Exploring the association of massive pegmatites and supervolcanoes

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Geography and Geology


Massive complex pegmatites, such as Tanco, Bikita, and Greenbushes, are notable not only for their size, but also their complex chemistry and rare nature. Given the relative rareness along with the high silica, high viscosity, and high volatile content of both these pegmatite melts and supervolcanoes, we have begun a comparative analysis of the geochemistry of the magmas in order to build the argument for their association. In addition to the properties above, complex rare-element pegmatite melts are noted for the presence of REE, other rare elements, and the flux components B, P, and F, resulting in below-solidus crystallization. An initial analysis of various supervolcanoes has shown their melts to be consistent with pegmatite melts, containing flux components, REE and other rare elements including Li, Ta, Nb, Zr and U. Both types of systems have shallow, H (sub 2) O-saturated magma chambers with similar chemical signatures, suggesting a clear link. Notable trends in data show the tectonic setting to play a major factor in aluminum content, phosphorous content and overall signature. In both pegmatites and supervolcanoes, those forming from subduction and/or continental collision yield peraluminous, S-type magmas with a high phosphorous content, while those forming from hot spots or rift zones yield subaluminous to metaluminous, A-type magmas with a low phosphorous content. Future work includes an analysis of elemental isotopes in zircon crystals with the hope of achieving a stronger, more definitive link between massive pegmatites and supervolcanoes.