée de moins de 2Ma, et constituée d’édifices plus petits, formés suite à la migration de matériel issu du panache sous le plateau ASP. Le panache présente en outre un mouvement propre de l’ordre de 1-2 cm/an vers le sud-ouest. Les compositions élémentaires et isotopiques (Sr-Nd-Pb-Hf) des laves émises sur le plateau ASP sont très variables et révèlent que manteau sous-jacent est hétérogène. Il consiste en un manteau appauvri contaminé par des lambeaux de croûte continentale inférieure, composés de granulites à grenat et plagioclase, probablement délaminée pendant la fracturation du Gondwana. Les résultats de cette étude affermissent donc le modèle proposé de recyclage dans le manteau supérieur de granulites comme origine de l’anomalie DUPALThe Amsterdam-St Paul plateau (ASP) is an oceanic plateau built from the interaction between ASP hotspot and the Southeast Indian ridge. P volcanic chain, called the chain of the dead Poets (CDP), lies to its northward and related to the hotspot intraplate activity. Their study reveals that ASP plume composition comes from oceanic crust and pelagic sediments recycled in the mantle through a 1,5Ga subduction process, ASP plume activity is pulsatile and occurs preferentially on weakness zones. The CDP construction results thus from (1) the plume pulses and (2) the diffuse divergent boundary between the Capricorn and Australian plates. K-Ar datings reveal that this volcanic chain is made of two generations of seamounts: (1) an old one, of about 9Ma and made of large edifices which had probably a sub-aerial period and (2) a young one, younger than 2Ma, and made of small edifices related to some pounded plume pulse material. In addition, ASP plume has an own motion of about 1-2 cm/yr to the south-west. The ASP plateau lavas compositions (major and trace elements and Sr-Nd-Pb-Hf isotopes) show en important variability and reveal that the underlying mantle is heterogeneous. It is made of a depleted mantle with lower continental crust strips in the form of garnet-plagioclase granulites, probably delaminated during the Gondwana breakup. The lower continental crust s one of the hypotheses for DUPAL anomaly origin and our data support this assumption
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Janin, Myriam. "Le plateau d'Amsterdam-St Paul : Caractérisation du point chaud éponyme et évolution de son interaction avec la dorsale Sud-est indienne." Phd thesis, Université de Bretagne occidentale - Brest, 2010. http://tel.archives-ouvertes.fr/tel-00592036.
Full textAbstract:
Le plateau Amsterdam-St. Paul (ASP) est un plateau océanique issu de l'interaction entre le point chaud éponyme et la dorsale sud-est Indienne. Il est prolongé au nord-est par la chaîne des Poètes Disparus (CDP pour Chain of the Dead Poets), une chaine volcanique liée à l'activité intraplaque du point chaud. L'étude du plateau et de la chaîne révèle que la composition du point chaud ASP nécessite la présence dans le manteau source de croute océanique chargée de sédiments pélagiques recyclée via subduction il y a 1,5Ga. Le panache ASP s'exprime en surface de manière discontinue, par le biais de pulses, et à la faveur de zone de faiblesses telles que les dorsales, les zones de fractures et les zones de déformation diffuse. De ce fait, la construction de la chaîne est directement liée (1) aux pulses du panache et (2) à la déformation diffuse engendrée par le mouvement des plaques Capricorne et Australie. Des datations K-Ar révèlent que cette chaine est constituée de deux générations de volcans : (1) une ancienne génération datée à ~9Ma et constituée d'édifices de taille importante, ayant probablement eu une phase émergée et (2) une jeune génération, âgée de moins de 2Ma, et constituée d'édifices plus petits, formés par la migration de matériel issu du panache sous le plateau ASP lors du dernier pulse et à l'épanchement en surface à la faveur de zones de faiblesse. L'orientation de la chaîne et des édifices qui la composent indique que le maximum de divergence entre les plaques Capricorne et Australie se produit selon une orientation N155°. En outre, le panache présente un mouvement propre de l'ordre de 1-2 cm/an vers le sud-ouest qui a contribué à son rapprochement de la dorsale. Ce mouvement à l'encontre des flux asthénosphériques implique un ancrage du panache, confirmant son origine profonde. Les compositions élémentaires et isotopiques (Sr-Nd-Pb-Hf) des laves émises sur le plateau ASP révèlent l'interaction entre le panache, le manteau supérieur Indien et l'influence de l'anomalie DUPAL. Le manteau supérieur Indien sous le plateau ASP est hétérogène et consiste en un manteau appauvri contaminé par des lambeaux de croute continentale inférieure, composés de granulites à grenat et plagioclase, probablement délaminée pendant la fracturation du méga-continent Gondwana. Les résultats de cette étude affermissent donc le modèle proposé de recyclage dans le manteau supérieur de granulites comme origine de l'anomalie DUPAL. La présence de ces trois pôles (point chaud, manteau supérieur et croute continentale inférieure), ainsi que leurs mélanges en proportions variables, entrainent une grande variabilité de compositions dans les laves du plateau. L'apparente homogénéité de l'île d'Amsterdam, l'un des sommets émergés du plateau, se révèle donc être un biais lié à la présence de réservoirs magmatiques intermédiaires dans sa structure.
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Maurer, Victor Câmara. "Caracterização geocronológica (U-Pb), geoquímica e isotópica (Sr, Nd, Hf) do complexo Rio Capivari no terreno Embu." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/44/44143/tde-17062016-141231/.
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O Complexo Rio Capivari (CRC) é constituído por ortognaisses migmatíticos de composições graníticas a tonalíticas e anfibolitos subordinados (magmas toleíticos) em lascas tectônicas no Terreno Embu. As composições dos gnaisses do CRC são predominantemente cálcio-alcalinas a álcali-cálcicas. Idades U-Pb em núcleos de zircão com zoneamento oscilatório indicam cristalização magmática dos protólitos em três períodos principais 2.4, 2.2-2.1 e 2.0 Ga. Idades metamórficas foram reconhecidas em bordas de zircão totalmente escuras nas imagens de catodoluminescência e variam entre 620-590 Ma. A suíte sideriana (2.4 Ga) apresenta caráter juvenil, como evidenciado pelos valores positivos de \'\'épsilon\'\'IND.Nd\' (+3.8) e \'\'épsilon\'\'IND.Hf\' (+0.3 a +4.8) e pela ausência de núcleos de zircão herdado, comumente encontrados em rochas que sofreram retrabalhamento crustal. A suíte de idades riacianas (2.2-2.1 Ga) apresenta idades modelos TDM arqueanas (2.6-3.3 Ga), valores negativos de \'\'épsilon\'\'IND.Nd\' (-12.0 a -4.0) e negativos a levemente positivos de \'\'épsilon\'\'IND.Hf\' (-7.8 a +0.5). Portanto, tais rochas derivam de retrabalhamento de reservatórios crustais antigos. A suíte de idade orosiriana (2.0 Ga) apresenta fontes mais antigas e retrabalhadas com valores altamente negativos de \'\'épsilon\'\'IND.Nd\' (-10.4) e \'\'épsilon\'\'IND.Hf\' (-1.2 a -13.6), sugerindo prolongada residência crustal com idades modelo \'T IND.DM\' e \'T IND.Hf\' >3.3 Ga. As assinaturas de elementos traços em rocha total e a química de zircão sugerem fontes máficas para o gnaisse sideriano. Reservatórios de crosta média, mas de profundidades variáveis, parecem ser a principal fonte dos gnaisses riacianos e orosirianos. Análises em diagramas tectônicos discriminantes baseados em elementos traços de rocha total com elevadas razões \'La/Yb IND.