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Articles de revues sur le sujet « Eclogite melting »

Auteur : Grafiati

Publié le 9 mars 2023

Mis à jour le 10 mars 2023

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1

Gorbachev, N. S., A. V. Kostyuk, Yu B. Shapovalov, P. N. Gorbachev, A. N. Nekrasov, and D. M. Soultanov. "Critical phenomena and granatization of water-containing eclogite at P = 3,7-4,0 GPa, T = 1000-1300 °C." Доклады Академии наук 489, no. 4 (2019): 393–98. http://dx.doi.org/10.31857/s0869-56524894393-398.

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The phase relationships have been experimentally studied at eclogitization of basalts and the melting of H2O‑containing eclogite in the basalt-H2O system at P = 3,7-4,0 GPa, T = 1000-1300 C. It is established that the phase relationships depend on temperature. The formation of a supercritical fluid-melt occurs at T = 1000 C, P = 3,7 GPa, conversion eclogite-granatite occurs at T = 1000-1100 C, P = 3,9 GPa, partial melting of eclogite with the formation of Na-alkali silicate melt and clinopyroxenite restite at 1150 C and 1300 C. The supercritical fluid-melt has a high reactivity, resulting in the formation of megacrists of garnet, its enrichment with Ti, the replacement of garnet with clinopyroxene, the formation of ilmenite, K‑containing amphibole, the conversion of eclogite into garnetite as a result of mass crystallization of garnet.

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Dokukina, K. A., M. V. Mints, and A. N. Konilov. "Melting of eclogite facies sedimentary rocks in the Belomorian Eclogite Province, Russia." Journal of Metamorphic Geology 35, no. 4 (2016): 435–51. http://dx.doi.org/10.1111/jmg.12239.

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3

ShuaiQi, LIU, and ZHANG GuiBin. "Isotope fractionation during partial melting of eclogite." Acta Petrologica Sinica 37, no. 1 (2021): 95–112. http://dx.doi.org/10.18654/1000-0569/2021.01.07.

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4

Chu, Xu, Jay J. Ague, Yury Y. Podladchikov, and Meng Tian. "Ultrafast eclogite formation via melting-induced overpressure." Earth and Planetary Science Letters 479 (December 2017): 1–17. http://dx.doi.org/10.1016/j.epsl.2017.09.007.

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Cao, Wentao, Jane A. Gilotti, and Hans-Joachim Massonne. "Partial melting of zoisite eclogite from the Sanddal area, North-East Greenland Caledonides." European Journal of Mineralogy 32, no. 4 (2020): 405–25. http://dx.doi.org/10.5194/ejm-32-405-2020.

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Abstract. Metamorphic textures and a pressure–temperature (P–T) path of zoisite eclogite are presented to better understand the metamorphic evolution of the North-East Greenland eclogite province and this particular type of eclogite. The eclogite contained the mineral assemblage garnet, omphacite, kyanite, phengite, quartz and rutile at peak pressure. Partial melting occurred via breakdown of hydrous phases, paragonite, phengite and zoisite, based on (1) polymineralic inclusions of albite and K-feldspar with cusps into host garnet, (2) small euhedral garnet with straight boundaries against plagioclase, (3) cusps of plagioclase into surrounding phases (such as garnet), and (4) graphic intergrowth of plagioclase and amphibole next to anhedral zoisite grains. Isochemical phase equilibrium modeling of a melt-reintegrated composition, along with XNa-in-omphacite and Si-in-phengite isopleths, yields a peak pressure of 2.4±0.1 GPa at 830±30 ∘C. A peak temperature of 900±50 ∘C at 1.9±0.2 GPa is determined using the rim composition of small euhedral garnet, as predicted by modeling a crystallized melt pocket. Zoisite growth at the expense of kyanite suggests that the P–T path crossed the fields of zoisite growth at ∼1.9 GPa, 800–900 ∘C on the modeled phase diagram of the bulk rock. A point on the exhumation path at ∼1.3 GPa and 750 ∘C is derived from hornblende-plagioclase thermometry and Al-in-hornblende barometry. The study demonstrates that paragonite, phengite and zoisite could contribute to partial melting of eclogite at near-peak P and during exhumation.

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Spetsius, Zdzislaw, Ludmila Liskovaya, Alexander Ivanov, and Irina Bogush. "FEATURES OF GARNET AND CLINOPYROXENE IN DIAMONDIFEROUS ECLOGITES FROM THE UDACHNAYA KIMBERLITE PIPE, YAKUTIA: METASOMATOSIS EVIDENCE." Ores and metals, no. 4 (February 2, 2021): 45–53. http://dx.doi.org/10.47765/0869-5997-2020-10027.

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Mineralogy of diamondiferous eclogite xenolites showing metasomatosis evidence from the Udachnaya kimberlite pipe is discussed. The paper also reviews features of diamonds they contain, compositions of primary garnets and omphacites as well as alteration of structural and species compositions of original garnets and clinopyroxenes during metasomatosis. Based on pyrope structure update, two-phase garnet composition is suggested, which is mostly represented by complex pyrope associated with Ca-pyrope. In all samples, primary omphacite is replaced by another clinopyroxene variety depleted in Na2O, which is typical of partial melting products. Geothermometry results suggested that the eclogites formed within a temperature range of 1,000–1,2000 °C. Based on diamond morphology, data on total N content in diamonds and its aggregation, multiple stages of diamond formation in eclogites and the most probable growth of later diamond generations impacted by metasomatizing mantle fluids containing carbon are postulated. It is suggested that certain diamond formation stages probably had a time gap of several hundred million years.

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Litvin, Yu A., A. V. Kuzyura, and E. B. Limanov. "The role of garnetization of olivine in olivine-diopside-jadeite system in the ultramafic-mafic evolution of the upper-mantle magmatism (experiment at 6 GPa)." Геохимия 64, no. 10 (2019): 1026–46. http://dx.doi.org/10.31857/s0016-752564101026-1046.

