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Articles de revues sur le sujet "Calc-alkaline magmatism"
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Hernandez, Jean, Francois Dominique de Larouziere, Jean Bolze et Pierre Bordet. « Le magmatisme neogene betico-rifain et le couloir de decrochement trans-Alboran ». Bulletin de la Société Géologique de France III, no 2 (1 mars 1987) : 257–67. http://dx.doi.org/10.2113/gssgfbull.iii.2.257.
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Abstract The Miocene basin evolution of southeastern Spain and eastern Morocco is linked to a "shear zone" elongated from SW across the Alboran Sea. In Spain the magmatism is mostly calc-alkaline (or K-rich calc-alkaline). Most of the products are locatred on strike-slip faults (Almeria-Cabo de Gata). Lavas of dacitic compositions are interpreted as products of crustal anatexis. During Messinian time, lamproites are erupted over an extended area. Later (Plio-Quaternary), alkali basalts are located near Cartagena. In Morocco, calc-alkaline magmatism is not as developed as in Spain; late Tortonian-Messinian volcanoes (Gourougou, Guilliz) have erupted of shoshonitic lavas. Alkali basalts are abundant and appear from the end of Messinian to Quaternary all over northwestern Africa. In the studied area, there are no chronological nor geochemical polarity of the magmatism according to the existence of a Miocene subduction. The association of the magmatism with tectonics and basin evolution shows that it is linked with their aperture. The structure of the lithosphere, as it appears from the geophysical data, shows the existence of two different crusts, separated by the western part of the "shear zone". Trans-Alboran calc-alkaline magmatism is clearly correlated with the activity of this "shear zone", from Miocene to present time.
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Homonnay, Emmanuelle, Jean-Marc Lardeaux, Michel Corsini, Asmae El Bakili, Delphine Bosch, Olivier Bruguier et Mohamed Ouazzani-Touhami. « Arc-related high-K magmatism in the Ceuta Peninsula (Internal Rif, Spain) : discovery and consequences ». Geological Magazine 156, no 08 (30 octobre 2018) : 1385–99. http://dx.doi.org/10.1017/s0016756818000717.
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AbstractWe document the occurrence of micro-diorite magmatic sills, with magmatic enclaves, in the Ceuta Peninsula within metapelites from the Lower Sebtides units (Internal Rif). All magmatic rocks show a primary magmatic mineralogy and geochemical signature diagnostic for high-K calc-alkaline to shoshonitic island arc magmatism. Moreover, these rocks are significantly affected by secondary metamorphic transformations under greenschist- to amphibolite-facies conditions, regionally dated atc. 21 Ma. Geometric relationships between the sills and the main regional foliation, developed under intermediate-pressure granulite-facies conditions atc. 28 Ma, demonstrate that the sills emplaced during the late stage of this main tectonic event. New U–Pbin situanalyses of monazite performed on the micro-diorite sills provide an age of 20.64 ± 0.19 Ma, coherent with this chronological framework and interpreted as the age of greenschist-facies re-equilibration. The discovery of pre-Miocene high-K calc-alkaline to shoshonitic arc-related magmatism is clearly consistent with the subduction context proposed for the Alboran Basin evolution, according to geophysical investigations. In this framework, the Lower Sebtides units could be considered as part of the upper plate of the subduction system, while the Upper Sebtides must be regarded as the lower subducted plate.
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Goulart, Luís Emanoel Alexandre, et Mauricio Antonio Carneiro. « Evolution of arc magmatism in the Carmópolis de Minas Layered Suite, Minas Gerais, Brazil : Sm-Nd and Rb-Sr isotope geochemistry ». Rem : Revista Escola de Minas 66, no 4 (décembre 2013) : 447–54. http://dx.doi.org/10.1590/s0370-44672013000400007.
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The Carmópolis de Minas Layered Suite (CMLS) is a Neoarchean Unit metamorphosed at amphibolite- to granulite-facies conditions, comprised of metaultramafic rocks, amphibolites and metarhyolites. The CMLS is marked by two distinct phases of tholeiitic and calc-alkaline magmatism. Previous geochemical data and regional constraints suggest that the CMLS is possibly a metamorphosed arc-tholeiitic suite of the type boninite-basalt-andesite-rhyolite, interpreted in this study as a dismembered remnant of the juvenile oceanic arc. The rocks of tholeiitic affinity record a signature of depleted to enriched mantle with positive to weakly negative εNd(t) and predominantly positive εSr(t) values, indicating some degree of crustal assimilation. The rocks of calc-alkaline affinity present a signature of juvenile crust with εNd(t) close to the CHUR and weakly positive εSr(t) values. The Sm-Nd isochron age of 2736 ± 300 Ma obtained with εNd(i) = +0.4, suggests the edification of an intra-oceanic arc during the late phases of the Rio das Velhas Tectonothermal Event. The arc evolution involved tholeiitic magmatism in the early stages in association with calc-alkaline magmatism, of probably anatectic character, in the tardy-orogenic stages.
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Widana, Kurnia Setiawan, et Bambang Priadi. « Karakteristik Unsur Jejak Dalam Diskriminasi Magmatisme Granitoid Pulau Bangka ». EKSPLORIUM 36, no 1 (30 mai 2015) : 1. http://dx.doi.org/10.17146/eksplorium.2015.36.1.2766.
