Study On Characteristics Of Intrusive Rocks Related To Mineralization And Metallogenic Time Of Wunugetushan Cu-Mo Deposit, Inner Mongolia

The Wunugetushan large deposit is one of the typical porphyry deposits in NE China. It’s is located in the Erguna block, on the southern margin of the Mongol-Okhotsk Orogenic belt. Magmatic events are complex, and have experienced complicated tectonic evolution in the region. There are remains controversial about the metallogenic epoch, combination and characteristics of igneous rocks, the relationship between mineralization and tectonic-magmatic events. Therefore, this paper studied on the characteristics of field geology, petrology, mineralogy, geochemistry, isotopic geochronology.There are two stages of magmatism in Wunugetushan deposit: biotite adamellite and vein rocks; granodiorite-porphyry and neutral-acidic intrusive rocks,volcanic rocks. The lithology of granodiorite-porphyry changes a lot from top to bottom and the edge to the interior. In the top and the edge, granodiorite-porphyry has poly-phenocryst porphyritic texture and weak mineralization. And then, it has less phenocryst porphyritic texture and vein mineralization. In the bottom and the interior, it has granulitic texture and disseminated mineralization. According to the theory of metallogenesis by transmagmatic fluids, the poly-phenocryst porphyritic texture and disseminated structure can be used as petrographic indicators of the ore-bearing intrusions. Therefore, granodiorite-porphyry is mineralizing intrusive rocks.According to the LA-ICP MS zircon U-Pb ages of 8 samples, the author obtain the following understanding. Biotite adamellite with the dating of 191 ± 1.5Ma and quartz porphyry with the dating of 196 ± 1.2Ma formed in early Jurassic. Andesite formed in Middle Jurassic(169 ± 0.64Ma) and situated in the lower Tamulan formation. Zircons of the ore-bearing intrusions are complex. Through the analysis, the author thinks mineralization and magmatic activities occurred in the end of Middle Jurassic to late Jurassic.Geochemistry characteristics shows the mineralizing intrusive rocks belong to peraluminous high-k calc-alkaline granite. They are enriched in LREE with of Eu negative anomaly. In terms of trace elements, the granodiorite-porphyry are enriched in large ion lithophile elements(LILE) such as K, Rb, Ba, and high field strength elements(HFSE) such as Ce, Zr, Hf, Sm, depleted Nb, Ta, P and Ti, showing the characteristics of volcano arc granite. The granite settings discriminate diagrams show instrusive rocks as volcanic arc-intracontinental collision granite.Based on the above research, the Wunugetushan porphyry copper-molybdenum deposit is formed in a continent-continent collision setting between the Siberian and North China Cratons,to a intracontinental collision setting after the time of the Mogol-Okhotsk ocean closure.