Geology, Geochemistry and Origin of the Hongshan Porphyry‐Cryptoexplosive Breccia Type Copper Deposit in Huichang County, Jiangxi Prvince

Abstract

Abstract The Hongshan porphyry‐cryptoexplosive breccia type copper deposit occurs in a metamorphic rock series of the Mesoproterozoic Zhongcun Group. Orebodies are distributed inside and outside porphyry‐cryptoexplosive breccia pipes. The deposit involves five ore‐forming types, i.e the porphyry type, cryptoexplosive breccia type, contact‐zone veinlet‐disseminated type, in‐pipe fracture‐zone filling‐replacement type and out‐of‐pipe fracture‐zone filling‐replacement type, forming an ore‐forming system of “five ore‐forming types within a single rock body”. Fluid inclusion and isotope geochemical studies indicate the following: S, Pb, O and Sr were derived from the lower crust, Nd was derived from the continental crust or depleted mantle and rare earth elements (REE) and trace elements have the crustal source characters; fluids consist dominantly of formation water, metamorphic water and ***meteoric water with a part of magmatic mater, heat came from porphyry while the latter originated from partial melting caused by shear heating in the lower crust and upper mantle. According to its origin the deposit is classified as the hypabyssal and near‐surface, meso‐ and hypothermal copper deposit associated with the late Yanshanian porphyry‐cryptoexplosive breccia.