(N)\' (>10), Nb/Yb (>2) e Th/Yb (>1), somados aos valores de \'Y IND.2\'\'O IND.3\' (<3000 ppm), U/Yb (>0.5) e Nb/Yb (0.01-0.10) da química de zircão, sugerem que ambas as suítes de idades foram geradas em ambientes de arco magmático continental, mas com um gap de 200-300 Ma entre o gnaisse sideriano e os gnaisses riacianos sem dados ou informações geológicas. Perfis multielementos (elementos traços) comparativos entre representação de amostras típicas de arco continental associado à subducção de crosta oceânica (margem andina) e amostras de arcos de ilha (Ilhas Mariana) confirmam afinidade com ambiente de arco continental para o CRC, associado à subducção de placa oceânica, principalmente para o gnaisse sideriano. Apesar de pouco representativo, devido ao número de amostras (n=1), uma acresção juvenil em 2.4 Ga colabora para uma dinâmica contínua da evolução da crosta continental. O papel desempenhado pelo CRC na evolução geral do Terreno Embu permanece enigmático. Os dados isotópicos de \'\'épsilon\'\'IND.Nd(590)\' e \'ANTPOT.87 Sr\'/\'ANTPOT.88 Sr IND.(i)\' do CRC (-27.3 a -19.7 e 0.704 a 0.722, respectivamente) indicam evolução temporal não compatível com o requerido para as fontes dos granitos ediacaranos do Terreno Embu, que exigem a participação de reservatórios mais primitivos (\'\'épsilon\'\'IND.Nd(590)\' -13 a -7) e empobrecidos em Rb (\'ANTPOT.87 Sr\'/\'ANTPOT.88 Sr IND.(i)\' \'\'QUASE IGUAL A\' 0,710).The Rio Capivari Complex (RCC) comprises migmatitic orthogneisses with granitic to tonalitic compositions and subordinate amphibolites (tholeiitic magmas), that occur in tectonics contacts within the Embu Terrane. The RCC orthogneisses are predominantly calc-alkaline to alkali-calcic. U-Pb zircon ages obtained on oscillatory zoned zircon cores indicate protolith magmatic crystallization into three main periods 2.4, 2.2-2.1 and 2.0 Ga. CL-dark zircon rims yield dates between 620-590 Ma, interpreted as metamorphic overprinting. The Siderian suite (2.4 Ga) show juvenile character, as evidenced by positive \'\'épsilon\'\'IND.Nd(t)\' (+3.8) and \'\'épsilon\'\'IND.Hf(t)\' (+0.3 to +4.8) values and absence of inherited zircon grains, commonly found in reworking crustal rocks. The Rhyacian suite (2.2-2.1 Ga) has Archean model ages (\'T IND.DM\' = 2.6-3.3 Ga), negative values of \'\'épsilon\'\'IND.Nd(t)\' (-12.0 to -4.0) and negative to slightly positive \'\'épsilon\'\'IND.Hf(t)\' values (-7.8 to +0.5). Therefore, such rocks most likely derived from reworking of older crustal reservoirs. The Orosirian suite (2.0 Ga) has even older sources with strongly negative \'\'épsilon\'\'IND.Nd(t)\' (-10.4) and \'\'épsilon\'\'IND.Hf(t)\' (-1.2 to -13.6) suggesting prolonged crustal residence time with \'T IND.DM\' and \'T IND.HF\' > 3.3 Ga. Whole-rock trace element and zircon chemistry indicate mafic sources for the Siderian suite. Middle crust reservoirs, at varying depths, appear to be the main source of the Rhyacian and Orosirian suites. According to analysis in discriminating tectonic diagrams the whole rock trace elements with high ratios \'La/Yb IND.(N)\' (> 10), Nb/Yb (> 2) and Th/Yb (> 1), added to the amounts of \'Y IND.2\'\'O IND.3\' (<3,000 ppm), U/Yb (> 0.5) and Nb/Yb (0.01 to 0.10) from zircon chemistry, suggest that all three suites were generated on continental magmatic arc environments, but with a gap of 200-300 Ma between the Siderian suite and the Rhyacian and Orosirian suites without data or geological information. Comparative multi-elements profiles (trace elements) between representation of typical continental arc samples associated with the oceanic crust subduction (Andean margin) and samples of island arcs (Mariana Islands) confirm affinity with continental arc environment for the RCC, associated with subduction oceanic plate, mainly for the Siderian suite. In spite of the small dataset, the results of this study indicate a juvenile accretion at 2.4 Ga, what suggests a continuous dynamic of continental crust evolution. The RCC role on the tectonic evolution of the Embu terrane remains enigmatic. The isotopic data \'\'épsilon\'\'IND.Nd(590)\' and \'ANTPOT.87 Sr\'/\'ANTPOT.88 Sr(i)\' of the RCC (-27.3 to -19.7 and 0.704-0.722, respectively) indicate an evolution not compatible with the sources for the Ediacaran granites of the Embu Terrane, requiring the participation of more primitive reservoirs (\'\'épsilon\'\'IND.Nd(590)\' -13 to -7) (ANTPOT.87 Sr\'/\'ANTPOT.88 Sr(i)\'\'QUASE IGUAL A\' 0.710).
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Carpentier, Marion. "Composition chimique des sédiments entrant dans la zone de subduction des Petites Antilles." Phd thesis, Universite Libre de Bruxelles, 2007. http://tel.archives-ouvertes.fr/tel-00187335.
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Les laves provenant de l'arc des Petites Antilles sont caractérisées par une grande variabilité chimique et leurs compositions isotopiques suggèrent une contribution variable de matériel crustal ancien dans leur genèse. L'arc des Petites Antilles est également caractérisé par une zonation chimique nord-sud, les laves des îles du sud présentant généralement des signatures isotopiques crustales plus fortes que celles des îles du nord. Nous avons tenté dans cette étude d'établir s'il existe des variations de la composition chimique des sédiments entrant en subduction le long de l'arc, et si d'éventuels changements de leur composition peuvent expliquer les variations chimiques observées au sein des laves. Pour ce faire, nous avons réalisé une étude géochimique approfondie (majeurs, traces, isotopes du Sr, du Nd, de l'Hf et du Pb) du flux sédimentaire potentiellement entrant dans la zone de subduction à différentes latitudes. L'échantillonnage comprend des sédiments forés au niveau des sites 543 (nord de l'arc) et 144 (extrême sud de l'arc) lors des campagnes DSDP 78A et 14 respectivement, et des sédiments provenant de l'île de la Barbade (sud de l'arc). Les échantillons présentent une grande hétérogénéité lithologique correspondant globalement à un mélange en proportion variable entre une composante détritique et une composante biogénique (siliceuse ou carbonatée). De plus, au niveau du site 144, des niveaux très riches en matière organique (black shales) datant du Cénomanien supérieur au Santonien (~ 95 à 84 Ma) ont été forés. Ces formations correspondent à l'enregistrement des Oceanic Anoxic Events 2 et 3. Nous avons montré que la « dilution » variable de la fraction détritique par la composante biogénique est le facteur qui contrôle largement les variations de concentrations en éléments traces observées. De plus, nous avons révélé un enrichissement en U extrêmement important au sein des black shales du site 144. Les signatures isotopiques de l'Hf, du Nd et du Pb sont dominées par la composante détritique, alors que celle du Sr, dans le cas d'échantillons riches en carbonates est dominée par celle de l'eau de mer. Les sédiments des trois sites présentent des compositions isotopiques du Pb fortement radiogéniques par rapports aux sédiments océaniques « classiques », que nous avons associées à une forte contribution de matériel issu de l'altération des cratons guyanais et brésilien dans la composante détritique. De plus, la décroissance radioactive de l'U dans les black shales du site 144 a généré des rapports 206-207Pb/204Pb extrêmement radiogéniques.
