Journal articles on the topic 'Transitional to OIB-type compositions'
To see the other types of publications on this topic, follow the link: Transitional to OIB-type compositions.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Transitional to OIB-type compositions.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Halama, Ralf, Jean-Louis Joron, Benoît Villemant, Gregor Markl, and Michel Treuil. "Trace element constraints on mantle sources during mid-Proterozoic magmatism: evidence for a link between the Gardar (South Greenland) and Abitibi (Canadian Shield) mafic rocks." Canadian Journal of Earth Sciences 44, no. 4 (April 1, 2007): 459–78. http://dx.doi.org/10.1139/e06-108.
Full textAbstract:
Trace and major element compositions of mid-Proterozoic (1.20–1.16 Ga) basaltic lava flows and dikes from the Gardar Province (South Greenland) provide evidence for two geochemically distinct magma sources. Based on distinct features of incompatible trace element ratios, such as Th/Ta, Th/Tb, or Th/Hf, they differ by the composition of their mantle source and by their partial melting trends. One mantle source is compositionally transitional between mid-ocean ridge basalt (MORB)-type and ocean-island basalt (OIB)-type sources with relatively low Ta/Hf ratios (~0.2), moderate enrichment in light rare-earth elements (LREE), and slightly positive initial εNd values (+2). It can be attributed to either a lithospheric mantle source or a depleted astenospheric mantle plume component that has been enriched shortly prior to eruption. The other mantle source is characterized by high Ta/Hf ratios (~0.6), a more pronounced LREE enrichment, and initial εNd values around 0. Elevated CeN/YbN (7.0–9.8) and TbN/YbN ratios (1.6–1.8) of the rocks derived from this source indicate the presence of garnet during melting, suggesting melt generation at depths > 70 km. This mantle source has the geochemical characteristics of an OIB-type source and is interpreted as originating from a mantle plume. Samples from the slightly younger (1.14 Ga) Abitibi dike swarm (Superior Province, Canada), spatially connected to the Gardar Province, show very similar trace element characteristics and the same two distinct magma sources can be identified. The geochemical similarities between the magma sources in South Greenland and Canada support the idea of a genetic link between the two magmatic provinces. This link strengthens the idea that the system was a long-lived major intracontinental rift zone.
2
R. Halama, T. Wenzel, B. G. J. Upton, W. Siebel, and G. Markl. "A geochemical and Sr-Nd-O isotopic study of the Proterozoic Eriksfjord Basalts, Gardar Province, South Greenland: Reconstruction of an OIB signature in crustally contaminated rift-related basalts." Mineralogical Magazine 67, no. 5 (October 2003): 831–53. http://dx.doi.org/10.1180/0026461036750147.
Full textAbstract:
AbstractBasalts from the volcano-sedimentary Eriksfjord Formation (Gardar Province, South Greenland) were erupted at around 1.2 Ga into rift-related graben structures. The basalts have compositions transitional between tholeiite and alkaline basalt with MgO contents <7 wt.% and they display LREE-enrichment relative to a chondritic source. Most of the trace element and REE characteristics are similar to those of basalts derived from OIB-like mantle sources. Initial 87Sr/86Sr ratios of clinopyroxene separates range from 0.70278 to 0.70383 and initial ϵNd values vary from –3.2 to +2.1. The most unradiogenic samples overlap with the field defined by carbonatites of similar age and can be explained by mixing of isotopically depleted and enriched mantle components. Using AFC modelling equations, the Sr-Nd isotope data of the more radiogenic basalts can successfully be modelled by addition of <5% lower crustal granulite-facies gneisses as contaminants. δ18Ov-smow values of separated clinopyroxene range from +5.2 to +6.0% and fall within the range of typical mantle-derived rocks. However, up to 10% mixing with an average lower crustal component are permitted by the data.
3
ALDANMAZ, E., M. K. YALINIZ, A. GÜCTEKIN, and M. C. GÖNCÜOĞLU. "Geochemical characteristics of mafic lavas from the Neotethyan ophiolites in western Turkey: implications for heterogeneous source contribution during variable stages of ocean crust generation." Geological Magazine 145, no. 1 (November 30, 2007): 37–54. http://dx.doi.org/10.1017/s0016756807003986.
Full textAbstract:
AbstractThe Late Triassic to Late Cretaceous age mafic lavas from the Neotethyan suture zone ophiolites in western Turkey exhibit a wide diversity of geochemical signatures, indicating derivation from extremely heterogeneous mantle sources. The rocks as a whole can be divided into three broad subdivisions based on their bulk-rock geochemical characteristics: (1) mid-ocean ridge basalts (MORB) that range in composition from light rare earth element (LREE)-depleted varieties (N-MORB; (La/Sm)N<1) through transitional MORB to LREE enriched types (E-MORB; (La/Sm)N>1); (2) the ocean island basalt (OIB)-type alkaline volcanic rocks with significant enrichment in LILE, HFSE and L-MREE, and a slight depletion in HREE, relative to normal mid-ocean ridge basalts (N-MORB); and (3) the supra-subduction zone (SSZ)-type tholeiites originated from arc mantle sources that are characterized by selective enrichments in fluid-soluble large ion lithophile elements (LILE) and LREE relative to the high field strength elements (HFSE). The formation of MORB tholeiites with variable enrichments and depletions in incompatible trace elements is probably related to the processes of crust generation along an oceanic spreading system, and the observed MORB–OIB associations can be modelled by heterogeneous source contribution and mixing of melts from chemically discrete sources from sub-lithospheric reservoirs. Evaluation of trace element systematics shows that the inferred heterogeneities within the mantle source regions are likely to have originated from continuous processes of formation and destruction of enriched mantle domains by long-term plate recycling, convective mixing and melt extraction. The origin of SSZ-type tholeiites with back-arc basin affinities, on the other hand, can be attributed to the later intra-oceanic subduction and plate convergence which led to the generation of supra-subduction-type oceanic crust as a consequence of imparting a certain extent of subduction component into the mantle melting region. Mixing of melts from a multiply depleted mantle source, which subsequently received variable re-enrichment with a subduction component, is suggested to explain the generation of supra-subduction-type oceanic crust. The geodynamic setting in which much of the SSZ-type ophiolitic extrusive rocks from western Turkey were generated can be described as an arc-basin system that is characterized by an oceanic lithosphere generation most probably associated with melting of mantle material along a supra-subduction-type spreading centre.
4
Khudoley, Andrey K., Andrei V. Prokopiev, Kevin R. Chamberlain, Aleksandr D. Savelev, Richard E. Ernst, Sergey V. Malyshev, Artem N. Moskalenko, and Olga Yu Lebedeva. "Late Ordovician Mafic Magmatic Event, Southeast Siberia: Tectonic Implications, LIP Interpretation, and Potential Link with a Mass Extinction." Minerals 10, no. 12 (December 10, 2020): 1108. http://dx.doi.org/10.3390/min10121108.
Full textAbstract:
A geochronological, isotopic, and geochemical study of the Suordakh event of mafic magmatic intrusions on the southeast Siberian margin was undertaken. U-Pb baddeleyite dating of a mafic sill intruding lower Cambrian rocks, yielded a 458 ± 13 Ma emplacement age. The chemical composition and stratigraphic setting of this dated sill differed from that previously attributed to the Suordakh event, implying that additional intrusions, previously mapped as Devonian, potentially belonged to the Suordakh event. No correlation between L.O.I. and concentration of highly mobile major and trace elements was documented, showing small or no influence of hydrothermal alteration on the chemical composition of the intrusions. A new tectonic reconstruction located an island arc and active margin relatively close to the study area. However, all samples had chemical compositions close to that of OIB and did not display Ta-Nb and Ti-negative anomalies, nor other features typical for subduction-related magmatism. The major and trace element distribution was most characteristic of within-plate basalts with the mantle source composition being transitional from spinel to garnet lherzolite. Combining four U-Pb baddeleyite dates of mafic sills and dykes from southeast Siberia, the age of the Suordakh event was estimated at 454 ± 10 Ma. The area of the Suordakh event was at least 35,000–40,000 km2 (an estimate including sills previously interpreted as Devonian), and could be increased with additional dating in Southeastern Siberia. Similar ages for within-plate intrusions were reported from South Korea, West Mongolia, South Argentina, North Iran and Northwest Canada, and these ca. 450 Ma ages were collectively close in timing with the latest Ordovician (Hirnantian) mass extinction. More high-precision dating is necessary to fully test a link between the Suordakh event (and the other age-correlative events) and the end-Ordovician mass extinction.
5
Chandra, Rakesh, Rajeev Upadhyay, and Anshu K. Sinha. "Subduction and collision related magmatism in the Shyok Suture and eastern Karakoram." Journal of Palaeosciences 48, no. (1-3) (December 31, 1999): 183–209. http://dx.doi.org/10.54991/jop.1999.1303.
Full textAbstract:
The Shyok Suture is represented by distinct sets of volcano-plutonic rock assemblages. The high-Mg tholeiitic basalt and calc-alkaline andesites of the Shyok Volcanics have a subduction zone chemical signature. The REE data on tholeiitic basalt suggest a chemical affinity between primitive N-MORB to E-MORB. The calc-alkaline andesites, however, resembles to transitional nature of basalt between E-MORB to OIB. The geochemical data and regional tectonic setting suggest a close similarity between the Shyok Volcanics of northern Ladakh and the Chalt Volcanics of Kohistan.
The mildly deformed trondhjemite-tonalite-granodiorite of the Tirit Granitoids are composite plutons located south of the Shyok Suture melange. These granitoids are subalkaline, I-type and represented by volcanic arc chemical signatures. The regional tectonic setting, the nature of occurrence and the composition of Tirit Granitoids are similar to the plutonic suites of northern Kohistan (Gindai, Matum Das and Nomal plutons).
The eastern Karakoram Batholith is dominated by quartz monzonite-tonalite-granodiorite and granite. The subalkaline to calc-alkaline Karakoram Batholith is constituted by both I-and S-type granitoids with volcanic arc and syn-collision chemical signatures. REE data suggest that the I-type granitoids of eastern Karakoram are calc-alkaline magmatism of a subduction zone environment. In contrast, most of the S-type granitoids are crust-derived peraluminous granitoids. New Rb/Sr isotopic whole rock age data indicates that an S-type intrusive phase was active in the eastern Karakoram region during 83±9 Ma. The syn-collision nature of these granitoids are similar to those of north Sost pluton and Karambar pluton of northern Kohistan.
This indicates that the collision between Kohistan-Ladakh arc and Karakoram block was active during 83±9 Ma.
6
Wang, Qing, Zhao Yang Ding, Jing Da, Kun Ran, and Zhi Tong Sui. "Factors Influencing Bonding Strength of Geopolymer-Aggregate Interfacial Transition Zone." Advanced Materials Research 224 (April 2011): 1–7. http://dx.doi.org/10.4028/www.scientific.net/amr.224.1.
Full textAbstract:
Fundamental studies on geopolymer are increased rapidly because of its potential commercial applications. However, little work has been done on the relationship of the interfacial transitional zone between geopolymer and aggregate and its influence on the final chemical and physical properties of geopolymeric products derived from waste materials. In this paper, factors that influencing the interfacial transition zone of geopolymer concrete such as the type of the aggregate and the oxide compositions of raw materials was studied. The microstructure was also observed through relative devices. The presented results show that bonding strength of geopolymer-marble interfacial transitional zone, of which the 28d bonding strength reached up to 7.9 MPa, was higher than that of geopolymer-granite. The bonding strength of geopolymer-marble/geopolymer-granite interfacial transitional zone increased and finally reached up to 7.9 MPa/4.3 MPa with the molar ratio of n(SiO2)/n(Al2O3) increased within the range of 2.6～2.9. Both geopolymer-marble and geopolymer-granite bonding strength decreased as the molar ratio of n(SiO2)/ n(Na2O) increased. The mechanical properties of interfacial transitional zone between geopolymer and stone were affected by the oxide component of the geopolymer and the type of the raw materials.
7
BRIAND, BERNARD, JEAN-LUC BOUCHARDON, PAUL CAPIEZ, and MICHEL PIBOULE. "Felsic (A-type)–basic (plume-induced) Early Palaeozoic bimodal magmatism in the Maures Massif (southeastern France)." Geological Magazine 139, no. 3 (May 2002): 291–311. http://dx.doi.org/10.1017/s0016756802006477.
Full textAbstract:
The Maures Massif forms an important piece of the southernmost part of the Variscan belt of western Europe. This massif exhibits high-grade bimodal felsic–basic volcanic complexes, a distinctive lithological feature documented elsewhere in similar domains of the European Variscides and referred to the Cambro-Ordovician extensional episode. Two major alkalic and tholeiitic compositional groups and subordinate transitional metabasites have been identified, occurring at several distinct horizons or in bimodal complexes. This chemical diversity is interpreted in terms of variable degrees of partial melting of progressively depleted mantle source(s), which experienced melting at different depths, from garnet to spinel stability domains, during a progressive mantle upwelling associated with intracontinental rifting. This setting is reinforced by the presence of metabasites with compositions similar to continental flood basalts, showing slightly humped REE patterns, and interpreted as resulting from the melting of a partially depleted source at a relatively low degree of melting, in the garnet–spinel transition zone. The metafelsites from the tholeiitic bimodal complex exhibit the distinctive major and trace element characteristics of A-type rhyolites. Their elemental variations are consistent with fractional crystallization of major and accessory phases, but some discontinuous REE profiles result from a hydrothermal fractionation mechanism. The modelling of common anhydrous fractionating assemblages suggests that these A-type compositions may be derived from the associated tholeiites by extensive degrees of fractionation (90 %) with some continental crust involvement, or by anhydrous partial melting (∼30 %) of an underplated mafic parent of tholeiitic composition. The bimodal character of the Late Cambrian Maures magmatism, together with the chemistry of the various metabasites and metafelsites, suggests plume-induced intracontinental magmatic activity, resulting in lithospheric thinning prior to the onset of rifting and break-up of the Palaeozoic continental lithosphere, at this northern margin of Gondwana.
