Genetic types of orebodies in the Xitieshan lead-zinc deposit, Qinghai Province, Western China

Abstract：The Xitieshan lead-zinc deposit is located close to the northern margin of the Qaidam basin, Qinghai Province, Western China. Both stratiform and vein-type orebodies occur in each of the three units of the Ordovician Tanjianshan group. These units are the O3tnb schist, the transition zone between O3tnb and the marble layer, and the O3tna-2 schist. In addition, there are irregular orebodies in the marble layer. Based on investigation of orebody distribution, and ore structures and textures, genetic types of the orebodies are summarized. Stratiform orebodies in all the three strata can be ascribed to the SEDEX-type. Among them, those hosted in the O3tnb schist and in the transition zone between the O3tnb schist and the marble are proximal, while vein-type mineralisations stratigraphically bellow these orebodies are thought to represent feeding zones. By contrast, stratiform orebodies in the O3tna-2 schist were formed by distal exhalative sedimentation. Irregular orebodies in the marble layers are likely to have been formed by post-orogenic hydrothermal mobilization/remobilization of metals from surrounding rocks or the stratiform orebodies. Vein-type orebodies in the O3tna-2 schist were also produced by post-orogenic hydrothermal overprinting, and possibly served as feeding zones for the irregular orebodies in the marbles.