Un mélange entre le manteau appauvri et les sédiments du site 543 reproduit les compositions isotopiques des laves de la partie nord de l'arc. Pour la partie sud de l'arc un mélange entre les sédiments les plus radiogéniques en Pb du site 144 et le manteau appauvri explique les compositions des laves des îles de la Martinique à Grenade. Une contribution croissante des black shales du nord vers le sud est nécessaire, et est de plus en accord avec l'augmentation du nord vers le sud de l'âge du plancher océanique subduit. Enfin, quelques sédiments de l'île de la Barbade présentent certaines caractéristiques compatibles avec leur implication dans la genèse des laves de la partie sud de l'arc.
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Handley, Heather K. "Geochemical and Sr-Nd-Hf-O isotopic constraints on volcanic petrogenesis at the Sunda Arc, Indonesia." Thesis, Durham University, 2006. http://etheses.dur.ac.uk/2670/.
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The Sunda island arc of Indonesia formed as a result of the northward subduction of the Indo- Australian Plate beneath the Eurasian Plate. Along-arc variations in the composition and thickness of the overriding Eurasian plate and variation in the type and amount of sediment deposited on the subducting plate create differential effects on Sunda arc lava geochemistry. Detailed study of volcanic rocks from Salak, Gede Volcanic Complex (GVC) in West Java and Ijen Volcanic Complex (IVC) in East Java was carried out in order to establish the relative importance and contributions of various potential source components and composition-modifying processes at individual volcanic centres, prior to investigating petrogenetic variation along the arc. Differentiation processes play a major role in modifying the geochemical composition of Sunda arc magmas. However, the relative importance and traceable impact of the different processes varies at each volcanic centre. Fractional crystallisation of a typical Javan island arc mineral assemblage exerts the largest control on major and trace element composition of the volcanic rocks. Distinct intra-volcanic complex differentiation trends at rvc and Salak are spatially controlled and are explained by independent conduits and multiple magma reservoirs at different depths in the crust - linked to sub-volcanic structure. Shallow level contamination by typical upper-crustal continental material is insignificant during magmatic differentiation at Salak, GVC and IVC. However, at Salak there is some evidence for assimilation of material similar in composition to the volcanic rocks. Deep fractionation of a phase in which HFSE and HREE are compatible (e.g. amphibole) is inferred in the evolution of most Javan magmas. Magmatism at Salak, GVC and IVC is the product of shallow, relatively homogeneous, fertile, Indian Ocean MORB-like mantle that has been enriched by slab- derived component(s) sourced from the altered oceanic crust and subducted sediment. Hf and Nd isotope ratios of Javan lavas show that the subducted sedimentary source component is heterogeneous and reflects spatial variations in sediment compositions on the down-going plate along the Java Trench. A progressive eastward increase in Sr isotope ratio of volcanic rocks across West and Central Java broadly correlates with inferred lithospheric thickness. A significant change in crustal architecture (i.e. thickness) occurs between Central and East Java. This transition may represent the south-eastern boundary of Sundaland (pre-Tertiary arc basement).
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Xia, Xiaoping. "Spot U-Pband Hf isotope analyses of detrital zircons from the khondalites in the western block of the North China craton." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B35773698.
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Xia, Xiaoping, and 夏小平. "Spot U-Pband Hf isotope analyses of detrital zircons from the khondalites in the western block of the North China craton." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B35773698.
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Luo, Yan. "U-Pb age and Hf isotopic study of detrital zircons from the Liaohe Group constraints on the evolution of the Jiao-Liao-Ji Belt, North China craton /." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B36639242.
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Vezinet, Adrien. "Différenciation et stabilisation de la croûte continentale archéenne, l'exemple de la marge Nord du craton du Kaapvaal en Afrique du Sud." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSES054/document.
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Le travail de thèse reporté dans ce manuscrit se focalise sur la reconnaissance ainsi que l'expression des processus de différenciation crustale à l'Archéen. Cet éon représente à lui tout seul 1/3 des temps géologiques, et se caractérise notamment par des lithologies diagnostiques, ainsi que des contextes géodynamiques complexes. La majorité des études sont portées sur l’investigation des phases alumineuses qui permettent de contraindre précisément les événements métamorphiques au-cours d’une géodynamique d’épaississement crustal. Toutefois, ces phases alumineuses représentent rarement plus de 10% des terrains archéens, alors qu’ils sont faits à plus de 75% de gneiss orthodérivés. L'étude qui suit est une caractérisation du complexe de gneiss gris composite de la marge Nord du craton archéen du Kaapvaal en Afrique du Sud. Les résultats produits durant cette investigation ont amené à plusieurs conclusions importantes au regard de la géodynamique archéenne. L'étude isotopique U-Pb/Lu-Hf sur zircon couplée à des analyses pétro-métamorphiques montre que la construction d’un complexe de gneiss gris composite correspond à une géodynamique prolongée dans le temps, accomplie au-travers de processus de différenciations crustales internes à la Zone accrétée, 1.e. le bloc crustal évolue en système thermodynamiquement fermé. Les complexes de gneiss gris ne sont que modérément étudiés toutefois, les informations contenues dans ces lithologies apparaissent complémentaires avec celles obtenues par les études métamorphiques sur les lithologies alumineuses. Il est donc nécessaire d'approfondir ce type d’investigations afin de mieux contraindre les modèles géodynamiques archéensThe PhD work presented in this manuscript focuses on the recognition and the manifestation of Archean crustal differentiation processes. The Archean eon which represents 1/3 of the geological record is featured by both lithologies unrecognized in younger eons and cryptic geodynamics. Most of investigations concentrate on the characterisation of aluminium-rich lithologies that allow an accurate determination of the pressure-temperature evolution underwent by crustal materials during crustal thickening geodynamics. However, aluminium-rich lithologies - mainly represented by metasediments - account for only 10% on average of Archean terranes whereas orthoderived gneisses - which also testify for crustal differentiation processes - form around 75% of these terranes. The following contribution depicts an Archean composite grey gneiss complex located at the northern edge of the Kaapvaal craton is South Africa. Results carried out during this PhD study have major consequences on Archean geodynamics. The zircon U-Pb/Lu-Hf isotope Investigation coupled with strong petro-metamorphic observations show that composite grey gneiss complexes may be built over a protracted time span, achieved through self-refinement of crustal materials, i.e. the crustal block evolved in a thermodynamically closed system. Grey gneiss compiexes are only moderately investigated even though information enclosed in these lithologies is complementary with those from aluminium-rich rocks. Therefore, deeper investigations of these geological objects must be a central scope in order to improve the knowledge of the Archean eon and appears necessary for the building of even more realistic geotectonic models
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Schmidberger, Stefanie. "Hf, Sr, Nd and Pb isotope systematics and major and trace element compositions of the Archean subcratonic lithosphere beneath Somerset Island, Arctic Canada." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37656.