8
Slovenec, Damir, Boško Lugović, and Irena Vlahović. "Geochemistry, petrology and tectonomagmatic significance of basaltic rocks from the ophiolite mélange at the NW External-Internal Dinarides junction (Croatia)." Geologica Carpathica 61, no. 4 (August 1, 2010): 273–92. http://dx.doi.org/10.2478/v10096-010-0016-1.
Full textAbstract:
Geochemistry, petrology and tectonomagmatic significance of basaltic rocks from the ophiolite mélange at the NW External-Internal Dinarides junction (Croatia)At the NW inflexion of the Sava-Vardar Suture Zone ophiolite mélanges, known as the Kalnik Unit, form the surface of the slopes of several Pannonian inselbergs in the SW Zagorje-Mid-Transdanubian Zone. The Mt Samoborska Gora ophiolite mélange, thought to be a part of the Kalnik Unit, forms a separate sector obducted directly onto Dinaric Triassic carbonate sediments. Basaltic rocks, the only magmatic rocks incorporated in the mélange, include Middle-Triassic (Illyrian-Fassanian) alkali within-plate basalts and Middle Jurassic (uppermost Bathonian-Lower Callovian) tholeiitic basalts. The latter sporadically constitute composite olistoliths, and are geochemically divided into N-MORB-like (high-Ti basalts) and transitional MORB/IAT (medium-Ti basalts). These geochemically different rocks suggest crystallization at various tectonomagmatic settings, which is also indicated by the rock paragenesis and host clinopyroxene compositions. Alkali basalts reflect melts derived from an OIB-type enriched mantle source [Ti/V= 62.2-82.4; (La/Lu)cn= 6.4-12.8] with Nd-Sr isotope signatures close resembling the Bulk Earth [εNd(T=235 Ma)= + 1.6 to + 2.5]. They are recognized as preophiolite continental rift basin volcanic rocks that closely predate the opening of the Repno oceanic domain (ROD) of the Meliata-Maliac ocean system. The high-Ti and medium-Ti basalts from composite blocks derived from a similar depleted mantle source (εNd(T=165 Ma) = + 6.01 vs. + 6.35) succesively metasomatized by expulsion of fluids from a subducting slab leading to a more pronounced subduction signature in the latter [Ti/V=31.6-44.8 and (Nb/La)n=0.67-0.90 vs. Ti/V=21.5-33.9 and (Nb/La)n=0.32-0.49]. These composite blocks indicate crust formation in an extensional basin spreading over the still active subducting ridge. The majority of high-Ti basalts may represent the fragments of older crust formed at a spreading ridge and incorporated in the mélange of the accretionary wedge formed in the proto-arc-fore-arc region. The Mt Samoborska Gora ophiolite mélange represents the trailing edge of the Kalnik Unit as a discrete sector that records the shortest stage of tectonomagmatic evolution related to intraoceanic subduction in the ROD.
9
Anderson, Robert G., Jonah Resnick, James K. Russell, G. J. Woodsworth, Michael E. Villeneuve, and Nancy C. Grainger. "The Cheslatta Lake suite: Miocene mafic, alkaline magmatism in central British Columbia." Canadian Journal of Earth Sciences 38, no. 4 (April 1, 2001): 697–717. http://dx.doi.org/10.1139/e00-121.
Full textAbstract:
New mapping, mineralogical, and geochemical studies help characterize late Tertiary primitive, alkaline, sodic basanite, alkali olivine basalt, transitional basalt, and diabase in the Nechako River, Whitesail Lake, and McLeod Lake map areas of central British Columbia and distinguish the Miocene Cheslatta Lake suite. The suite encompasses scattered erosional remnants of topographically distinct, columnar-jointed, olivine-phyric basalt and diabase volcanic necks, dykes, and associated lava flows north of the Anahim volcanic belt and west of the Pinchi Fault. Volcanic centres at Alasla Mountain and at Cutoff Creek, near Cheslatta Lake, are proposed as type areas. Olivine, plagioclase, and pyroxene phenocrysts, megacrysts, and (or) xenocrysts; common ultramafic xenoliths; and rare but significant plutonic and metamorphic xenoliths are characteristic. Basanite, transitional basalt, and alkali olivine basalt groundmass contain plagioclase, clinopyroxene, Fe-Ti oxides, feldspathoid, olivine, and apatite. The Cheslatta Lake suite is characterized by its alkaline character, olivine-rich (>10 wt.%) normative mineralogy, and silica-undersaturated nature (>1 wt.% normative nepheline; hypersthene-normative rocks are uncommon). Mg numbers vary between 7242. Some samples encompass near-primitive mantle melt compositions. Cheslatta Lake suite rocks in the Nechako River area are distinguished from the underlying Eocene Endako and stratigraphically higher Neogene Chilcotin groups basaltic andesite lavas within the study area, and from the Chilcotin Group basalt in the type area south of the Anahim volcanic belt, by form, preserved thickness, phenocrystxenocryst mineralogy, amygdule abundance, included xenoliths, isotopic age, and major and incompatible, high field strength, and rare-earth trace element contents.
10
Xue, Yuan, Ningyue Sun, and Guowu Li. "Evolution of Nb–Ta Oxide Minerals and Their Relationship to the Magmatic-Hydrothermal Processes of the Nb–Ta Mineralized Syenitic Dikes in the Panxi Region, SW China." Minerals 11, no. 11 (October 29, 2021): 1204. http://dx.doi.org/10.3390/min11111204.
Full textAbstract:
Previous geochemical and petrological studies have concluded that initially magmatic Nb–Ta mineralization is often modified by post-magmatic hydrothermal fluids; however, there is still a lack of mineralogical evidence for the syenite-related Nb–Ta deposit. From the perspective of Nb–Ta minerals, the pyrochlore supergroup minerals have significance for indicating the fluid evolution of alkaline rock or related carbonatite type Nb–Ta deposits. The Panzhihua–Xichang (Panxi) region is a famous polymetallic metallogenic belt in southwestern China, abound with a huge amount of Nb–Ta mineralized syenitic dikes. This study focuses on the mineral textures and chemical compositions of the main Nb–Ta oxide minerals (including columbite-(Fe), fersmite, fergusonite-(Y), and especially pyrochlore group minerals) in samples from the Baicao and Xiaoheiqing deposits, in the Huili area, Panxi region, to reveal the magma evolution process of syenitic-dike-related Nb–Ta deposits. The Nb–Ta oxides in the Huili syenites are commonly characterized by a specific two-stage texture on the crystal scale, exhibiting a complex metasomatic structure and compositional zoning. Four types of pyrochlore group minerals (pyrochlores I, II, III, and IV) formed in different stages were identified. The euhedral columbite-(Fe), fersmite, and pyrochlores I and II minerals formed in the magmatic fractional crystallization stage. Anhedral pyrochlore III minerals are linked to the activity of magma-derived hydrothermal fluids at the late stages of magma evolution. The pyrochlore IV minerals and fergusonite-(Y) tend to be more concentrated in areas that have undergone strong albitization, which is a typical phenomenon of hydrothermal alteration. These mineralogical phenomena provide strong evidences that the magmatic-hydrothermal transitional stage is the favored model for explaining the Nb–Ta mineralization process. It is also concluded that the changes in chemical composition and texture characteristics for pyrochlore group minerals could serve as a proxy for syenite-related Nb–Ta mineralization processes.
11
Whalen, Joseph B., Neil Rogers, Cees R. van Staal, Frederick J. Longstaffe, George A. Jenner, and John A. Winchester. "Geochemical and isotopic (Nd, O) data from Ordovician felsic plutonic and volcanic rocks of the Miramichi Highlands: petrogenetic and metallogenic implications for the Bathurst Mining Camp." Canadian Journal of Earth Sciences 35, no. 3 (March 1, 1998): 237–52. http://dx.doi.org/10.1139/e97-102.
Full textAbstract:
Middle Ordovician felsic magmatism contemporaneous with Bathurst Camp Pb-Zn volcanogenic massive sulphide(VMS) deposits consists of strongly altered volcanic to subvolcanic rocks, belonging to the Tetagouche Group, and relativelyunaltered granitoid plutons, which are divided into northern, central, and southern groups within the Miramichi Highlands.Calc-alkalic felsic volcanic rocks and northern plus central plutons have EpsilonNd(T) values ranging from -8.2 to -1.9 and -4.0 to +0.3, respectively. They exhibit within-plate-type volcanic and transitional I- to A-type granite geochemical characteristics.Granitoid rock Delta18O values range from +8.0 to +10.1. Published granitoid rock Pb isotopic compositions overlapunpublished galena data from Bathurst VMS deposits. Field, geochemical, and isotopic evidence indicate that these volcanicand granitoids rocks are consanguineous and mainly derived from Proterozoic orolder infracrustal sources. Alkalic felsic volcanic rocks, and associated alkaline basaltic rocks, are more juvenile (EpsilonNd(T) = +3.2 to +4.2) and were possibly derivedfrom slightly enriched mantle sources. Southern plutons exhibit continental arc-type features. The felsic magmatism and VMS deposits likely formed in an Okinawa-type back-arc basin developed from rifting the Early Ordovician Popelogan continentalarc, of which the southern plutons are remnants. Correlations between pluton groups and volcanic formations indicate that felsic magmatism was erupted through and onto the Miramichi Group. As most felsic volcanic formations lack plutonicequivalents, the Tetagouche Group probably does not represent disrupted slices of an originally conformable stratigraphic section. This supports a model in which thrust slices juxtapose remnants of volcanic centres erupted at different locationswithin a back-arc basin.
12
Lavrynenko, О. М., and B. G. Shabalin. "Modeling of the Phase Formation Processes on the Steel Surface Contacting with Water Medium under Conditions of Deep Geological Repository." Nuclear Power and the Environment 20 (2021): 60–72. http://dx.doi.org/10.31717/2311-8253.21.1.5.
Full textAbstract:
The experimental modeling of the corrosive phase formation processes was performed under conditions approaching the initial and transitional stages of evolution of the deep geological repository (the hydrogen index of the medium lied in the range of 9–12 and a temperature was 50–70 °C). The specificity of the system of rotating disk electrode made it possible to determine the phase composition of corrosion products formed under oxidative conditions (the near surface layer, NSL) and, conditionally, reductive — on the steel surface (SL) covered by NSL, that significantly complicated the access of oxygen into the reaction area. It was determined that phase composition of the corrosion products at the pH0 values 9–11 was identical and it is regulated by the compensative action of cathodic half-reaction of oxygen reducing on the steel surface. Green Rust and magnetite or non-stoichiometric spinel ferrite characterized by coagulative type of the structure and spherical particle shape were determined as the main phases of SL. Iron oxyhydroxides — goethite and lepidocrocite were presented as the phases of NSL. Increase in the pH0 to 12 changes the chemical mechanism of the corrosion process and it leads to the formation of weak crystallized iron oxyhydroxide phases. It was proved the main phase formed under corrosion of steel at 50–70 °C was spinel ferrite. Its morphology is presented as the cubic shaped particles that evidences about condensingcrystallizing mechanism of their formation. Generally, the presence of Co2+ and Mn2+ cations does not influence on the phase formation process and the phase composition as well, whereas the iron oxyhydroxides with admixture of Mn2+ and Mn3+ oxygen compounds are dominant in the sediment compositions when they are formed in the presence of Mn7+.
13
Борисов, А. Е., А. Н. Канищев, and В. А. Козлов. "The Effect of Mineral Additives on the Physical and Mechanical Properties of Reinforced Organic Mineral Soils." НАУЧНЫЙ ЖУРНАЛ СТРОИТЕЛЬСТВА И АРХИТЕКТУРЫ, no. 2(66) (June 24, 2022): 87–93. http://dx.doi.org/10.36622/vstu.2022.66.2.008.