Texte intégralRésumé :
Geologi Pulau Bangka disusun oleh variasi granit sebagai Granitoid Klabat yang tersebar di berbagai lokasi. Unsur jejak dapat diaplikasikan dalam diskriminasi magmatisme dalam pembentukan granitoid tersebut. Tujuan penelitian ini adalah mengetahui karakteristik granitoid yang tersebar di Pulau Bangka berdasarkan geokimia unsur jejak untuk diaplikasikan dalam mempelajari magmatisme, sumber dan situasi tektoniknya.Metode analisis geokimia yang diaplikasikan dengan menggunakan Analisis Aktivasi Neutron (AAN) dan portableX-Ray Fluorescence (pXRF) untuk analisis kualitatif dan kuantitatif pada 27 sampel dari Granitoid Klabat di Pulau Bangka.Hasil penelitian ini menyimpulkan Granitoid Bangka Utara (Belinyu) dan Bangka Tengah sebagai percampuran kerak-mantel dengan afinitas Calc-Alkaline, karakteristik Tipe I sedangkan Granitoid Bangka Selatan dan Barat asal kerak dengan afinitas High-KCalc-Alkaline sebagai Tipe S. Diharapkan diskrimasi magmatisme granitoid bermanfaat dalam memberikan panduan eksplorasi bahan galian nuklir di Pulau Bangka. Geology of Bangka Island consists by variation of granite as Klabat Granitoid scattered in various locations. Trace elements can be applied in magmatism discrimination of granitoid.The purpose of this study was to determine the characteristics Bangka Island granitoid based on trace element geochemistry to be applied in the study of magmatism, source and tectonic situation. Geochemical analyses method used are the Neutron Activation Analysis (NAA) and portableX-Ray Fluorescence (pXRF) for qualitative and quantitative analyses on 27 samples of Klabat granitoid on Bangka Island. This study concluded granitoid East Bangka (Belinyu) and Central Bangka as crust-mantle mixing with affinityCalc-Alkaline, characteristic of I Type while South and West Bangka granitoid crust origin with affinity high K Calc-Alkaline as S Type. Expectedmagmatismdiscrimination ofgranitoidhelpfulin providingradioactive mineral explorationguidein BangkaIsland.
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Cambeses, Aitor, José F. Molina, Irene Morales, Concepción Lázaro, Juan A. Moreno, Pilar Montero et Fernando Bea. « Compositional Evolution of the Variscan Intra-Orogenic Extensional Magmatism in the Valencia del Ventoso Plutonic Complex, Ossa-Morena Zone (SW Iberia) : A View from Amphibole Compositional Relationships ». Minerals 11, no 4 (18 avril 2021) : 431. http://dx.doi.org/10.3390/min11040431.
Texte intégralRésumé :
The Ossa-Morena Zone (OMZ), SW Iberia, has numerous Lower Carboniferous compositionally zoned plutons that formed in a Variscan intra-orogenic extensional setting. This magmatism shows a wide compositional variation comprising alkaline, transitional, and calc-alkaline suites. The calc-alkaline suite was produced by hybridization of alkaline magmas with felsic melts generated by crustal anatexis related to the intrusion of mafic magmas in the middle crust. In this work, we present a textural and mineralogical study of the Variscan Valencia del Ventoso main pluton from the OMZ to track the compositional evolution of magmas during hybridization using constraints from amphibole compositions and to determine the P-T conditions of emplacement using amphibole-based thermobarometry. This pluton exhibits reverse zoning with an inner facies containing alkaline dolerites, gabbros, and quartz diorites, an intermediate facies with transitional diorites, and an outer facies with calc-alkaline quartz diorites to monzogranites. Magmas from the intermediate and border facies crystallized under oxidizing conditions at relatively low temperatures (range: 640–760 °C) and ca. 280–300 MPa, implying near H2O-saturated conditions. These rock facies show mineralogical evidence of hybridization between alkaline to mildly alkalic and calc-alkaline magmas. The former is inferred from the occurrence of antecrysts of labradorite-andesine, high-Ti pargasite-hastingsite, and biotite with deficiency in tetrahedral-site occupancy, a distinctive feature of biotite from the inner facies alkaline dolerites. This contrasts with later crystallization from the calc-alkaline magma of andesine-oligoclase, low-Ti magnesiohornblende-edenite, and biotite with full tetrahedral-site occupancy. Constraints from amphibole-melt compositional relationships in antecrystic high-Ti amphibole suggest that the alkaline magmatic component could have a high- to ultra-K affinity.
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İLBEYLİ, N. « Mineralogical–geochemical constraints on intrusives in central Anatolia, Turkey : tectono-magmatic evolution and characteristics of mantle source ». Geological Magazine 142, no 2 (mars 2005) : 187–207. http://dx.doi.org/10.1017/s0016756805000476.
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Collision-related rocks intrude metamorphic rocks overthrust by ophiolitic units to make up the Central Anatolian Crystalline Complex. A wide variety of rock types were produced by the latest Cretaceous magmatism in the complex. These rocks can be divided into three distinct units: (1) calc-alkaline (Ağaçören, Behrekdağ, Cefalıkdağ, Çelebi, Ekecikdağ, Halaçlı, Karamadazı, Kösefakılı, Terlemez, Üçkapılı, Yozgat); (2) sub-alkaline (Baranadağ); and (3) alkaline (Atdere, Davulalan, Eğrialan, Hamit, İdişdağı, Karaçayır). The calc-alkaline rocks are metaluminous/peraluminous I- to S-type plutons ranging from monzodiorite to granite. The sub-alkaline rocks are metaluminous I-type plutons ranging from monzonite to granite. The alkaline rocks are metaluminous to peralkaline plutons, predominantly A-type, ranging from foid-bearing monzosyenite to granite. These plutons crystallized under varying pressures (5.3–2.6 kbar) and a wide range of temperatures (858–698 °C) from highly oxidized magmas (log fO2 −17 to −12). All intrusive rocks display enrichment in LILE and LREE compare to HFSE and have high 87Sr/86Sr and low 143Nd/144Nd ratios. These characteristics indicate that these rocks are derived from a mantle source containing large subduction components, and have experienced assimilation coupled with fractional crystallization (AFC) during uprise through crust. The coexistence of calc-alkaline and alkaline magmatism in the complex may be ascribed to mantle source heterogeneity before collision. Either thermal perturbation of the metasomatized lithosphere by delamination of the thermal boundary layer or removal of a subducted plate (slab breakoff) are the likely mechanisms for the initiation of the collision-related magmatism in the complex.
