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Basalt
About: Basalt is a research topic. Over the lifetime, 18687 publications have been published within this topic receiving 805136 citations.
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TL;DR: Two geochemical proxies are particularly important for the identification and classification of oceanic basalts: the Th-Nb proxy for crustal input and hence for demonstrating an oceanic, non-subduction setting; and the Ti-Yb proxy, for melting depth and hence indicating mantle temperature and thickness of the conductive lithosphere as mentioned in this paper.
2,487 citations
TL;DR: In this article, a table of element abundances in the continental crust, calculated on the basis of a 1:1 mixture of granite and basalt abundances, is presented.
2,460 citations
Book Chapter•
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
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
Book Chapter•
01 Sep 1983
TL;DR: In this paper, the relative contributions of the subduction and lithosphere components to the composition of active continental margin basalts can be calculated from their MORB-normalized geochemical patterns.
Abstract: Volcanic are basalts can usually be distinguished from basalts erupted in other settings by their selective enrichments in LIL elements and also, in some cases, in light rare-earth elements and P. Ibis enrichment component is independent of the nature of the overlying mantle wedge and is assumed to be subduction-derived. However, basalts erupted at active continental margins carry an additional geochemical component, which is not observed in basalts front oceanic island arcs. This component, which contains Nb, Ta, Zr and Hf in addition to the elements mentioned above, cannot realistically have a subduction or crustal origin and is thus assumed to be derived from trace element enriched metasomatized sub-continental lithosphere. The relative contributions of the subduction and lithosphere components to the composition of active continental margin basalts can be calculated from their MORB-normalized geochemical patterns. In a typical basalt, from Central Chile, the subduction zone can be shown to make the dominant contribution to its content of Rb, K, Ba, 71 and Sr, whereas the lithosphere contributes the greater proportion of its content of Ce, Sm and P and all its content of Ta, Nb, Zr, Hf, Ti, Y and Yb.
2,176 citations