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Hf, Sr, Nd and Pb isotopes, and major, trace and rare earth elements (REE) were determined for a suite of peridotite and pyroxenite xenoliths, constituent garnet and clinopyroxene and the host Nikos kimberlite (100 Ma) from Somerset Island, in order to constrain the chemical and isotopic composition of the lithosphere beneath the northern Canadian craton. The refractory Nikos peridotites are characterized by high olivine forsterite contents (avg. Fo = 92.3) and depletions in incompatible major elements (Fe, Al, Ca), but are enriched in incompatible trace elements, such as large ion lithophile elements (LILE) and light rare earth elements (LREE), while having approximately chondritic heavy rare earth element (HREE) contents. Mass balance calculations using REE contents of clinopyroxene and garnet indicate that calculated LREE abundances for the Nikos xenoliths are significantly lower (e.g. Nd ~50%) than those of the analyzed whole-rocks. These results suggest the presence of small amounts of a kimberlite-related LREE-rich interstitial component (i.e. ~1% kimberlite liquid and/or ~0.01% apatite) to account for the excess LREE abundances, with little effect on the HREE budgets of the xenoliths.The 143Nd/144Nd(0.1Ga) (0.51249--0.51276) isotopic compositions of the Nikos peridotites are little variable and overlap those of the Nikos kimberlite at the time of sample transport. The low-temperature peridotites (<1100°C) that sample the shallow lithosphere are characterized by more radiogenic 176Hf/177Hf(0.1Ga) (0.28296--0.28419) and Pb (206Pb/204Pb (0.1Ga) = 17.82--19.03), but lower 87Sr/ 86Sr(0.1Ga) (0.7047--0.7066) isotopic ratios than those of the high-temperature peridotites (>1100°C; 0.28265--0.28333; 17.18--18.30; 0.7064--0.7085, respectively). Incompatible trace element compositions of the xenoliths confirm this depth stratification indicating that shallow and deep (>160 km) Somerset lithosphere are characterized by distinct chemical and isotopic characteristics.
The Lu-Hf isotope compositions of the low-temperature peridotites plot along a 2.8 Ga reference isochron, which is consistent with an interpretation that the shallow Somerset lithosphere stabilized in the Archean to depth of ~150 km. The deep lithospheric mantle, which is probably younger, does not share the same petrogenetic history and may contain recycled material (altered oceanic crust and sedimentary component?). The Hf isotope compositions for the shallow low-temperature peridotites indicate that part of the lithosphere beneath the Canadian craton is characterized by more radiogenic Hf isotope signatures than estimates for "depleted" mantle.
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Luo, Yan, and 羅彥. "U-Pb age and Hf isotopic study of detrital zircons from the Liaohe Group: constraints on the evolution of theJiao-Liao-Ji Belt, North China craton." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B36639242.
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Bizzarro, Martin. "Major element and isotope geochemistry (Sr, Nd and Hf) of mantle derived peridotites, carbonatites and kimberlites from Canada and Greeland; insights into mantle dynamics." Thèse, Chicoutimi : Montréal : Université du Québec à Chicoutimi ; Université du Québec à Montréal, 2003. http://theses.uqac.ca.
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Thèse (D.Ress.Min.) -- Université du Québec à Chicoutimi, programme extensionné à l'Université du Québec à Montréal, 2002.Bibliogr.: f. 105-109. Document électronique également accessible en format PDF. CaQCU
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Dell'Oro, Trent Arthur. "Sr-Nd-Hf-Pb isotope and trace element geochemistry of the Natkusiak Formation continental flood basalts of the Neoproterozoic Franklin large igneous province, Victoria Island, Canada." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/43518.
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The Neoproterozoic (ca. 723 Ma) Franklin large igneous province (LIP) located on Victoria Island, Arctic Canada, consists of the Natkusiak Formation continental flood basalts and a sill-dominated feeder system exposed in the Minto Inlier. The Franklin LIP is temporally linked with the breakup of Laurentia from Siberia and the Sturtian glaciation or “Snowball Earth”. Recent mapping shows that the Natkusiak Formation, preserved in two lobes (northern and southern), has a thin basal unit, ~50 m thick, followed by two ~500 m thick cycles (1 and 2) of basaltic sheet-flows. Sr-Nd-Pb-Hf isotopic compositions, major element oxides, and trace element concentrations of the Natkusiak basalts allow for the characterization of mantle source components and the extent of crustal contamination. Four geochemical groups (southern low- and high-Ti basalts; northern low- and high-Ti basalts) are defined. The basal basalts (low-Ti, 1.0-1.2 wt.% TiO₂) are distinguished from the overlying cycle 1 and 2 basalts (high-Ti, 1.2-1.8 wt.% TiO₂). The high-Ti basalts are characterized by a narrow range in ⁸⁷Sr/⁸⁶Sri (0.7027-0.7045), high εNdi and εHfi, and relatively low ²⁰⁶Pb/²⁰⁴Pbi, ²⁰⁷Pb/²⁰⁴Pbi, and ²⁰⁸Pb/²⁰⁴Pbi compared to the low-Ti basalts (⁸⁷Sr/⁸⁶Sri = 0.7033-0.7057). The northern (low- and high-Ti) basalts are isotopically distinct from the southern (low- and high-Ti) basalts with lower εNdi values for a given ⁸⁷Sr/⁸⁶Sri. The chemistry of the coeval Franklin intrusions mainly overlaps that of the northern basalts and they show only limited isotopic correlation with the southern basalts, which indicates that the southern basalts were fed from a separate feeder system. Significant major and trace element and isotopic differences between the low- and high-Ti basalts are inconsistent with the effects of crustal contamination and are related to different mantle source compositions, with a garnet-bearing source for the low-Ti basalts and a spinel-bearing source for the high-Ti basalts. A shift in mantle source region, likely reflected by an episode of syn-volcanic extension, occurred after the emplacement of the low-Ti basalts, which represent the earliest volcanic products of the Franklin LIP.
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Linde, G. M., J. H. Trexler, P. H. Cashman, G. Gehrels, and W. R. Dickinson. "Three-Dimensional Evolution of the Early Paleozoic Western Laurentian Margin: New Insights From Detrital Zircon U-Pb Geochronology and Hf Isotope Geochemistry of the Harmony Formation of Nevada." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/626478.
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Uranium-lead (U-Pb) geochronology and Hafnium (Hf) isotope geochemistry of detrital zircons of the Harmony Formation of north central Nevada provide new insights into the tectonic evolution of the Late Paleozoic western Laurentian margin. Using laser-ablation inductively coupled plasma mass spectrometry, 10 arenite samples were analyzed for U-Pb ages, and 8 of these samples were further analyzed for Hf isotope ratios. Three of the sampled units have similar U-Pb age peaks and Hf isotope ratios, including a 1.0-1.4Ga peak with epsilon Hf values of +12 to -3 and a 2.5-2.7Ga peak with epsilon Hf values of +7 to -5. The remaining seven samples differ significantly from these three, but are similar to one another; having age peaks of 1.7-1.9Ga with epsilon Hf of +10 to -20 and age peaks of 2.3-2.7Ga with epsilon Hf of +6 to -8. The data confirm the subdivision of the Harmony Formation into two petrofacies: quartzose (Harmony A) and feldspathic (Harmony B). The three samples with 1.0-1.4 and 2.5-2.7Ga peaks are the Harmony A, which originated in the central Laurentian craton. The other seven samples are the Harmony B, which originated in eastern Alberta-western Saskatchewan, north of the Harmony A source. We propose that all Harmony Formation strata were deposited near eastern Alberta and subsequently tectonically interleaved with Roberts Mountains allochthon strata. We interpret that the entire package was tectonically transported south along the western Laurentian margin and then emplaced eastward onto the craton during the Late Devonian-Early Mississippian Antler orogeny.
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Santos, Gustavo Macedo de Paula. "Quimioestratigrafia isotópica (C, O, Sr, Li, Mg) e proveniência sedimentar (U-Pb, Hf, Sm-Nd) do grupo Bambuí no sul da bacia do São Francisco." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/44/44141/tde-26042018-092122/.
