Topic
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: In this article, an analysis of an extensive adakite geochemical database identifies two distinct compositional groups: high-SiO2 adakites (HSA) which represent subducted basaltic slab-melts that have reacted with peridotite during ascent through mantle wedge and low-Si O 2 adakitic mantle wedge.
2,125 citations
TL;DR: The A-type granitoids can be divided into two chemical groups as mentioned in this paper : oceanic-island basalts and island-arc basalts, and these two types have very different sources and tectonic settings.
Abstract: The A-type granitoids can be divided into two chemical groups. The first group (A1) is characterized by element ratios similar to those observed for oceanic-island basalts. The second group (A2) is characterized by ratios that vary from those observed for continental crust to those observed for island-arc basalts. It is proposed that these two types have very different sources and tectonic settings. The A1 group represents differentiates of magmas derived from sources like those of oceanic-island basalts but emplaced in continental rifts or during intraplate magmatism. The A2 group represents magmas derived from continental crust or underplated crust that has been through a cycle of continent-continent collision or island-arc magmatism.
2,043 citations
TL;DR: In this paper, the effects of different types of bulk lower and upper crustal contamination of a within-plate alkali basalt on the Th, Hf, Ta and radiogenic isotope concentrations of the residual liquids are calculated in detail.
1,904 citations
1,797 citations
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