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Peritectic mechanisms, controlling fractional ultrabasic-basic evolution of the upper mantle magmatism and genesis of the peridotitepyroxeniteeclogite rock series, are substantiated in theory and experiment. Melting phase relations of a differentiated mantle material are studied with polythhermal section method in the multicomponent olivineclinopyroxene/omphacitecorundumcoesite system with boundary compositions duplicated these of peridotitic and eclogitic minerals. The peritectic reaction of orthopyroxene and melt with formation of clinopyroxene (the opthopyroxene clinopyroxenization reaction) has been determined at a liquidus surface of the ultrabasic olivineorthopyroxeneclinopyroxenegarnet system. As a result of the reaction the temperature-regressive univariant curve olivine + clinopyroxene + garnet + melt is formed. A further evolution of magmatism has experimentally studied at 6 GPa in the ultrabasic-basic olivinediopsidejadeitegarnet system with changeable compositions of the diopsidejadeite solid solutions (controlling the clinopyroxene omphacite mineralogy). Peritectic reaction of olivine and melt with formation of garnet was established on the liquidus surface of the ternary olivinediopsidejadeite system as the mechanism of olivine garnetization and going to the univariant curve omphacitegarnetmelt with formation of bimineral eclogites. Structure of the liquidus surface for the olivinediopsidejadeitegarnet system is inferred, and its role as a physic-chemical bridge between ultrabasic olivinebearing peridotitepyroxenitic and basic silica-saturated eclogitic compositions of the garnetperidotite facies matter. The new experimental physic-chemical results reveal the genetic links between ultrabasic and basic rocks as well as mechanisms of the uninterrupted fractional magmatic evolution and petrogenesis from the olivinebearing peridotitepyroxenitic to silica-saturated eclogite-grospyditicrocks. This provides an explanation for the uninterrupted composition trends for rock-forming components in clinopyroxenes and garnets of the differentiated rocks of the garnetperidotite facieis.

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Schorn, Simon, Michael I. H. Hartnady, Johann F. A. Diener, Chris Clark, and Chris Harris. "H2O-fluxed melting of eclogite during exhumation: an example from the eclogite type-locality, Eastern Alps (Austria)." Lithos 390-391 (June 2021): 106118. http://dx.doi.org/10.1016/j.lithos.2021.106118.

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Spetsius, Zdislav V., and Lawrence A. Taylor. "Partial Melting in Mantle Eclogite Xenoliths: Connections with Diamond Paragenesis." International Geology Review 44, no. 11 (2002): 973–87. http://dx.doi.org/10.2747/0020-6814.44.11.973.

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Rapp, Robert P., Nobumichi Shimizu, and Marc D. Norman. "Growth of early continental crust by partial melting of eclogite." Nature 425, no. 6958 (2003): 605–9. http://dx.doi.org/10.1038/nature02031.

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Laurie, Angelique, and Gary Stevens. "Water-present eclogite melting to produce Earth's early felsic crust." Chemical Geology 314-317 (July 2012): 83–95. http://dx.doi.org/10.1016/j.chemgeo.2012.05.001.

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Sobolev, Alexander V., Albrecht W. Hofmann, Dmitry V. Kuzmin, et al. "The Amount of Recycled Crust in Sources of Mantle-Derived Melts." Science 316, no. 5823 (2007): 412–17. http://dx.doi.org/10.1126/science.1138113.

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Plate tectonic processes introduce basaltic crust (as eclogite) into the peridotitic mantle. The proportions of these two sources in mantle melts are poorly understood. Silica-rich melts formed from eclogite react with peridotite, converting it to olivine-free pyroxenite. Partial melts of this hybrid pyroxenite are higher in nickel and silicon but poorer in manganese, calcium, and magnesium than melts of peridotite. Olivine phenocrysts' compositions record these differences and were used to quantify the contributions of pyroxenite-derived melts in mid-ocean ridge basalts (10 to 30%), ocean island and continental basalts (many >60%), and komatiites (20 to 30%). These results imply involvement of 2 to 20% (up to 28%) of recycled crust in mantle melting.

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13

Skublov, Sergey G., Aleksey V. Berezin, Xian-Hua Li, et al. "Zircons from a Pegmatite Cutting Eclogite (Gridino, Belomorian Mobile Belt): U-Pb-O and Trace Element Constraints on Eclogite Metamorphism and Fluid Activity." Geosciences 10, no. 5 (2020): 197. http://dx.doi.org/10.3390/geosciences10050197.

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This report presents new data on U-Pb geochronology, oxygen isotopes, and trace element composition of zircon from a pegmatite vein crosscutting an eclogite boudin on Stolbikha Island, Gridino area, Belomorian mobile belt (BMB). The zircon grains occur as two distinct populations. The predominant population is pegmatitic and shows dark cathodoluminescence (CL); about a third of this population contains inherited cores. The second zircon population is typical of granulite and exhibits a well-defined sectorial (mosaic) zoning in CL. Both the inherited cores and sectorial in CL zircons appear to have been captured from metabasites as xenocrysts during the pegmatite vein formation. A U-Pb age of 1890 ± 2 Ma for the main zircon population is interpreted as the age of the pegmatite injection. This value is close to the age threshold for the BMB eclogites (~1.9 Ga) and unambiguously defines the upper age limit for the eclogite metamorphism. The pegmatite formation is thus related to partial melting events that occurred during the retrograde amphibolite-facies metamorphism shortly after the eclogitization. A U-Pb date of 2743 ± 10 Ma obtained for the sectorial in CL zircons is considered as the age of the granulite-facies metamorphism established previously within the BMB. The values of δ18O in the zircon populations overlap in a broad range, i.e., δ18O in the pegmatitic zircons varies from 6.1‰ to 8.3‰, inherited cores show a generally higher δ18O of 6.7–8.8‰, and in the captured granulitic zircons δ18O is 6.2–7.9‰. As a result of fluid attack during the final stage of the pegmatite vein formation, the composition of the pegmatitic zircons in terms of non-formula elements (REE, Y, Ca, Sr, Ti) has become anomalous, with the content of these elements having been increased by more than tenfold in the alteration zones. Our data provide new constraints on the timing of eclogite metamorphism within the BMB and show that the late-stage pegmatite-related fluids exerted a very pronounced influence on trace element abundances in zircon, yet had no significant impact on the isotopic composition of oxygen.

