The Au-Cu polymetallic mineralization system related to intermediate to felsic intrusive rocks and the prospecting prediction in Xiahe-Hezuo area of Gansu, West Qinling orogenic belt

The distribution of magmatic rocks and mineral deposits in Xiahe-Hezuo area has a zoning characteristics:The intrusive rocks in northern Xiahe-Hezuo fault have larger scales and are mainly batholiths and stocks.The mineralization in intrusive rocks is dominated by medium and high temperature elements, such as Cu, Au, W, Mo, Pb and Zn, and is controlled jointly by the contact zone at the edge of rock mass and the fracture.The intrusive rocks to the south of Xiahe-Hezuo fault are smaller and are mainly small stocks and dikes.The mineralization in intrusive rocks is dominated by medium and low temperature elements and is controlled by the fracture.Geochemical characteristics in this area show that the intrusive rocks have the dual characteristics of magnesium diorite and TTG rock suite, and structurally belong to crust-mantle structure that is "thermal shell" + "thermal mantle"; therefore, the metallogenic condition in this area is extremely favorable. S, H, O and other stable isotope characteristics show that the ore-forming material was mainly derived from the hydrothermal fluid in the mantle magma and, in the later period, there occurred the participation of atmospheric precipitation.The Au-Cu polymetallic ore-forming system in Xiahe-Hezuo area was associated with medium-acid intrusive rocks.Therefore, exploration should be focused on searching for remote low temperature hydrothermal gold and antimony deposits in the shallow part and searching for porphyry and skarn deposits in the depth to the south of Xiahe-Hezuo fault, due to the shallow denudation degree.However, the prospecting should be based on porphyry and skarn deposits to the north of Xiahe-Hezuo fault characterized by a high denudation.