The indicator role of alkaline-basaltoid volcanism and vortex geodynamics in the origin of unconventional diamonds in the West Pacific zone of the continent–ocean transition

Abstract

Introduction: For the first time, the question of the prospects for diamonds of unconventional genesis in the West Pacific transition zone has been raised. In the Cenozoic, the tectonomagmatic activation of the transition zone was carried out under the influence of lower mantle plumes - the apophyses of the African and Pacific superplumes, adiabatic melting, which led to WPB volcanic outbursts of the CAB and OIB types, respectively. Plume upwelling contributed to the removal of diamonds from their stability zone. The carbonate strata of the subducting plate or superdeep hydrogen–methane gases rising from the core– lower mantle boundary served as the source of carbon. Materials and Methods: Research methods included the identification of faults and structures of the central type. The radioisotope age, petrological and geochemical composition, and radiogenic isotopes of Pb, Nd, and Sr were determined at analytical centres in Russia, Germany, and the United States. Results and Discussion: The petrological and geochemical properties of alkaline basaltoids indicate that the CAB and OIB types of volcanism belong mainly to the tephrite–leucite, kamafugitic, and lamproite series, which can serve as one of the criteria for the potential diamond content of this zone. Other criteria include: 1) the presence of an ancient basement and a weakened tectonic framework of the transition zone; 2) vortex geodynamics, which contributed to the pulling of diamond-bearing mantle melts into cyclonic and anticyclonic eddies. Conclusion: Marginal seas and areas of the surrounding land can be attributed to objects that are promising for the discovery of small diamonds in places of manifestation of OIB volcanism, and larger accumulations of large crystals in the areas of activation of ancient platforms and manifestations of CAB volcanism.