Full textAbstract:
Постановка задачи. Исследуется влияние минеральных добавок на физико-механические свойства укрепленных портландцементом грунтов с высоким содержанием гумуса, а также возможность использования данных грунтов в дорожном строительстве. Результаты. Определены значения прочности и коэффициента морозостойкости составов органоминеральных грунтов с содержанием гумусовых веществ, укрепленных минеральным вяжущим с добавкой песка в различном соотношении. Для оценки влияния минеральных вяжущих (цемента) и дополнительной (полимерной добавки) на структуру получаемого материала использовали цемент как в чистом виде, так и в сочетании с полимерной добавкой. Использование песка как структурного заполнителя дает возможность применять грунт с высоким содержание гумусовых веществ, укрепленный вяжущими материалами, в конструкциях дорожных одежд. Выводы. Предложены различные композиционные составы укрепления грунтов с применением в качестве вяжущих веществ портландцемента, полимерных добавок и гашеной извести с использованием песка как минерального заполнителя. Укрепленный грунт в зависимости от района применения можно использовать в качестве основания переходного типа дорожной одежды и дополнительного слоя основания облегченного типа дорожной одежды, что позволит снизить транспортные расходы на доставку и оплату дорожно-строительных материалов. Statement of the problem. The aim of the work is to study the effect of mineral additives on the physical and mechanical properties of Portland cement-reinforced soils with a high humus content, as well as to assess the possibility of using these soils in road construction. Results. In the course of the study, the values of the strength and the coefficient of frost resistance of organic and mineral soil compositions with the content of humus substances reinforced with a mineral binder with the addition of sand in different proportions were determined. To compare the effect of mineral binders (cement) and an additional (polymer additive) on the structure of the resulting material, cement was used both in pure form and cement in combination with a polymer additive. The use of sand as a structural aggregate makes it possible to apply a soil with a high content of humus substances, reinforced with binding materials, in the structures of road clothes. Conclusions. Various compositional compositions of soil strengthening with the use of Portland cement as binders, polymer additives, slaked lime using sand as a mineral filler are proposed. The reinforced soil, depending on the area of application, can be used as a base of a transitional type of pavement and an additional layer of a lightweight type of pavement base, which will reduce transport costs for the delivery and payment of road construction materials.
14
Trunilina, Vera A. "Evolution of the Late Mesozoic Magmatism of the Omulevka Terrane of the North Part of the Verkhoyansk–Kolyma Orogenic Region." Minerals 11, no. 11 (October 29, 2021): 1208. http://dx.doi.org/10.3390/min11111208.
Full textAbstract:
This article presents the results of a study of Late Mesozoic intrusive formations of the Omulevka terrane of the Verkhoyansk–Kolyma orogenic region. The research area covers the Selennyakh block of the Omulevka terrane and the territory adjacent to the south. The compositions of rock-forming, accessory and restitic minerals and geochemical features of intrusive rocks are considered. The methods of optical microscopy, microprobe, silicate and spectral analyses were used. There are the following several stages in the evolution of magmatism: (1) the Late Jurassic supra-subduction (gabbro, dolerites), (2) the beginning of the Early Cretaceous-transitional from supra-subduction to marginal-continental (gabbro-diorites, diorites, granodiorites), (3) the Early Cretaceous of active continental margin (granodiorites, granites), (4) the Late Cretaceous postorogenic or continental-riftogenic (alkali-feldspar granites of A-type), (5) the Late Cretaceous continental riftogenic (subalkaline gabbroids and basaltoids). In the process of evolution from stage one to stage four, there was an increase in the silicic acid content, total alkalinity and ferruginousity of rocks with the movement of magmogeneration levels to higher and higher horizons of the lithosphere (calculated pressure from 1.6–1.4 GPa to 0.6–0.9 GPa). At the same time, the preservation of high temperatures of magmogeneration (1000–1150 °C) and crystallization implies the supply of additional heat from an external (deep) source during the formation of granitoid melts. The magmatic activity is completed by the intrusion of subalkaline derivatives of a deep hearth, formed by metasomatized lherzolites. All the studied igneous rocks are either direct mantle fusions, or bear signs of the participation of mantle matter in the generation of parent melts in crustal substrates: the presence of tschermakite in gabbroids, nonequilibrium structures, the composition of early generations of biotites corresponding to biotites of mantle and crust-mantle derivatives, the presence of pyroxenes and accessory minerals characteristic of mantle magmas in granitoids. In the diagram Al-Na-K-2Ca–Fe + Ti + Mg, the composition points of the studied intrusive rocks tend to the mixing trend. In general, the research results suggest that the evolution of the Late Mesozoic intrusive magmatism of the studied territory and the specific matter of rock compositions were caused by the crust-mantle interaction as a result of the rise of mantle diapirs in the crust from a long-existing deep hearth of the main melt.
15
Tardy, M., H. Lapierre, D. Bosch, A. Cadoux, A. Narros, L. C. Struik, and P. Brunet. "Le terrane de Slide Mountain (Cordillères canadiennes) : une lithosphère océanique marquée par des points chauds." Canadian Journal of Earth Sciences 40, no. 6 (June 1, 2003): 833–52. http://dx.doi.org/10.1139/e03-010.
Full textAbstract:
The Slide Mountain Terrane consists of Devonian to Permian siliceous and detrital sediments in which are interbedded basalts and dolerites. Locally, ultramafic cumulates intrude these sediments. The Slide Mountain Terrane is considered to represent a back-arc basin related to the Quesnellia Paleozoic arc-terrane. However, the Slide Mountain mafic volcanic rocks exposed in central British Colombia do not exhibit features of back-arc basin basalts (BABB) but those of mid-oceanic ridge (MORB) and oceanic island (OIB) basalts. The N-MORB-type volcanic rocks are characterized by light rare-earth element (LREE)-depleted patterns, La/Nb ratios ranging between 1 and 2. Moreover, their Nd and Pb isotopic compositions suggest that they derived from a depleted mantle source. The within-plate basalts differ from those of MORB affinity by LREE-enriched patterns; higher TiO2, Nb, Ta, and Th abundances; lower εNd values; and correlatively higher isotopic Pb ratios. The Nd and Pb isotopic compositions of the ultramafic cumulates are similar to those of MORB-type volcanic rocks. The correlations between εNd and incompatible elements suggest that part of the Slide Mountain volcanic rocks derive from the mixing of two mantle sources: a depleted N-MORB type and an enriched OIB type. This indicates that some volcanic rocks of the Slide Mountain basin likely developed from a ridge-centered or near-ridge hotspot. The activity of this hotspot is probably related to the worldwide important mantle plume activity that occurred at the end of Permian times, notably in Siberia.
16
Chauvet, François, Henriette Lapierre, Delphine Bosch, Stéphane Guillot, Georges Mascle, Jean-Claude Vannay, Jo Cotten, Pierre Brunet, and Francine Keller. "Geochemistry of the Panjal Traps basalts (NW Himalaya): records of the Pangea Permian break-up." Bulletin de la Société Géologique de France 179, no. 4 (July 1, 2008): 383–95. http://dx.doi.org/10.2113/gssgfbull.179.4.383.
Full textAbstract:
AbstractThe late Lower to Middle Permian Panjal Traps (NW Himalaya, India-Pakistan) represent the greatest magmatic province erupted on the northern Indian platform during the Neotethys opening. New geochemical and isotopic analyses were performed on basalts from the eastern borders of the traps (SE Zanskar-NW Spiti area) in order to characterize this volcanism, to discuss its compositional variations in comparison to Panjal counterparts and its relationships with the opening of Neotethys. Lavas show features of tholeiitic low-Ti (< 1.6%) continental flood basalts with LREE, Th enrichments and Nb-Ta negative anomalies. Trace element ratios combined with εNdi values (−3.6 to +0.9) and high Pb isotopic ratios suggest that these tholeiitic basalts were derived from an OIB-like mantle contaminated at various degrees by a continental crust component. Previous geochemical features are broadly similar to those of the coeval Panjal volcanic sequences identified westwards (Ladakh, Kashmir and Pakistan). Present geochemical constraints obtained for the Panjal Traps basalts suggest they originated from rapid effusion of tholeiitic melts during opening of the Neotethys Ocean. Similar magmatism implying an OIB-type reservoir is contemporaneously recognized on and along the adjacent Arabian platform. Both Indian and Arabian Permian volcanics were emplaced during coeval syn-rift to post rift transition. These Lower to Middle Permian south Neotethyan continental flood magmatism are regarded as associated to a passive rifting. In this scheme, OIB-type isotopic signature would be related either to a melting episode of syn-rift up-welling mantle plumes or to a melting of a regional abnormally hot and enriched mantle.
17
Haapala, Ilmari, and O. Tapani Rämö. "Tectonic setting and origin of the Proterozoic rapakivi granites of southeastern Fennoscandia." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 83, no. 1-2 (1992): 165–71. http://dx.doi.org/10.1017/s0263593300007859.
Full textAbstract:
ABSTRACTThe 1·65–1·54 Ga rapakivi granites of southeastern Fennoscandia represent the silicic members of a bimodal magmatic association in which the mafic members are tholeiitic diabase dykes and minor gabbroic-anorthositic bodies. They are metaluminous to slightly peraluminous A-type granites and occur as high-level batholiths and stocks in an E-W-trending belt extending from Soviet Karelia to southwestern Finland. The Soviet Karelian granites were emplaced into the contact zone between Archaean craton and Svecofennian juvenile 1·9Ga-old crust, while the Finnish granites were intruded into the Svecofennian crust. Deep seismic soundings show that the rapakivi granites and the contemporaneous, mainly WNW or NW-trending diabase dyke swarms are situated in a zone of relatively thin crust. Below the Wiborg Batholith there exists a domal structure in the lithosphere in which a transitional zone (mafic underplate) occurs between the crust and the mantle.The Nd isotopic evolution of the rapakivi granites (εNd(T) −3·1—−0·2) corresponds to the evolution of the 1·9Ga-old Svecofennian crust, as do their Pb isotopic compositions. This implies that the Finnish granites represent anatectic melts of the Svecofennian crust. In contrast, the Soviet Karelian granites show isotopic composition indicative of substantial incorporation of Archaean lower crust material. Petrochemical modelling of one of the Finnish batholiths shows that its parental magma could have been generated by c. 20% melting of a granodioritic source and that fractional crystallisation was important during the subsequent evolution of this magma.The rapakivi granites are redefined as A-type granites that show the rapakivi texture at least in larger batholiths. The field, geochemical, and seismic data indicate that the classical Finnish rapakivi granites were generated in an anorogenic extensional regime by partial melting of the lower/middle crust. The melting, and possibly also the extensional tectonics, were related to upwellings of hot mantle material which led to intrusion of mafic magmas at the base and into the crust.
18
Lü, Zhao-Ying, Chang-Qian Ma, Yuan-Yuan Liu, Fu-Hao Xiong, Chang-Xin Wei, Mu-Long Chen, Gui-Cheng Xue, and Yu-Sheng He. "Petrogenesis of the Jurassic Guiping Complex in the Southwestern South China Block: Insights into the Subduction Processes of the Paleo-Pacific Slab." Minerals 11, no. 8 (July 26, 2021): 807. http://dx.doi.org/10.3390/min11080807.
Full textAbstract:
Late Jurassic NE-trending A-type granitoids are widespread in the Shihang belt, South China, though their petrogenesis and geodynamic settings remain controversial. The Guiping complex is located on the southwest margin of the Shihang belt. In this study, the petrography, major and trace element geochemistry, whole-rock Sr-Nd isotopes, and zircon U-Pb geochronology of the Guiping complex were investigated. The Guiping complex is composed of the Fenghuangling and Xishan plutons; both plutons yielded zircon U-Pb ages of ca. 160 Ma. The Fenghuangling pluton has low SiO2 content of 54.26% to 60.31%, whereas the Xishan pluton exhibits high SiO2 content of 65.19% to 71.18%. Both of them are metaluminous and belong to the high-K calc-alkaline series and are enriched in large-ion lithophile elements (LILEs) such as Rb, Th, U, and Pb. The Fenghuangling and Xishan plutons showed enrichment in light rare earth elements (LREEs) and high-field strength elements (Nb, Ta, Zr, and Hf) and depletion in heavy rare earth elements (HREEs). Marked Nb and Ta negative anomalies were not observed. Due to the high contents of Zr + Ce + Nb + Y and high Ga/Al ratios, all the samples belonged to the group of A-type granites. The Fenghuangling and Xishan plutons had low ISr (mainly in the range of 0.7046–0.7058) and high εNd(t) (−0.60 to 1.94) values, though obviously different from those of the Precambrian basement in South China. Furthermore, they lie between the ocean island basalt (OIB) of the asthenosphere and the arc basaltic rocks of the enriched lithospheric mantle. Therefore, we proposed that the basaltic parental magma of the Guiping complex originated from partial melting of the enriched lithospheric mantle, which was metasomatized by asthenosphere-related OIB-type basaltic magma. Mafic microgranular enclaves in the Xishan pluton displayed positive Nb and Ta anomalies, which is consistent with OIB-type basalts. The enclaves also had similar Sr-Nd isotopic compositions to the Xishan pluton. That indicated that the enclaves were probably formed by mixing of the OIB-type basaltic magma and the Xishan pluton. In conclusion, the formation of the Late Jurassic NE-trending A-type granite belt was attributed to back-arc extension as a result of the rollback of the Paleo-Pacific Plate.
19
Tamayo*, Rodolfo A., René C. Maury*, Graciano P. Yumul, Mireille Polvé, Joseph Cotten, Carla B. Dimantala, and Francia O. Olaguera. "Subduction-related magmatic imprint of most Philippine ophiolites: implications on the early geodynamic evolution of the Philippine archipelago." Bulletin de la Société Géologique de France 175, no. 5 (September 1, 2004): 443–60. http://dx.doi.org/10.2113/175.5.443.
