Geological and geochemical features of the Ganheba gold deposit, Lueyang, South Qinling

Abstract：The Ganheba gold deposit is the first gold deposit found in the Mianxian-Lueyang tectonic mélange belt of the Qinling orogenic belt. The formation of the gold deposit went through the phase of deposition of sedimentary rocks and formation of the basement in the pre-Mianxian-Lueyang restricted ocean, the phase of gold preconcentration in the sediments of the Mianxian-Lueyang restricted ocean and the phase of continental collision and amalgamation between the Yangtze plate and Qinling plate and structural stacking and reworking and gold concentration derived after orogeny. Favorable host rocks (containing 3.66×10-9 Au) is the material basis for gold mineralization and ductile-brittle progressive structural deformation is the key ore-controlling factor. The Ganheba gold deposit is the product of the combined action of the rocks and the structure. Fluid inclusion study shows that the homogenization temperatures of the ore fluids ranged from 137 to 280℃ in the main mineralization stage of the deposit, which shows the features of mesothermal-epithermal mineralization. The salinities ranged from 4.5 to 23.1wt% NaClequiv. at the early to middle stages of mineralization．The δ34S values of pyrite ranged from +9.91 to +15.45‰, showing the feature of enrichment in heavy sulfur. The sulfur of volcanic origin shows strong fractionation, and in addition, crustal sulfur from sedimentary rocks was also introduced, showing the feature of the mineralization that underwent strong geological reworking in the late phase. Gold occurs mainly as independent microgranular minerals and the paragenesis of ore elements are Au-Ag-As-Sb-Cu-Pb-Zn, showing the geological features of a Carlin-like gold deposit.