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Martin, Adam P., Alan F. Cooper, Richard C. Price, Philip R. Kyle, and John A. Gamble. "Chapter 5.2b Erebus Volcanic Province: petrology." Geological Society, London, Memoirs 55, no. 1 (2021): 447–89. http://dx.doi.org/10.1144/m55-2018-80.

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AbstractIgneous rocks of the Erebus Volcanic Province have been investigated for more than a century but many aspects of petrogenesis remain problematic. Current interpretations are assessed and summarized using a comprehensive dataset of previously published and new geochemical and geochronological data. Igneous rocks, ranging in age from 25 Ma to the present day, are mainly nepheline normative. Compositional variation is largely controlled by fractionation of olivine + clinopyroxene + magnetite/ilmenite + titanite ± kaersutite ± feldspar, with relatively undifferentiated melts being generated by <10% partial melting of a mixed spinel + garnet lherzolite source. Equilibration of radiogenic Sr, Nd, Pb and Hf is consistent with a high time-integrated HIMUsensu strictosource component and this is unlikely to be related to subduction of the palaeo-Pacific Plate around 0.5 Ga. Relatively undifferentiated whole-rock chemistry can be modelled to infer complex sources comprising depleted and enriched peridotite, HIMU, eclogite-like and carbonatite-like components. Spatial (west–east) variations in Sr, Nd and Pb isotopic compositions and Ba/Rb and Nb/Ta ratios can be interpreted to indicate increasing involvement of an eclogitic crustal component eastwards. Melting in the region is related to decompression, possibly from edge-driven mantle convection or a mantle plume.

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Yaxley, G. M. "The Refractory Nature of Carbonate during Partial Melting of Eclogite: Evidence from High Pressure Experiments and Natural Carbonate-Bearing Eclogites." Mineralogical Magazine 58A, no. 2 (1994): 996–97. http://dx.doi.org/10.1180/minmag.1994.58a.2.253.

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Soldner, Jérémie, Chao Yuan, Karel Schulmann, et al. "Grenvillean evolution of the Beishan Orogen, NW China: Implications for development of an active Rodinian margin." GSA Bulletin 132, no. 7-8 (2019): 1657–80. http://dx.doi.org/10.1130/b35404.1.

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Abstract New geochemical and geochronological data are used to characterize the geodynamic setting of metasediments, felsic orthogneisses, and eclogite and amphibolite lenses forming the Beishan complex, NW China, at the southern part of the Central Asian Orogenic Belt. The metasediments correspond compositionally to immature greywackes receiving detritus from a heterogeneous source involving a magmatic arc and a Precambrian continental crust. Metagranitoids, represented by felsic orthogneisses, show both composition of greywacke-derived granitic melt with incompatible trace element patterns similar to the host metasediments. The eclogite lenses are characterized by high Nb contents (5.34–27.3 ppm), high (Nb/La)N (&gt;1), and low Zr/Nb ratios (&lt;4.5), which together with variable and negative whole-rock εNd(t) (–4.3 to –10.3) and zircon εHf(t) (–5.0 to + 2.3) values indicate an origin of enriched mantle source as commonly manifested by back-arc basalts at stretched continental margins. Combined with monazite rare earth element analysis, the in situ monazite U-Pb dating of metagraywacke (880.7 ± 7.9) suggests garnet growth during a high-temperature (HT) metamorphic event. Together with U-Pb dating of zircon metamorphic rims in amphibolite (910.9 ± 3.0 Ma), this indicates that the whole crustal edifice underwent a Grenvillian-age metamorphic event. The protolith ages of the eclogite (889.3 ± 4.8 Ma) and orthogneiss (867.5 ± 1.9 Ma) suggest that basalt underplating and sediment melting were nearly coeval with this HT metamorphism. Altogether, the new data allow placing the Beishan Orogen into a Grenvillean geodynamic scenario where: (1) The late Mesoproterozoic to early Neoproterozoic was marked by deposition of the greywacke sequence coeval with formation of an early arc. (2) Subsequently, an asthenospheric upwelling generated basaltic magma underneath the thinned subcontinental mantle lithosphere that was responsible for HT metamorphism, melting of the back-arc basin greywackes and intrusion of granitic magmas. These events correspond to a Peri-Rodinian supra-subduction system that differs substantially from the Neoproterozoic ophiolite sequences described in the Mongolian part of the Central Asian Orogenic Belt, thus indicating important lateral variability of supra-subduction processes along the Rodinian margin.

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Shatskiy, Anton, Altyna Bekhtenova, Anton V. Arefiev, and Konstantin D. Litasov. "Melt Composition and Phase Equilibria in the Eclogite-Carbonate System at 6 GPa and 900–1500 °C." Minerals 13, no. 1 (2023): 82. http://dx.doi.org/10.3390/min13010082.

