Abstract The recently discovered Hanshan gold deposit in northern Gansu Province, northwestern China, is hosted by a WNW-striking shear zone in Ordovician andesite and basalt. Mineralization consists of surface to near-surface oxidized ore (the yellow sandy gossan type) and three types of primary ore, i.e. early-stage quartz-sericite-pyrite ores in stockworks, early-stage disseminated ore, and the most important late-stage quartzcalcite-sulfide veins. The ore system is characterized by variable degrees of potassic and silicic alteration. Late-stage gold-related fluid inclusions have homogenization temperatures between 170 to 310C, with a peak around 260C and low salinities. The ore fluids had high contents of CO2, CH4, and N2. Sulfur isotope measurements of 1.9 to +1.7per mil for hydrothermal pyrites could be consistent with a hydrothermal fluid source from the mantle, but the oxygen and carbon isotope data from calcite and quartz suggest mixing between mantle and crustal fluid sources. K-Ar ages for hydrothermal sericite from ore zones are 213.93.1 and 224.43.2Ma. Due to the arid Cenozoic climate, a yellow gold-bearing gossan developed, which consists of jarosite, gypsum, and relict quartz. It could be a widespread and useful prospecting guide for gold in northwestern China.