Full textAbstract:
Abstract The basement complexes of the Philippine archipelago include at least 20 ophiolites and ophiolitic complexes. These complexes are characterised by volcanic sequences displaying geochemical compositions similar to those observed in MORB, transitional MORB-island arc tholeiites and arc volcanic rocks originating from modern Pacific-type oceans, back-arc basins and island arcs. Ocean island basalt-like rocks are rarely encountered in the volcanic sequences. The gabbros from the ophiolites contain clinopyroxenes and plagioclases showing a wide range of XMg and An values, respectively. Some of these gabbros exhibit mineral chemistries suggesting their derivation from basaltic liquids formed from mantle sources that underwent either high degrees of partial melting or several partial melting episodes. Moreover, some of the gabbros display a crystallization sequence where orthopyroxene and clinopyroxene appeared before plagioclase. The major element compositions of coexisting orthopyroxenes and olivines from the mantle peridotites are consistent with low to high degrees of partial melting. Accessory spinels in these peridotites display a wide range of XCr values as well with some of them above the empirical upper limit of 0.6 often observed in most modern mid-oceanic ridge (MOR) mantle rocks. Co-existing olivines and spinels from the peridotites also exhibit compositions suggesting that they lastly equilibrated under oxidizing mantle conditions. The juxtaposition of volcanic rocks showing affinities with modern MOR and island arc environments suggests that most of the volcanic sequences in Philippine ophiolites formed in subduction-related geodynamic settings. Similarly, their associated gabbros and peridotites display mineralogical characteristics and mineral chemistries consistent with their derivation from modern supra-subduction zone-like environments. Alternatively, these rocks could have, in part, evolved in a supra-subduction zone even though they originated from a MOR-like setting. A simplified scenario regarding the early geodynamic evolution of the Philippines is proposed on the basis of the geochemical signatures of the ophiolites, their ages of formation and the ages and origins of the oceanic basins actually bounding the archipelago, including basins presumed to be now totally consumed. This scenario envisages the early development of the archipelago to be largely dominated by the opening and closing of oceanic basins. Fragments of these basins provided the substratum on top of which the Cretaceous to Recent volcanic arcs of the Philippines were emplaced.
20
Aléon, Jérôme, Alice Aléon-Toppani, Bernard Platevoet, Jacques-Marie Bardintzeff, Kevin D. McKeegan, and François Brisset. "Alkali magmatism on a carbonaceous chondrite planetesimal." Proceedings of the National Academy of Sciences 117, no. 15 (March 30, 2020): 8353–59. http://dx.doi.org/10.1073/pnas.1919550117.
Full textAbstract:
Recent isotopic and paleomagnetic data point to a possible connection between carbonaceous chondrites and differentiated planetary materials, suggesting the existence, perhaps ephemeral, of transitional objects with a layered structure whereby a metal-rich core is enclosed by a silicate mantle, which is itself overlain by a crust containing an outermost layer of primitive solar nebula materials. This idea has not received broad support, mostly because of a lack of samples in the meteoritic record that document incipient melting at the onset of planetary differentiation. Here, we report the discovery and the petrologic–isotopic characterization of UH154-11, a ferroan trachybasalt fragment enclosed in a Renazzo-type carbonaceous chondrite (CR). Its chemical and oxygen isotopic compositions are consistent with very-low-degree partial melting of a Vigarano-type carbonaceous chondrite (CV) from the oxidized subgroup at a depth where fluid-assisted metamorphism enhanced the Na content. Its microdoleritic texture indicates crystallization at an increasing cooling rate, such as would occur during magma ascent through a chondritic crust. This represents direct evidence of magmatic activity in a carbonaceous asteroid on the verge of differentiating and demonstrates that some primitive outer Solar System objects related to icy asteroids and comets underwent a phase of magmatic activity early in the Solar System. With its peculiar petrology, UH154-11 can be considered the long-sought first melt produced during partial differentiation of a carbonaceous chondritic planetary body, bridging a previously persistent gap in differentiation processes from icy cometary bodies to fully melted iron meteorites with isotopic affinities to carbonaceous chondrites.
21
Zozulya, Dmitry R., Kåre Kullerud, Enrico Ribacki, Uwe Altenberger, Masafumi Sudo, and Yevgeny E. Savchenko. "The Newly Discovered Neoproterozoic Aillikite Occurrence in Vinoren (Southern Norway): Age, Geodynamic Position and Mineralogical Evidence of Diamond-Bearing Mantle Source." Minerals 10, no. 11 (November 18, 2020): 1029. http://dx.doi.org/10.3390/min10111029.
Full textAbstract:
During the period 750–600 Ma ago, prior to the final break-up of the supercontinent Rodinia, the crust of both the North American Craton and Baltica was intruded by significant amounts of rift-related magmas originating from the mantle. In the Proterozoic crust of Southern Norway, the 580 Ma old Fen carbonatite-ultramafic complex is a representative of this type of rocks. In this paper, we report the occurrence of an ultramafic lamprophyre dyke which possibly is linked to the Fen complex, although 40Ar/39Ar data from phenocrystic phlogopite from the dyke gave an age of 686 ± 9 Ma. The lamprophyre dyke was recently discovered in one of the Kongsberg silver mines at Vinoren, Norway. Whole rock geochemistry, geochronological and mineralogical data from the ultramafic lamprophyre dyke are presented aiming to elucidate its origin and possible geodynamic setting. From the whole-rock composition of the Vinoren dyke, the rock could be recognized as transitional between carbonatite and kimberlite-II (orangeite). From its diagnostic mineralogy, the rock is classified as aillikite. The compositions and xenocrystic nature of several of the major and accessory minerals from the Vinoren aillikite are characteristic for diamondiferous rocks (kimberlites/lamproites/UML): Phlogopite with kinoshitalite-rich rims, chromite-spinel-ulvöspinel series, Mg- and Mn-rich ilmenites, rutile and lucasite-(Ce). We suggest that the aillikite melt formed during partial melting of a MARID (mica-amphibole-rutile-ilmenite-diopside)-like source under CO2 fluxing. The pre-rifting geodynamic setting of the Vinoren aillikite before the Rodinia supercontinent breakup suggests a relatively thick SCLM (Subcontinental Lithospheric Mantle) during this stage and might indicate a diamond-bearing source for the parental melt. This is in contrast to the about 100 Ma younger Fen complex, which were derived from a thin SCLM.
22
Whittle, Thomas, and Siegbert Schmid. "Diffraction Studies of Tungsten Bronze Type Relaxor Ferroelectrics." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C78. http://dx.doi.org/10.1107/s2053273314099215.
Full textAbstract:
Ferroelectric materials are essential for modern electronic applications, from consumer electronics to sophisticated technical instruments. Relaxor ferroelectric materials provide the advantage of high dielectric constants over broad temperature ranges not seen in traditional ferroelectrics. Tungsten bronze type compounds have been shown to display a variety of industrially relevant optical and electronic properties amongst others. There is a fundamental relationship between the physical properties displayed by ferroelectrics and the crystal structures in which they form. Of particular interest are compositions and temperatures near phase transition. These are import because near phase transitions, particularly morphotropic phase transitions, electromechanical properties are often dramatically enhanced. [1,2] This work focuses on the structural investigation of the tungsten bronze type relaxor ferroelectric materials in the BaxSr3-xTi1-yZryNb4O15 (0 ≤ x ≤ 3; 0 ≤ y ≤ 1) system. A combination of X-ray, neutron (ToF and constant wavelength) and electron diffraction were employed to map the entire room temperature phase space. In addition, morphotropic phase boundary compositions were determined accurately. Variable temperature synchrotron X-ray diffraction studies were utilised to further explore the phase diagram for non-ambient conditions. Temperature dependent phase transitions were determined and the relationship between composition and transition temperature analysed. Structural models used in this work resulted from Rietveld refinements against powder diffraction data. [3] This work will shed light on new lead free relaxor ferroelectric materials.
23
Hodych, Joseph P., and Richard A. Cox. "Ediacaran U–Pb zircon dates for the Lac Matapédia and Mt. St.-Anselme basalts of the Quebec Appalachians: support for a long-lived mantle plume during the rifting phase of Iapetus opening." Canadian Journal of Earth Sciences 44, no. 4 (April 1, 2007): 565–81. http://dx.doi.org/10.1139/e06-112.
Full textAbstract:
It has been suggested that the rifting phase of Iapetus Ocean opening in Quebec involved a long-lived mantle plume centered near the Sutton Mountains whose dominant magmatism was first of continental flood basalt composition and later of ocean-island basalt (OIB) composition. We dated the Lac Matapédia and Mt. St.-Anselme basalts, which are thought to have originated from this plume and have dominant OIB-like composition. The U–Pb dating was done on individual zircon crystals using a laser ablation microprobe linked to an inductively coupled plasma – mass spectrometer. Zircons from two basalt flows at Lac Matapédia yielded ages of 565 ± 6 and 556 ± 5 Ma. Zircons from a basalt flow at Mt. St.-Anselme yielded an age of 550 ± 7 Ma. Although the basalts are allochthonous, these should be their ages of extrusion onto Laurentia, as shown by Grenvillian ages yielded by inherited zircons in both Lac Matapédia flows and by zircons in a granitic pebble from the Mt. St.-Anselme Formation. Our dating supports the hypothesis of a long-lived (~615 to ~550 Ma) Sutton Mountains mantle plume involved in Iapetus rifting. It does so by closing a possible gap of ~10 Ma between the end of flood basalt and the beginning of OIB magmatism, and by supporting ~540 (rather than ~570) Ma for the rift-to-drift transition in Quebec. Because plumes move slowly, this hypothesis implies that Laurentia moved slowly from ~615 to ~550 Ma. This is consistent with paleomagnetic evidence, although very rapid true polar wander at ~590 Ma may need to be invoked.
24
ÇELİK, ÖMER FARUK. "Metamorphic sole rocks and their mafic dykes in the eastern Tauride belt ophiolites (southern Turkey): implications for OIB-type magma generation following slab break-off." Geological Magazine 144, no. 5 (July 6, 2007): 849–66. http://dx.doi.org/10.1017/s0016756807003573.
Full textAbstract:
The metamorphic sole rocks observed between the Pozantı–Karsantı ophiolite and the melange unit are located on the eastern part of the Tauride carbonate platform. They consist of ortho-amphibolites at the top and metasedimentary lithologies at the base. Amphibolites from the metamorphic sole rocks are represented by OIB, MORB and IAT based on their major, trace and REE compositions. The isolated dolerite dykes intrude both the metamorphic sole rocks and the ophiolitic unit at different structural levels. The dolerite dykes cutting the metamorphic sole rocks are enriched in LILE and depleted in HFSE. Enrichment in LILE such as Th, relative to HFSE, is indicative of the presence of a subduction component. Flat-lying REE patterns of the dolerite dykes also confirm an IAT source. Pyroxenite and albitite dykes also cut the metamorphic sole rocks. REE patterns of pyroxenite dykes show prominent LREE enrichment, similar to that observed in within-plate alkaline basalts. The alkaline isolated pyroxenite dykes were probably the result of late-stage magmatism fed by melts that originated from an OIB source, shortly before the emplacement of the Pozantı–Karsantı ophiolite onto the Tauride carbonate platform. A hydrothermal alteration stage is characterized by albitite formation in the joints of the metamorphic sole rocks and by secondary mineralization along the contact zones of dolerite dykes. Mineral parageneses in the metamorphic sole rocks exhibit amphibolite and greenschist-facies assemblages. Geothermobarometric studies based on a newly recognized mineral assemblage (e.g. kyanite) and chemical compositions of minerals in the metamorphic sole rocks indicate that the metamorphic temperature during the metamorphism was 570–580°C and the pressure was around 5–6 kbar.
25
Sakai, Shunta, Naoto Hirano, Yildirim Dilek, Shiki Machida, Kazutaka Yasukawa, and Yasuhiro Kato. "Tokoro Belt (NE Hokkaido): an exhumed, Jurassic – Early Cretaceous seamount in the Late Cretaceous accretionary prism of northern Japan." Geological Magazine 158, no. 1 (June 24, 2019): 72–83. http://dx.doi.org/10.1017/s0016756819000633.
Full textAbstract:
AbstractThe Tokoro Belt exposed in NE Hokkaido (Japan) represents part of a Late Cretaceous accretionary complex, which includes variously metamorphosed volcanic rocks that are interbedded with chert, lenticular limestone and some fore-arc sedimentary rocks. The Tokoro Belt is notably different from other Late Cretaceous accretionary complexes around the Pacific Rim because of widespread occurrence of basalts and volcaniclastic rocks in it. The Nikoro Group, characterized by widespread occurrence of volcanic rocks, is divided into western, eastern and southern sections based on the internal structure, geochemical affinities and metamorphic grades of their volcanic lithologies. OIB (ocean island basalt)-type volcanic rocks with low-grade metamorphic overprint predominate in the western and southern sections, whereas MORB (mid-ocean ridge basalt)- and OIA (ocean island alkaline basalt)-type rocks in the eastern section with partly high-pressure metamorphism make up the northern part of the eastern section. Trace element patterns display transitional trends from MORB to OIA geochemical affinities. OIB-type rocks display trace element characteristics similar to those of shield volcano lavas on Hawaii, rather than small and mainly alkaline, Polynesian hotspot lavas; furthermore, they show significant HREE (heavy rare earth element) enrichment probably caused by plume–ridge interaction. Widespread OIBs in the Tokoro Belt represents tectonic slices of a large (>80 km wide) Hawaiian-style, seamount shield volcano on the Izanagi oceanic plate that was accreted into the continental margin of Far East Asia in the Late Cretaceous.
