Abstract: The discovery of Gaoerqi leadzincsilver deposit is not only an important prospecting achievement in ErlianDongwuqi polymetallic metallogenic belt, but also a significant breakthrough for prospecting blind deposits. This paper, based on the study of geochemistry, zircon UPb geochronology and LuHf isotopes of orebearing granites, has provided constraints on petrogenesis, magma source and rockforming tectonic settings and other issues of the orebearing rocks. The orebearing rocks are mainly porphyriticlike mediumcoarse grained monzogranite and mediumfine grained syenogranite. The contents of SiO2, Na2O+K2O and REEs are of higher values, but the contents of P2O5, TiO2, CaO and MgO are of lower values in the orebearing rocks. The contents of SiO2 and Na2O+K2O are 646%-7912% and 559%-1017%, respectively. The Eu element has a characteristic of strong negative anomaly. The orebearing rocks are not only rich in Rb, K and other LILE, but also rich in Zr, Hf and other HFS. The orebearing rocks are with strong depletions in Ba, Sr, P, Ti, Eu, etc. The orebearing rocks are with higher values of εHf(t) between 44 and 140, and have younger crust model ages with values of tDCc between 424 Ma and 1,042 Ma, which reveals that the granites mainly derive from the partial melting of young accreted crust which derives from depleted mantle. The granites are with characteritics of A2type granites, and form in the plate extension phase after collision orogenesis. The LAICPMS UPb isotope ages of zircons are (3068±19) Ma and (3104±23) Ma, respectively, which proves the zircons belong to the products of tectonic magmatism in Late Carboniferous. It reveals that the main collision between North China and Siberian plates has finished in this period, and has entered the postcollision extension phase.

Key words: Gaoerqi silverleadzinc deposit, Atype granite, postcollision extension, Late Carboniferous, Inner Mongolia