Asish Basu

University of Texas at Arlington, Earth and Environmental Sciences, Emeritus

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Since 2020 Professor Emeritus, Chair and Professor of the Departments. at the University of Texas (2013-2020) and University of Rochester , Rochester, NY (1978-2013, 2086-98 as Chair), Taught mineralogy-petrology and geochemistry, conducted research in solid earth geochemistry, acted as advisors to 10 PhD, and 20 Master' thesis in both these institutions. Published more than 100 scientific papers , about a dozen in Science and Nature, Earth and Planetray Science Letters, Geochimica Cosmichimica Acta and many others. Petrology.-geochemistry of the mantle , flood basalts geochronology-geochemistry , mass extinctions at the K-Pg and Permian -Triassic boundaries, crust-mantle evolution and Archean crsut

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High- <sup>3</sup> He Plume Origin and Temporal-Spatial Evolution of the Siberian Flood Basalts

Science, Aug 11, 1995

An olivine nephelinite from the lower part of a thick alkalic ultrabasic and mafic sequence of vo... more An olivine nephelinite from the lower part of a thick alkalic ultrabasic and mafic sequence of volcanic rocks of the northeastern part of the Siberian flood basalt province (SFBP) yielded a 40Ar/39Ar plateau age of 253.3 ± 2.6 million years, distinctly older than the main tholeiitic pulse of the SFBP at 250.0 million years. Olivine phenocrysts of this rock showed 3He/4He ratios up to 12.7 times the atmospheric ratio; these values suggest a lower mantle plume origin. The neodymium and strontium isotopes, rare earth element concentration patterns, and cerium/lead ratios of the associated rocks were also consistent with their derivation from a near-chondritic, primitive plume. Geochemical data from the 250- million-year-old volcanic rocks higher up in the sequence indicate interaction of this high-3He SFBP plume with a suboceanic-type upper mantle beneath Siberia. More than 20 years after Morgan (1) pos- tulated the connections between continen- tal flood basalt provinces (CFBPs), mantle plume activity, and continental rifting, there is now some general agreement on the role of deep mantle plumes in CFBP gener- ation. Questions remain, however, regarding the nature of dispersal of the plume head in the upper mantle beneath the rel- atively cooler and rigid lithosphere, and the timing of melting initiated by the arrival of the hot plume at the base of the lithosphere is a topic of current investigations (2-5). In this report, we use 3He/4He as a diagnostic tracer to infer a lower mantle plume origin for the SFBP, the largest Phanerozoic CFBP; on the basis of combined isotopic and trace element characteristics, we also infer the involvement of an upper mantle component analogous to the present-day suboceanic mantle. We provide 40Ar/19Ar geochrono- logic data, He isotopic measurements, rare earth element (REE) data, and Sm-Nd and Rb-Sr isotope systematics data on a suite of alkalic ultrabasic and mafic volcanic rocks

Asish Basu

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