关键词: 成岩时代, 元素地球化学, 斑岩铜成矿系统, 岩石成因, 地球动力学, 六九山铜矿床, 大兴安岭

Abstract:

The Liujiushan Cu deposit is located in the eastern end of the northern Great Hinggan Range, part of the easternmost edge of Central Asian orogenic belt. This study presents detailed field geology, petrography, elemental geochemistry and geochronology of diorite porphyry and monzonite porphyry to reveal the petrogenesis and geodynamic setting of these intrusive rocks. Magmatic zircons from diorite porphyry and monzonite porphyry yielded a weighted average age of （132.6±2.6） Ma (n=5) and （132.4±1.3） Ma (n=22), respectively. The LA-ICP-MS zircon U-Pb ages show these intrusive rocks were emplaced at ~132 Ma, consistenting with the molybdenite Re-Os isotopic dating of （134.1±0.8） Ma, which constrains Cu mineralization to the Early Cretaceous. The diorite porphyry (52.98%-59.83% w(SiO2)) and monzonite porphyry (66.90%-67.56% w(SiO2)) are classified as intermediate to acidic hypabyssal intrusive rocks, enriched in the large ion lithophilic elements and deleted in high field strength elements, representing island arc alkaline and of adakitic rock types, respectively. Their parental magmas originated from an enriched mantle. All these studies show that the diagenesis and mineralization resulted from subduction of the Kula slab beneath Eurasian continent.

Key words: diagenesis age, elemental geochemistry, porphyry Cu ore system, petrogenesis, geodynamic, Liujiushan Cu deposit, Great Hinggan Range