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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: This article showed that anomalous enrichment in incompatible elements of this nearside reservoir dramatically lowers the melting temperature of the source rock for these magmas and may have resulted in 4 to 13 times more magma production under the nearside crust, even without any contribution from radioactivity.
Abstract: The Moon’s Earth-facing hemisphere hosts a geochemically anomalous region, the Procellarum KREEP Terrane, which is widely thought to have provided radiogenic heat for mantle melting from ~3.9 to ~1 billion years ago. However, there is no agreement on such a link between this region and the earliest pulse of post-differentiation crust-building magmatism on the Moon at ~4.37 billion years ago; whether this early magmatism was global or regional has been debated. Here we present results of high-temperature experiments that show the nearside geochemical anomaly may have caused asymmetric early crust building via mantle melting-point depression. Our results demonstrate that the anomalous enrichment in incompatible elements of this nearside reservoir dramatically lowers the melting temperature of the source rock for these magmas and may have resulted in 4 to 13 times more magma production under the nearside crust, even without any contribution from radioactivity. From thermal numerical modelling, we show that radiogenic heating compounds this effect and may have resulted in an asymmetric concentration of post-magma-ocean crust building on the lunar nearside. Our findings suggest that the nearside geochemical anomaly has influenced the thermal and magmatic evolution of the Moon over its entire post-differentiation history. Early magmatism on the Moon’s nearside may have been enhanced by a geochemical anomaly lowering the melting point of the mantle source region, according to high-temperature experiments and thermal numerical modelling.

22 citations

Journal ArticleDOI
TL;DR: The Ipueirinha Group is a succession of metavolcanic-sedimentary rocks that is mostly composed of marine terrigenous sedimentary rocks represented by immature metarhythmites and quartzites, local metaultramafites, and rare lenses of metamarl as mentioned in this paper.

22 citations

Journal ArticleDOI
Abstract: Garnet and clinopyroxene megacrysts found in the Uintjiesberg and Lekkerfontein kimberlites, southern Africa, have been analysed for their major and trace element compositions. Minerals from both megacrysts suites define coherent geochemical trends that can be attributed to differentiation via crystallisation in a closed system. Clinopyroxene megacrysts from both localities are of the subcalcic, low-Cr variety and have Mg#’s that range from 0.821 to 0.890, whereas garnets have Mg#’s in the range 0.702 to 0.824. Clinopyroxene megacrysts from both localities are strongly light rare earth element (REE) enriched when normalised to chondrites (La/Ybn ∼5), whereas garnets are all strongly LREE depleted (La/Ybn <0.014) with flat HREE patterns; both mineral types show strongly subparallel REE patterns. Primitive mantle normalised trace element patterns are likewise subparallel, with clinopyroxene megacrysts reflecting strong incompatible element enrichment and garnet megacrysts incompatible element depletion. Quantitative modelling of REE patterns in both garnet and clinopyroxene megacrysts provides compelling evidence that an ocean island basalt (OIB)-like parental magma, rather than a primary kimberlite magma, gave rise, over an extended (∼60 to 75%) crystallisation period, to the megacryst suite minerals from both localities. Variations in Sr and high field strength element abundances are consistent with this model.

22 citations

Journal ArticleDOI
TL;DR: In this paper, a model for the formation of primary melts with the simultaneous participation of two types: plume and fluid-saturated suprasubductional, localized beneath the active continental margin.

22 citations

Journal ArticleDOI
TL;DR: In this paper, peridotite and orthopyroxenite xenoliths of the Cr-Diopside Group are found in ∼2 Ma basanitic cinder at the La Olivina locality in north central Mexico.
Abstract: Peridotite and orthopyroxenite xenoliths of the Cr-Diopside Group are found in ∼2 Ma basanitic cinder at the La Olivina locality in north central Mexico. The samples form continuous arrays on chemical and isotopic covariation diagrams and have similar coarse-granular textures and equilibration temperatures (∼950°–1050°C). Sr and Nd isotopic compositions of acid-washed diopsides (eNd = +1.9 to +13.3; 87Sr/86Sr = 0.70220 to 0.70328) indicate long-term depletion of Rb relative to Sr and Nd relative to Sm, similar to asthenospheric (mid-ocean ridge basalt (MORB)) mantle. Lead isotopic compositions for all but one of the samples are generally higher in 206Pb and 207Pb, relative to 204Pb, than is typical of MORB (206Pb/204Pb = 18.53 to 19.40; 207pb/204pb = 15.57 to 15.62). The peridotite suite as a whole is significantly depleted in both clinopyroxene and incompatible trace element concentrations (Sm/Nd = 0.5 to 0.8; [Nd] = 1.19–2.69 μg/g). Isotopic and chemical systematics require that more than one depletion episode occurred in the history of the suite. Assuming that the La Olivina mantle had CHUR-like (chrondrite uniform reservoir) isotopic compositions prior to any of the depletion events, the initial event must have occurred at least ∼735 Ma ago. The final depletion event could have occurred no more than ∼280 Ma ago and involved a melt extraction of about 5–10% of the existing mass. Nd isotopic similarities between the peridotites and late Paleozoic arc-related basaltic rocks occurring in the Coahuila terrane to the southeast of La Olivina suggest that the final melting event may have produced this magmatism. The calculated magnitude of the presumed late Paleozoic melting and melt extraction implies that the La Olivina mantle was asthenospheric at that time. The peridotites contain veins of websterite that have resulted from mid-Cenozoic magmatic activity in the La Olivina region, indicating that the peridotites were in place and attached to the continent prior to the mid-Cenozoic. Increased buoyancy of the newly depleted asthenosphere coupled with a delamination of previously existing lithosphere, suggested by other studies, may have led to the accretion of the La Olivina mantle to the crust by the early Mesozoic (end of the Ouachita orogeny). Several La Olivina peridotites that have Sr-Nd isotopic compositions that indicate long-term depletion of incompatible elements have subsequently been enriched in these elements. These peridotites contain hydrous minerals and have rare earth element patterns that show enrichment of the light REE relative to the heavy REE. The Sr-Nd-Pb isotopic compositions of these samples indicate that the enriching agent contained isotopic components also present in the two episodes of Cenozoic magmatism in the La Olivina region. However, no satisfactory combination of agents directly related to the two magmatic events can account for the observed isotopic compositions of the enriched samples. This suggests that the enriching agent was not related to either of these magmatic episodes and that the isotopic components are not necessarily coupled together in the mantle regions producing the Cenozoic magmas.

22 citations


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