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Melting phase relations in the eclogite-carbonate system were studied at 6 GPa and 900–1500 °C. Starting mixtures were prepared by blending natural bimineral eclogite group A (Ecl) with eutectic Na-Ca-Mg-Fe (N2) and K-Ca-Mg-Fe (K4) carbonate mixtures (systems Ecl-N2 and Ecl-K4). In the Ecl-N2 system, the subsolidus assemblage is represented by garnet, omphacite, eitelite, and a minor amount of Na2Ca4(CO3)5. In the Ecl-K4 system, the subsolidus assemblage includes garnet, clinopyroxene, K2Mg(CO3)2, and magnesite. The solidus of both systems is located at 950 °C and is controlled by the following melting reaction: Ca3Al2Si3O12 (Grt) + 2(Na or K)2Mg(CO3)2 (Eit) = Ca2MgSi3O12 (Grt) + [2(Na or K)2CO3∙CaCO3∙MgCO3] (L). The silica content (in wt%) in the melt increases with temperature from < 1 at 950 °C to 3–7 at 1300 °C, and 7–12 at 1500 °C. Thus, no gradual transition from carbonate to kimberlite-like (20–32 wt% SiO2) carbonate-silicate melt occurs even as temperature increases to mantle adiabat. This supports the hypothesis that the high silica content of kimberlite is the result of decarbonation at low pressure. As temperature increases from 950 to 1500 °C, the melt Ca# ranges from 58–60 to 42–46. The infiltration of such a melt into the peridotite mantle should lower its Ca# and causes refertilization from harzburgite to lherzolite and wehrlitization.

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Dobrescu, Anca. "Pre-Variscan granitoids with adakitic signature at west Getic basement of the South Carpathians (Romania): constraints on genesis and timing based on whole-rock and zircon geochemistry." Geologica Acta 19 (April 14, 2021): 1–17. http://dx.doi.org/10.1344/geologicaacta2021.19.4.

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Research on two strata-like intrusions from Slatina-Timiş (STG) and Buchin (BG) at West Getic Domain of the South Carpathians (Semenic Mountains) identified granitoids with adakitic signature in a continental collision environment. Whole-rock geochemical composition with high Na2O, Al2O3 and Sr, depleted Y (18ppm) and HREE (Yb 1.8ppm) contents, high Sr/Y (40), (La/Yb)N (10) ratios and no Eu anomalies overlaps the High-Silica Adakites (HSA) main characteristics, though there are differences related to lower Mg#, heavy metal contents and slightly increased 87Sr/86Sr ratios. Comparison with HSA, Tonalite-Trondhjemite-Granodiorite (TTG) rocks and melts from experiments on basaltic sources suggests partial melting at pressures exceeding 1.25GPa and temperatures of 800-900ºC (confirmed by calculated Ti-in zircon temperatures) as the main genetic process, leaving residues of garnet amphibolite, garnet granulite or eclogite type. The adakitic signature along with geochemical variations observed in the STG-BG rocks indicate oceanic source melts affected by increasing mantle influence and decreasing crustal input that may restrict the tectonic setting to slab melting during a subduction at low angle conditions. An alternative model relates the STG-BG magma genesis to garnet-amphibolite and eclogite partial melting due to decompression and heating at crustal depth of 60-50km during syn-subduction exhumation of eclogitized slab fragments and mantle cumulates. The granitoids were entrained into a buoyant mélange during collision and placed randomly between two continental units. U-Pb zircon ages obtained by LA-ICP-MS and interpreted as Ordovician igneous crystallization time and Variscan recrystallization imprint are confirmed by trace-element characteristics of the dated zircon zones, connecting the STG-BG magmatism to a pre-Variscan subduction-collision event. The rich zircon inheritance reveals Neoproterozoic juvenile source and older crustal components represented by Neoarchean to Paleoproterozoic zircons.

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Vanderhaeghe, Olivier, Oscar Laurent, Véronique Gardien, et al. "Flow of partially molten crust controlling construction, growth and collapse of the Variscan orogenic belt: the geologic record of the French Massif Central." BSGF - Earth Sciences Bulletin 191 (2020): 25. http://dx.doi.org/10.1051/bsgf/2020013.

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We present here a tectonic-geodynamic model for the generation and flow of partially molten rocks and for magmatism during the Variscan orogenic evolution from the Silurian to the late Carboniferous based on a synthesis of geological data from the French Massif Central. Eclogite facies metamorphism of mafic and ultramafic rocks records the subduction of the Gondwana hyperextended margin. Part of these eclogites are forming boudins-enclaves in felsic HP granulite facies migmatites partly retrogressed into amphibolite facies attesting for continental subduction followed by thermal relaxation and decompression. We propose that HP partial melting has triggered mechanical decoupling of the partially molten continental rocks from the subducting slab. This would have allowed buoyancy-driven exhumation and entrainment of pieces of oceanic lithosphere and subcontinental mantle. Geochronological data of the eclogite-bearing HP migmatites points to diachronous emplacement of distinct nappes from middle to late Devonian. These nappes were thrusted onto metapelites and orthogneisses affected by MP/MT greenschist to amphibolite facies metamorphism reaching partial melting attributed to the late Devonian to early Carboniferous thickening of the crust. The emplacement of laccoliths rooted into strike-slip transcurrent shear zones capped by low-angle detachments from c. 345 to c. 310 Ma is concomitant with the southward propagation of the Variscan deformation front marked by deposition of clastic sediments in foreland basins. We attribute these features to horizontal growth of the Variscan belt and formation of an orogenic plateau by gravity-driven lateral flow of the partially molten orogenic root. The diversity of the magmatic rocks points to various crustal sources with modest, but systematic mantle-derived input. In the eastern French Massif Central, the southward decrease in age of the mantle- and crustal-derived plutonic rocks from c. 345 Ma to c. 310 Ma suggests southward retreat of a northward subducting slab toward the Paleotethys free boundary. Late Carboniferous destruction of the Variscan belt is dominantly achieved by gravitational collapse accommodated by the activation of low-angle detachments and the exhumation-crystallization of the partially molten orogenic root forming crustal-scale LP migmatite domes from c. 305 Ma to c. 295 Ma, coeval with orogen-parallel flow in the external zone. Laccoliths emplaced along low-angle detachments and intrusive dykes with sharp contacts correspond to the segregation of the last melt fraction leaving behind a thick accumulation of refractory LP felsic and mafic granulites in the lower crust. This model points to the primordial role of partial melting and magmatism in the tectonic-geodynamic evolution of the Variscan orogenic belt. In particular, partial melting and magma transfer (i) triggers mechanical decoupling of subducted units from the downgoing slab and their syn-orogenic exhumation; (ii) the development of an orogenic plateau by lateral flow of the low-viscosity partially molten crust; and, (iii) the formation of metamorphic core complexes and domes that accommodate post-orogenic exhumation during gravitational collapse. All these processes contribute to differentiation and stabilisation of the orogenic crust.

