Topic
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 paper, a new calculation of the crustal composition is based on the proportions of upper crust (UC) to felsic lower crust (FLC) to mafic lower-crust (MLC) of about 1.6:0.4.
5,317 citations
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TL;DR: In this paper, the average chemical compositions of the continental crust and the oceanic crust (represented by MORB), normalized to primitive mantle values and plotted as functions of the apparent bulk partition coefficient of each element, form surprisingly simple, complementary concentration patterns.
3,062 citations
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01 Jan 1982
TL;DR: In this paper, discrimination diagrams are drawn which highlight these various characteristics and therefore enable volcanic arc basalts to he recognized in cases where geological evidence is ambiguous, and the results indicate that the Oman ophiolite complex was made up of back-arc oceanic crust intruded by the products of volcanic arc magmatism.
Abstract: Volcanic are basalts are all characterized by a selective enrichment in incompatible elements of low ionic potential, a feature thought to be due to the input of aqueous fluids from subducted oceanic crust into their mantle source regions. Island arc basalts are additionally characterized by low abundances (for a given degree of fractional crystallization) of incompatible elements of high ionic potential, a feature for which high degrees of melting, stability of minor residual oxide phases, and remelting of depleted mantle are all possible explanations. Calc-alkaline basalts and shoshonites are additionally characterized by enrichment of Th, P, and the light REE in addition to elements of low ionic potential, a feature for which one popular explanation is the contamination of their mantle source regions by a melt derived from subducted sediment.
By careful selection of variables, discrimination diagrams can be drawn which highlight these various characteristics and therefore enable volcanic arc basalts to he recognized in cases where geological evidence is ambiguous. Plots of Y against Cr, K[Yb, Ce/Yb, or Th/Yb against Ta/Yb, and Ce/Sr against Cr are all particularly successful and can be modelled in terms of vectors representing different petrogenctic processes. An additional plot of Ti/Y against Nb/Y is useful for identifying 'anomalous' volcanic arc settings such as Grenada and parts of the Aleutian arc. Intermediate and acid rocks from volcanic are settings can also be recognized using a simple plot of Ti against Zr.
The lavas from the Oman ophiolite complex provide a good test of the application of these techniques. The results indicate that the complex was made up of back-arc oceanic crust intruded by the products of volcanic arc magmatism.
2,373 citations
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TL;DR: Asimow et al. as mentioned in this paper derived an estimate for the chemical composition of the depleted MORB mantle (DMM), the source reservoir to mid-ocean ridge basalts (MORBs), which represents at least 30% the mass of the whole silicate Earth.
2,340 citations
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TL;DR: In this paper, the global major element variations can be explained by ∼8-20% melting of the mantle at associated mean pressures of 5-16 kbar, and the lowest extents of melting occur at shallowest depths in the mantle and are associated with the deepest ocean ridges.
Abstract: Regional averages of the major element chemistry of ocean ridge basalts, corrected for low-pressure fractionation, correlate with regional averages of axial depth for the global system of ocean ridges, including hot spots, cold spots, and back arc basins, as well as “normal” ocean ridges. Quantitative consideration of the variations of each major element during melting of the mantle suggests that the global major element variations can be accounted for by ∼8–20% melting of the mantle at associated mean pressures of 5–16 kbar. The lowest extents of melting occur at shallowest depths in the mantle and are associated with the deepest ocean ridges. Calculated mean primary magmas show a range in composition from 10 to 15 wt % MgO, and the primary magma compositions correlate with depth. Data for Sm, Yb, Sc, and Ni are consistent with the major elements, but highly incompatible elements show more complicated behavior. In addition, some hot spots have anomalous chemistry, suggesting major element heterogeneity. Thermal modeling of mantle ascending adiabatically beneath the ridge is consistent with the chemical data and melting calculations, provided the melt is tapped from throughout the ascending mantle column. The thermal modeling independently predicts the observed relationships among basalt chemistry, ridge depth, and crustal thickness resulting from temperature variations in the mantle. Beneath the shallowest and deepest ridge axes, temperature differences of approximately 250°C in the subsolidus mantle are required to account for the global systematics.
1,550 citations