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Incompatible element
About: Incompatible element is a research topic. Over the lifetime, 2420 publications have been published within this topic receiving 154052 citations.
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TL;DR: In this paper, the gabbros from new discovered Zhongcang ophiolitic melange are studied through petrology, whole-rock geochemistry, zircon U-Pb dating and Lu-Hf isotope.
Abstract: In order to investigate the evolution of Shiquanhe-Yongzhu-Jiali ophiolitic melange belt, the gabbros from new discovered Zhongcang ophiolitic melange are studied through petrology, whole-rock geochemistry, zircon U-Pb dating and Lu-Hf isotope. The gabbros investigated in this paper contain cumulate gabbro and gabbro dike, and they have undergone greenschist-amphibolite facies metamorphism. The chondrite normalized rare earth element (REE) patterns of most of these rocks show flat types with slightly light REE (LREE) depletion and the N-MORB normalized incompatible elements diagrams indicate depletion in high field strength elements (HFSE) (Nb, Ta) and enrichment in large ion lithophile elements (LILE). These gabbros have island arc and mid-ocean ridge basalt affinities, suggesting that they were originated in an oceanic back arc basin. Whole rock geochemistry and high positive ɛ
Nd(t) values show that these gabbros were derived from ∼30% partial melting of a spinel lherzolite mantle, which was enriched by interaction with slab-derived fluids and melts from sediment. U-Pb analyses of zircons from cumulate gabbro yield a weighted mean age of 114.3±1.4 Ma. Based on our data and previous studies, we propose that an intra-oceanic subduction system and back arc basin operated in the Neo-Tethy Ocean of central Tibet during Middle Jurassic and Early Cretaceous, resembling modern active intra-oceanic subduction systems in the western Pacific.
43 citations
TL;DR: In this article, major and trace element plus Sr−Nd−Hf−Pb isotope analyses of 56 whole rocks from throughout the Arenal volcano eruption were performed using least squares and MELTS models despite the mineral complexity of the rocks.
43 citations
TL;DR: The Coire Uaigneich Granophyre (CUG) was formed by the mixing of two magmas as mentioned in this paper, one of which contained relict quartz and zircon, and the other was an acid differentiate of basaltic magma and was enriched in incompatible elements such as Zr and Y.
Abstract: Field relations, petrographic features, major and selected trace element compositions, and Sr- and Pb- isotope characteristics indicate that the Coire Uaigneich Granophyre (CUG) was formed by the mixing of two magmas. One of these, a liquid of high 87Sr/86Sr ratio (ca. 0.731) formed by the anatexis of late Precambrian Torridonian sediments, contained relict quartz and zircon. The other liquid was an acid differentiate of basaltic magma and was enriched in incompatible elements such as Zr and Y. The two magmas mixed in the proportions of approximately two parts anatectic melt to one part acid differentiate. Hydrothermal metamorphism had no significant effect on the bulk chemistry of the CUG.
43 citations
TL;DR: Petrographic, major and trace element data for xenoliths from the andesitic Avacha volcano (Kamchatka) were reported in this article, where the authors identify "rapidly crystallized" veins that cut wall-rock olivine without petrographic evidence of reaction, and "reactive" veins subdivided into 'thick' (0*5-1 mm) and 'thin' (<€0* 5 mm).
Abstract: We report petrographic, major and trace element data for xenoliths from the andesitic Avacha volcano (Kamchatka), which host orthopyroxene (opx)-rich veins of mantle origin formed either by rapid crystallization of intruded melts or by their interaction with the host harzburgite. Studies of such veins may give better insights into sub-arc mantle processes (in particular on a millimetre to centimetre scale) than those of (1) arc xenoliths that do not preserve solidified initial metasomatizing agents, (2) massif peridotites, probably modified during their emplacement, or (3) arc magmatic rocks, which provide indirect information. We seek to trace the evolution of these agents as they react with the host peridotite and to assess their impact on the wall-rocks. The veins cross-cut spinel harzburgite and consist mainly of opx with minor olivine, clinopyroxene (cpx) and/or amphibole. We identify 'rapidly crystallized' veins that cut wall-rock olivine without petrographic evidence of reaction, and 'reactive' veins subdivided into 'thick' (0*5-1 mm) and 'thin' (<€0*5 mm). Minerals in the rapidly crystallized veins are depleted in rare earth elements (REE) and high field strength elements (HFSE) and enriched in fluid-mobile elements relative to REE. Minerals in the reactive veins have higher Ti, Al, Cr and alkalis than minerals in the rapidly crystallized veins, as well as highly variable trace element abundances, especially in reaction zones, thin veins and related metasomatic pockets in the host peridotite. They commonly show U-shaped REE patterns and positive Zr and Hf spikes in normalized trace element patterns. Our data, supported by recent reports, show that the rapidly crystallized veins formed between 1200°C and 900°C from a liquid derived by fluid-fluxed melting of a refractory (harzburgitic) mantle source depleted in heavy REE. The reactive veins formed via 'fractionation-reactive percolation' from fractionated hydrous derivatives of the melts that precipitated the rapidly crystallized veins. These liquids re-equilibrated with the host through diffusion and fluid-assisted dissolution-precipitation reactions, whose end-products are thin reactive veins and metasomatic pockets with distinctive U-shaped REE patterns and Zr-Hf spikes. Some Avacha xenoliths contain veins of Fe-rich amphibole deposited from the host magma that penetrated fractures in the peridotite fragments during their transport to the surface. These products of contamination were mistakenly attributed to mantle metasomatism in previous studies of other suites of Avacha mantle xenoliths. Trace element abundances in such veins are higher than for reactive veins of mantle origin, but both have similar trace element patterns (U-shaped REE patterns and Zr-Hf spikes) suggesting that 'fractionation-reactive percolation' also took place during their formation and is common during interaction of refractory peridotites with percolating melts and fluids. Metasomatic pockets of cpx and amphibole replacing coarse opx and spinel in the host peridotites commonly occur in the vicinity of fractures that lead to reactive opx-rich veins. The cpx and amphiboles in the pockets show progressive depletion in middle REE and HFSE at constant light REE and/or large ion lithophile elements away from the veins towards the host. This indicates that residual hydrous fluids expelled from the source veins enriched the wall-rock peridotites in incompatible elements but were progressively modified by reaction with the host with increasing percolation distance. This process produces disseminated pockets of metasomatic minerals with a broad range of compositions from a single initial liquid and strongly affects the trace element budgets of the harzburgite xenoliths from Avacha. We show that melts and fluids are likely to undergo profound transformation as they travel through and react with the refractory host mantle, even on a millimetre to centimetre scale. The composition of the initial metasomatizing agents can only be inferred from the composition of the metasomatic phases in mantle rocks combined with appropriate partition coefficients if these phases come from well-equilibrated mineral assemblages located close to melt and/or fluid sources.
43 citations
TL;DR: In this paper, Petrography and whole-rock major and trace element geochemistry of 38 samples mainly from a drill core through the entire Fedorivka layered intrusion (Korosten Pluton), as well as mineral compositions (microprobe analyses and separated mineral fraction analyses of plagioclase, ilmenite, magnetite and apatite) of 10 samples.
42 citations