Mechanism of germanium enrichment in the world-class Huize MVT Pb-Zn deposit, southwestern China

The world-class Huize deposit hosts significant germanium (Ge) resources in the Sichuan-Yunan-Guizhou (SYG) Mississippi Valley-type (MVT) Pb-Zn province of China. The distribution and enrichment mechanism of Ge is still poorly understood. In the main ore-forming stage of Huize, we identified six sphalerite colors from C1 (black) to C6 (white) in transmitted light. Two color sequences are confirmed, including C1 -> C2 -> C3 -> C6 and C1 -> C2 -> C4 -> C5 -> C6. We used multiple analytical methods to reveal the Ge distribution and incorporation mechanism into sphalerite and the possible enrichment factors. Our results show that Ge occurs as argutite (GeO2), and in the sphalerite crystal lattice, C1 and C3 sphalerite has up to 593 ppm Ge. Two substitution mechanisms, i.e., Ge4+ + square((vacancy)) -> 2Zn(2+) (e.g., C1 and C2) and Ge4+ + 2Cu(+) -> 3Zn(2+) (e.g., C2, C3, C4, and C5), are inferred from the Huize sphalerite. They show different spatial structures of sphalerite and a weak shift of the white line observed by high-resolution X-ray absorption near-edge structure (XANES) spectroscopy. The trace-element composition of sphalerite suggests that reduced sulfur content of the ore-forming fluid contributes to Ge enrichment, followed by high temperature (> 300 degrees C).