scispace - formally typeset
Search or ask a question
Topic

Incompatible element

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


Papers
More filters
Journal ArticleDOI
TL;DR: The Izu-Bonin-Mariana arc contains a unique group of shoshonitic volcanoes from along the magmatic front of this intraoceanic arc as mentioned in this paper.
Abstract: The Izu-Bonin-Mariana arc contains a unique group of shoshonitic volcanoes from along the magmatic front of this intraoceanic arc Shoshonites are greatly enriched in incompatible elements compared to lavas typically found in primitive arc settings but have fractionations of lithophile (LIL) and high-field strength (HFSE) incompatible elements characteristic of convergent margin magmas and thus are characterized by an unusually large “subduction component” New geochemical and isotopic data for Izu-Bonin-Mariana shoshonites and related rocks are presented and interpreted to examine the origin of these enrichments Enrichments are associated with distinctive isotopic compositions, including the most radiogenic Pb (206Pb/204Pb ∼ 1947) and least radiogenic Nd (eNd ∼ 56) from along the magmatic front of the arc Despite highly elevated concentrations of fluid-mobile lithophile elements in the lavas, the similarity of diagnostic element ratios (eg, Ba/La, Pb/Ce, and U/Th) to those in mid-ocean ridge basalts and ocean island basalts indicates little role for fluid-induced elemental fractionation in the generation of these shoshonites Modeling isotopic data allows up to 6% subducted sediments to be involved, but oxygen isotopic evidence limits this to <3% Low-P fractionation explains most of the chemical variations observed in these shoshonites Removal of <2% Ti-rich phases could fractionate HFSE from LIL, indicating an important role for low-P fractionation Although many features of these shoshonites are consistent with a greater role for subducted sediments, such a role is not accompanied by an unequivocal and universal signal in both isotopic compositions and trace element abundances and fractionations This signifies a large role for both equilibration of these melts with mantle and for low-pressure fractionation

100 citations

Journal ArticleDOI
TL;DR: In this paper, geochemical data are reported for samples from the flanks and floor of the southern Kenya Rift Valley in the Lake Magadi area, and from two central volcanoes located within the rift valley.
Abstract: Geochemical data are reported for samples from the flanks and floor of the southern Kenya Rift Valley in the Lake Magadi area, and from two central volcanoes located within the rift valley. Rift lavas include samples of Singaraini and Ol Tepesi basalts on the eastern flank, Kirikiti basalts from the western flank, and plateau trachytes from the rift valley floor. Central volcano samples are from Ol Esayeiti and Lenderut located on the eastern flank. The rift basalts are mildly ne-normative, moderately evolved (Mg#=0.39–0.62) alkali basalts and show an overall range in differentiation. Incompatible trace element abundances are moderately elevated (Nb=17–51; Zr=93–274; La=17–55 ppm) and show strongly coherent variations and constant inter-element ratios (e.g. Zr/Nb=4.2–5.5; Nb/Ta=17.5±0.4; (La/Sm)n=7.3±1.1); isotope ratios are restricted in range (87Sr/86Sr=0.70393–0.70436; 143Nd/144Nd=0.51272–0.51280; 206Pb/204Pb=19.87–19.92; 207Pb/204Pb=15.68–15.70; 208Pb/204Pb=39.56–39.71). Central volcano lavas are more alkaline in character and include basanite (Ol Esayeiti; Mg# >60) and hawaiite to benmoreite (Lenderut; Mg#=0.48–0.38). Incompatible element ratio are similar to those of the rift basalts, although the chondrite normalised REE patterns are steeper (La/Sm)n=17.4±1.2). 87Sr/86Sr (0.70358, 0.70391), 143Nd/144Nd (0.51280, 0.51267), 206Pb/204Pb (19.96,20.17), 207Pb/204Pb (15.66,15.76) and 208Pb/204Pb (39.80,40.00) ratios of Ol Esayeiti basanites are similar to the rift basalts, whereas the Lenderut lavas have unusually low143Nd/144Nd (0.512388–0.512453) ratios for their 87Sr/86Sr (0.70370–0.70481) ratios, and distinctly less radiogenic and variable Pb isotope compositions (206Pb/204Pb=17.93–19.01; 207Pb/204Pb=15.43–15.58; 208Pb/204Pb=37.91–39.14). An integrated model is developed in which the geochemical signature of the lavas is attributed to variable degrees of melting to depths within the garnet stability field, and in the presence of residual amphibole. The stability fields of these phases in P–T space indicates that the lavas must have formed within the sub-continental lithosphere rather than within the underlying ambient asthenosphere or a rising mantle plume. The subcontinental lithospheric mantle must therefore extend to a depth of at least 75 km beneath the Lake Magadi area, which contrasts with recent gravity models for the area, which infer that lithospheric mantle is absent beneath this section of the southern Kenya Rift.

