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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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Journal ArticleDOI
TL;DR: The geochemical characteristics of mantle xenoliths (spinel lherzolites) in Quaternary alkaline basalts from the northwestern Ethiopian plateau provide new insight into the conditions of melting associated with the Afar plume.
Abstract: The geochemical characteristics of mantle xenoliths (spinel lherzolites) in Quaternary alkaline basalts from the northwestern Ethiopian plateau provide new insight into the conditions of melting associated with the Afar plume. The major element compositions of the spinel lherzolites are in the range of those of the primitive mantle. The high modal content of the clinopyroxene (14–23%) indicate that the mantle xenoliths are fertile spinel lherzolites that have experienced insignificant partial melting. However, enrichment in highly incompatible elements (LREE, Ba, Pb, Th, and U) and the absence of any typical metasomatic minerals indicate that the spinel lherzolites underwent an event of later cryptic metasomatic enrichment induced by plume–related, hydrous fluid–rich silicate melts. The 87Sr/86Sr (0.70184–0.70324), 143Nd/144Nd (0.51313–0.51338), and 206Pb/ 204Pb (17.17–19.06) values of the clinopyroxene separate from the spinel lherzolites display systematic variations between those of depleted MORB mantle (DMM) and enriched compositions interpreted as related to the Afar mantle plume. The mineral compositions yield an estimated temperature and pressure in the range of 921– 973 °C and 13–17 kbar, respectively, indicating that the mantle xenoliths originated at shallow depths of 40 to 55 km above the Afar mantle plume.

3 citations

Book ChapterDOI
01 Jan 1975
TL;DR: In this paper, an upper mantle model based upon the inclusions in kimberlite has conspicuously higher Mg/Mg + Fe, and differs in other important respects from hypothetical pyrolite models and from models based on ultramafic nodules in basalts, although it has some similarities with a model based on alpine-type garnet peridotites.
Abstract: The ultramafic nodules in kimberlite are little altered samples of the upper mantle. Source mantle (garnet-lherzolite), residual mantle (garnet-harzburgite and harzburgite), primary magma (ultrabasic) and high-pressure cumulates (eclogite) are all represented. Twenty-seven new analyses of ultramafic rocks and 24 new analyses of their constituent minerals are presented and used in conjunction with published data to demonstrate that the upper mantle sampled by kimberlite displays a mineralogical and chemical variation reflecting very deep seated partial melting events which produced from the rocks affected about 15 % of ultrabasic primary magma at a temperature not much more than 50°C above the solidus. The majority of the subcontinental mantle section sampled by kimberlite is not, however, a totally depleted residuum, but is potentially fertile source mantle. An upper mantle model based upon the inclusions in kimberlite has conspicuously higher Mg/Mg + Fe, and differs in other important respects from hypothetical “pyrolite” models and from models based on ultramafic nodules in basalts, although it has some similarities with a model based on alpine-type garnet peridotites. Primary magmas in equilibrium with the magnesian source rocks indicated by the kimberlite model are themselves so magnesian and poor in incompatible elements that extensive fractionation of eclogite and/or olivine is required in order to account for the chemistry of apparently parental tholeiite magmas erupted at the earth's surface. The nickel contents of these erupted magmas do not constitute a bar to previous extensive olivine fractionation.

3 citations

Journal ArticleDOI
TL;DR: Factor analysis of the same samples provides a number of underlying causes that control their chemistry; most important of all is the heavy mineral content followed by the influence of basaltic detritus form the Harrah.

3 citations

Journal ArticleDOI
TL;DR: In this paper, it was shown that trace element enrichment and MORB-like features of the Solander and Little Solander volcanic rocks require a strong fractionation mechanism to impart the high incompatible element concentrations and subduction-related (e.g. high LILE/HFSE) geochemical signatures.
Abstract: Subduction-related Quaternary volcanic rocks from Solander and Little Solander Islands, south of mainland New Zealand, are porphyritic trachyandesites and andesites (58.20–62.19 wt% SiO2) with phenocrysts of amphibole, plagioclase and biotite. The Solander and Little Solander rocks are incompatible element enriched (e.g. Sr ~931–2,270 ppm, Ba ~619–798 ppm, Th ~8.7–21.4 ppm and La ~24.3–97.2 ppm) with MORB-like Sr and Nd isotopic signatures. Isotopically similar quench-textured enclaves reflect mixing with intermediate (basaltic-andesite) magmas. The Solander rocks have geochemical affinities with adakites (e.g. high Sr/Y and low Y), whose origin is often attributed to partial melting of subducted oceanic crust. Solander sits on isotopically distinct continental crust, thus excluding partial melting of the lower crust in the genesis of the magmas. Furthermore, the incompatible element enrichments of the Solander rocks are inconsistent with partial melting of newly underplated mafic lower crust; reproduction of their major element compositions would require unrealistically high degrees of partial melting. A similar argument precludes partial melting of the subducting oceanic crust and the inability to match the observed trace element patterns in the presence of residual garnet or plagioclase. Alternatively, an enriched end member of depleted MORB mantle source is inferred from Sr, Nd and Pb isotopic compositions, trace element enrichments and eHf ≫ 0 CHUR in detrital zircons, sourced from the volcanics. 10Be and Sr, Nd and Pb isotopic systematics are inconsistent with significant sediment involvement in the source region. The trace element enrichments and MORB-like Sr and Nd isotopic characteristics of the Solander rocks require a strong fractionation mechanism to impart the high incompatible element concentrations and subduction-related (e.g. high LILE/HFSE) geochemical signatures of the Solander magmas. Trace element modelling shows that this can be achieved by very low degrees of melting of a peridotitic source enriched by the addition of a slab-derived melt. Subsequent open-system fractionation, involving a key role for mafic magma recharge, resulted in the evolved andesitic adakites.

3 citations

Journal ArticleDOI
TL;DR: In this article, the authors suggest that the shoshonite magmas were formed by partial melting of a mantle source enriched by contemporaneous adakitic magmas derived by melting of subducted oceanic crust.
Abstract: 2.7 Ga shoshonites occur in the Upper Keewatin Assemblage of the Shoal Lake-Lake of the Woods area in the northwestern part of the late Archean Wabigoon Belt, Superior Province, Canada. They are enriched both in large-ion lithophile elements (K, Rb, Sr, Ba and Th) and compatible elements (Mg, Ni and Cr). Their incompatible element abundance patterns exhibit a negative Ta anomaly and high La/Yb and Sr/Y ratios, similar to adakitic volcanic rocks in the same area. We suggest that the shoshonite magmas were formed by partial melting of a mantle source enriched by contemporaneous adakitic magmas derived by melting of subducted oceanic crust. We further speculate on the origin of Timiskaming alkaline volcanic rocks, located 1100 km to the east in the Abitibi Greenstone Belt, Superior Province, the archetypal example of late Archean alkaline magmatism. It seems probable that the mantle sources of Timiskaming alkaline rocks also were metasomatized by adakitic magmas, but that this source enrichment occurred 20-30 m.y. prior to the Timiskaming magmatism.

3 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20237
202216
202157
202056
201960
201851