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Aarons, Sarah M., Jesse R. Reimink, Nicolas D. Greber, Andy W. Heard, Zhe Zhang et Nicolas Dauphas. « Titanium isotopes constrain a magmatic transition at the Hadean-Archean boundary in the Acasta Gneiss Complex ». Science Advances 6, no 50 (décembre 2020) : eabc9959. http://dx.doi.org/10.1126/sciadv.abc9959.
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Plate subduction greatly influences the physical and chemical characteristics of Earth’s surface and deep interior, yet the timing of its initiation is debated because of the paucity of exposed rocks from Earth’s early history. We show that the titanium isotopic composition of orthogneisses from the Acasta Gneiss Complex spanning the Hadean to Eoarchean transition falls on two distinct magmatic differentiation trends. Hadean tonalitic gneisses show titanium isotopic compositions comparable to modern evolved tholeiitic magmas, formed by differentiation of dry parental magmas in plume settings. Younger Eoarchean granitoid gneisses have titanium isotopic compositions comparable to modern calc-alkaline magmas produced in convergent arcs. Our data therefore document a shift from tholeiitic- to calc-alkaline–style magmatism between 4.02 and 3.75 billion years (Ga) in the Slave craton.
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AGHAZADEH, MEHRAJ, ANTONIO CASTRO, ZAHRA BADRZADEH et KATHARINA VOGT. « Post-collisional polycyclic plutonism from the Zagros hinterland : the Shaivar Dagh plutonic complex, Alborz belt, Iran ». Geological Magazine 148, no 5-6 (24 juin 2011) : 980–1008. http://dx.doi.org/10.1017/s0016756811000380.
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AbstractThe petrological and geochronological study of the Cenozoic Shaivar Dagh composite intrusion in the Alborz Mountain belt (NW Iran) reveals important clues to decipher complex relations between magmatic and tectonic processes in the central sectors of the Tethyan (Alpine–Himalayan) orogenic belt. This pluton is formed by intrusion at different times of two main magmatic cycles. The older (Cycle 1) is formed by calc-alkaline silicic rocks, which range in composition from diorites to granodiorites and biotite granites, with abundant mafic microgranular enclaves. The younger cycle (Cycle 2) is formed by K-rich monzodiorite and monzonite of marked shoshonitic affinity. The latter form the larger volumes of the exposed plutonic rocks in the studied complex. Zircon geochronology (laser ablation ICP-MS analyses) gives a concordia age of 30.8 ± 2.1 Ma for the calc-alkaline rocks (Cycle 1) and a range from 23.3 ± 0.5 to 25.1 ± 0.9 Ma for the shoshonitic association (Cycle 2). Major and trace element relations strongly support distinct origins for each magmatic cycle. Rocks of Cycle 1 have all the characteristic features of active continental margins. Shoshonitic rocks (Cycle 2) define two continuous fractionation trends: one departing from a K-rich basaltic composition and the other from an intermediate, K-rich composition. A metasomatized-mantle origin for the two shoshonitic series of Cycle 2 is proposed on the basis of comparisons with experimental data. The origin of the calc-alkaline series is more controversial but it can be attributed to processes in the suprasubduction mantle wedge related to the incorporation of subducted mélanges in the form of silicic cold plumes. A time sequence can be established for the processes responsible of the generation of the two magmatic cycles: first a calc-alkaline cycle typical of active continental margins, and second a K-rich cycle formed by monzonites and monzodiorites. This sequence precludes the younger potassic magmas as precursors of the older calc-alkaline series. By contrast, the older calc-alkaline magmas may represent the metasomatic agents that modified the mantle wedge during the last stages of subduction and cooked a fertile mantle region for late potassic magmatism after continental collision.
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Petrov, G. A., N. I. Tristan, G. N. Borozdina et A. V. Maslov. « The final stage of the Acid Island Arc magmatism in the Northern Urals ». Доклады Академии наук 489, no 2 (20 novembre 2019) : 166–69. http://dx.doi.org/10.31857/s0869-56524892166-169.
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For the first time, the time of completion of the formation of calc-alkaline volcanic complexes of the Devonian Island Arc (Franian) in the Northern Urals was determined. It is shown that the late Devonian volcanic rocks of the Limka series have geochemical characteristics that bring them closer to the rocks of developed island arcs and active continental margins. The detected delay of the final episode of calc-alkaline volcanism in the Northern Urals in comparison with the similar event in the southern Urals may be due to the oblique nature of the subduction.
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Chandra, Rakesh, Rajeev Upadhyay et Anshu K. Sinha. « Subduction and collision related magmatism in the Shyok Suture and eastern Karakoram ». Journal of Palaeosciences 48, no (1-3) (31 décembre 1999) : 183–209. http://dx.doi.org/10.54991/jop.1999.1303.
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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.
Thèses sur le sujet "Calc-alkaline magmatism"
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Wyers, Gerard Paul. « Petrogenesis of calc-alkaline and alkaline magmas from the southern and eastern Aegean Sea, Greece / ». The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu148758688918709.
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D'ADDA, PAOLO. « Eo-alpine evolution of the central southern alps. Insights from structural analysis and new geochronological constraints ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2011. http://hdl.handle.net/10281/19018.
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The timing of the Alpine deformation in the Central Southern Alps (CSA or Orobic Alps) has always been a debated topic, since the scarcity of reliable absolute age constraints has prevented an accurate chronological reconstruction of the evolution of this sector of the European Alps.
In this work, detailed structural analyses performed in different areas of the CSA allowed us to distinguish different compressive features within both the crystalline basement and the sedimentary cover. The integration of these field data with new isotopic data provides time constraints for the reconstruction of the evolution of the CSA during the Alpine orogeny.
In the northern sector of the belt a Variscan polymetamorphic basement is stacked southward on the Permian to Mesozoic cover along two main regional faults (Orobic and Porcile thrusts). Fault zones, slightly postdating a first folding event of Alpine age (D3), experienced a complex evolution through the ductile and brittle deformation regime, showing greenschists facies mylonites overprinted by a penetrative cataclastic deformation (D4). Generation of fault-related pseudotachylytes marks the onset of brittle conditions, lasting up to the youngest episodes of fault activity.