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Klemme, Stephan, Jonathan D. Blundy, and Bernard J. Wood. "Experimental constraints on major and trace element partitioning during partial melting of eclogite." Geochimica et Cosmochimica Acta 66, no. 17 (2002): 3109–23. http://dx.doi.org/10.1016/s0016-7037(02)00859-1.

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Cao, Yu-ting, Liang Liu, Dan-ling Chen, et al. "Partial melting during exhumation of Paleozoic retrograde eclogite in North Qaidam, western China." Journal of Asian Earth Sciences 148 (October 2017): 223–40. http://dx.doi.org/10.1016/j.jseaes.2017.09.009.

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Rapp, Robert Paul, E. Bruce Watson, and Calvin F. Miller. "Partial melting of amphibolite/eclogite and the origin of Archean trondhjemites and tonalites." Precambrian Research 51, no. 1-4 (1991): 1–25. http://dx.doi.org/10.1016/0301-9268(91)90092-o.

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Zhang, Peng-Fei, Yan-Jie Tang, Yan Hu, et al. "Review of melting experiments on carbonated eclogite and peridotite: insights into mantle metasomatism." International Geology Review 54, no. 12 (2012): 1443–55. http://dx.doi.org/10.1080/00206814.2012.663645.

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Zeng, Yunchuan, Mihai N. Ducea, Jifeng Xu, Jianlin Chen, and Yan-Hui Dong. "Negligible surface uplift following foundering of thickened central Tibetan lower crust." Geology 49, no. 1 (2020): 45–50. http://dx.doi.org/10.1130/g48142.1.

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Abstract This study used clinopyroxene (cpx) compositions and zircon Hf-O isotopes of Eocene adakitic rocks (EARs) from the Qiangtang block to resolve the mechanism(s) responsible for the formation of the central Tibetan Plateau. The two leading and opposing hypotheses for the origin of these rocks are (1) partially molten foundered lower crust, and (2) partial melting of continentally subducted upper crust. The consensus is that some crustal sources within the mantle have reached eclogite facies, while evidence remains insufficient. Reverse zonation for cpx in high Mg# andesitic samples shows a low Mg# core with lower Sr and Sr/Y than the high Mg# rim, suggesting derivation of parent magma by interaction between some eclogite-derived felsic melts and mantle peridotite. Overall, the mantle-like zircon δ18O (mean value of ∼5.9‰) and εHf(t) (up to +6.7) values argue for a mafic source rather than buried upper-crustal rocks. Given the EARs were formed within a short time span after the end of crustal shortening, the original felsic melts were most likely derived from the foundered and eclogitized lower crust. The foundering process explains the early Eocene low-relief topography and the intermediate, eclogite-free modern crustal composition of central Tibet. Surface uplift as a response to lithosphere removal, however, was likely negligible, based on various lines of evidence, including sediment provenance, isotope paleoaltimetry, and thermochronology, perhaps because the central Tibetan crust was weak.

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Baziotis, I., and E. Mposkos. "GEOCHEMISTRY AND TECTONIC SETTING OF ECLOGITE PROTOLITHS FROM KECHROS COMPLEX IN EAST RHODOPE (N.E. GREECE)." Bulletin of the Geological Society of Greece 43, no. 5 (2017): 2522. http://dx.doi.org/10.12681/bgsg.11659.

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Eclogites and partially amphibolitized eclogites from the metamorphic Kechros complex in East Rhodope are studied in order to provide the geodynamic framework for the origin of their protoliths. Geochemical evidence from whole rock major and trace element concentrations shows two distinct protolith groups. The low-Fe-Ti eclogites (Charakoma locality) have low-TiO2 content (<0.67 wt%), negative Nb anomalies, positive Sr anomalies, small negative Zr and Hf anomalies and variable enrichments in LILE (e.g. Rb and Ba). The REE patterns are characterized by strong LREE enrichment (LaN/YbN=5.45-5.81), HREE depletion (GdN/YbN=1.60-1.63) and HREE abundance within the rangeof 9-10 × chondrite. The high-Fe-Ti eclogites (Kovalo and Virsini locality) have variable Sr contents, small to moderate LILE enrichment, HREE`s similar to MORB values and absence of Nb anomalies. The REE patterns of the Kovalo and Virsini eclogites are characterized by LREE depletion and relative flat MREE HREE patterns at approximately 20-30 × chondrite concentrations. Our results suggest that the protoliths of the Low-Ti eclogites show a continental rifting tectonic environment. In contrast, the protoliths of the High-Ti eclogites indicate formation of their protoliths by partial melting in an extensional oceanic environment.

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Benmammar, Anissa, Julien Berger, Antoine Triantafyllou, et al. "Pressure-temperature conditions and significance of Upper Devonian eclogite and amphibolite facies metamorphisms in southern French Massif central." BSGF - Earth Sciences Bulletin 191 (2020): 28. http://dx.doi.org/10.1051/bsgf/2020033.

