An early Cretaceous analogue of the ~ 2.5 Ga Malanjkhand porphyry Cu deposit, Central India

Abstract

The ~2.5 Ga Malanjkhand Cu mineralization is hosted by adakitic granitoids in central India. The mineralization represents a large Cu deposit. However, significant debate still surrounds its identification as an analogue of modern circum-Pacific style porphyry Cu deposits. The controversy is intricately linked to several first-order geological issues, such as: the onset of modern plate tectonics and ensuing supercontinent cycles, temporal evolution of the Earth's continental crust coupled with buoyancy of the sub-continental lithospheric mantle (SCLM) and oxidation state of the sub-arc mantle wedge. The petrology and geochemistry of the early Cretaceous Lower Yangtze River Belt (LYRB) adakitic granitoids, central-eastern China that hosts several porphyry Cu deposits are similar to the ~2.5Ga Malanjkhand adakitic granitoids of central India, hosting Cu mineralization. The relict amphibole chemistry of both, the LYRB and Malanjkhand granitoids reveals similar “porphyry mineralizing trends” implying high concentrations of H2O and elevated fO2 conditions of the ore-bearing shallowly emplaced adakitic granitoids. Consequently, the Malanjkhand and LYRB adakitic granitoids were generated in near-identical tectonothermal regimes. The LYRB porphyry Cu deposits belong to the circum–Pacific metallogenic belt of the Eurasian active continental margin. Collectively, the mineralogical, petrological and geochemical similarities of the Malanjkhand and the LYRB adakitic granitoids imply porphyry style mineralization of the Malanjkhand Cu deposit. The identification of Malanjkhand mineralization as a truly Neoarchean porphyry Cu deposit along with coeval adakites, calc-alkaline rhyolites, high-Mg andesites (HMA), followed by rift-related tholeiites and A2-type granites helps to constrain the tectonic evolution of central India. The rarity of porphyry Cu deposits in the Earth's early history is primarily attributed to their lack of preservation. This study opens up exploration possibilities for hitherto unexplored and concealed porphyry Cu deposits in other geologically favorable Precambrian terranes comprising shallowly emplaced adakitic granitoids.