Thrusting along this structures also produced thrusting within the Permian-Triassic cover with the formation of different south-verging thrust stacks. This first thrusting event was followed by the activation of new deeper thrust surfaces leading to the emplacement of three regional anticlines (Orobic Anticlines) which tilted to the south the previously stacked units. During this long compressive stage (Orobic-Porcile thrusts and Orobic Anticlines) the sedimentary cover of the CSA was also involved in thrusting and different stacks of Mesozoic units were emplaced to the south. 40Ar/39Ar dating of the pseudotachylyte matrix of 9 samples from both the Orobic and Porcile thrusts give two separated age clusters: Late Cretaceous (80-68 Ma) and Early to Middle Eocene (55-43 Ma). These new data provide evidence that the pre-Adamello evolution of the CSA was characterized by the superposition of different tectonic events accompanying the exhumation of the deepest part of the belt through the brittle-ductile transition. The oldest pseudotachylyte ages demonstrate that south-verging regional thrusting in the CSA was already active during the Late Cretaceous, concurrently with both the HP metamorphism that affected the Austroalpine units of the eastern Alps, and the development of a syn-orogenic foredeep basin where the Upper Cretaceous Lombardian Flysch was deposited.
In the Early to Middle Eocene a minor reactivation of the Orobic and Porcile thrusts occurred, as testified by the youngest pseudotachylyte ages obtained by 40Ar/39Ar dating. This event was probably related with the closure of the Ligurian-Piedmont and the ongoing of the Europe-Adria collision.
South of the Orobic Anticlines system the Triassic sedimentary succession is stacked into several units bounded by south-verging low-angle thrust faults, which are related to different steps of crustal shortening. Different thrust stacks occur within the Triassic cover between the Como Lake to the west and the Adamello batholith to the east. They usually have an antiformal arrangement and are separated by each other by different N-S trending transverse zones, such as the poorly known Grem-Vedra Transverse Zone (GVTZ), formed during complex deformational phenomena in a transpressional regime coeval with thrust emplacement. The GVTZ formed during the southward imbrication of the older thrust sheets of the Menna-Arera group, strongly interacting with syn-thrust ductile structures, and was reactivated during the growth of the Orobic Anticlines belt. The GVTZ and other transverse zones of the CSA probably reflect the occurrence of pre-existing fault systems that characterize the Norian to Jurassic rifting history of the Lombardian basin, and were reactivated as strike-slip features during Alpine tectonics.
In the Gandino and Presolana areas thrust surfaces are cut by high-angle extensional and strike-slip faults, which controlled the emplacement of hypabissal magmatic intrusions that post-date thrusts motions. Intrusion ages based on SHRIMP U-Th-Pb zircon dating span between 42±1 and 39±1 Ma, suggesting close time relationships with the earliest Adamello intrusion stages and, more in general, with the widespread calc-alkaline magmatism described in the Southern Alps. Fission track ages of magmatic apatites are indistinguishable from U-Pb crystallization ages of zircons, suggesting that the intrusion occurred in country rocks already exhumed above the partial annealing zone of apatite (depth < 2-4 km).
These data indicate that the northern and central sectors of the CSA were already structured and largely exhumed in the Middle Eocene and no major internal deformations has occurred in these areas after the Bartonian. Neogene deformations were instead concentrated further south, along the frontal part of the belt (Milano Belt).
These new data provide a direct evidence that thrusting and nappe stacking were active during Late Cretaceous times not only in the Eastern Alps, but also in the CSA, significantly extending southward the sector of the Alpine belt affected by the Cretaceous orogenic event. In this view, the Late Cretaceous Southern Alps can be interpreted as the south-verging retrobelt of a pre-collisional orogenic wedge, which formed during the subduction of the Alpine Tethys beneath the attenuated northern Adria margin.
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Armstrong, Robin Neil. « The ore forming potential of calc alkaline systems : a magmatic perspective ». Thesis, University of Southampton, 1999. https://eprints.soton.ac.uk/42081/.
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The association of porphyry copper style mineralisation with extensive calc alkaline igneous activity is not in doubt. However, the role of the magmatic system in the formation of such deposits is still not fully understood. Extensive works have investigated the associated alterations, ore petrology, fluid compositions and the theoretical models of ore metal transference from magma to hydrothermal fluid. Despite these numerous studies, little or no information on the chemical composition and physical processes that occur in the magmatic system has been forthcoming. Silicate melt inclusions provide a method of directly sampling the volatile and ore metal content of magmatic systems. A study of a copperrich andesite from Hahajima, Japan, demonstrates that though the majority of calc alkaline systems have the potential to form a porphyry copper deposit, the physiochemical conditions of the magma chamber prevent most from doing so. The melt inclusions contain significant amounts of copper (up to 2000 ppm), which exceed the average andesitic melt copper content by several orders of magnitude. Measured average water content of 3.3 wt%, and a CI/H2O ratio of 0.06 from the melt inclusions are typical of those expected for an arc andesite. The analysis of samples from the Morenci and Chino porphyry copper deposits of the SW USA showed that the melt inclusions contained a maximum of c. 700 ppm Cu. By employing a fractional crystallisation model it is possible to demonstrate that melt responsible for the formation of these deposits was not an exotic copper-rich melt. However, both of these deposits displayed trace element characteristics similar to those of Adakites. A study of copper-rich quartz-included biotites from Morenci demonstrated that the parental magma of this system had a small but significant amount of crustal contamination. The copper enrichment in these biotites is the consequence of the mineral's interaction with a copper-carrying exsolved magmatic volatile phase which was in equilibrium with the melt. The quartz phenocrysts from Morenci, which host the melt inclusions and biotites have a complex history of growth and resorption. These events are faithfully recorded by the quartz's zoning. It is possible by the application of existing crystallisation models to demonstrate that during the later stages of the Morenci magma's crystallisation that a magmatic volatile phase was undergoing cycles of undersaturation, saturation and exsolution. This 'pumping' of volatiles was driven by the phenomenon of undercooling. These studies of calc-alkaline magmatic systems and their contribution to the porphyry copper-forming process, serve to provide some ground truths to the current models used to understand their formation and may provide the basis for the development of future exploration tools.
