High-Cd sphalerite in the Pangxidong Pb-Zn-Ag deposit (Yunkai Domian, South China): Insight for physicochemical condition of orogenic-type deposit

Abstract

The Pangxidong Pb-Zn-Ag-(Au) deposit is one of the representative orogenic-type Au-bearing polymetallic deposits in the Yunkai Domian, Cathaysia Block, South China, and both its vein- and altered rocks-type orebodies are controlled by the regional NE-trending Bobai-Cenxi Fault and its subordinate faults. Metallogenic potential of critical metals, such as Cd, In, Ga and Ge, hosted in these orogenic-type polymetallic deposits, have never been evaluated. We, therefore, selected the Pangxidong to conduct a series of field survey, microscopic observation, electron probe micro-analyzer (EPMA) and laser ablation inductively coupled plasm mass spectrometer (LA-ICP-MS) investigation. We identified two generations of sphalerite with different mineral assemblages and mineralogical features, and both sphalerite generations have the relatively higher Cd, Cu, Ag and Au contents, against the lower Ga, Ge, In and Sn contents. Notably, an extremely elevated Cd content was detected in the earlier SpA (4869–47194 ppm, mean = 15976 ppm), against those in the later SpB (5629–9980 ppm, mean = 7224 ppm). Further temperature evaluation using GGIMFis geothermometer indicates that the earlier SpA (229–367 ℃, mean = 239 ℃) have a slightly higher crystallization temperature than the later SpB (228–240 ℃, mean = 233 ℃). Collectively, we highlight that the Pangxidong sphalerite have different minor and trace element associations and concentrations against most other Zn-Pb deposit styles such as MVT and skarn system, and therefore represents a novel sphalerite type from the orogenic-type deposit.