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Neste trabalho são apresentados novos dados isotópicos de C, O, Sr, Mg e Li e elementares de Elementos Terras Raras (ETR) para as rochas carbonáticas do Grupo Bambuí, no sul da Bacia do São Francisco. Também são apresentadas idades U-Pb e isótopos de Hf em zircão detrítico e dados isotópicos de Sm-Nd em amostras de rocha total de rochas siliciclásticas no mesmo setor da bacia. Os dados quimioestratigráficos permitem dividir as três formações basais do Grupo Bambuí em três intervalos quimioestratigráficos (chemostratigraphic intervals - CI), cada qual registrando um estágio evolutivo da bacia. O CI-1 corresponde à capa carbonática da Formação Sete Lagoas que apresenta excursão isotópica negativa de C, valores de \'delta\'¹³C negativos e razões 87Sr/86Sr crescentes de 0,7074 a 0,7082. Este intervalo marca o início da transgressão marinha que inundou o Cráton do São Francisco onde a bacia estava sujeita a controles locais na química marinha, gerando carbonatos com padrões planares de distribuição normalizada de ETR e com variações acopladas de \'delta\'7Li e \'delta\'26Mg dependentes das fácies sedimentares. O intervalo CI-2 corresponde à porção intermediária da Formação Sete Lagoas na qual foi reportada a ocorrência de Cloudina sp. (550-542 Ma). As rochas carbonáticas deste intervalo apresentam valores de \'delta\'¹³C ao redor de 0%o, \'delta\'7Li ao redor de 16%o, \'delta\'26Mg de aproximadamente -3,5%o e razões 87Sr/86Sr entre 0,7080 e 0,7087, dentro do padrão esperado para o limite Ediacarano-Cambriano. Neste estágio, a transgressão marinha culminou com a conexão da Bacia do São Francisco com outras bacias gondwânicas, permitindo migração de fauna e homogeneização isotópica. Apesar de alguns sinais geoquímicos de caráter global, o cenário intracontinental da bacia a mantinha sujeita a controles locais, observados no enriquecimento de ETR leves em relação aos pesados e por duas excursões negativas nos valores de \'delta\'7Li perfeitamente acopladas a excursões positivas de\'delta\'26Mg. O intervalo CI-3 engloba as formações Sete Lagoas superior, Serra de Santa Helena e Lagoa do Jacaré e seus calcários com valores de \'delta\'¹³C bastante positivos (acima de +3%o) e razões 87Sr/86Sr ao redor de 0,7075, abaixo das esperadas para o limite Ediacarano-Cambriano. O CI-3 marca a restrição da bacia em relação ao reservatório geoquímico e isotópico global, provavelmente pelo soerguimento dos orógenos marginais ao cráton. Tal soerguimento provocou aumento da taxa de denudação e consequente decréscimo da intensidade de intemperismo nas áreas fontes, reduzindo o fluxo dissolvido para a bacia, observado no desacoplamento dos sistemas isotópicos de Mg e Li, e ciclos de decréscimo das razões Sr/Ca e 26Mg removidos pela precipitação carbonática. A diminuição da intensidade de intemperismo e a declividade das áreas fontes tornaram o fluxo dissolvido oriundo de carbonatos mais importantes que os de silicatos, resultando em diminuição das razões 87Sr/86Sr, no aparecimento de distribuições normalizadas de ETR com padrão \"água do mar\", na restrição do suprimento de sulfato na bacia e consequente metanogênese. Os dados geocronológicos mostram que não houve uma reorganização significativa nas áreas de fontes para a bacia desde a deposição das fácies mais finas da Formação Carrancas e Laminito Moema até a deposição da Lagoa do Jacaré. Embora não resolva as principais questões de idade e geotectônicas da bacia, esta constatação é mais um argumento a favor da ausência de uma discordância na base da Formação Sete Lagoas, o que sugere que a glaciação na base da Bacia do São Francisco é provavelmente do Ediacarano Médio / Superior. Se existir esta discordância, a única idade absoluta disponível para a capa carbonática sugere que a glaciação seria Sturtiana (~720 Ma).This work presents new C, O, Sr, Mg and Li isotope data and Rare Earth Element (REE) concentrations for the carbonate rocks of the Bambuí Group, in the southern São Francisco Basin. U-Pb and Hf geochronology in detrital zircon grains and whole rock Sm-Nd ages in siliciclastic rocks in the same area are also presented. The chemostratigraphic data allow subdividing the three lower units of the Bambuí Group in three Chemostratigraphic Intervals (CI), each one recording a different evolution stage of the basin. The CI-1 comprises the Sete Lagoas Formation cap carbonates that display C isotope negative excursion, very negative \'delta\'¹³C values and 87Sr/86Sr ratios increasing upwards from 0.7074 to 0.7082. This intervals marks the start of the marine transgression over the São Francisco Craton in which the basin was subject to local controls over seawater, as shown by the flat type shale normalized REE distributions and coupled facies dependent \'delta\'Li and \'delta\'26Mg values variations. The CI-2 corresponds to the middle portion of the Sete Lagoas Formation where the Cloudina sp. (550-542 Ma) occurrence was described. The carbonate rocks of this interval display \'delta\'¹³C values around 0%o, \'delta\'7Li values around 16%o, \'delta\'26Mg around -3.5%o and 87Sr/86Sr between 0.7080 and 0.7087 that are expected for the Ediacaran-Cambrian limit. During this stage, the marine transgression provided connection of the São Francisco basin to other West Gondwana basins, allowing fauna migration and isotope homogenization. In spite of the global geochemical signals observed, the intracontinental scenario kept the basin subject to local controls, as shown by the enrichment in light REE and two perfectly coupled \'delta\'7Li and \'delta\'26Mg negative excursions. The CI-3 comprises the limestones of the upper Sete Lagoas, Serra de Santa Helena and Lagoa do Jacaré formations and with very positive \'delta\'¹³C values (> +3%o) and 87Sr/86Sr ratios around 0.7075, lower than those expected for the Ediacaran-Cambrian limit. The CI-3 records the restriction of the basin in relation to the global ocean geochemical and isotope reservoir, probably by the uplift of the craton\"s marginal orogens. Such uplift caused higher denudation rates and consequent decrease in the weathering intensity of the source areas, diminishing the dissolved influx to the basin that is observed in the Mg and Li isotope systems decouplement and in cycles of Sr/Ca ratios and 26Mg decrease by carbonate precipitation removal. The weathering intensity decrease caused the dissolved influx from carbonates to be more important than the one from silicates, resulting in the drop down of the 87Sr/86Sr ratios, the appearance of the \"seawater\" REE shale normalized distributions, and sulphate supply restriction driving methanogenesis. The geochronological data show that no significant reorganization of the basin source areas occurred from the deposition of the Carrancas Formation and Moema Laminites finer facies to the Lagoa do Jacaré Formation. Although the data do not solve the age and geotectonic questions, they add another argument against the existence of an unconformity at the base of the Sete Lagoas Formation, suggesting that the glaciation of the São Francisco Basin is likely Middle to Late Ediacaran in age. If there is an unconformity, the only available absolute age suggests it is a Sturtian Glaciation (~720 Ma).
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Böttcher, Ingo [Verfasser]. "Geochemie magmatischer Prozesse in quartären Vulkaniten der Chaîne des Puys, Massif Central, Frankreich : kombinierte Sr-, Nd-, Hf-Isotopie in Lavaströmen und Grundgebirge / vorgelegt von Ingo Böttcher." [Clausthal-Zellerfeld] : [Univ.-Bibliothek], 2008. http://d-nb.info/991252373/34.
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Zeng, Wen. "The evolution of the metamorphic series in the NW Fujian Province, the NE Cathaysia Block, and the significance in the reconstruction of Precambrian Supercontinents." Thesis, Curtin University, 2010. http://hdl.handle.net/20.500.11937/1091.