26
Abdel-Rahman, Abdel-Fattah M., and P. Stephen Kumarapeli. "Geochemistry of mantle-related intermediate rocks from the Tibbit Hill volcanic suite, Quebec Appalachians." Mineralogical Magazine 62, no. 04 (August 1998): 487–500. http://dx.doi.org/10.1180/002646198547864.
Full textAbstract:
Abstract We present a study on major and trace element geochemistry of some intermediate lithologies from the predominantly basaltic Tibbit Hill volcanic suite in the Humber Zone of the Quebec Appalachians. The intermediate rocks probably formed as lava flows in the volcanic sequence. Their presence shows that this rift-related, c. 554 Ma volcanic sequence is not bimodal (basaltic-comenditic) as previously thought, but consists of a spectrum of compositions ranging from mafic through intermediate to felsic lithologies. The entire volcanic sequence is poly-deformed and generally metamorphosed to greenschist facies conditions. The intermediate rocks of the Tibbit Hill Formation are trachyandesitic, trachytic and comenditic in composition, and exhibit a wide range of SiO2 content (52 to 68 wt.%). Mg is highly depleted in most samples. Variations of silica versus the alkalis show that most of the samples are alkaline in nature. The rocks display a tholeiitic trend on a standard AFM diagram. In general, the examined rocks also exhibit a wide range of Sr (15 to 174 ppm), Rb (0 to 156 ppm), Zr (155 to 899 ppm), Nb (18 to 123 ppm), and Y (18 to 94 ppm). The concentration of Hf and Ta are generally low (6.6–14.8 ppm, and 3.3–6.6 ppm, respectively), compared to those of Zr and Nb. Nevertheless, these rocks contain relatively high concentrations of the HFS elements, thus reflecting an enriched source. The suite is also relatively enriched in the rare earth elements (REE), and exhibits fractionated, subparallel REE pattems; the latter are generally uniform and conformable. Chemical features of these volcanic rocks are typical of those of anorogenic A1 type suites, related to hotspots, mantle plumes, or continental rift zones. This is consistent with earlier interpretation of volcanism associated with an Iapetan RRR triple junction, occurring shortly before the onset of seafloor spreading. At that stage of crustal evolution, alkaline to transitional basaltic magma pierced into the crust, and experienced fractionation to produce the liquids of intermediate composition. Rare earth element geochemical modelling supports the hypothesis that the most evolved composition for which REE data are available (comendite; 67.9 wt.% SiO2) was produced by 20% fractional crystallization of the least evolved trachyandesite (56.7 wt.% SiO2) of this intermediate volcanic assemblage.
27
Peng, Zidong, Changle Wang, Simon W. Poulton, Xiaoxue Tong, Kurt O. Konhauser, and Lianchang Zhang. "Origin of the Neoarchean VMS-BIF Metallogenic Association in the Qingyuan Greenstone Belt, North China Craton: Constraints from Geology, Geochemistry, and Iron and Multiple Sulfur (δ33S, δ34S, and δ36S) Isotopes." Economic Geology 117, no. 6 (September 1, 2022): 1275–98. http://dx.doi.org/10.5382/econgeo.4920.
Full textAbstract:
Abstract The association of volcanogenic massive sulfide (VMS) deposits and Algoma-type banded iron formations (BIFs) in many Precambrian terranes indicates a link between submarine hydrothermal processes, seawater chemistry, and chemical sedimentation. The Neoarchean (~2.55 Ga) Qingyuan greenstone belt VMS-BIF metallogenic association, located on the north margin of the North China craton, is a typical example of such an association. The stratigraphy of the Qingyuan greenstone belt includes three units (from the oldest to youngest): (1) the Shipengzi Formation, composed of tholeiitic-transitional arc basalts with negative Nb anomalies, interlayered normal mid-ocean ridge basalts (N-MORBs) and FI-type dacites, and BIFs; (2) the Hongtoushan Formation, consisting of polycyclic bimodal suites of N-MORB-type basalts and FII-type dacites, as well as VMS mineralization and minor BIFs; and (3) the Nantianmen Formation, composed of schist, quartzite, and marble with minor basalts and BIFs. Positive Fe isotope compositions (δ56Fe of 0.48–0.69‰) for magnetite in the silicate BIF of the Shipengzi Formation indicate partial oxidation of aqueous Fe(II). Using a dispersion-reaction model, the relatively high δ56Fe values (0.72–1.04‰) estimated for primary ferric (oxyhydr)oxides in this BIF constrain local dissolved O2 contents of the Neoarchean surface ocean to 10–4 to 10–3 μmol/L. By comparison, negative δ56Fe values for magnetite (–0.83 to –0.65‰) in silicate BIFs of the Hongtoushan Formation and the Nantianmen Formation suggest deposition from a residual water column that was depleted in 56Fe. Following the formation of the bulk of the VMS deposits in the Hongtoushan Formation, a significant change to positive magnetite δ56Fe values (0.79–1.04‰) occurs in the youngest sulfide-bearing BIF in the Nantianmen Formation. This implies that the VMS-related hydrothermal vents injected a large mass of unfractionated ferrous iron into the ocean. Negative Δ33S anomalies in sedimentary pyrite of bedded VMS ores (avg of –0.08 ± 0.007‰, n = 6) and sulfide-bearing BIFs (avg of –0.06 ± 0.007‰, n = 3) of the Qingyuan greenstone belt, along with mass-independent fractionations (with an average Δ36S/Δ33S ratio of –1.1 ± 0.3), are best explained by incorporation of seawater sulfate of atmospheric photochemical origin during their formation. The systematic differences in whole-rock geochemistry and Δ33S values for different types of VMS ores imply variable seawater sulfate contributions to their mineralization. Our results are consistent with global anoxic conditions during the Neoarchean to Paleoproterozoic transition (i.e., at 2.5 Ga), and confirm that formation of the VMS-BIF metallogenic association took place in dominantly anoxic, ferruginous basins at different depths, with the VMS-related hydrothermal system contributing significant Fe to the deposition of BIFs.
28
Zheng, Hao, Li-Feng Zhong, Argyrios Kapsiotis, Guan-Qiang Cai, Zhi-Feng Wan, and Bin Xia. "Post-spreading Basalts from the Nanyue Seamount: Implications for the Involvement of Crustal- and Plume-Type Components in the Genesis of the South China Sea Mantle." Minerals 9, no. 6 (June 23, 2019): 378. http://dx.doi.org/10.3390/min9060378.
Full textAbstract:
Fresh samples of basalts were collected by dredging from the Nanyue intraplate seamount in the Southwest sub-basin of the South China Sea (SCS). These are alkali basalts displaying right-sloping, chondrite-normalized rare earth element (REE) profiles. The investigated basalts are characterized by low Os content (60.37–85.13 ppt) and radiogenic 187Os/188Os ratios (~0.19 to 0.21). Furthermore, 40Ar/39Ar dating of the Nanyue basalts showed they formed during the Tortonian (~8.3 Ma) and, thus, are products of (Late Cenozoic) post-spreading volcanism. The Sr–Nd–Pb–Hf isotopic compositions of the Nanyue basalts indicate that their parental melts were derived from an upper mantle reservoir possessing the so-called Dupal isotopic anomaly. Semiquantitative isotopic modeling demonstrates that the isotopic compositions of the Nanyue basalts can be reproduced by mixing three components: the average Pacific midocean ridge basalt (MORB), the lower continental crust (LCC), and the average Hainan ocean island basalt (OIB). Our preferred hypothesis for the genesis of the Nanyue basalts is that their parental magmas were produced from an originally depleted mantle (DM) source that was much affected by the activity of the Hainan plume. Initially, the Hainan diapir caused a thermal perturbation in the upper mantle under the present-day Southwest sub-basin of the SCS that led to erosion of the overlying LCC. Eventually, the resultant suboceanic lithospheric mantle (SOLM) interacted with OIB-type components derived from the nearby Hainan plume. Collectively, these processes contributed crustal- and plume-type components to the upper mantle underlying the Southwest sub-basin of the SCS. This implies that the Dupal isotopic signature in the upper mantle beneath the SCS was an artifact of in situ geological processes rather than a feature inherited from a Southern Hemispheric, upper mantle source.
29
Zabrodina, Elena Al'bertovna. "“Sacred Theology” of Nicholas of Cusa in the portraits and altar paintings of the artists of the Early Netherlandish painting." Человек и культура, no. 4 (April 2020): 21–32. http://dx.doi.org/10.25136/2409-8744.2020.4.33349.
Full textAbstract:
The subject of this research is the processes that unfolded in the spiritual sphere of the Netherlandish society of the XV century, which can be assessed by the treatises of the prominent philosopher and figure of the Catholic Church Nicholas of Cusa (1401-1464), as well as by the images, scenes, artistic techniques used by Netherlandish artists of that time such brothers van Eyck, Rogier van Weyden, Hans Memling, Petrus Christus, Hieronymus Bosch, Robert Kampin, and others. Main attention is given to the comparison of the views of Nicholas of Cusa, as well as the manner and ideological program that can be seen in the work of the XV century artists. The scientific novelty consists in demonstration of just how the views of Nicholas of Cusa correlate to the worldview of the people of the XV century – transitional period from the Medieval Era to the Modern Age. Perceptions of the Netherlanders of that time of the world and people’s place within it, of divine predestination and everyday life are reflected in the orders for a new type of altar compositions and portraits. The conducted analysis uses specific examples to reveal the theme of commonness of the worldview in the examined chronological period. Comparison of the paintings and thoughts of Nicholas of Cusa demonstrate the commonness of views that reflect the transformational era in the history of art.
30
Archibald, D. B., S. M. Barr, J. B. Murphy, C. E. White, T. G. MacHattie, E. A. Escarraga, M. A. Hamilton, and C. R. M. McFarlane. "Field relationships, petrology, age, and tectonic setting of the Late Cambrian–Ordovician West Barneys River Plutonic Suite, southern Antigonish Highlands, Nova Scotia, Canada." Canadian Journal of Earth Sciences 50, no. 7 (July 2013): 727–45. http://dx.doi.org/10.1139/cjes-2012-0158.
Full textAbstract:
The West Barneys River Plutonic Suite consists of gabbro, syenite-monzonite, alkali-feldspar syenite to quartz alkali-feldspar syenite, and alkali-feldspar granite outcropping in an area of ∼100 km2 in the southern Antigonish Highlands. Magma mixing and mingling textures indicate a comagmatic relationship between some of the mafic and intermediate–felsic lithologies. However, nine U–Pb (zircon) ages, three by thermal ionization mass spectrometry (TIMS) and six by laser-ablation – inductively coupled plasma – mass spectrometry (LA–ICP–MS), from the West Barneys River suite and the lithologically similar Cape Porcupine Complex located 60 km to the east range from ca. 495 to 460 Ma, indicating that emplacement occurred over a significant span of time. Intermediate to felsic rocks consist mainly of perthitic K-feldspar and variable amounts of quartz; interstitial granophyre is present in some samples, consistent with shallow emplacement. Mafic phases are Fe-rich amphibole and clinopyroxene, and in some units, fayalite. Intermediate and felsic samples have chemical characteristics of within-plate ferroan A-type granitoid rocks. Gabbroic rocks consist of plagioclase (oligoclase–labradorite) and augite/diopside with less abundant orthopyroxene, olivine, biotite, and ilmenite/magnetite. Their chemical compositions are transitional from tholeiitic to alkalic and characteristic of continental within-plate mafic rocks. The εNd values are similar in gabbroic, syenitic, and granitic samples, ranging between 0.9 and 4.9, consistent with a co-genetic origin for the mafic and intermediate/felsic components of the suite, and derivation from Avalonian subcontinental lithospheric mantle in an extensional environment.
31
KOZLOV, Pavel Sergeevich. "On the relationships between the Al2SiO5 polymorphs during formation of blastomylonites (North Yenisei Ridge)." NEWS of the Ural State Mining University 1 (March 15, 2021): 25–32. http://dx.doi.org/10.21440/2307-2091-2021-1-25-32.
Full textAbstract:
Relevance. When mapping the vast areas of the Precambrian polymetamorphic complexes in the North Yenisei Ridge, there is a problem of metamorphism interpretation and phasing of geological development of a particular area along with thrust tectonics. The solution of these issues is also of great importance for the purposes of areas delineation of metamorphic rocks that are favorable for the detection of high-alumina (andalusite, kyanite, sillimanite) schists. Purpose of the work: to substantiate and itemize some geological prospecting, mineralogical and petrological indicator criteria for the development of high-alumina garnet-kyanite-staurolite blastomylonites of dislocation metamorphism formed by andalusite-bearing rocks of regional metamorphism. Research methodology: detailed mapping of structural-metamorphic zoning of dislocation (collisional) metamorphism in the Mayakon key area with sampling of polymetamorphic rocks for petrographic studies of mineral parageneses. Investigation of polished thin sections of polymetamorphic rocks by microprobe analysis with elucidation of minerals zoning, their chemical composition, calculation of the Р–Т paths of metamorphism and determination of the absolute age of blastomylonite formation based on the 40Ar/39Ar dating of biotite. Analysis and generalization of the results obtained for the Mayakon area and their comparison with other key areas of the North Yenisei Ridge. Results. At the Mayakon potential area, a progressive metamorphic zoning of kyanite-bearing blastomylonites has been identified, and the transitional I, outer II, middle III, and inner zones are determined as the dislocation metamorphism intensifies towards the Panimba thrust fault. Based on the compositions of garnets, biotite, and plagioclase, the P–T paths of the early regional metamorphism of andalusite-sillimanite type and late local kyanitesillimanite type were calculated. A list of geological prospecting, petrological and isotope-geochronological criteria for recognizing blastomylonites among rocks of regional metamorphism in thrust zones has been substantiated and itemized. Conclusions. Method of polymetamorphism reconstruction in the North Yenisei Ridge shows that tectonic inversion conditions took place in the Neoproterozoic, in the late Tonian era (~850 Ma ago In terms of occurrences, they are related to the final stage of the Grenville orogeny (1.1–0.85 Ga). The formation of blastomylonites of dislocation (collisional) metamorphism by metapelites of regional metamorphism in thrust zones is accompanied by an increase in the number of mineral phases and leads to a reduction in usable space of high-alumina andalusite schists.
