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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 article, the extinction of spreading at 3.3 Ma seems to have led to a temporary magma oversupply with E-MORB signatures, where enriched materials have preferentially participated in the melting.
Abstract: The fossilized Antarctic-Phoenix Ridge (APR) with three segments (P1, P2, and P3), Drake Passage, is distant from the known hotspots, and consists of older N-MORB formed prior to the extinction of spreading and younger E-MORB after extinction. The older N-MORB (3.5–6.4 Ma) occur in the southeastern flank of the P3 segment (PR3) and the younger E-MORB (1.4–3.1 Ma) comprise a huge seamount at the former ridge axis of the P3 segment (SPR) and a big volcanic edifice at the northwestern flank of the P2 segment (PR2). The PR3 basalts have higher Mg#, K/Ba, and CaO/Al2O3 and lower Zr/Y, Sr, and Na80 (fractionation-corrected Na2O to 8.0% MgO) with slight enrichment in incompatible elements and almost flat REE patterns. The SPR and PR2 basalts are highly enriched in incompatible elements and LREE. The extinction of spreading at 3.3 Ma seems to have led to a temporary magma oversupply with E-MORB signatures. Geochemical signatures such as Ba/TiO2, Ba/La, and Sm/La suggest the heterogeneity of upper mantle and formation of E-MORB by higher contribution of enriched materials (e.g., metasomatized veins) to mantle melting than the N-MORB environment. E-MORB magmas beneath the APR seen to have been produced by low-degree melting at deeper regime, where enriched materials have preferentially participated in the melting. The occurrence of E-MORB at the APR is a good example to better understand what kinds of magmatism would occur in association with extinction of the ridge spreading.
33 citations
TL;DR: In this article, the authors report the quadruple sulfur isotope compositions, sulfur contents and speciation major and trace elements (including copper and chlorine abundances) of eleven basalts collected in the Garrett transform fault.
33 citations
TL;DR: In this paper, the formation of a basin-scale impact on the Moon at 4.20 ± 0.07 ǫ Ga based on the 147 Sm − 143 Nd isochron age of a noritic anorthosite melt rock from lunar breccia 67955 is investigated.
33 citations
TL;DR: In this article, the authors defined a lower-crustal interaction zone, defined to be the part of the lower crust at or above its solidus, which is defined as the region of lower crust reaching postorogenic thermal equilibrium slowly and had essentially the same thickness as it did prior to deformation.
Abstract: Neogene through Pleistocene lava flows of the Nevados de Payachata region (lat 18°S) on the Altiplano of northern Chile fall into two discrete chemical groups defined by age and incompatible element concentrations The Neogene suite (105-66 Ma) has trace element concentrations comparable to arc magmas erupted on thin crust in central Chile Pleistocene lava flows (029-0 Ma) are enriched in incompatible elements relative to Neogene samples but have similar Sr, Nd, and Pb isotopic ratios Incompatible element enrichment in mafic rocks reflects deep-crustal or subcrustal processes Neogene volcanism in northern Chile immediately followed a period of intense crustal thickening Uplift rates accelerated at ∼15 Ma, indicating that the "thin-crust"-type Neogene magmas actually traversed a thickened crust The isotopic and trace element relations are the result of contamination of mantle-derived basalts in an upwardly growing lower-crustal interaction zone, defined to be the part of the lower crust at or above its solidus Because the lower crust reaches postorogenic thermal equilibrium slowly, the lower-crustal interaction zone during Neogene magmatism had essentially the same thickness as it did prior to deformation Thermal relaxation of the lower crust after thickening produced an upwardly growing column of crust near its solidus Only 15 my after crustal thickening did ascending, mantle-derived mafic magmas encounter previously unmelted, fertile crust near its solidus in the upper fringes of the interaction zone Here the magmas were contaminated with incompatible element-enriched crustal melts, forming the parental magmas for the Pleistocene suite
33 citations
TL;DR: In this article, a three-stage model for the evolution of seafloor peridotites is proposed, involving a former depletion event, during which the IBM forearc peridots experienced 20-25% polybaric fractional melting during adiabatic upwelling; a second depletion event characterised by a marked impoverishment in modal orthopyroxene, related to the upraise migration of ultra-depleted melts; and a late interaction between a relatively small volume of residual melts and the refractory mantle sequence.
Abstract: Serpentinised spinel harzburgites to orthopyroxene-rich spinel dunites recovered during the Ocean Drilling Program (ODP) Leg 195 on top of the South Chamorro Seamount (southern sector of the Mariana forearc, West Pacific Ocean), along with additional spinel harzburgites from Conical and Torishima Seamounts (northern Mariana and Izu-Bonin forearc, respectively), previously collected during the ODP Leg 125, have been investigated to shed light on the nature and evolution of forearc mantle in the intra-oceanic supra-subduction environment. All the samples show a marked heterogeneity in terms of petrographic, mineralogical and geochemical features that suggests a complex, multistage evolution involving, at variable extent, partial melting, reactive porous flow melt migration and subsolidus metamorphic re-equilibration under decreasing T and open system conditions. Geochemical evidence of the interaction between peridotites and various melts/fluids is the ubiquitous enrichment in highly incompatible elements, such as Large Ion Lithophile Elements (LILE). As for the high-T evolution of these peridotites, a three-stages-model is proposed, involving: 1) a former depletion event, during which the IBM forearc peridotites experienced 20-25% polybaric fractional melting during adiabatic upwelling; 2) a second depletion event characterised by a marked impoverishment in modal orthopyroxene, related to the upraise migration of ultra-depleted melts; 3) a late interaction between a relatively small volume of residual melts and the refractory mantle sequence. Oxidation state of the mantle minerals meanly decreases from north (Torishima Seamount) to south (South Chamorro), according to significant different contributions coming from the subducted Pacific Plate. In particular, the absence of a marked oxidation in South Chamorro peridotites suggests that the percolating melts during Stage 2 had not significant slab-derived component. This observation lead us to conclude that a thermal anomaly in the western Pacific mantle rather than the injection of hydrous components must be the “engine” determining the extreme depletion of the oceanic forearc peridotites and the arc formation. In this frame, it is proposed that IBM peridotites during Stage 1 underwent decompression partial melting and contributed to arc volcanism as actual mantle source. Successively, they were emplaced at relatively shallow levels (Stage 2), constituting the top of a strongly refractory mantle column and being percolated by melts produced by plumbing sources of the arc volcanism.
33 citations