An analysis of structural ore-controlling role in Xiaoqingling area

Abstract：The Xiaoqinling gold ore concentration area is known for its great uplift amplitude, high denudation extent, intense tectonic movement, clear structural features and concentrated distribution of ore deposits. The study area experienced four periods of folding, comprising from early to late plastic flow folding→regional EW-trending main folding →NS-trending crossing superimposed folds→transverse folding of vertical uplift, and was subjected to four periods of shearing, in order of plastic flowing →brittle ductile transpression→ductile brittle tenso-shearing →brittle forward detachment caused by uplift. The main stage brittle-ductile shearing was developed in the main limb of the weak tectonic belt. The third phase ductile-brittle shearing process of Yanshanian period provided favorable ore-hosting conditions for the large-scale injection of ore-forming fluids and mineralization. Researches show that the ore-forming fluids were mainly derived from the depth and, through the multistage evolution of mantle plume, injected into the ductile shear zone to form ore deposits via accumulation. In the ore district, there often exist one or two main ore veins which control more than 50% of metallic reserves.