The Tawenchahanxi Fe-polymetallic deposit is a medium-sized deposit newly discovered in Qimantag area of Qinghai Province. In this area the orebody and metallogenic rock body are both covered by Quaternary eolian sandstone. By using LA-ICP-MS zircon U-Pb isotope dating, the authors obtained the petrogenetic age of the granite diorite porphyry (236.0±2.3 Ma.) which is the main ore-forming rock mass in the ore deposit. The result is close to the age of Tawenchahanxi deposit. It might have been formed at the collision-post collision conversion stage of Late Paleozoic to Early Mesozoic tectono-magmatic cycle associated with the crustal thickening setting. On the basis of chronological, petrologic and geochemical studies, the authors have revealed that the granodiorite porphyry is a peraluminous, high K calc-alkaline series granite, which is enriched in LREE and HFSE and depleted in HREE and LILE, with medium negative Eu anomalies. The granodiorite porphyry belongs to the I-type and crust-mantle magma mixing source, related to regional large-scale mantle magma underplating and crust-mantle magma mixing. The Tawenchahanxi Fe-polymetallic deposit is a typical skarn deposit, which is mainly distributed in the contact zone between granodiorite porphyry and Qimantag Group carbonatite. There are two type of orebodies (metasomatic iron-oxide orebody and veinlet sulfide polymetallic orebody) in the ore deposit, and the evolution of the ore-forming fluid can be divided into skarn stage, retrograde alteration stage and sulfide-quartz stage.