Isotopes, DUPAL, LLSVPs, and Anekantavada

摘要: Abstract The mantle perspective provided by radiogenic isotope geochemistry has evolved over the last 40 years. Although idea of an upper depleted in incompatible elements extraction partial melt remains, ideas about lower have from simple primitive material occupying two-thirds to a heterogeneous, multicomponent mantle. is sampled plumes rising it, and although each compositionally unique, these can be divided into 5 or 6 genera with compositional similarity within suggesting they similar ways. dominant signature that lithospheric carried deep through subduction, subduction erosion, continental foundering, processes also polluted refertilized stable confirms presence recycled material, including derived continents, oceans atmosphere. Noble gas ratios provide dramatically different perspective: reservoirs noble gases isolated convecting for entire history Earth. Neither likely wrong conclusion drawn plumes, at least some them, draw on both difference content may well such isotopic dominates any mixture these. In meantime, suprachondritic 142 Nd/ 144 Nd ratio modern reopened question composition Earth therefore If this not entirely result nebular heterogeneity, then “primitive mantle”, defined as given rise lithosphere mantle, appears light rare earths, other U Th. This would e range 3 7, which matches most common compositions observed oceanic island basalts, particularly those PREMA genera. cannot truly even way, instead, it consist balanced mix enriched components only limited contribution long-isolated, nearly material. As geochemical evolved, so geophysical one, now reveals highly heterogeneous lowermost dominated two large low-shear-wave velocity provinces (LLSVPs) beneath Africa South Pacific associated DUPAL anomaly. latter actually anomalies, SOPITA, closely LLSVP. Mantle been shown preferentially margins structures, while zones overly apparently cold high-seismic regions surrounding LLSVPs. LLSVPs appear hot dense, PRIMA-like present many plumes. Geoneutrino studies eventually resolve questions, total amount Th whether are concentrated