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This thesis focuses on the Paleoproterozoic to Late Paleozoic basement evolution of the metamorphic rocks scattered in the NW Fujian Province, the NE Cathaysia Block the southeastern area of South China. Field observation, systematic sampling and petrographic investigation combined with of whole rock geochemistry, zircon U-Pb, Lu-Hf isotopes, trace elements, amphibole and biotite 40Ar/39Ar analyses and mineral chemistry study were applied in this project to determine the nature, ages and relations of the leucosomes, felsic paragneiss and mafic metamorphic rocks in study area and their implications to the reconstruction of the Precambrian Rodina Supercontinent.Following conclusions are made: 1. Based on this study, according to their metamorphism and deformation characteristics, the metamorphic rock series in the study area can be divided into two types, moderately to strongly metamorphosed rock series that experienced ductile deformation and moderately metamorphosed rock series that have experienced ductile deformations. New La-ICPMS U-Pb zircon ages presented here and in previous study suggest that the original lithostratigraphy should be abandoned and the terminology “Complex” should be used instead of “Group” and “Formation” for the high grade metamorphic rock series in northwestern Fujian, where the protoliths were strongly reworked by Early Paleozoic tectono-thermal events.2. Obvious zircon U-Pb age peaks of ~1800 Ma suggest that the protoliths ofthe Cathaysia Block be comparable to the basements of North America ratherthan those of Eastern India and East Antarctica. Although the peaks of ~1800Ma are also present in Western Australia, their 176Hf/177Hf ratios (0.280706 -0.281510) are apparently lower than those of zircons from SW Cathaysia (0.281515 - 0.282098) and from this study (0.281232 - 0.282213, NECathaysia). Besides, detrital zircons in Cathaysia and NW Yangtze indicatesignificant juvenile input during Paleo- to Mesoproterozoic according to thezircon Hf isotopes, which are distinctly different from Western Australia.These evidences suggest that the basement of the Cathaysia share similaritieswith that of North America, lending support for the Rodinia configurationproposed by Li et al. (2008), in which Cathaysia was next to western Laurentia before and during the late Mesoproterozoic assembly of Rodinia.2. Obvious zircon U-Pb age peaks of ~1800 Ma suggest that the protoliths of the Cathaysia Block be comparable to the basements of North America rather than those of Eastern India and East Antarctica. Although the peaks of ~1800 Ma are also present in Western Australia, their 176Hf/177Hf ratios (0.280706 - 0.281510) are apparently lower than those of zircons from SW Cathaysia (0.281515 - 0.282098) and from this study (0.281232 - 0.282213, NE Cathaysia). Besides, detrital zircons in Cathaysia and NW Yangtze indicate significant juvenile input during Paleo- to Mesoproterozoic according to the zircon Hf isotopes, which are distinctly different from Western Australia. These evidences suggest that the basement of the Cathaysia share similarities with that of North America, lending support for the Rodinia configuration proposed by Li et al. (2008), in which Cathaysia was next to western Laurentia before and during the late Mesoproterozoic assembly of Rodinia.3. The protoliths of the felsic paragneiss in the NW Fujian area are immaturesediments, consisting of greywacke, arkose and lithic arenite compositions.The significant input of the paragneiss protolith was dominantly formed byseveral magmatic events during Neoproterozoic (820 ± 6 Ma, 780 ± 6 Ma, 776± 6 Ma, 758 ± 3 Ma, 740 ± 8 Ma and 722 ± 9 Ma), probably deposited notearly than middle Neoproterozoic (~680 Ma). Many metamorphic rockscontain 0.99 - 0.72 Ga detrital magmatic zircons, which are interpreted asreflecting the tectono-thermal events related to the assembly and break-up of the Rodinia supercontinent during the Neoproterozoic.4. In this study, new La-ICPMS U-Pb anatectic zircon data from the NWFujian area suggest that the strong and widespread tectono-thermal eventswere related to the orogeny probably having started during the MiddleCambrian and lasted until the Middle Devonian, consisting of at least threemain episodes (~473 Ma, ~445 Ma, ~423 Ma), with major orogeny events(including syn- to post-orogenic melting) constrained between ~473 Ma and~407 Ma in the NE Cathaysia, and between ~468 Ma and ~415 Ma in the SWCathaysia. The age peaks in the Cathaysia Block (ca. 488, 471, 455, 440 and415 Ma) are within the age range of the Qinling-Tongbai-Dabie orogen during 512 - 406 Ma. This suggests a possible linkage or interaction of the two orogens.5. The duration of the “Caledonian” orogeny in the NW Fujian area was noshorter than ~50 Myr, starting at ~473 Ma (~Early Ordovician) or earlier, andterminating at ~423 Ma (~Middle Silurian) or later. The “Caledonian”orogenic event in the Cathaysia Block was likely due to an intracontinentalcollision rather than the subduction of oceanic crust or arc-continentalcollision. Considering the inhomogeneous cooling paths for the Tianjingping,the Jiaoxi and Mayuan complexes, and different time restraint of thewidespread anatectic and magmatic events occurred in different places, the“Caledonian” tectono-thermal events in the Cathaysia Block might vary between different segments of the orogen.
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Holbik, Sven P. "Arc Crust-Magma Interaction in the Andean Southern Volcanic Zone from Thermobarometry, Mineral Composition, Radiogenic Isotope and Rare Earth Element Systematics of the Azufre-Planchon-Peteroa Volcanic Complex, Chile." FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1524.
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The Andean Southern Volcanic Zone (SVZ) is a vast and complex continental arc that has been studied extensively to provide an understanding of arc-magma genesis, the origin and chemical evolution of the continental crust, and geochemical compositions of volcanic products. The present study focuses on distinguishing the magma/sub-arc crustal interaction of eruptive products from the Azufre-Planchon-Peteroa (APP 35°15’S) volcanic center and other major centers in the Central SVZ (CSVZ 37°S - 42°S), Transitional SVZ (TSVZ 34.3-37.0°S), and Northern SVZ (NSVZ 33°S - 34°30’S). New Hf and Nd isotopic and trace element data for SVZ centers are consistent with former studies that these magmas experienced variable depths of crystal fractionation, and that crustal assimilation is restricted to the lower crustal depths with an apparent role of garnet. Thermobarometric calculations applied to magma compositions constrain the depth of magma separation from mantle sources in all segments of the SVZ to(70-90 km). Magmatic separation at the APP complex occurs at an average depth of ~50 km which is confined to the mantle lithosphere and the base of the crust suggesting localized thermal abrasion both reservoirs. Thermobarometric calculations indicate that CSVZ primary magmas arise from a similar average depth of (~54 km) which confines magma separation to the asthenospheric mantle. The northwards along-arc Sr-Nd-Hf isotopic data and LREE enrichment accompanied with HREE depletion of SVZ mafic magmas correlates well with northward increasing crustal thickness and decreasing primary melt separation from mantle source regions indicating an increased involvement of lower crustal components in SVZ magma petrogenesis.
The study concludes that the development of mature subduction zones over millions of years of continuous magmatism requires that mafic arc derived melts stagnate at lower crustal levels due to density similarities and emplace at lower crustal depths. Basaltic underplating creates localized hot zone environments below major magmatic centers. These regions of high temperature/partial melting, and equilibration with underplated mafic rocks provides the mechanism that controls trace element and isotopic variability of primary magmas of the TSVZ and NSVZ from their baseline CSVZ-like precursors.
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Viehmann, Sebastian [Verfasser], Michael [Akademischer Betreuer] [Gutachter] Bau, Andrea [Gutachter] Koschinsky-Fritsche, Carsten [Gutachter] Münker, and J. Elis [Gutachter] Hoffmann. "The evolution of Precambrian environments and their impact on the trace element and Hf-Nd isotopic compositions of ancient seawater / Sebastian Viehmann ; Gutachter: Michael Bau, Andrea Koschinsky-Fritsche, Carsten Münker, J. Elis Hoffmann ; Betreuer: Michael Bau." Bremen : IRC-Library, Information Resource Center der Jacobs University Bremen, 2016. http://d-nb.info/1137054441/34.
