Geological characteristics and genesis of the Dashiwan-cobalt manganese deposit in Huixian County, West Qinling mountains

The Dashiwan cobalt-manganese deposit in Huixian County is located in the eastern section of the Yuntai-Miba mineralization belt in the West Qinling orogenic belt. The ore body occurs in two sets of ore bearing formations: the limestone intercalated siliceous rock formation and the limestone siliceous rock formation in the fourth segment of the Upper Silurian zhuowukuo Formation. In order to further guide the exploration work in the region, a special mapping of the construction structure of the Dashiwan cobalt-manganese mining area was carried out, combined with trench exploration and old cave logging. The relationship between the construction structure and mineralization was analyzed, and the geological characteristics and mineralization laws were summarized. It is believed that the genetic type of the deposit is a sedimentary reformed cobalt-manganese deposit. The research results indicate that the contact zone between siliceous rocks and limestone in the fourth segment of the zhuowukuo Formation (siliceous calcium surface) is the main ore-forming space, followed by the interlayer fault zone in the limestone siliceous rock formation. The main direction of the ore control structure is in the near EW direction. The mineralization of ore deposits has the characteristic of multiple stages, which corresponds to multiple stages of tectonic movements; The late Caledonian period was the main initial enrichment stage of this deposit, while the Indosinian period was an important tectonic period. During this period, the nearly EW trending compression thrust nappe structure superimposed and transformed the original sedimentary layers; The NE and NNE trending compressional and torsional faults during the Yanshanian period cut and dislocated the early ore-bearing geological bodies, providing favorable space for the subsequent leaching and enrichment of cobalt and manganese, and controlling the occurrence state of cobalt and manganese mineralization in the post mineralization tectonic units.