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The southwestern French Massif central in western Rouergue displays an inverted metamorphic sequence with eclogite and amphibolite facies units forming the top of the nappe stack. They are often grouped into the leptyno-amphibolite complex included, in this area, at the base of the Upper Gneiss Unit. We sampled garnet micaschists and amphibolites to investigate their metamorphic history with isochemical phase diagrams, thermobarometry and U-Pb zircon dating. Our results demonstrate that two different tectono-metamorphic units can be distinguished. The Najac unit consists of biotite-poor phengite-garnet micaschists, a basic-ultrabasic intrusion containing retrogressed eclogites and phengite orthogneisses. Pressure and temperature estimates on micaschists with syn-kinematic garnets yield a prograde with garnet growth starting at 380 °C/6–7 kbar, peak pressure at 16 kbar for 570 °C, followed by retrogression in the greenschist facies. The age of high pressure metamorphism has been constrained in a recent publication between ca. 383 and 369 Ma. The Laguépie unit comprises garnet-free and garnet-bearing amphibolites with isolated lenses, veins or dykes of leucotonalitic gneiss. Thermobarometry and phase diagram calculation on a garnet amphibolite yield suprasolidus peak P-T conditions at 710 °C, 10 kbar followed by retrogression and deformation under greenschist and amphibolite facies conditions. New U-Pb analyses obtained on igneous zircon rims from a leucotonalitic gneiss yield an age of 363 ± 3 Ma, interpreted as the timing of zircon crystallization after incipient partial melting of the host amphibolite. The eclogitic Najac unit records the subduction of a continental margin during Upper Devonian. It is tentatively correlated to a Middle Allochthon, sandwiched between the Lower Gneiss Unit and the Upper Gneiss Unit. Such an intermediate unit is still poorly defined in the French Massif central but it can be a lateral equivalent of the Groix blueschists in the south Armorican massif. The Uppermost Devonian, amphibolite facies Laguépie unit correlates in terms of P-T-t evolution to the Upper Gneiss Unit in the Western French Massif central. This Late Devonian metamorphism is contemporaneous with active margin magmatism and confirms that the French Massif central belonged to the continental upper plate of an ocean-continent subduction system just before the stacking of Mississippian nappes.

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Leitch, A. M., and G. F. Davies. "Mantle plumes and flood basalts: Enhanced melting from plume ascent and an eclogite component." Journal of Geophysical Research: Solid Earth 106, B2 (2001): 2047–59. http://dx.doi.org/10.1029/2000jb900307.

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Liu, Qiang, ZhenMin Jin, and JunFeng Zhang. "An experimental study of dehydration melting of phengite-bearing eclogite at 1.5–3.0 GPa." Science Bulletin 54, no. 12 (2009): 2090–100. http://dx.doi.org/10.1007/s11434-009-0140-4.

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de Hoÿm de Marien, Luc, Pavel Pitra, Florence Cagnard, and Benjamin Le Bayon. "Prograde and retrograde P–T evolution of a Variscan high-temperature eclogite, French Massif Central, Haut-Allier." BSGF - Earth Sciences Bulletin 191 (2020): 14. http://dx.doi.org/10.1051/bsgf/2020016.

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The P–T evolution of a mafic eclogite sample from the Haut-Allier was studied in order to constrain the dynamic of the Variscan subduction in the eastern French Massif Central. Three successive metamorphic stages M1, M2 and M3, are characterized by assemblages comprising garnet1-omphacite-kyanite, garnet2-plagioclase, and amphibole-plagioclase, respectively, and define a clockwise P–T path. These events occurred at the conditions of eclogite (M1; ∼ 20 kbar, 650 °C to ∼ 22.5 kbar, 850 °C), high-pressure granulite (M2; 19.5 kbar and 875 °C) and high-temperature amphibolite facies (M3; < 9 kbar, 750–850 °C), respectively. Pseudosection modelling of garnet growth zoning and mineralogy of the inclusions reveal a prograde M1 stage, first dominated by burial and then by near isobaric heating. Subsequent garnet1 resorption, prior to a renewed growth of garnet2 is interpreted in terms of a decompression during M2. High-pressure partial melting is predicted for both the M1 temperature peak and M2. M3 testifies to further strong decompression associated with limited cooling. The preservation of garnet growth zoning indicates the short-lived character of the temperature increase, decompression and cooling cycle. We argue that such P–T evolution is compatible with the juxtaposition of the asthenosphere against the subducted crust prior to exhumation driven by slab rollback.

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Feng, Peng, Lu Wang, Michael Brown, Tim E. Johnson, Andrew Kylander-Clark, and Philip M. Piccoli. "Partial melting of ultrahigh-pressure eclogite by omphacite-breakdown facilitates exhumation of deeply-subducted crust." Earth and Planetary Science Letters 554 (January 2021): 116664. http://dx.doi.org/10.1016/j.epsl.2020.116664.

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Vrabec, M., J. C. M. de Hoog, and M. Janak. "Partial melting of zoisite eclogite and its significance for trace-element cycling in subduction zones." Geochimica et Cosmochimica Acta 70, no. 18 (2006): A676. http://dx.doi.org/10.1016/j.gca.2006.06.1264.

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MIYAZAKI, Takahiro, Daisuke NAKAMURA, Akihiro TAMURA, Martin SVOJTKA, Shoji ARAI, and Takao HIRAJIMA. "Evidence for partial melting of eclogite from the Moldanubian Zone of the Bohemian Massif, Czech Republic." Journal of Mineralogical and Petrological Sciences 111, no. 6 (2016): 405–19. http://dx.doi.org/10.2465/jmps.151029c.

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Zou, Zongqi, Zaicong Wang, Stephen Foley, et al. "Origin of low-MgO primitive intraplate alkaline basalts from partial melting of carbonate-bearing eclogite sources." Geochimica et Cosmochimica Acta 324 (May 2022): 240–61. http://dx.doi.org/10.1016/j.gca.2022.02.022.

