Research Progress on Petrogenesis and Niobium-Tantalum Mineralization of Permian Alkaline Rocks in the Panxi Region
Niobium(Nb)and tantalum(Ta)elements are significantly strategic key metal resources.Alkaline rocks have attracted considerable attention due to their enrichment of rare earth elements.In recent years,significant research progress has been made in Permian peralkaline-metaaluminous-peraluminous syenite and granite as well as associated niobium-tantalum deposits developed in the Panxi region,Emeishan Igneous Province,focusing on their geochronology and metallogenic ages,geochemical characteristics,petrogenesis,and Nb-Ta enrichment mechanisms.In the axis of the mantle plume,the Emeishan high-Ti basalt magma,formed by partial melted mantle peridotite,created small-scale A-type granite and alkalic-metaaluminous syenite in the magma chamber through fractional crystallization and liquid immiscibility.The underplating mantle-derived magma convection provided significant heat energy for the partial melting of basic gabbro,leading to the formation of widely distributed peralkaline-metaluminous syenite and granite.Simultaneously,peraluminous granite was formed when a small proportion of the juvenile crust or the Yangtze basement is involved in the process of partial melting.The research shows that the enrichment process of Nb-Ta is controlled by both magma crystallization differentiation and hydrothermal metasomatism.The alkaline magma from the mantle preferentially crystallizes plagioclase,amphibole,apatite,and other minerals through crystallization differentiation,leading to the initial enrichment of Nb and Ta elements in the syenite.The F-Na rich hydrothermal fluid from the syenite acts on rock by metasomatism,which results in alteration such as albitization,aegirinization,and fluorization.The early magmatic niobium-tantalum minerals were decomposed due to metasomatism,with the Nb and Ta elements being reactivated,migrated,and precipitated to form hydrothermal pyrochlore and titanite.
alkaline rockpetrogenesishydrothermal alterationNb-Ta mineralizationthe Panxi region
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