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Romanova, Irina. "Volcanology and geochemistry of the Cretaceous volcaniclastic deposits and basalts from Ori Massif, Shatsky Rise Oceanic Plateau." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/108162/1/Irina_Romanova_Thesis.pdf.
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This study enhanced our understanding of the origin and evolution of Ori Massif, Shatsky Rise Oceanic Plateau. Key findings are: 1. Volcaniclastic deposits were formed by Surtseyan style phreatomagmatic activity, suggesting that the summit of Ori Massif was shallow-marine to near sea-level; 2. Basaltic fragments from the volcaniclastic deposits provide further evidence for geochemical variation of magmas from Ori Massif and indicate a significant involvement of depleted mantle in its source; 3. Element mobility during seawater alteration of basalts from Ori and Tamu Massifs depends on stratigraphy, cooling rates and magma chemistry.
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Majumder, Santanu. "Pollution assessment of arsenic in groundwater: geochemistry and analytical aspects." Doctoral thesis, Universitat de Girona, 2013. http://hdl.handle.net/10803/125308.
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Apart from the geological controls that can cause As mobilization in groundwater in the Bengal Delta Plain, local anthropogenic factors may also contribute to some extent. Investigations showed that As(III) get enriched in the groundwater after the monsoonal season. This could be due to the enhanced reducing conditions in the aquifer post-monsoonal recharge. The larger inorganic colloids were responsible to scavenge As(III) and the smaller organic/organo-metallic colloids were found to scavenge As(V). A study was carried out to improve the Solar Oxidation and Removal of Arsenic (SORAS) for rural population, using tomatoes instead of lemons, showing that tomato was more efficient and cost-effective than lemon or lime. A novel technique combining hollow fiber liquid phase microextraction (HF-LPME) with Total Reflection X-Ray Fluorescence (TXRF) for the determination and speciation of As in groundwater was developed. The results in the laboratory samples were found encouraging and applied to natural samples successfullyAdemás de los controles geológicos, los factores antropogénicos contribuyen también a la movilización de arsénico en el agua subterránea del Bengal Delta Plain. La concentración de As(III) aumenta después de la temporada del monzón, debido a las condiciones más reductoras en el acuífero. El As(III) se encuentra asociado a coloides inorgánicos de mayor tamaño mientras que los coloides orgánicos/organometálicos más pequeños contienen As(V). Se llevó a cabo un estudio para mejorar el proceso SORAS (Solar Oxidation and Removal of Arsenic) comparando diferentes fuentes de citrato, y demostrando que el tomate es más eficiente y económico que el limón o la lima. Se ha desarrollado un método novedoso para la determinación y especiación de As basado en microextracción en fase líquida en fibra hueca (HF-LPME) combinados con fluorescencia de rayos X con reflexión total (TXRF), y que ha sido aplicado con éxito en diferentes muestras de aguas naturales
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Yeshanew, Fitsum Girum. "Crustal evolution of the Arabian–Nubian Shield : Insights from zircon geochronology and Nd–Hf–O isotopes." Doctoral thesis, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-145479.
Full textAbstract:
The Arabian–Nubian Shield (ANS) represents a major site of juvenile Neoproterozoic crustal addition on Earth and documents Neoproterozoic tectonics bracketed by two supercontinent cycles, namely the fragmentation of Rodinia and the amalgamation of Gondwana. There is general consensus that the ANS formed by juvenile magmatic arc accretion and subsequent shield–wide post–tectonic magmatism. However, detailed understanding about the timing of events and the nature of magma sources in parts of the shield are lacking. To date, there are no isotopic data from the Paleozoic sedimentary sequences of the ANS, except those from the northern part. New zircon U–Pb, δ18O and whole–rock Nd isotopes are presented for plutonic rocks from the eastern Ethiopia, Yemen and southernmost Arabian Shield in Saudi Arabia. This thesis also presents the first combined in situ zircon U–Pb–O–Hf isotope data on the Cambrian–Ordovician sandstones of the Arabian Shield. The results are used to elucidate the crustal evolution of these parts of the ANS and to evaluate terrane correlations. Specifically, the nature of crustal growth, i.e., relative proportions of juvenile magmatic additions vs. crustal reworking, nature of the magma source and mechanism of crust formation (plume material vs. subduction zone enrichment) and understanding the provenance of the Cambrian–Ordovician sandstone sequences were important research questions addressed. The results from Paper I suggest that the eastern Ethiopian Precambrian basement is dominated by reworking of pre-Neoproterozoic supracrustal material unlike contemporaneous rocks in the remaining parts of Ethiopia— indicating the presence of two distinct lithospheric blocks of contrasting isotopic compositions in Ethiopia. Metamorphic age distributions suggest that the eastern Ethiopian block was amalgamated with the juvenile Western Ethiopian Shield during ca. 580–550 Ma. Importantly, the suture between them may represent the northern continuation of a major suture identified further south in Africa along which Gondwana amalgamated. Similarly, the Abas terrane in Yemen (Paper II) is dominated by reworking of pre–Neoproterozoic crust and shows age and isotopic compositions that are inconsistent with the Afif terrane of Saudi Arabia, precluding correlation between the two regions. The trace element systematics of plutonic rocks from the southernmost Arabian Shield (paper III) point to enrichment due to subduction component, bear no evidence of a plume component, and are consistent with the adakite-like chemistry of some of the subduction–related plutonic samples. This reinforces the notion that the shield grew through juvenile magmatic arc additions. The combined zircon U–Pb–O–Hf data of the Cambrian–Ordovician sandstones (Paper IV) indicate their derivation from both the adjacent juvenile ANS and the more southerly crustal blocks that are dominated by reworking of pre–Neoproterozoic crust. The remarkable similarity in age spectra and homogeneity of Cambrian sandstones deposited across the northern margin of Gondwana point to continental–scale sediment mixing and dispersal regulated by the supercontinent cycle.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.
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Brand, Natalie Bronwyn. "Isotopic fingerprinting (Sr-Nd-Hf-Os-C-O) of mantle source regions to kimberlite magmatism beneath the eastern Superior Craton, Canada." Thesis, 2016. http://hdl.handle.net/10539/21010.