Livres sur le sujet "Calc-alkaline magmatism"
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Buddington, Andrew M. The Similkameen Batholith of north-central Washington and south-central British Columbia : The petrotectonic significance of an alkaline/calc-alkaline magmatic complex. 1990.
Trouver le texte intégralChapitres de livres sur le sujet "Calc-alkaline magmatism"
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Lustrino, Michele, Claudio Chiarabba et Eugenio Carminati. « Igneous activity in central-southern Italy : Is the subduction paradigm still valid ? » Dans In the Footsteps of Warren B. Hamilton : New Ideas in Earth Science. Geological Society of America, 2022. http://dx.doi.org/10.1130/2021.2553(28).
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ABSTRACT The Pliocene–Quaternary igneous record of the Tyrrhenian Sea area features a surprisingly large range of compositions from subalkaline to ultra-alkaline and from ultrabasic to acid. These rocks, emplaced within the basin and along its margins, are characterized by strongly SiO2-undersaturated and CaO-rich to strongly SiO2-oversaturated and peraluminous compositions, with sodic to ultrapotassic alkaline and tholeiitic to calc-alkaline and high-K calc-alkaline affinities. We focused on the different models proposed to explain the famous Roman Comagmatic Region, part of the Quaternary volcanism that spreads along the eastern side of the Tyrrhenian area, in the stretched part of the Apennines thrust-and-fold belt. We reviewed data and hypotheses proposed in the literature that infer active to fossil subduction up to models that exclude subduction entirely. Many field geology observations sustain the interpretation that the evolution of the Tyrrhenian-Apennine system was related to subduction of the western margin of Adria continental lithosphere after minor recycling of oceanic lithosphere. However, the lateral extent of the subducting slab in the last millions of years, when magmatism flared up, remains debatable. The igneous activity that developed in the last millions of years along the Tyrrhenian margin is here explained as originating from a subduction-modified mantle, regardless of whether the large-scale subduction system is still active.
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Vaughan, Jeremy, Carl E. Nelson, Guillermo Garrido, Jose Polanco, Valery Garcia et Arturo Macassi. « Chapter 20 : The Pueblo Viejo Au-Ag-Cu-(Zn) Deposit, Dominican Republic ». Dans Geology of the World’s Major Gold Deposits and Provinces, 415–30. Society of Economic Geologists, 2020. http://dx.doi.org/10.5382/sp.23.20.
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Abstract The world-class Pueblo Viejo Au deposit in the central Dominican Republic is one of the largest high-sulfidation epithermal Au deposits globally, with past production plus resources and reserves of 41.7 million ounces (Moz) in the Moore and Monte Negro deposits. Mineralization occurs within a 2- × 2-km Early Cretaceous volcano-sedimentary basin filled with felsic volcanic and volcaniclastic rocks, interlayered carbonaceous sedimentary units, and underlying andesitic flows and tuffs. The volcanic stratigraphy was developed during a period of tholeiitic magmatism that transitioned to calc-alkaline magmatism at the time of emplacement of the late- to postmineral Monte Negro dike (~109 Ma). Additional geologic controls to mineralization include high-angle, NE- and NW-faulting, phreatomagmatic breccias, and possible volcanic domes. Mineralization is present across the stratigraphic sequence, with mineralization at Moore dominantly hosted within quartz-bearing volcaniclastic rocks and overlying carbonaceous sedimentary units, whereas that at Monte Negro is in the andesitic sequence as well as overlying epiclastic and sedimentary units. Alteration at the shallowest level is dominated by quartz-pyrophyllite, whereas alunite alteration defines the deep roots to the ore-forming environment. Mineralization comprises early disseminated-type and late veins filled with pyrite ± sphalerite. Hypogene ore is refractory in nature, with Au in solid solution or as mineral inclusions within arsenian pyrite. Re-Os ages of 113.4 ± 2.6 Ma for auriferous pyrite along with new geologic observations appear to confirm an Early Cretaceous age for mineralization, although Re-Os enargite ages suggest the possibility of a second mineralization event in the Eocene.
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Lee, Well-Shen, Daniel J. Kontak, Jeremy P. Richards, Tony Barresi et Robert A. Creaser. « Superimposed Porphyry Systems in the Dawson Range, Yukon ». Dans Tectonomagmatic Influences on Metallogeny and Hydrothermal Ore Deposits : A Tribute to Jeremy P. Richards (Volume I), 29–48. Society of Economic Geologists, 2021. http://dx.doi.org/10.5382/sp.24.03.
