| Abstract:Being one of the four main orefields in the Tongling ore concentration area along the Middle and Lower Yangtze Valley copper-iron-gold metallogenic belt, the Tongguanshan orefield consists of the Tongguanshan copper deposit, the Tianmashan sulfur-gold deposit and the Jinkouling copper-gold deposit. In the orefield, Silurian to Triassic strata are exposed at the surface, and the in-trusives include the Tongguanshan quartz diorite, the Tianebaodanshan quartz diorite and the Jinkouling granodiorite. According to attitudes of the orebodies, characteristics of mineralizations and types of alterations, the orebodies can be classified into skarn orebodies, stratiform orebodies and veinlet disseminated orebodies. Orebodies of different attitudes are decided by different host structures: skarn orebodies are controlled by structures of the contact zone, stratiform orebodies are governed by C2 + 3/D3w interωlayer detachment surface structures, and where these two kinds of structures are intersected with each other, the (shaped or Y-shaped orebodies are formed. The formation of the stratiform orebodies experienced two ore-forming stages, i. e. , when the copper-, gold-bearing magmatic hydrothermal fluids formed by Yanshanian magmatic activity moved along the interlayer structures, they replaced, superimposed upon and reformed the copper-bearing pyrite bed formed by Late Carboniferous sedimentation and thus yielded stratiform copper-sulfur orebodies or sulfur-copper orebodies. Studies of lead and oxygen isotope data and ore-forming temperatures show that the ore-forming materials and ore-bearing hydrothermal fluids were derived mainly from magma and partly from strata. The multi-phase and protracted natures as well as pulsation of the activities of the regional basement rock-controlling fractural structures led to the evolution and differentiation of the magma chamber and, as a result, there exist differences not only in petrologic characters but also in copper and gold potentials of the intrusive bodies. Different ore species are attributed to different copper and gold potentials at different magmatic stages. |