32
Cantrell, David, Peter Swart, and Royal Hagerty. "Genesis and characterization of dolomite, Arab-D Reservoir, Ghawar field, Saudi Arabia." GeoArabia 9, no. 2 (April 1, 2004): 11–36. http://dx.doi.org/10.2113/geoarabia090211.
Full textAbstract:
ABSTRACT This study reports the results of an investigation into the nature, origin and significance of linear dolomite trends across the Arab-D reservoir in Ghawar field. In the course of this study, three distinct types of dolomite were identified based on petrographic and geochemical criteria: fabric-preserving (FP), non-fabric-preserving (NFP) and baroque dolomite. Fabric-preserving (FP) dolomite is very finely crystalline dolomite in which details of the original limestone fabric are usually well preserved. Beds of FP dolomite typically occur as thin, sheet-like or stratigraphic layers that are always intimately associated with the overlying anhydrite. This dolomite is interpreted to have formed very early in the diagenetic history of the sediment, by dense, highly evaporated magnesium-rich brines associated with the overlying anhydrite. In contrast, NFP dolomite is a medium crystalline, non-baroque dolomite in which all traces of the original limestone fabric have been obliterated. This dolomite also typically occurs as stratigraphic beds, although it is not restricted to the uppermost part of the Arab-D but occurs throughout the reservoir. The NFP dolomite is the most common type present in the reservoir, and is interpreted on the basis of its general geochemical similarity to the FP dolomites to have mostly formed from hypersaline fluids, although some NFP dolomite is thought to represent a transitional form with the third dolomite type, baroque dolomite. Strontium isotopic ratios suggest that both the FP and most of the NFP dolomite formed very early, at or shortly after deposition of the original sediment. The third type of dolomite, baroque, is a coarsely crystalline dolomite with “saddle-shaped” crystals displaying undulose extinction in thin section. It is rare in the reservoir and appears to be limited to wells that contain abnormally thick sections of dolomite; in extreme cases, baroque dolomite is vertically pervasive. Geochemically, baroque dolomite is distinctive with high iron and very low oxygen isotopic compositions, and is interpreted to have formed from high temperature fluids during burial diagenesis. These fluids are suggested to have ascended up into the reservoir from depth along a fault/facture system, relatively late in the diagenetic history of the rock.
33
Tang, Wenting, Hejiu Hui, Dmitri A. Ionov, Wei Chen, Lisha Zhang, and Yongjiang Xu. "Metasomatism-controlled hydrogen distribution in the Spitsbergen upper mantle." American Mineralogist 105, no. 9 (September 1, 2020): 1326–41. http://dx.doi.org/10.2138/am-2020-7290.
Full textAbstract:
Abstract Hydrogen concentrations in minerals of peridotite xenoliths in alkali basaltic rocks from Quaternary volcanoes in northwest Spitsbergen were measured using polarized Fourier transform infrared spectroscopy (FTIR) to trace the effects of geologic processes on hydrogen distribution in the continental lithospheric mantle. The mineral grains show hydrogen profiles with lower concentrations at rims suggesting diffusive hydrogen loss during the entrapment and transport of the xenoliths in magma. However, hydrogen concentrations in the centers of the grains are uniform and appear to represent hydrogen abundances in the Spitsbergen upper mantle. The olivine, orthopyroxene, and clinopyroxene contain 1–10, 130–290, and 350–560 ppm H2O, respectively. Hydrogen abundances away from metasomatic melt conduits recorded by Type 1 xenoliths are correlated with the concentrations of incompatible trace elements, indicating that hydrogen distribution is related to mantle metasomatism. By contrast, hydrogen near the melt conduits, recorded by Type 2 xenoliths, shows no regular correlations with incompatible trace elements (except Nb in clinopyroxene) and may be affected by fractional crystallization of amphibole in the conduits. Hydrogen contents decrease away from the melt conduits and are controlled by the interaction between the depleted host mantle and percolating metasomatic melts. Therefore, the metasomatic melt could have variably hydrated the Spitsbergen upper mantle via different processes. The H2O/Ce ratios of the melt in equilibrium with clinopyroxene near the metasomatic melt conduits range from 93 to 218, i.e., within the oceanic island basalt (OIB) range. This is consistent with that the metasomatic melt could have been derived from OIB-type sources evidenced by the Sr-Nd isotope compositions of the xenoliths.
34
Greenough, John D., and Kevin MacKenzie. "Igneous Rock Associations 18. Transition Metals in Oceanic Island Basalt: Relationships with the Mantle Components." Geoscience Canada 42, no. 3 (July 29, 2015): 351. http://dx.doi.org/10.12789/geocanj.2015.42.071.
Full textAbstract:
Incompatible elements and isotopic ratios identify three end-member mantle components in oceanic island basalt (OIB); EM1, EM2, and HIMU. We estimate compatible to mildly incompatible transition metal abundance trends (Ni, Co, Fe, Cu, Cr, V, Mn, Sc, and Zn) in “primitive” basalt suites (Mg# = Mg/(Mg + 0.9*Fe) atomic = 0.72) from 12 end-member oceanic islands by regressing metals against Fe/Mg ratios in sample suites, and solving for concentrations at Mg/Fe = 1 (Mg# = 0.72). Using the transition metal estimates, exploratory statistics reveal that islands ‘group’ based on mantle component type even when La/Yb ratios are used to compensate metal concentrations for percentage melting. Higher chalcophile Zn (and Pb, earlier work) in EM1 and EM2 compared to HIMU, and higher Cr (3+) and Sc in HIMU relative to EM1, support views that HIMU represents subduction-processed ocean floor basalt. Incompatible elements, ratios and isotopes indicate that EM1 is Archean, EM2 is Proterozoic or younger, and both are related to sediment subduction. As found with incompatible elements, EM1 and EM2 show similar ‘compatible’ element concentrations, but lower (multi-valence) Cr, Fe and Mn in EM1 could indirectly reflect increasing oxidation of subducted sediment between the Archean and Proterozoic. Alternatively, changes in subduction processes that yielded peak continental formation in the Neoarchean, and craton-suturing in the Paleoproterozoic may account for EM1–EM2 differences. EM1 shows similar or lower Cr, Ni and Co compared to HIMU and EM2 suggesting that economic viability of layered intrusions, which have extreme EM1-like signatures, is unrelated to high metals in EM1 mantle sources, but that high % melting appears important. Because core-concentrated transition metals correlate with mantle component type, lithospheric recycling apparently controls their concentrations in OIB and core-mantle interaction may be unimportant.RÉSUMÉLes éléments incompatibles et les rapports isotopiques permettent de délimiter trois termes extrêmes de composants mantéliques dans des basaltes insulaires océaniques (OIB), soit EM1, EM2, et HIMU. Nous estimons les tendances d’abondance de métaux de transition (Ni, Co, Fe, Cu, Cr, V, Mn, Sc, and Zn) compatibles à modérément incompatibles dans des suites de basaltes « primitifs » (Mg# = Mg/(Mg + 0,9*Fe) rayon atomique = 0,72) sur 12 termes extrêmes de matériaux insulaires océaniques, par régression des concentrations des métaux sur les rapports Fe/Mg dans des échantillons des suites, la détermination étant définie au rapport Mg/Fe = 1 (Mg# = 0,72). L’utilisation d’une approche statistique exploratoire sur les estimations de métaux de transition montre que la composition des îles se « regroupent » en fonction du type de composition du manteau, cela même lorsque les ratios La/Yb sont utilisés pour compenser les concentrations de métaux pour déterminer le pourcentuel de fusion. Le caractère plus chalcophile du Zn (et Pb, travail antérieur) dans EM1 et EM2 comparé à HIMU, et la plus grande teneur en Cr (3+) et Sc dans HIMU par rapport à EM1, accréditent l’idée que HIMU représente le basalte de subduction des fonds océaniques. Les éléments incompatibles, les ratios et les isotopes montrent que EM1 est archéen, que EM2 est protérozoïque ou plus jeune, et que les deux sont liés à la subduction sédimentaire. Comme constaté pour les éléments incompatibles, EMI et EM2 affichent une compatibilité similaire des concentrations en éléments « compatibles », toutefois une concentration inférieure en Cr (multivalent), Fe et Mn dans EM1 pourrait refléter indirectement une oxydation croissante des sédiments subduits entre l’Archéen et le Protérozoïque. Par ailleurs, les changements dans les mécanismes de subduction qui ont mené à un maximum de formation continentale au Néoarchéen et à des épisodes de sutures cratoniques au Paléoprotérozoïque, peuvent expliquer les différences entre EM1 et EM2. La teneur similaire ou inférieure en Cr, Ni et Co de EM1 par rapport à HIMU et EM2 permet de croire que la viabilité économique des intrusions stratifiées – lesquelles montrent des signatures extrêmes EM1 – est sans rapport avec les sources mantéliques à fortes teneurs en métaux, mais que le fort pourcentuel de fusion qui importerait. Parce que la concentration du noyau en métaux de transition correspond avec le type de composant du manteau, c’est le recyclage lithosphérique qui contrôle apparemment leurs concentrations dans l'OIB, et l'interaction noyau-manteau pourrait être sans importance.
35
Gao, Lihua, Zhigang Song, Chao Han, Mei Han, Chenlin Zhu, Di Xia, Zuozhen Han, and Shuangjian Li. "Petrogenesis, Magma Source, and Geodynamics of Paleogene Mafic Rocks, Huimin Sag, Jiyang Depression, Eastern China." Geofluids 2022 (June 8, 2022): 1–18. http://dx.doi.org/10.1155/2022/1571066.
Full textAbstract:
A suite of Paleogene mafic rocks was collected from boreholes in the Huimin Sag of the Jiyang Depression with the aim of investigating the petrogenesis and nature of mantle source for these rocks and further providing insights into the characteristic of related mantle plume. Whole-rock geochemical data indicate that the mafic rocks have relatively lower SiO2 (42.93%–48.57%) contents and similar characteristics to alkaline basalt and belong to transitional calc-alkaline series. These samples were clearly enriched in LREEs and depleted in HREEs and were also characterized by the enrichment of LILEs, incompatible elements, and HFSEs, similar to those of the Ocean Island Basalt (OIB). In addition, they exhibited Pb enrichment; Y, Pr, and Yb depletion; absence of Nb-Ta anomalies; high Hf and low Zr; and Rb/Yb ratios exceeding 1.0, indicating characteristics of intraplate rift-type alkaline basalt. The samples exhibited (Th/Ta)PM and (La/Nb)PM ratios less than 1 and plotted within the OIB, EMI, and EMII fields, indicating that crustal components had no role in the generation of the rocks. With the exception of individual samples that have a distinctive range of ε Nd values, the majority of samples have complex ε Nd values of -1.15 to 5.56, indicating a mixture of different sources, which was also apparent in the δ18O-87Sr/86Sr diagram, in which the samples plot close to the downward nonlinear curve. Based on the isotopic and trace elemental analyses, these igneous rocks are intraplate rift-type alkaline basalt and are of mantle plume origin. The variations in 87Sr/86Sr, 143Nd/144Nd, ε Nd values, LREEs, and HFSEs were probably due to the different locations of the mantle plume for different samples. The primary magma of the rocks likely originated from the melting of a mantle plume and the further metasomatism of lithospheric mantle, continental, or oceanic crust.
36
Chandra, Dhanesh, Renee A. Lynch, Wei Ding, and John J. Tomlinson. "Phase Diagram Studies on Neopentylglycol and Pentaerythritol-Thermal Energy Storage Materials." Advances in X-ray Analysis 33 (1989): 445–52. http://dx.doi.org/10.1154/s037603080001987x.
Full textAbstract:
AbstractPentaerythritol (PE) and neopentylglycol (NPG) are organic molecular crystals which have hydrogen-bonded lattices with layered- and chain-type structures, respectively. The PE undergoes solid-state phase transitions at 416K, from tetragonal to a cubic (γ’) structure and NPG also undergoes this transition at 317K from a monoclinic to a cubic (γ) structure. The phase transitions in binary PE-NPG solid solutions show more than one solid-solid transition in which the NPG-rich β transforms to γ at a constant temperature but the transition of the PE-rich a phase to γ’ passes through a two-phase field at a temperature that varies as a function of composition. Structural analyses by high-temperature x-ray diffractometry have revealed some new, interesting transitions. A phase diagram has been constructed for 0-30 mol% NPG in the PE-NPG system, using x-ray diffraction and differential scanning calorimetry results, and work is in progress to complete this diagram. The variation of lattice parameters as a function of temperature in the α, γ and γ’ phases for PE+20 mol% NPG are presented here, together with a discussion of phase transitions for certain compositions.
