Zircon U-Pb Dating, Geochemical Characteristics and Geological Significance of the Quartz Diorite Porphyrite from the Boluogaxiong Gold Deposit in East Kunlun

The quartz diorite porphyrite in the Boluogaxiong gold deposit, located in the eastern section of East Kunlun metallogenic belt, is closely associated with gold mineralization in the space. Based on the studies of zircon LA-ICP-MS U-Pb age and geochemistry, this paper mainly discusses the source, petrogenesis, tectonic setting, age and prospecting significance of the porphyrite. Detailed lithogeochemical studies show that the Boluogaxiong quartz diorite porphyrite belongs to metaluminous calc–alkaline to high–K calc–alkaline series. The diorite porphyrite is enriched in LILE, LREE and Pb, relatively depleting in HFSE, with no obvious Eu anomaly. Rb/Sr, Nb/Ta and Zr/Hf reflect the characteristics of crust-mantle mixing magma origin. LA-ICP-MS zircon U-Pb dating shows that the Boluogaxiong quartz diorite porphyrite was formed at 226.6±1.6 Ma(MSWD=0.41), in the Late Triassic, Indosinian period, corresponding to the Paleo-Tethys tectonic-magmatic cycle in eastern Kunlun orogenic belt. Based on a combined study of previous geochronology and evolution of regional structures, the authors consider that the diorite porphyrite is the product of crust remelting in post–collisional extention stage of the orogen, which suggests the Eastern Kunlun orogeny had begun its post-collisional stage in the Late Triassic, 228 Ma. Indosinian mafic–intermediate dykes, especially diorite porphyrites always have close spatiotemporal and genetic relationship with gold mineralization in East Kunlun, and we should pay sufficient attention to Indosinian mafic–intermediate dykes in further ore-prospecting work.