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ABSTRACT Superimposed porphyry systems are a subset of telescoped porphyry deposits, whereby significantly younger ore zones overprint older, nongenetically related systems. Recognition of superimposed features in porphyry systems is important for determining and assessing their prospectivity. The Mount Nansen gold corridor in the southern Dawson Range gold belt of Yukon, Canada, contains porphyry prospects and epithermal deposits with enigmatic genetic models. Geologic, petrologic, temporal (U-Pb zircon, Re-Os molybdenite), and geochemical (whole-rock) studies are used to demonstrate the presence of superimposed porphyry systems in this district. The arc-related episodic magmatism of the Mount Nansen gold corridor has been classified into four intrusive suites: (1) Late Triassic Minto, (2) mid-Cretaceous Whitehorse, (3) Late Cretaceous Casino (eLKc; 80–72 Ma), and (4) Late Cretaceous Prospector Mountain (lLKp; 72–65 Ma). Geochemical fingerprinting of these suites indicates intermediate to evolved, calc-alkaline compositions with a common lower crust melt source. The eLKc and lLKp suites lack an Eu anomaly and show increasing amounts of light rare earth element (LREE) enrichment and heavy rare earth element (HREE) depletion over time. These features suggest that garnet was stable in the melt source and oxidized magmas were generated in these Late Cretaceous suites. The mildly alkaline lLKp and associated Carmacks Group shoshonitic basalts reflect localized extension in an overall compressive arc setting in the Mount Nansen gold corridor, hence a setting conducive for Au-rich porphyry and epithermal systems. The ca. 79 to 72 Ma Casino suite is commonly interpreted as the causative magmatic event for most well-endowed porphyry deposits (76 to 74 Ma in age) in the Dawson Range gold belt. However, our detailed study of the Klaza setting shows that at this locality, intermediate-sulfidation epithermal veins are a distal expression of a Prospector Mountain-age (ca. 71 Ma) porphyry system, which overprints two Casino-age porphyry systems (ca. 77 and 80 Ma). The Mount Nansen gold corridor thus hosts at least two spatially and temporally overprinting Late Cretaceous magmatic-hydrothermal systems in the Dawson Range gold belt. Importantly, recognition of this feature at other porphyry deposit settings in the Dawson Range gold belt (e.g., Freegold Mountain district) is critical as it provides the potential for metal (Cu-Au-Mo)-enriched hypogene ore shells.
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Amato, Jeffrey M., Cheryl Foley, Matthew Heizler et Richard Esser. « 40Ar/39Ar and U-Pb geochronology, geochemistry, and tectonic setting of three episodes of Cretaceous-Eocene calc-alkaline magmatism in the Lake Clark Region, southwestern Alaska ». Dans Special Paper 431 : Tectonic Growth of a Collisional Continental Margin : Crustal Evolution of Southern Alaska, 455–75. Geological Society of America, 2007. http://dx.doi.org/10.1130/2007.2431(18).
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René, Miloš. « Investigation of Accessory Minerals from the Blatná Granodiorite Suite, Bohemian Massif, Czech Republic ». Dans Mineralogy [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.102628.
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The Central Bohemian magmatic complex belongs to the Central European Variscan belt. The granitic rocks of this plutonic complex are formed by several suites of granites, granodiorites, and tonalites, together with small bodies of gabbros, gabbro diorites, and diorites. The granodiorites of the Blatná suite are high-K, calc-alkaline to shoshonitic, and metaluminous to slightly peraluminous granitic rocks. Compared to the common I-type granites, granodiorites of the Blatná suite are enriched in Mg (1.0–3.4 wt.% MgO), Ba (838–2560 ppm), Sr. (257–506 ppm), and Zr (81–236 ppm). For granodiorites of the Blatná suite is assemblage of apatite, zircon, titanite, and allanite significant. Zircon contains low Hf concentrations (1.1–1.7 wt.% HfO2). The composition of titanite ranges from 83 to 92 mol.% titanite end-member. Allanite is relatively Al-poor and displays Feox. ratio 0.2–0.5.
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Gioncada, A., P. Fulignati, L. Vezzoli, R. Omarini, D. Bosch, O. Bruguier, R. Mazzuoli et V. Lopez-Azarevich. « Magmatic Sulfides from the Rincón-Portezuelo de las Ánimas Volcanic Complex, Northwest Argentina : Insights on Magma Fertility and Comparison with Mineralized Volcanic Systems ». Dans Tectonomagmatic Influences on Metallogeny and Hydrothermal Ore Deposits : A Tribute to Jeremy P. Richards (Volume I), 101–20. Society of Economic Geologists, 2021. http://dx.doi.org/10.5382/sp24.07.
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Abstract The composition and fate of magmatic sulfides are some of the most critical factors invoked to play a role in the chalcophile metal fertility of arc magmas. Examination of magmatic sulfide accessory minerals in nonmineralized volcanic systems may help to understand the behavior of chalcophile metals at sulfide saturation. This study presents compositional data on magmatic sulfides in lavas of the late Miocene Rincón-Portezuelo de las Ánimas Volcanic Complex, northwest Argentina. This is the easternmost magmatic occurrence in the back arc of the Southern Central Andes, at 27°S, about 75 km northeast from the world-class Bajo de la Alumbrera porphyry Cu-Au deposit. At this latitude the late Miocene volcanic activity migrated eastward as a consequence of the shallowing slab subduction. Both copper-rich and pyrrhotite magmatic sulfide inclusions have been identified in the Rincón-Portezuelo de las Ánimas volcanic suite, straddling the high K calc-alkaline–shoshonite boundary. We discuss the sulfide composition in the framework of magmatic evolution and in comparison to the metal content of magmatic sulfides of the coeval Farallón Negro Volcanic Complex, associated with the Bajo de la Alumbrera porphyry Cu-Au and other mineralized systems. The results show that sulfide liquid, exsolved from silicate melts of intermediate composition, stores Cu, Pb, Ag, and Bi in crystal mushes, reducing the mineralizing potential of residual melts while fertilizing the middle-upper crust. Gold behavior seems to be controlled by additional mechanisms, linked to the magma source or to an early partitioning into an S-bearing fluid phase. The high Au/Cu ratio of sulfides formed as monosulfide solid solution may be associated with the potassic character of the magmas in this sector of the Central Andes.
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Moritz, Robert, Pierre Hemon, Alexey Ulianov, Richard Spikings, Massimo Chiaradia et Vagif Ramazanov. « Jurassic-Early Cretaceous Magmatic Arc Maturation and Ore Formation of the Central Tethyan Metallogenic Belt : Evidence from the Gedabek Mining District, Lesser Caucasus, Azerbaijan ». Dans Tectonomagmatic Influences on Metallogeny and Hydrothermal Ore Deposits : A Tribute to Jeremy P. Richards (Volume II), 181–203. Society of Economic Geologists, 2021. http://dx.doi.org/10.5382/sp.24.11.