37
KRASNOV, K. V., N. M. CHALAYA, and V. S. OSIPCHIK. "Research of technological properties of mixed compositions based on polyolefin thermoplastic elastomers." Plasticheskie massy 1, no. 1-2 (March 30, 2022): 14–15. http://dx.doi.org/10.35164/0554-2901-2022-1-2-14-15.
Full textAbstract:
Technological properties – phase transitions of mixed compositions based on polyolefin thermoplastic elastomers have been studied. The melting point and glass transition temperature of compositions were determined by DSC and DMA methods. The influence of the type of elastomer on the melting and glass transition temperatures of a mixed composite material is revealed.
38
Marzoli, Andrea, Hervé Bertrand, Nasrrddine Youbi, Sara Callegaro, Renaud Merle, Laurie Reisberg, Massimo Chiaradia, et al. "The Central Atlantic Magmatic Province (CAMP) in Morocco." Journal of Petrology 60, no. 5 (April 19, 2019): 945–96. http://dx.doi.org/10.1093/petrology/egz021.
Full textAbstract:
Abstract The Central Atlantic Magmatic Province (CAMP) is a large igneous province (LIP) composed of basic dykes, sills, layered intrusions and lava flows emplaced before Pangea break-up and currently distributed on the four continents surrounding the Atlantic Ocean. One of the oldest, best preserved and most complete sub-provinces of the CAMP is located in Morocco. Geochemical, geochronologic, petrographic and magnetostratigraphic data obtained in previous studies allowed identification of four strato-chemical magmatic units, i.e. the Lower, Intermediate, Upper and Recurrent units. For this study, we completed a detailed sampling of the CAMP in Morocco, from the Anti Atlas in the south to the Meseta in the north. We provide a complete mineralogical, petrologic (major and trace elements on whole-rocks and minerals), geochronologic (40Ar/39Ar and U–Pb ages) and geochemical set of data (including Sr–Nd–Pb–Os isotope systematics) for basaltic and basaltic–andesitic lava flow piles and for their presumed feeder dykes and sills. Combined with field observations, these data suggest a very rapid (<0·3 Ma) emplacement of over 95% of the preserved magmatic rocks. In particular, new and previously published data for the Lower to Upper unit samples yielded indistinguishable 40Ar/39Ar (mean age = 201·2 ± 0·8 Ma) and U–Pb ages (201·57 ± 0·04 Ma), suggesting emplacement coincident with the main phase of the end-Triassic biotic turnover (c.201·5 to 201·3 Ma). Eruptions are suggested to have been pulsed with rates in excess of 10 km3/year during five main volcanic pulses, each pulse possibly lasting only a few centuries. Such high eruption rates reinforce the likelihood that CAMP magmatism triggered the end-Triassic climate change and mass extinction. Only the Recurrent unit may have been younger but by no more than 1 Ma. Whole-rock and mineral geochemistry constrain the petrogenesis of the CAMP basalts. The Moroccan magmas evolved in mid-crustal reservoirs (7–20 km deep) where most of the differentiation occurred. However, a previous stage of crystallization probably occurred at even greater depths. The four units cannot be linked by closed-system fractional crystallization processes, but require distinct parental magmas and/or distinct crustal assimilation processes. EC-AFC modeling shows that limited crustal assimilation (maximum c.5–8% assimilation of e.g. Eburnean or Pan-African granites) could explain some, but not all the observed geochemical variations. Intermediate unit magmas are apparently the most contaminated and may have been derived from parental magmas similar to the Upper basalts (as attested by indistinguishable trace element contents in the augites analysed for these units). Chemical differences between Central High Atlas and Middle Atlas samples in the Intermediate unit could be explained by distinct crustal contaminants (lower crustal rocks or Pan-African granites for the former and Eburnean granites for the latter). The CAMP units in Morocco are likely derived from 5–10% melting of enriched peridotite sources. The differences observed in REE ratios for the four units are attributed to variations in both source mineralogy and melting degree. In particular, the Lower basalts require a garnet peridotite source, while the Upper basalts were probably formed from a shallower melting region straddling the garnet–spinel transition. Recurrent basalts instead are relatively shallow-level melts generated mainly from spinel peridotites. Sr–Nd–Pb–Os isotopic ratios in the CAMP units from Morocco are similar to those of other CAMP sub-provinces and suggest a significant enrichment of the mantle-source regions by subducted crustal components. The enriched signature is attributed to involvement of about 5–10% recycled crustal materials introduced into an ambient depleted or PREMA-type mantle, while involvement of mantle-plume components like those sampled by present-day Central Atlantic Ocean Island Basalts (OIB, e.g. Cape Verde and Canary Islands) is not supported by the observed compositions. Only Recurrent basalts may possibly reflect a Central Atlantic plume-like signature similar to the Common or FOZO components.
39
Whittle, Thomas A., Teng Lu, Peter Blanchard, James R. Hester, Qinfen Gu, Yun Liu, and Siegbert Schmid. "Synthesis, structure and dielectric properties of the Sr3Ti1−xZrxNb4O15, (0 ≤ x ≤ 1), series of tungsten bronze type compounds." CrystEngComm 22, no. 30 (2020): 4994–5001. http://dx.doi.org/10.1039/d0ce00425a.
Full text
40
Bogina, Maria, Boris Belyatsky, Evgenii Sharkov, Alexey Chistyakov, and Robert Krymsky. "Origin of the Middle Paleoproterozoic Tiksheozero Ultramafic-Alkaline-Carbonatite Complex, NE Fennoscandian Shield: Evidence from Geochemical and Isotope Sr-Nd-Hf-Pb-Os Data." Minerals 11, no. 6 (May 27, 2021): 570. http://dx.doi.org/10.3390/min11060570.
Full textAbstract:
This article reports new geochemical, Sr-Nd-Hf-Pb and Re-Os data on the rocks of the Middle Paleoproterozoic (1.99 Ga) Tiksheozero ultramafic-alkaline-carbonatite complex confined to the northeastern margin of the Karelian Craton. We focus on the poorly studied silicate rocks. Based on petrographic and geochemical research, the silicate rocks are subdivided into two groups: an ultramafic-mafic series depleted in REE, and other incompatible elements and an alkaline series enriched in these elements. Isotope studies showed that all rocks have juvenile isotope signatures and were likely derived from a primitive OIB-type mantle source with possible contributions of the subcontinental lithospheric mantle (SCLM). Insignificant crustal contamination is recorded by Pb and Os isotopic compositions. The incompatible element enrichment in the alkaline rocks and depletion in ultramafic-mafic rocks of the mildly alkaline series with allowance for insignificant crustal contamination confirm their derivation from different primary melts. However, a narrow range of Sr, Nd, Hf, and Pb isotope compositions and compact clusters in 207Pb/204Pb-206Pb/204Pb, Nd-87Sr/86Sr and Hf-Nd isotope diagrams indicate their origination from a common mantle source. A model of subsequent two-stage melting is being most consistent with the geochemical data for this complex.
41
Mikhailov, A. V., and K. Schlegel. "Equinoctial transitions in the ionosphere and thermosphere." Annales Geophysicae 19, no. 7 (July 31, 2001): 783–96. http://dx.doi.org/10.5194/angeo-19-783-2001.
Full textAbstract:
Abstract. Equinoctial summer/winter transitions in the parameters of the F2-region are analyzed using ground-based ionosonde and incoherent scatter observations. Average transition from one type of diurnal NmF2 variation to another takes 20–25 days, but cases of very fast (6–10 days) transitions are observed as well. Strong day-time NmF2 deviations of both signs from the monthly median, not related to geomagnetic activity, are revealed for the transition periods. Both longitudinal and latitudinal variations take place for the amplitude of such quiet time NmF2 deviations. The summer-type diurnal NmF2 variation during the transition period is characterized by decreased atomic oxygen concentration [O] and a small equatorward thermospheric wind compared to winter-type days with strong poleward wind and increased [O]. Molecular N2 and O2 concentrations remain practically unchanged in such day-to-day transitions. The main cause of the F2-layer variations during the transition periods is the change of atomic oxygen abundance in the thermosphere related to changes of global thermospheric circulation. A possible relationship with an equinoctial transition of atomic oxygen at the E-region heights is discussed.Key words. Atmospheric composition and structure (thermosphere – composition and chemistry) – Ionosphere (ionosphere- atmosphere interactions; ionospheric disturbances)
42
Kaneno, Yasuyuki, Itsuko Nakaaki, and Takayuki Takasugi. "Cold rolling and recrystallization textures in L12-type Co3Ti ordered alloys." Journal of Materials Research 17, no. 10 (October 2002): 2567–77. http://dx.doi.org/10.1557/jmr.2002.0373.
Full textAbstract:
The texture development during cold rolling and recrystallization of L12-type Co3Ti alloys was investigated as functions of alloy composition and rolling reduction. Two kinds of fully annealed Co3Ti alloys with different alloy compositions (Co77Ti23 and Co78Ti22), whose initial textures and grain sizes were almost identical, were used. After 70% reduction, the cold-rolling textures of both alloys were composed of strong α-fiber and weak β-fiber textures, in which the intensity of {011}〈211〉 orientation was higher than those of {112}〈111〉 and {123}〈634〉 orientations, indicating that texture transition from copper type to brass type occurred in cold-rolled Co3Ti alloys. This texture transition was more prominently recognized in the Co78Ti22 alloy, whose chemical composition was more off-stoichiometric. On the other hand, the recrystallization textures of both alloys were considerably weak, and their orientation spreads were more significant with increasing rolling reduction. Also, the recrystallization textures were basically independent of alloy composition in contrast to the rolling textures.
43
DANELIAN, TANIEL, and ALASTAIR H. F. ROBERTSON. "Neotethyan evolution of eastern Greece (Pagondas Mélange, Evia island) inferred from radiolarian biostratigraphy and the geochemistry of associated extrusive rocks." Geological Magazine 138, no. 3 (May 2001): 345–63. http://dx.doi.org/10.1017/s0016756801005337.
Full textAbstract:
This paper presents new radiolarian biostratigraphic and igneous/metamorphic geochemical data for a Mesozoic volcanic–sedimentary mélange on the island of Evia (Euboea or Evvoia), eastern Greece. This mélange includes dismembered thrust sheets and blocks of radiolarian chert and basalt. Biostratigraphic age data show that radiolarites interbedded with basalt-derived, coarse clastic sediments near the base of a coherent succession were deposited in Middle and Late Triassic time (Late Ladinian–Carnian, Norian?). Geochemical evidence shows that associated extrusive rocks, of inferred Triassic age, range from ‘enriched’ alkaline basalts, to ‘transitional’ basalts, and more ‘depleted’ mid-ocean ridge-type basalts. Amphibolite facies meta-basalts from the metamorphic sole of the over-riding Evia ophiolite exhibit similar chemical compositions. Both the basalts and the meta-basalts commonly show an apparent subduction-related influence (e.g. relative Nb depletion) that may have been inherited from a previous subduction event in the region. The basalts are interpreted to have erupted during Middle–Late Triassic time (Late Ladinian–Carnian), related to initial opening of a Neotethyan ocean basin adjacent to a rifted continental margin. Radiolarites located stratigraphically higher in the coherent succession studied are dated as Middle Jurassic (Late Bathonian–Early Callovian). Similar-aged radiolarites are depositionally associated with ophiolitic rocks (including boninites), in some other areas of Greece and Albania. During initial ocean basin closure (Bajocian–Bathonian) the adjacent shallow-water carbonate platform (Pelagonian zone) disintegrated to form basins in which siliceous sediments were deposited and highs on which shallow-water carbonates continued to accumulate. This facies differentiation is seen as a response to crustal flexure as the Neotethyan ocean began to close. The over-riding Pagondas Mélange and other similar units in the region are interpreted as accretionary prisms related to subduction of Neotethyan oceanic crust in Middle–Late Jurassic time. These mélanges were emplaced, probably diachronously during Oxfordian–Kimmeridgian time, when the passive margin collapsed, creating a foredeep ahead of advancing thrust sheets of mélange and ophiolites.
44
Fei, Xianghui, Zhaochong Zhang, Zhiguo Cheng, and M. Santosh. "Factors controlling the crystal morphology and chemistry of garnet in skarn deposits: A case study from the Cuihongshan polymetallic deposit, Lesser Xing'an Range, NE China." American Mineralogist 104, no. 10 (October 1, 2019): 1455–68. http://dx.doi.org/10.2138/am-2019-6968.
