Ore deposition controlled by detachment zones： A case study of Mofanggou style gold deposits in western Shandong

Abstract： Mofanggou style gold deposits refer to gold telluride deposits occurring in calcareous dolomite and dolomitic limestone in the Early Cambrian Zhushadong Formation in the Tongshi area，western Shandong. According to recent geological exploration, the horizon of the orebodies is relatively persistent and widespread, with relatively continuous mineralization. Deposits of this style have great resource potential and ore prospects. The notable wall-rock alteration types include pyritization-sericitization-silification, kaolinization, calcitization and fluoritization. The formation of gold telluride deposits is closely related to pyritization-sericitization-silification. The favorable structural sites for forming this style of deposit are the core region of the western Shandong mantle branch and secondary detachment zones above the main detachment zone between the Archean crystalline basement and Cambrian covers surrounding the Tongshi uplift. Ore-forming materials were derived from a deep source (the mantle) and the emplacement of orebodies is controlled by the main and secondary detachment zones. As the secondary detachment zones are distributed parallelly to bedding, the orebodies show the stratiform feature.