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Chen, Dan-Ling, Liang Liu, Yong Sun, et al. "Felsic veins within UHP eclogite at xitieshan in North Qaidam, NW China: Partial melting during exhumation." Lithos 136-139 (April 2012): 187–200. http://dx.doi.org/10.1016/j.lithos.2011.11.006.

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Xiong, Xiao-Lin. "Trace element evidence for growth of early continental crust by melting of rutile-bearing hydrous eclogite." Geology 34, no. 11 (2006): 945. http://dx.doi.org/10.1130/g22711a.1.

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Butvina, V. G., O. G. Safonov, and Yu A. Litvin. "Experimental study of eclogite melting with participation of the H2O-CO2-KCl fluid at 5 GPa." Doklady Earth Sciences 427, no. 2 (2009): 956–60. http://dx.doi.org/10.1134/s1028334x09060154.

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GAO, X. Y., Y. F. ZHENG, and Y. X. CHEN. "Dehydration melting of ultrahigh-pressure eclogite in the Dabie orogen: evidence from multiphase solid inclusions in garnet." Journal of Metamorphic Geology 30, no. 2 (2011): 193–212. http://dx.doi.org/10.1111/j.1525-1314.2011.00962.x.

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Hammouda, Tahar. "High-pressure melting of carbonated eclogite and experimental constraints on carbon recycling and storage in the mantle." Earth and Planetary Science Letters 214, no. 1-2 (2003): 357–68. http://dx.doi.org/10.1016/s0012-821x(03)00361-3.

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Shkodzinskiy, V. S. "Происхождение магм и вулканических взрывов в океанических и субдукционных областях с учетом данных о горячей гетерогенной аккреции Земли". Bulletin of the North-East Science Center, № 1 (28 березня 2022): 40–48. http://dx.doi.org/10.34078/1814-0998-2022-1-40-48.

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The obtained numerous proofs of hot heterogeneous accretion of the Earth and the calculated quantitative models of magmas lead to a fundamentally new solution for the genetic problems of magmatic petrology. They indicate the formation of geospheres and the initial substance of magmas resulted from fractionation of the global magmatic ocean, which arose as a result of a huge impact heat release during mantle accretion. Due to the increase in temperature as accretion progressed, a reverse geothermal gradient first existed in the mantle, and on the early Earth there were no modern geodynamic conditions. The gradual warming of the mantle by the initially very hot core led to the formation of a direct geothermal gradient and convection as well as oceanic and subduction regions in the Neoproterozoic. In the oceans, magmas are formed as a result of decompression melting during the surfacing of eclogite lenses, which emerged by way of filling impact craters with melts of the synaccretionary magmatic ocean. Magmas of subduction regions are the result of frictional melting of the magmatic ocean differentiates. Volcanic explosions occur under the influence of high pressure of the gas phase preserved by decompressional solidification of magmas at the shallow stage of ascent.

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Drummond, M. S., M. J. Defant, and P. K. Kepezhinskas. "Petrogenesis of slab-derived trondhjemite–tonalite–dacite/adakite magmas." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 87, no. 1-2 (1996): 205–15. http://dx.doi.org/10.1017/s0263593300006611.

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ABSTRACT:The prospect of partial melting of the subducted oceanic crust to produce arc magmatism has been debated for over 30 years. Debate has centred on the physical conditions of slab melting and the lack of a definitive, unambiguous geochemical signature and petrogenetic process. Experimental partial melting data for basalt over a wide range of pressures (1–32 kbar) and temperatures (700–1150°C) have shown that melt compositions are primarily trondhjemite–tonalite–dacite (TTD). High-Al (> 15% Al2O3 at the 70% SiO2 level) TTD melts are produced by high-pressure (≥ 5 kbar) partial melting of basalt, leaving a restite assemblage of garnet + clinopyroxene ± hornblende. A specific Cenozoic high-Al TTD (adakite) contains lower Y, Yb and Sc and higher Sr, Sr/Y, La/Yb and.Zr/Sm relative to other TTD types and is interpreted to represent a slab melt under garnet amphibolite to eclogite conditions. High-Al TTD with an adakite-like geochemical character is prevalent in the Archean as the result of a higher geotherm that facilitated slab melting. Cenozoic adakite localities are commonly associated with the subduction of young (<25 Ma), hot oceanic crust, which may provide a slab geotherm (≍9–10°C km−1) conducive for slab dehydration melting. Viable alternative or supporting tectonic effects that may enhance slab melting include highly oblique convergence and resultant high shear stresses and incipient subduction into a pristine hot mantle wedge. The minimum P–T conditions for slab melting are interpreted to be 22–26 kbar (75–85 km depth) and 750–800°C. This P–T regime is framed by the hornblende dehydration, 10°C/km, and wet basalt melting curves and coincides with numerous potential slab dehydration reactions, such as tremolite, biotite + quartz, serpentine, talc, Mg-chloritoid, paragonite, clinohumite and talc + phengite. Involvement of overthickened (>50 km) lower continental crust either via direct partial melting or as a contaminant in typical mantle wedge-derived arc magmas has been presented as an alternative to slab melting. However, the intermediate to felsic volcanic and plutonic rocks that involve the lower crust are more highly potassic, enriched in large ion lithophile elements and elevated in Sr isotopic values relative to Cenozoic adakites. Slab-derived adakites, on the other hand, ascend into and react with the mantle wedge and become progressively enriched in MgO, Cr and Ni while retaining their slab melt geochemical signature. Our studies in northern Kamchatka, Russia provide an excellent case example for adakite-mantle interaction and a rare glimpse of trapped slab melt veinlets in Na-metasomatised mantle xenoliths.

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Liu, Qiang, and Yao Wu. "Dehydration melting of UHP eclogite and paragneiss in the Dabie orogen: Evidence from laboratory experiment to natural observation." Chinese Science Bulletin 58, no. 35 (2013): 4390–96. http://dx.doi.org/10.1007/s11434-013-6075-9.