Full textAbstract:
Abstract The grossular-andradite solid solutions in garnet from skarn deposits in relation to hydrothermal processes and physicochemical conditions of ore formation remain controversial. Here we investigate garnet occurring in association with calcic and magnesian skarn rocks in the Cuihongshan polymetallic skarn deposit of NE China. The calcic skarn rocks contain three types of garnets. (1) Prograde type I Al-rich anisotropic garnets display polysynthetic twinning and a compositional range of Grs18–80Adr10–75. This type of garnet shows markedly low rare earth element (REE) contents (3.27–78.26 ppm) and is strongly depleted in light rare earth elements (LREE, 0.57–44.65 ppm) relative to heavy rare earth elements (HREE, 2.31–59.19 ppm). They also display a significantly negative Eu anomaly (Eu/Eu* of 0.03–0.90). (2) Fe-rich retrograde type II garnets are anisotropic with oscillatory zoning and own wide compositional variations (Grs1–47Adr30–95) with flat REE (13.73–377.08 ppm) patterns. (3) Fe-rich retrograde type III isotropic garnets display oscillatory zoning and morphological transition from planar dodecahedral {110} crystal faces to {211} crystal faces in the margin. Types III garnets exhibit relatively narrow compositional variations of Grs0.1–12Adr85–97 with LREE-enrichment (0.80–51.87 ppm), flat HREE patterns (0.15–2.46 ppm) and strong positive Eu anomalies (Eu/Eu* of 0.93–27.07 with almost all >1). The magnesian skarn rocks contain euhedral isotropic type IV Mn-rich garnet veins with a composition of Grs10–23Sps48–62Alm14–29. All calcic garnets contain considerable Sn and W contents. Type II garnet containing intermediate compositions of andradite and grossular shows the highest Sn contents (64.36–2778.92 ppm), albeit the lowest W range (1.11–468.44 ppm). Birefringence of garnet is probably caused by strain from lattice mismatch at a twinning boundary or ion substitution near intermediate compositions of grossular-andradite. The fine-scale, sharp, and straight garnet zones are probably caused by self-organization, but the compositional variations of zones from core to rim are probably caused by external factors. The zoning is likely driven by external factors such as composition of the hydrothermal fluid. REE concentrations are probably influenced by the relative proportion and temperature of the system. Moreover, the LREE-HREE fractionation of garnet can be attributed to relative compositions of grossular-andradite system. The W and Sn concentrations in garnet can be used as indicators for the exploration of W-Sn skarn deposits.
45
Whittle, Thomas A., and Siegbert Schmid. "Structural investigation of tungsten bronze-type relaxor ferroelectrics in the BaxSr3−xTiNb4O15 system." Powder Diffraction 29, S1 (November 10, 2014): S15—S18. http://dx.doi.org/10.1017/s0885715614000980.
Full textAbstract:
Compounds in the BaxSr3−xTiNb4O15 series with x = 0.0–3.0 were synthesised. Synchrotron X-ray diffraction data were collected for each member synthesised. Rietveld refinements were performed for all compositions. A composition-dependent phase transition between orthorhombic and tetragonal symmetries was found. Cation ordering was observed between barium and strontium atoms in the two distinct A site cavities
46
Pingitore, N. E., B. F. Ponce, L. Estrada, M. P. Eastman, H. L. Yuan, L. C. Porter, and G. Estrada. "Calorimetric analysis of the system Ag2S–Ag2Se between 25 and 250 °C." Journal of Materials Research 8, no. 12 (December 1993): 3126–30. http://dx.doi.org/10.1557/jmr.1993.3126.
Full textAbstract:
Differential scanning calorimetry (DSC) demonstrates that compounds in the pseudobinary system Ag2S–Ag2Se undergo rapid, reversible solid-state phase changes at temperatures between approximately 70 and 178 °C. These temperatures vary systematically with composition, with highs at the pure end members, Ag2S (178 °C) and Ag2Se (134 °C), and a low in the compositional range of approximately Ag2S0.4Se0.6 to Ag2S0.3Se0.7 (70 °C). These data are consistent with the presence of two solid solutions in this system at ambient conditions: the Ag2S–III-type, monoclinic, ranging to approximately Ag2S0.4Se0.6 and the Ag2Se-II-type, orthorhombic, extending from Ag2Se to Ag2S0.3Se0.7. Entropies of transition of 6 to 9 e.u. characterize compositions within the Ag2S-III-type solid solution, whereas values of 13 to 16 e.u. mark members of the Ag2Se-II-type solid solution. The high-temperature allotrope is presumably a continuous solid solution between Ag2S-II and Ag2Se-I, which have similar body-centered cubic structures.
47
Lei, Ming, Zhengfu Guo, Wenbin Zhao, Maoliang Zhang, and Lin Ma. "Coexisting Late Cenozoic Potassic and Sodic Basalts in NE China: Role of Recycled Oceanic Components in Intraplate Magmatism and Mantle Heterogeneity." Lithosphere 2020, no. 1 (September 1, 2020): 1–28. http://dx.doi.org/10.2113/2020/8875012.
Full textAbstract:
Abstract This study presents an integrated geochemical study of the Wudalianchi-Erkeshan potassic basalts and Halaha sodic basalts of NE China, and uses these data to further our understanding of the petrogenetic relationships between the coeval potassic and sodic basalts in this region. The potassic basalts with high concentrations of K2O have arc-like trace-element compositions and enriched Sr-Nd-Hf isotopic compositions with unradiogenic 206Pb/204Pb values (16.77–16.90). In contrast, the sodic basalts with high concentrations of Na2O have OIB-like trace-element compositions and depleted Sr-Nd-Hf isotopic compositions with radiogenic 206Pb/204Pb values (18.27–18.40). These data suggest that the potassic and sodic basalts were derived from mixed depleted mid-ocean-ridge basalt mantle (DMM) and enriched mantle source end-members, where the enriched end-members are ancient sediment for the potassic basalts and Pacific oceanic crust for the sodic basalts. The combined geophysical and geochemical data indicate that these two enriched end-members are located in the mantle transition zone. We propose that partial melting of upwelling asthenospheric mantle comprising ambient DMM and recycled materials shifting from the ancient sediment to the Pacific oceanic crust could have produced the coeval potassic and sodic basalts in NE China. The proposed mantle sources for the potassic and sodic basalts indicate that the upper mantle beneath NE China was highly heterogeneous during late Cenozoic.
48
Yeo, Chang Hyun. "The Characteristics and Changes of the Builders of the Ancient Tombs in Samga, Hapcheon, between the 4th and 6th Centuries, as seen from Funerary Artifacts." Yeongnam Archaeological Society, no. 87 (May 30, 2020): 109–49. http://dx.doi.org/10.47417/yar.2020.87.109.
Full textAbstract:
The ancient tombs in Samga, Hapcheon, are proof of an ancient unglazed stoneware culture that follows the production and distribution systems of the inland Haman style. The stoneware excavated from Samga’s ancient tombs share similar compositions and change patterns with Haman-style stoneware. Tombs built after the early 4th century’s type I-1 separate-pit wooden chamber tombs were strikingly different from the previous tombs of Samhan Period in terms of size and the artifacts buried therein. The type I-1 wooden chamber tombs belonged to the local rulers of the Samga area in Hapcheon. This discovery suggests the emergence of a small state in the area, away from the center of Byeonhan and Jinhan, and a glimpse of the social and economic background of the builders of the Samga’s ancient tombs of that period. The early 5th century saw a temporary emergence of similar stoneware types across the Yeongnam region. The ancient tombs in Samga also held a type of stoneware culture centered on mounted cups that characterized the transitional period until the establishment of the post-Gaya stoneware style. Before the establishment of the post-Gaya stoneware style in the early 5th century, the ancient tombs in Samga already featured large wooden chamber tombs with crushed stones covering their entire lengths. The overwhelming size of the chamber and the quality of the funerary artifacts indicate that the tombs belonged to the highest rulers of western Gyeongsangnam-do as well as Samga area. The emergence of the builders of the ancient tombs in Samga in the late 5th century represents the establishment of the stratified central-tomb-peripheral-tomb system and the emergence of multi-chamber tombs in the Sogaya region. Specifically, the same assemblage and stylistic changes centered on stoneware styles appeared, with the establishment of a weaponry system focused on iron helmets and war swords. The artifacts from gigantic multichamber tombs built on hills in this period confirm the introduction and spread of foreign culture. These artifacts also show the pattern of exchange among Gaya factions in the area and their expansion. The cultures of Aragaya and, in particular, Daegaya began in the early 6th century, as can be seen from the tombs of local rulers. However, the style of the tombs implies that the multi-chamber tombs built with methods unique to the area continued until the first half of the 6th century. The funerary artifacts found in the M-2, 3, and 4 tombs in Zone I—which include iron-plate ritual utensils with bird decorations, round-pommel swords with three-leaf patterns, and horse harnesses—show that the ancient tombs in Samga are the central tombs of Sogaya, which is further supported by the internal and external capabilities of the area.
49
Giri, Rohit Kumar, Praveer Pankaj, N. V. Chalapathi Rao, Ramananda Chakrabarti, and Dinesh Pandit. "Petrogenesis of an alkaline lamprophyre (camptonite) with ocean island basalt (OIB)-affinity at the NW margin of the Cuddapah basin, eastern Dharwar craton, southern India." Neues Jahrbuch für Mineralogie - Abhandlungen Journal of Mineralogy and Geochemistry 196, no. 2 (November 1, 2019): 149–77. http://dx.doi.org/10.1127/njma/2019/0179.
Full textAbstract:
We report petrology and geochemistry (including Sr and Nd isotopes) of a fresh lamprophyre at Ankiraopalli area at the north-western margin of Paleo-Mesoproterozoic Cuddapah basin, eastern Dharwar craton, southern India. Ankiraopalli samples possess a typical lamprophyre porphyritic-panidiomorphic texture with phenocrysts of kaersutite and diopside set in a plagioclase dominant groundmass. Combined mineralogy and geochemistry classify it as alkaline lampro- phyre in general and camptonite in particular. Contrary to the calc-alkaline and/or shoshonitic orogenic nature portrayed by lamprophyres occurring towards the western margin of the Cuddapah basin, the Ankiraopalli samples display trace element composition revealing striking similarity with those of ocean island basalts, Italian alkaline lamprophyres and highlights an anorogenic character. However, the87 Sr/86 Srinitial (0.710316 to 0.720016) and εNdinitial (– 9.54 to – 9.61) of the Ankiraopalli lamprophyre show derivation from an 'enriched' mantle source showing long term enrichment of incompatible trace elements and contrast from those of (i) OIB, and (ii) nearby Mahbubnagar alkaline mafic dykes of OIB affinity. Combining results of this study and recent advances made, multiple mantle domains are identified in the Eastern Dharwar craton which generated distinct Mesoproterozoic lamprophyre varieties. These include (i) Domain I, involving sub-continental lithospheric mantle source essentially metasomatized by subduction-derived melts/fluids (represented by orogenic calcalkaline and/or shoshonitic lamprophyres at the Mudigubba, the Udiripikonda and the Kadiri); (ii) Domain II, comprising a mixed sub-continental lithospheric and asthenospheric source (represented by orogenic-anorogenic, alkaline to calc-alkaline transitional lamprophyres at the Korakkodu), and (iii) Domain III, representing a sub-continental lithospheric source with a dominant overprint of an asthenospheric (plume) component (represented by essentially alkaline lamprophyres at the Ankiraopalli). Our study highlights the varied mantle source heterogeneities and complexity of geodynamic processes involved in the Neoarchean-Paleo/Mesoproterozoic evolution of the Eastern Dharwar craton.
50
LAPIERRE, H., D. BOSCH, A. NARROS, G. H. MASCLE, M. TARDY, and A. DEMANT. "The Mamonia Complex (SW Cyprus) revisited: remnant of Late Triassic intra-oceanic volcanism along the Tethyan southwestern passive margin." Geological Magazine 144, no. 1 (December 21, 2006): 1–19. http://dx.doi.org/10.1017/s0016756806002937.
Full textAbstract:
Upper Triassic volcanic and sedimentary rocks of the Mamonia Complex in southwestern Cyprus are exposed in erosional windows through the post-Cretaceous cover, where the Mamonia Complex is tectonically imbricated with the Troodos and Akamas ophiolitic suites. Most of these Upper Triassic volcanic rocks have been considered to represent remnants of Triassic oceanic crust and its associated seamounts. New Nd and Pb isotopic data show that the whole Mamonia volcanic suite exhibits features of oceanic island basalts (OIB). Four rock types have been distinguished on the basis of the petrology and chemistry of the rocks. Volcanism began with the eruption of depleted olivine tholeiites (Type 1) and oceanic island tholeiites (Type 2) associated with deep basin siliceous and/or calcareous sediments. The tholeiites were followed by highly phyric alkali basalts (Type 3) interbedded with pelagic Halobia-bearing limestones or white reefal limestones. Strongly LREE-enriched trachytes (Type 4) were emplaced during the final stage of volcanic activity. Nd and Pb isotopic ratios suggest that tholeiites and mildly alkali basalts derived from partial melting of heterogeneous enriched mantle sources. Fractional crystallization alone cannot account for the derivation of trachytes from alkaline basalts. The trachytes could have been derived from the partial melting at depth of mafic material which shares with the alkali basalts similar trace element and isotopic compositions. This is corroborated by the rather similar isotopic compositions of the alkali basalts and trachytes. The correlations observed between incompatible elements (Nb, Th) and εNd and Pb isotopic initial ratios suggest that the Mamonia suite was derived from the mixing of a depleted mantle (DMM) and an enriched component of High μ (μ = 238U/204Pb, HIMU) type. Models using both Nd and Pb isotopic initial ratios suggest that the depleted tholeiites (Type 1) derived from a DMM source contaminated by an Enriched Mantle Type 2 component (EM2), and that the oceanic tholeiites (Type 2), alkali basalts (Type 3) and trachytes (Type 4) were derived from the mixing of the enriched mantle source of the depleted tholeiites with a HIMU component. None of the Mamonia volcanic rocks show evidence of crustal contamination. The Upper Triassic within-plate volcanism likely erupted in a small southerly Neotethyan basin, located north of the Eratosthenes seamount and likely floored by oceanic crust.