Incompatible element

About: Incompatible element is a research topic. Over the lifetime, 2420 publications have been published within this topic receiving 154052 citations.

Fast assimilation of serpentinized mantle by basaltic magma

Abstract: The most abundant terrestrial lavas, mid-ocean ridge and ocean island basalt (MORB and OIB), are commonly considered to be derived from a depleted MORB-mantle component and more specific, variably enriched mantle plume sources. However, findings of oceanic lavas and mafic cumulates issued from melts, enriched in chlorine and having a radiogenic Sr ratio, can be attributed to an interaction between the asthenosphere-derived melts and lithospheric peridotite variably hydrated due to penetration of hydrothermal water down to and below Moho level. To constrain mechanisms and rates responsible for the interaction, we report results of experiments of reaction between serpentinite and tholeiitic basaltic melt. Results show that the reaction proceeds via a multi-stage mechanism: (i) transformation of serpentinite into Cr-rich spinel-bearing harzburgite containing pore fluid, (ii) partial melting and dissolution of the harzburgite assemblage with formation of interstitial hydrous melts, and (iii) final assimilation of the Cr-rich spinel-bearing harzburgite/dunite and formation of hybrid basaltic melts with high MgO and elevated Cr and Ni contents. Assimilation of serpentinite by basaltic melt may occur under elevated melt/rock ratios and may lead to chromitite formation. Our experiments provide evidence that MORB and high-Mg-Cr orthopyroxene-rich cumulates depleted in incompatible elements can be produced from common mid-ocean ridge basaltic melts modified by reaction with hydrated lithospheric peridotite. We established that the rate of assimilation of serpentinized peridotite is controlled by silica diffusion in the reacting hydrous basaltic melt.

Reverse magmatic evolution series of the Xiangshan volcanic intrusive complex

Abstract: The Xiangshan area as the largest volcanic-hosted uranium ore occurrence in China has received great attention.From eruption→viscous lava extrusion→intrusion,the SiO2 content,Rb/Sr and Rb/Ba of the Xiangshan volcanic-intrusive complex decreased,while the TFe (Fe2O3+FeO),CaO,MgO,P2O5 and TiO2 contents and the solidification index SI and δEu increased progressively,showing that the magmatic evolution has an antithetic relationship with the magmatic differentiation trend reflected by increasing acidity in the normal magma chamber,which is called the reverse magmatic evolution series.The incompatible element radios such as Th/U,Rb/Ba,Th/Nb,Th/Ta,Nb/Ta and La/Nb vary widely,showing no distinct synthetic or antithetic relationship with the major components such as SiO2.The REE distribution patterns also vary.These suggest that the volcanic eruption facies,viscous lava extrusion facies and intrusive facies were derived from different sources.

Multi-stage sulfide evolution of the Moran Ni sulfide ore, Kambalda, Western Australia: insights into the dynamics of ore forming processes of komatiite-hosted deposits

Abstract: The Moran komatiite-hosted Ni sulfide deposit at Kambalda (Australia) is one of the better preserved orebodies at Kambalda. Its geochemical signature is used to investigate the evolution of the sulfide mineralization. The orebody has several parts, including a flanking segment where massive sulfides formed relatively early and a central portion in a 40-m-deep erosional embayment representing a later generation of massive and net-textured sulfides. Basal massive sulfides within the deep embayment vary systematically in their chalcophile element contents (Ni, PGE, Au, Te, As, Bi). Elements compatible in monosulfide solid solution (MSS) exhibit the highest concentration at the edge of the orebody (up to 4.3 ppm Ir + Os + Ru + Rh), whereas incompatible elements are most concentrated in the centre (up to 11.2 ppm Pt + Pd + Au). This difference in element distributions is explained by fractional crystallization of sulfide melt from the edge towards the centre. To explain the vertical movement of the residual fractionated melt, a new model of sulfide crystallization is proposed. A low-viscosity boundary layer containing incompatible elements is formed between MSS and sulfide melt. This melt propagates with the crystallization front towards the centre of the sulfide melt pool. Trace element variations in pentlandite (e.g. Co) and composite Co- and Bi-bearing arsenide-telluride grains suggest that during the final stages of crystallization, an immiscible Co-As-Te-Bi melt is formed.

Rochas metamáficas associadas ao arco magmático de Goiás na região de Pontalina - GO

Abstract: In the Pontalina region, Goias, many metamafic bodies presenting various sizes are associated to gneiss and metasedimentary rocks occur within the Goias Magmatic Arc. Geochemical data shows that the metamafic rocks are of magmatic origin, present alkaline to sub alkaline compositions and tholeiitic affinities. The signatures in relation to the incompatible elements may be compared to that of the enriched mid ocean ridge basalt (E-MORB) or to that of island arc basalt (IAB). Isotopic studies indicate Neoproterozoic ages with T DM between 1.0 and 1.2 Ga and possibly they are related to oceanic crust subduction and formation of island arcs.

Comments on the progress on the applications of Re-Os isotopic study on the ophiolites.

Abstract: Re-Os isotopic systematics is the best tracer on studying the ophiolitic peridotite because,in contrast with the geochemical properties of Sm-Nd,Rb-Sr,U-Th-Pb and Lu-Hf,all of which are incompatible elements,Os is a compatible element in most mantle melting processes,so that it generally remains in the mantle,whereas the much more incompatible Re is extracted and enriched in the melt.This system therefore provides information that is different from,and complementary to,what we can learn from Sm-Nd,Rb-Sr,U-Th-Pb and Lu-Hf.Four points of progress have been made on the application of Re-Os studying on the ophiolite. First,determining the Re-Os characteristics of the ophiolite in which peridotites are low Re/Os and ~(187)Os/~(188) Os ratios,whereas lavas are high Re/Os and ~(187)Os/~(188)Os ratios;Secondly,dating of PGM within the ophiolitic chromitite by Re depleted ages supports the idea that the complicated ultramafic rocks of ophiolite are produced by multistage partial melting of mantle;Thirdly,measuring ~(187)Os/~(188)Os of MORB and the sulfides in abyssal peridotites (AP) indicate that there is no gap between the MORB and the most AP with higher ~(187)Os/~(188)Os ratios than DMM(0.1246),and gap still occurring between MORB and some AP with lower ~(187)Os/~(187)Os ratios than DMM, namely,Re-Os study on the ophiolite provides a new constraining on the geochemical relations on the residual peridotites and lavas; Finally,revealing that the ophiolitic peridotites contain the older sub-continental lithospheric mantle (SCLM),this case is not previously known before Re-Os analyzing.Although the Re-Os isotope made progresses on studying the ophiolite,more problems,such as dating the Phanerozoic ophiolitic peridotites,still want to be done further work due to the short time of application of Re-Os study on the ophiolite.