100 citations

Journal ArticleDOI
TL;DR: The origin of Apollo 11 basalts is discussed in terms of two hypotheses: (1) formation by a small degree of partial melting in the lunar interior, and (2) forming by prolonged near-surface crystallization differentiation in a lava lake as mentioned in this paper.
Abstract: The origin of Apollo 11 basalts is discussed in terms of two hypotheses: (1) formation by a small degree of partial melting in the lunar interior, and (2) formation by prolonged near-surface crystallization differentiation in a lava lake. The second hypothesis is rejected on the following grounds: Most Apollo 11 magmas are far removed from the plagioclase-pyroxene-ilmenite cotectic; fractional crystallization cannot explain the large variations in concentrations of incompatible trace elements in conjunction with the small variations in major-element compositions, particularly, Mg/Fe ratios; experimentally determined partition coefficients show that the high abundances of Cr and V in Apollo 11 rocks cannot be reconciled with the previous separation of large quantities of ore minerals and pyroxenes. On the other hand, the major-element and trace-element contents of Apollo 11 rocks can be readily explained by partial melting of source material that buffers the major-element compositions and causes enrichments of incompatible elements according to the degree of partial melting (first hypothesis). Two alternative sources have been suggested for Apollo 11 basalts formed by partial melting: (1) unfractionated pyroxenite source region at depths of 200–600 km, and (2) fractionated source region with incompatible elements (e.g. Ba, U, and rare earths) strongly enriched over chondritic abundances and containing plagioclase (approximate eucritic composition). Mass-balance calculations and plagioclase-stability conditions show that the second hypothesis requires Apollo 11 basalts to be generated by partial melting in the outer 150 km of the moon. This is very difficult to achieve one billion years after the moon's formation, since the outer 200 km will have cooled well below the solidus by conduction. Furthermore, magmas generated by partial melting of a plagioclase-bearing source region should have plagioclase on the liquidus, which is contrary to observation. The second hypothesis accordingly appears improbable. The first hypothesis is capable of explaining the major-element chemistry and the trace-element abundances (Eu; see below) in terms of a simple, single-stage model that is consistent with the moon's density, moment of inertia, and inferred thermal history. A possible explanation of the europium anomaly is suggested on the basis of the first hypothesis. It will be necessary to determine the appropriate partition coefficients in order to test this explanation. If the lunar highlands are anorthositic, extensive differentiation of the outer 150 km of the moon is required. This may have been caused by heating arising from partial conservation of gravitational potential energy during the final stage of accretion. Formation of Apollo 11 basalts by partial melting 3.7 billion years ago was probably the result of radioactive heating (U, Th) in the deep interior of the moon. A two-stage magmatic history for the moon is thus required. Similarities between compositions of Apollo 11 and terrestrial basalts and between their respective source regions are suggestive of a genetic relationship between moon and earth. Nevertheless, important differences in trace-element abundances, major-element compositions, and oxidation states exist. These abundance patterns are unfavorable to the traditional fission, binary planet, and capture hypotheses of lunar origin. However, they may be explicable in terms of the precipitation hypothesis proposed by the author. This maintains that during the later stages of accretion of the earth, a massive primitive atmosphere developed that was hot enough to evaporate selectively a substantial proportion of the silicates that were accreting on the earth. Subsequently, the atmosphere was dissipated and the relatively nonvolatile silicate components were precipitated to form a swarm of planetesimals or moonlets, from, which the moon accreted.

99 citations

Journal ArticleDOI
TL;DR: In this paper, solution-ICPMS analyses of Rb, Ba, Th, U, Nb, Ta, REE, Sr, Zr and Hf for acid-leached minerals of anhydrous spinel peridotites and websterites were performed.

99 citations

Journal ArticleDOI
TL;DR: Previous models of FAB origin by decompression melting but imply a source more depleted than normal MORB source mantle, which may reflect an influence of the Manus plume during subduction initiation.
Abstract: The Izu‐Bonin‐Mariana (IBM) fore arc preserves igneous rock assemblages that formed during subduction initiation circa 52 Ma. International Ocean Discovery Program (IODP) Expedition 352 cored four sites in the fore arc near the Ogasawara Plateau in order to document the magmatic response to subduction initiation and the physical, petrologic, and chemical stratigraphy of a nascent subduction zone. Two of these sites (U1440 and U1441) are underlain by fore‐arc basalt (FAB). FABs have mid‐ocean ridge basalt (MORB)‐like compositions, however, FAB are consistently lower in the high‐field strength elements (TiO2, P2O5, Zr) and Ni compared to MORB, with Na2O at the low end of the MORB field and FeO* at the high end. Almost all FABs are light rare earth element depleted, with low total REE, and have low ratios of highly incompatible to less incompatible elements (Ti/V, Zr/Y, Ce/Yb, and Zr/Sm) relative to MORB. Chemostratigraphic trends in Hole U1440B are consistent with the uppermost lavas forming off axis, whereas the lower lavas formed beneath a spreading center axis. Axial magma of U1440B becomes more fractionated upsection; overlying off‐axis magmas return to more primitive compositions. Melt models require a two‐stage process, with early garnet field melts extracted prior to later spinel field melts, with up to 23% melting to form the most depleted compositions. Mantle equilibration temperatures are higher than normal MORB (1,400 °C–1,480 °C) at relatively low pressures (1–2 GPa), which may reflect an influence of the Manus plume during subduction initiation. Our data support previous models of FAB origin by decompression melting but imply a source more depleted than normal MORB source mantle.

99 citations


Network Information
Related Topics (5)
Metamorphism
18.3K papers, 655.8K citations
94% related
Continental crust
11.1K papers, 677.5K citations
94% related
Basalt
18.6K papers, 805.1K citations
93% related
Mantle (geology)
26.1K papers, 1.3M citations
92% related
Zircon
23.7K papers, 786.6K citations
92% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20237
202216
202157
202056
201960
201851