The Mashan pyrite deposit is located in the central Ningwu
basin and is associated with the Washan subvolcanic pluton. The
stratigraphy around the deposit is dominated by an upper andesitic tuff unit, middle andesitic brecciated lava and trachyandesite units, and a lower andesite unit, with all belonging to the Dawangshan Formation. These units are thought to represent a caldera succession that was intruded by a subvolcanic gabbro–diorite porphyry (Zhao, 1993). The Mashan pyrite orebodies have transitional boundaries with the surrounding country rocks and are located along the contact between andesitic brecciated lava and trachyandesite units or within the trachyandesite (Fig. 9)