Full textAbstract:
A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2016.The northern sector of the Archaean Superior Craton has been a significant region for diamond exploration, hosting numerous alkaline intrusions of Proterozoic age. The focus of this study is on two kimberlite fields that are situated in eastern Canada, 400 km apart. These are the diamond-rich Renard pipes and dykes, and the Wemindji field, consisting of barren sheeted dykes. The nine diamondiferous Renard igneous bodies were emplaced between 655-630 Ma in the eastern sector of Laurentia into Archaean metamorphic rocks. Thin, subhorizontal Wemindji kimberlite sills were emplaced into granitic gneiss terrane of the Superior Province near Wemindji, Quebec, at 629 ± 29 Ma, along the inferred extension of the Kapuskasing Structural Zone. These kimberlite fields are grouped with the extensive Late Neoproterozoic magmatism of ultramafic and volatile-rich character, which is said to be associated with the breakup of Rodinia. Despite overall compositional similarity of the studied magmatic kimberlites, the material from Renard has higher concentrations of SiO2, Al2O3, MgO, and K2O, which reflects higher phlogopite abundances. The Wemindji sills show higher CaO concentrations due to high primary carbonate contents. Renard and Wemindji kimberlite incompatible trace element distributions are similar, with differences in Cs, Rb, and Sr corresponding to variable modal mineralogy. The initial 87Sr/86Sr ratios for the Renard kimberlites range between 0.70241 and 0.70765, while the Wemindji kimberlites have values between 0.70361 and 0.70442. Initial εNd values for the Renard kimberlites lie between +1.2 and +4.6, whereas the Wemindji kimberlite sills range between +0.2 and +4.8. Initial εHf values for the Renard kimberlites lie between +1.7 and +6.3, whereas the Wemindji kimberlite sills yielded values between +1.1 and +6.5. The overlapping Sr-Nd-Hf isotope compositions of these kimberlite suites indicate melt derivation from moderately depleted mantle sources. Osmium isotope compositions fall at the unradiogenic end for global kimberlites, with initial 187Os/188Os ratios ranging between 0.11539 and 0.12620 for Renard kimberlites, and between 0.11078 and 0.11729 for Wemindji kimberlites, with Os concentrations all below 1.3 ppb. These Os values suggest that an additional input from the CLM (i.e., ancient refractory cratonic peridotite), which is not reflected in the Hf and Nd radiogenic isotopes, is ii required. Both kimberlite suites depict mantle δ13C values (ca. -6 to –4 ‰), with evidence of hydrothermal alteration in the δ18O values (between 10 and 20 ‰ relative to SMOW). Production of an isotopically depleted melt occurred during the breakaway of Laurentia from Rodinia. Wemindji sits on the inferred extension of the Kapuskasing Structural Zone, which is suggested to have been a short-lived reactivated translithospheric rift-like feature, promoting CO2-rich melting conditions during the Late Neoproterozoic. The data from this study suggest that this ascending sublithospheric depleted melt component (more CO2-rich beneath Wemindji) interacted with a maximum input volume of 5% of the MARID-enriched CLM beneath the eastern Superior craton, and between 2% and 30% of ancient refractory cratonic peridotite. The lack of significant diamond in the Wemindji kimberlite dykes could be due to the resorption of the potential diamond in the CO2-rich kimberlite melt.
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Jeon, Heejin. "U-Pb, Lu-Hf and O isotopes in zircon from late palaeozoic granites across orogens, Southeastern Australia." Phd thesis, 2012. http://hdl.handle.net/1885/149621.
Full textAbstract:
Southeastern Australia, part of the Phanerozoic Tasmanides, is a unique region where large amounts of granite (~30% of the surface rocks) with a very wide range of compositions (S-, I- and A-types) were intruded in the Ordovician to Triassic.
The distinctive Carboniferous granites in the Lachlan Fold Belt (LFB) are transitional in time and space between the major magmatic episodes of the LFB and New England Orogen (NEO). There was a contemporaneous continental-arc developed in the NEO, products of which became the dominant source for the NEO Early Permian S-type granites. The Carboniferous granites in the LFB have characteristic compositions (K, Sr and LILE-enrichment and Y-depletion) similar to the Late Permian I-type granites (and to the S-type granites in part) in the NEO. The in situ microanalyses of zircon (both melt-precipitated and inherited; over 1280 grains analysed from 31 samples) from those granites, using SIMS and LA-MC-ICPMS, show that the Carboniferous magmatism in the LFB was closely related to the tectonic movement of the NEO, and that the granites with similar compositions which transect the two contrasting orogens had similar source compositions.
From the isotopic compositions of zircon from the Carboniferous granites in the LFB, it is evident that the granites are distributed in zones of different ages and Hf and O isotopic compositions. The zones are approximately parallel to the NEO boundary. It is likely that tectonic activity related to the NEO triggered the production of the Carboniferous magmas and their source rocks. The new data demonstrate, however, that the Carboniferous granites were not directly related to the contemporaneous arc volcanism in the NEO. The source rocks of the Carboniferous granites in each zone consisted of different mixtures between a mantle-like underplate and relatively mature pre-existing lower crust during the Devonian.
The distinctive O isotopic compositions of inherited zircon from the NEO S-type granites demonstrate that the source rock of the granites was a Carboniferous arc-related volcanogenic sedimentary pile which included increased amounts of Devonian volcanogenic sediments with time. The age difference between the inherited and melt-precipitated zircon indicates rapid crustal recycling to produce the peraluminous magmas within 15 Ma of source rock deposition. The I-type Moonbi Supersuite granites were generated from the underplate with a minor crustal contribution. As all the studied NEO granites have remarkably similar initial Hf isotopic compositions, the components comprising most of the NEO, including sediments, are similarly radiogenic, probably due to the geologic processes operating in the young accretionary orogen.
Combining all the results of U-Pb dating and Hf and O isotopic analyses of zircon from the Carboniferous granites in the LFB and the Permian I- and S-type granites in the NEO, it is also inferred that the source rocks of the studied granites had similar isotopic compositions. This suggests a potential petrogenetic link between the granites across the two orogens. From a source composition similar to that of the most primitive LCG, three igneous components have evolved in different ways depending on the nature of the crustal materials incorporated into each component.
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Howard, K. E. "Provenance of Palaeoproterozoic metasedimentary rocks in the eastern Gawler Craton, Southern Australia: Implications for reconstruction models of Proterozoic Australia." Thesis, 2006. http://hdl.handle.net/2440/123593.
Full textAbstract:
This item is only available electronically.Detrital zircon ages obtained from the Corny Point Paragneiss and the Massena Bay Gneiss in the southeastern Gawler Craton, Australia, constrain their deposition to the interval ca. <1880 Ma. The presence of 2020 Ma, 2450 Ma and 2520 Ma detrital zircons within the Corny Point Paragneiss constrains the source region for the sedimentary protoliths to three possible domains within Australia; the Gawler Craton, the Glenburgh Orogen in the Western Australian Proterozoic, and the North Australian Craton, all of which contain rock systems with similar ages. Whole rock εNd (1850Ma) values from the Corny Point Paragneiss range from -1 to -5. These values potentially preclude the Late Archaean to mid Proterozoic crust of the Gawler Craton as a sole or major source region due to its highly evolved average εNd (1850Ma) of around -10. Preclusion of the Gawler Craton as a source is apparently confirmed by Hf isotopic compositions of 2020 Ma detrital zircons from the Corny Point Paragneiss, which have εHf (2020Ma) ranging between +3 to +7. This compares with εHf (2020Ma) of -1 to -4 for zircons from the 2020 Ma Miltalie Gneiss in the Gawler Craton. Available Nd isotopic data suggests that the Glenburgh Orogen is too crustally evolved to have provided the majority of sediment into the Corny Point Paragneiss protolith. The 2020 Ma detrital Hf isotopic compositions of the Corny Point Paragneiss are similar to the 2020 Ma Wildman Siltstone (εHf (2020Ma) +2 to +7) in the Pine Creek Orogen in the North Australian Craton. Two possible scenarios can be extrapolated from the detrital zircon and Nd isotopic data; (1) the Corny Point Paragneiss sediment was derived from a source region within the North Australian Craton and could share source regions with the Wildman Siltstone, or (2) the sediments were derived from a Gawler Craton source region that included a dominant juvenile component of the 2020 Ma Miltalie Gneiss in the adjacent Gawler Craton which has since been eroded. In the first scenario, the absence of connection to the Gawler Craton allows for the Betts and Giles (2006) plate reconstruction model, which proposes that the Corny Point Paragneiss formed part of the North Australia Craton, and was sutured to the Proto Gawler Craton at 1730-1700 Ma. The second scenario highlights a significant limitation in evaluating the significance of provenance data, particularly when considering old potential source terrains that have undergone significant levels of denudation. The proximity of the Corny Point Paragneiss to the rifted southern and eastern margins of the Australian Proterozoic means a thorough evaluation of the palaeogeographic significance of the Corny Point Paragneiss detrital signature requires corresponding datasets from regions such as Antarctica which were formerly contiguous with the Gawler Craton.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2006