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Abstract The Jurassic to Early Cretaceous magmatic and metallogenic evolution of the Lesser Caucasus and Eastern Pontides segment of the Central Tethyan orogenic belt is still poorly understood. This study reports an investigation about the link between ore formation and magmatic evolution in the major Gedabek porphyry-epithermal mining district, which is located in the Somkheto-Karabagh belt, Azerbaijan. Long-lasting magmatic arc evolution of ~50 m.y., from the Middle Jurassic to the Early Cretaceous, is supported by new U-Pb zircon ages between 164.3 ± 0.7 and 125.1 ± 0.5 Ma. Middle Jurassic magmatic rocks have a dominantly tholeiitic to transitional and primitive island-arc composition, whereas Late Jurassic to Early Cretaceous magmatic rocks are calc-alkaline to shoshonitic and have mature island-arc compositions. Radiogenic isotopes document a higher mantle contribution during petrogenesis of the Late Jurassic-Early Cretaceous magmatic rocks. The combined data document progressive magmatic arc maturation and crustal thickening from the Middle Jurassic to the Early Cretaceous, accompanied by slab roll-back and asthenospheric upwelling. This evolution is shared by other areas of the Somkheto-Karabagh belt and its southern extension in the Kapan block, which also host porphyry-epithermal mining districts. Muscovite and K-feldspar from a porphyry Cu-related potassic alteration assemblage at the Gedabek deposit (overprinted by a younger intermediate- to high-sulfidation epithermal system) have yielded 40Ar/39Ar ages between 140.1 ± 1.0 and 136.3 ± 0.9 Ma. Together with a previous Re-Os molybdenite age, they document formation of the porphyry-epithermal systems at the end of the long magmatic arc maturation of the Gedabek district. Although ore-forming events were diachronous along the arc, the relative timing of magmatic evolution and ore formation at Gedabek is shared by the other Late Jurassic to Early Cretaceous mining districts of the Somkheto-Karabagh belt and the Kapan block. Our study demonstrates that long arc maturation and crustal thickening has taken place along the southern Eurasian margin from a Middle Jurassic nascent arc to an Early Cretaceous evolved arc. This evolution is in line with the essential prerequisites for the genesis of porphyry-epithermal systems in orogenic belts. It also provides evidence that Middle Jurassic to Early Cretaceous magmatic fertile systems and porphyry-epithermal centers have been preserved in this belt.
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Cahoon†, Emily B., Martin J. Streck† et Mark Ferns†. « Flood basalts, rhyolites, and subsequent volcanism of the Columbia River magmatic province in eastern Oregon, USA ». Dans From Terranes to Terrains : Geologic Field Guides on the Construction and Destruction of the Pacific Northwest, 301–52. Geological Society of America, 2021. http://dx.doi.org/10.1130/2021.0062(08).
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ABSTRACT The Miocene Columbia River Basalt Group (CRBG) is the youngest and smallest continental flood basalt province on Earth. This flood basalt province is a succession of compositionally diverse volcanic rocks that record the passage of the Yellowstone plume beneath eastern Oregon. The compositionally and texturally varied suite of volcanic rocks are considered part of the La Grande–Owyhee eruptive axis (LOEA), an ~300-km-long, north-northwest–trending, Middle Miocene to Pliocene volcanic belt that extends along the eastern margin of the Columbia River flood basalt province. Volcanic rocks erupted from and preserved within the LOEA form an important regional stratigraphic link between the flood basalt–dominated Columbia Plateau to the north, the north and bimodal basalt-rhyolite volcanic fields of the Snake River Plain to the east, the Owyhee Plateau to the south, and the High Lava Plains to the south and east; the latter two have time transgressive rhyolite centers that young to the east and west, respectively. This field-trip guide details a four-day geologic excursion that will explore the stratigraphic and geochemical relationships among mafic rocks of the CRBG and coeval and compositionally diverse silicic rocks associated with the early trace of the Yellowstone plume and High Lava Plains in eastern Oregon. The trip on Day 1 begins in Portland then traverses across the western axis of the Blue Mountains, highlighting exposures of the widespread, Middle Miocene Dinner Creek Welded Tuff and aspects of the Picture Gorge Basalt lava flows and northwest-striking feeder dikes situated in the central part of the CRBG province. Travel on Day 2 progresses eastward toward the eastern margin of the LOEA, examining a transition linking the Columbia River Basalt province with a northwestward-younging magmatic trend of silicic volcanism of the High Lava Plains in eastern Oregon. Initial field stops on Day 2 focus on the volcanic stratigraphy northeast of the town of Burns, which includes regionally extensive Middle to Late Miocene ash-flow tuffs and lava flows assigned to the Strawberry Volcanics. Subsequent stops on Day 2 examine key outcrops demonstrating the intercalated nature of Middle Miocene tholeiitic CRBG flood basalts, temporally coeval prominent ash-flow tuffs, and “Snake River–type” large-volume rhyolite lava flows cropping out along the Malheur River. The Day 3 field route navigates to southern parts of the LOEA, where CRBG rocks are associated in space and time with lesser known and more complex silicic volcanic stratigraphy forming Middle Miocene, large-volume, bimodal basalt-rhyolite vent complexes. Key stops will provide a broad overview of the structure and stratigraphy of the Middle Miocene Mahogany Mountain caldera and of the significance of intercalated sedimentary beds and Middle to Late Miocene calc-alkaline lava flows of the Owyhee basalt. Initial stops on Day 4 will highlight exposures of Middle to Late Miocene silicic ash-flow tuffs, rhyolite domes, and calc-alkaline lava flows overlying the CRBG across the northern and central parts of the LOEA. The later stops on Day 4 examine more silicic lava flows and breccias that are overlain by early CRBG-related rhyolite eruptions. The return route to Portland on Day 4 traverses the Columbia River gorge westward from Baker City. The return route between Baker and Portland on Day 4 follows the Columbia River gorge and passes prominent basalt outcrops of large volume tholeiitic flood lavas of the Grande Ronde, Wanapum, and Saddle Mountains Formations of the CRBG. These sequences of basaltic and basaltic andesite lavas are typical of the well-studied flood basalt dominated Columbia Plateau, and interbedded silicic and calc-alkaline lavas are conspicuously absent. Correlation between the far-traveled CRBG lavas and calcalkaline and silicic lavas considered during the excursion relies on geochemical fingerprinting and dating of the mafic flows and dating of sparse intercalated ashes.