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Liu, Qiang, Yao Wu, and Junfeng Zhang. "Experimental investigation on low-degree dehydration partial melting of biotite gneiss and phengite-bearing eclogite at 2 GPa." Journal of Earth Science 22, no. 6 (2011): 677–87. http://dx.doi.org/10.1007/s12583-011-0219-0.

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Litasov, Konstantin D., Anton Shatskiy, and Eiji Ohtani. "Melting and subsolidus phase relations in peridotite and eclogite systems with reduced COH fluid at 3–16 GPa." Earth and Planetary Science Letters 391 (April 2014): 87–99. http://dx.doi.org/10.1016/j.epsl.2014.01.033.

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Dasgupta, Rajdeep, Marc M. Hirschmann, and Nikki Dellas. "The effect of bulk composition on the solidus of carbonated eclogite from partial melting experiments at 3 GPa." Contributions to Mineralogy and Petrology 149, no. 3 (2005): 288–305. http://dx.doi.org/10.1007/s00410-004-0649-0.

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Song, Shuguang, Yaoling Niu, Li Su, Chunjing Wei, and Lifei Zhang. "Adakitic (tonalitic-trondhjemitic) magmas resulting from eclogite decompression and dehydration melting during exhumation in response to continental collision." Geochimica et Cosmochimica Acta 130 (April 2014): 42–62. http://dx.doi.org/10.1016/j.gca.2014.01.008.

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Spandler, C., G. Yaxley, D. H. Green, and A. Rosenthal. "Phase Relations and Melting of Anhydrous K-bearing Eclogite from 1200 to 1600 C and 3 to 5 GPa." Journal of Petrology 49, no. 4 (2007): 771–95. http://dx.doi.org/10.1093/petrology/egm039.

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Chen, Yi-Xiang, Yong-Fei Zheng, Xiao-Ying Gao, and Zhaochu Hu. "Multiphase solid inclusions in zoisite-bearing eclogite: evidence for partial melting of ultrahigh-pressure metamorphic rocks during continental collision." Lithos 200-201 (July 2014): 1–21. http://dx.doi.org/10.1016/j.lithos.2014.04.004.

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Tsuno, Kyusei, and Rajdeep Dasgupta. "Melting phase relation of nominally anhydrous, carbonated pelitic-eclogite at 2.5–3.0 GPa and deep cycling of sedimentary carbon." Contributions to Mineralogy and Petrology 161, no. 5 (2010): 743–63. http://dx.doi.org/10.1007/s00410-010-0560-9.

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Hageskov, Bjørn, and Bente Mørch. "Adakitic high-Al trondhjemites in the Proterozoic Østfold-Marstrand Belt, W Sweden." Bulletin of the Geological Society of Denmark 46 (June 25, 1999): 165–79. http://dx.doi.org/10.37570/bgsd-1999-46-14.

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This paper investigates the first identified intrusives in SE Norway–W Sweden with the specific signature of adakitic arc magmas, which in recent settings are preferably explained as partial melts extracted from subducted oceanic crust. The studied adakitic high–Al trondhjemites occur as sheets in the Koster archipelago, W Sweden, where they form the oldest recognized granitoids in the metasupracrustals of the Stora Le–Marstrand formation. The trondhjemites were intruded during a short ca. 1.59–1.58 Ga interlude between the early and the main orogenic events of the Gothian orogeny (1.6–1.56 Ga, Åhäll et al. 1998). This interlude is otherwise characterized by ‘ordinary’ calcalkaline magmatism which on Koster is predated by the trondhjemites. The typical adakitic signature suggests that the trondhjemitic magma was extracted from a MORB (Mid Ocean Ridge Basalt) like source, and that a hornblende eclogite restite was left in the region of melting. The restite composition indicates melt extraction at PT conditions in the range of 18–25 kb/800°C to 13-15 kb/950–1050°C. These requirement can only be met by subduction of warm (young or shear heated) oceanic crust beneath a crust including early Gothian metamorphosed and deformed Stora Le–Marstrand formation or by melting of metabasaltic material at a deep crustal level. The latter is a less likely possibility and demands that the Stora Le–Marstrand formation at the time of melt extraction was part of a > 45 km thick crust.

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Deng, Chenglai, Changqing Hu, Ming Li, and Wu Li. "Iron Isotope Composition of Adakitic Rocks: The Shangcheng Pluton, Western Dabie Orogen, Central China." Minerals 11, no. 12 (2021): 1356. http://dx.doi.org/10.3390/min11121356.

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There has been little research on the metal isotopic composition of adakitic rock. The main objective of our investigation was to obtain more knowledge on the iron isotopic composition of adakitic rocks and provide new evidence for the genesis of Shangcheng pluton from an iron isotope perspective. The Dabie orogen is divided into eastern and western areas by the Shangcheng-Macheng fault, and the Shangcheng pluton is located in the western Dabie orogen area. The iron isotopic composition of these rocks ranges from 0.08‰ to 0.20‰ (2SD, n = 3). The δ56Fe values of two rocks from the SGD (Sigudun) unit are relatively low (0.11 ± 0.03‰ and 0.08 ± 0.04‰), while the δ56Fe values of the other samples are basically consistent (0.18–0.2‰). Evidence from elemental geochemical characteristics and petrogenesis defines the Shangcheng pluton as adakitic rocks. Our investigation on the elemental and isotopic compositions hints that the enrichment of heavy iron isotopes cannot be explained by weathering/alteration and fluid exsolution. Fractional crystallization of magnetite may account for the enrichment of light iron isotopes in two rocks from the SGD unit, while the fractional iron isotope trend in the other five samples can be explained by Δ56Fecrystal-melt = ~0.035‰. Two investigated rocks from SGD units may have been derived from the partial melting of amphibolite, while the other five samples may have been derived from the partial melting of eclogite containing 10–15% garnet.

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