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Dostal, Jaroslav, Pierre Jutras et Reginald A. Wilson. « Geochemical and Nd isotopic constraints on the origin of uppermost Silurian rhyolitic rocks in the northern Appalachians (northern New Brunswick) : Tectonic implications ». Dans New Developments in the Appalachian-Caledonian- Variscan Orogen. Geological Society of America, 2022. http://dx.doi.org/10.1130/2021.2554(06).
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ABSTRACT Voluminous bimodal volcanic rocks of the Silurian (ca. 422–420 Ma) Dickie Cove Group in the Ganderia domain of northern New Brunswick, Canada, are subaerial units that were deposited in an extensional setting, with the mafic types corresponding to continental tholeiites. Felsic rocks are rhyolites with calc-alkaline affinities. They exhibit geochemical characteristics that are typical of A2-type felsic magmas, such as enrichments in the incompatible elements Zr, Nb, and Y, as well as high FeO*/(FeO* + MgO) and Ga/Al ratios. Their εNd(t) values are positive (+0.7 to +3.4) but lower than those of the associated basalts. Saturation thermometry has yielded average zircon crystallization temperature estimates for the rhyolites that are well above 900 °C. The geochemical data indicate that the felsic melts were likely sourced from heterogeneous Neoproterozoic lower crust and generated by dehydration melting triggered by heat derived from underplated mafic magma. Parent melts of the rhyolites underwent fractional crystallization in a complex magma chamber prior to eruption. The Nd isotopic data suggest that the lower crust of Ganderia is similar to that of Avalonia in northern mainland Nova Scotia, and that the two microcontinents shared a common Neoproterozoic history and origin as continental blocks rifted from neighboring parts of Gondwana. The tectono-magmatic setting of the Dickie Cove Group volcanic rocks is interpreted as being related to Pridolian, post-Salinic relaxation and slab breakoff, which generated volcanism initially constrained within the Chaleur zone of the Chaleur Bay synclinorium, a large domain of the northern Appalachians. This was followed later in the Pridolian by extensional collapse and widening of the area of magmatic activity, which then prograded into the Tobique zone farther to the southwest.
Actes de conférences sur le sujet "Calc-alkaline magmatism"
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Mosolf, Jesse G. « EOCENE HIGH-K, CALC-ALKALINE MAGMATISM WITHIN THE EASTERN LEWIS AND CLARK FAULT ZONE, WEST-CENTRAL MONTANA, USA ». Dans 113th Annual GSA Cordilleran Section Meeting - 2017. Geological Society of America, 2017. http://dx.doi.org/10.1130/abs/2017cd-292566.
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Wang, Dan, et Jing-Hui Guo. « Coeval Mantle-Derived Shoshonitic and Calc-Alkaline Plutons from the North China Craton : The 1.96 Ga Continental Arc Magmatism ? » Dans Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.2715.
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McCane, Jacob A., John Ridley et John Ridley. « LATE CRETACEOUS TO EARLY EOCENE LAMPROPHYRIC TEXTURAL AND PYROXENE MINERAL CHEMISTRY VARIATION FROM CALC-ALKALINE SUBDUCTION RELATED MAGMATISM AND THE CENTRAL MONTANA ALKALIC PROVINCE ». Dans GSA Annual Meeting in Phoenix, Arizona, USA - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019am-341091.
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Cottrell, Elizabeth, Laura Waters, Michelle Coombs, Katherine Kelley et Janine Andrys. « Calc-Alkaline Magmatic Trends at Crustal Pressure and High fO2 ». Dans Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.481.
Texte intégralRapports d'organisations sur le sujet "Calc-alkaline magmatism"
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Matte, S., M. Constantin et R. Stevenson. Mineralogical and geochemical characterisation of the Kipawa syenite complex, Quebec : implications for rare-earth element deposits. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/329212.
Texte intégralRésumé :
The Kipawa rare-earth element (REE) deposit is located in the Parautochton zone of the Grenville Province 55 km south of the boundary with the Superior Province. The deposit is part of the Kipawa syenite complex of peralkaline syenites, gneisses, and amphibolites that are intercalated with calc-silicate rocks and marbles overlain by a peralkaline gneissic granite. The REE deposit is principally composed of eudialyte, mosandrite and britholite, and less abundant minerals such as xenotime, monazite or euxenite. The Kipawa Complex outcrops as a series of thin, folded sheet imbricates located between regional metasediments, suggesting a regional tectonic control. Several hypotheses for the origin of the complex have been suggested: crustal contamination of mantle-derived magmas, crustal melting, fluid alteration, metamorphism, and hydrothermal activity. Our objective is to characterize the mineralogical, geochemical, and isotopic composition of the Kipawa complex in order to improve our understanding of the formation and the post-formation processes, and the age of the complex. The complex has been deformed and metamorphosed with evidence of melting-recrystallization textures among REE and Zr rich magmatic and post magmatic minerals. Major and trace element geochemistry obtained by ICP-MS suggest that syenites, granites and monzonite of the complex have within-plate A2 type anorogenic signatures, and our analyses indicate a strong crustal signature based on TIMS whole rock Nd isotopes. We have analyzed zircon grains by SEM, EPMA, ICP-MS and MC-ICP-MS coupled with laser ablation (Lu-Hf). Initial isotopic results also support a strong crustal signature. Taken together, these results suggest that alkaline magmas of the Kipawa complex/deposit could have formed by partial melting of the mantle followed by strong crustal contamination or by melting of metasomatized continental crust. These processes and origins strongly differ compare to most alkaline complexes in the world. Additional TIMS and LA-MC-ICP-MS analyses are planned to investigate whether all lithologies share the same strong crustal signature.