Metallogenic Features And Prospecting Direction Of Copper Polymetallic Ore Field In Yincan-Langlike Area,North Qilian,China

Yincan-Langlike area is located in Menyuan country of Qinghai province,which belongs to Lenglongling volcanic belt of North Qilian,China,the region mainly develops Yincan and Langlike this two copper polymetallic deposits.Based on the former research work, we carry out extensive researches, like mineralogical characteristics, trace element geochemistry,stable isotope, U-Pb zircon geochronology and so on, invest the Geological characteristics,genetic type, metallogenic mechanism, tectonic setting of mineralization area, metallogenic regularity, ore-controlling factors, metallogenic series, metallogenic model and other issues about metallogenic features for copper polymetallic deposit, and then compare with the typical deposits of the same type, summarize copper polymetallic deposit prospecting model and prospecting direction of this area. The main results are as follows:1. Yincan copper polymetallic deposit develops a basalt-rhyolite bimodal volcanic rocks,the basalt is characterized by high-Na, low-K and Ti, similar to island arc tholeiitic basalts,enriched Mg, high-Cr and Ni, with the attributes of mantle-derived primitive magma,the trace elements evidently indicate depletion of Nb and Sr-positive anomaly, relatively enriched in HREE; K2 O of Rhyolite content is very low, its apparent loss of trace elements Nb-Ta, Th, Sr and Ti, enriched in LILE; the mineralization mainly occurs in acidic volcanic(rhyolites).2. The main ejected phase of Langlike copper polymetallic deposits is andesite rock,subvolcanic facies rock is quartz diorite, the andesite and quartz diorite are both characteristics of enrichment in magnesium,high-Cr and Ni, significantly enriched in LILE and relatively depleted in HFSE, as well as slightly enriched in LREE; the mineralization deposits in the quartz diorite and its adjacent andesite.3. Studying on the deposit characteristics and mineralization of typical deposits,and estimating the Yincan copper polymetallic deposit is a intra-oceanic subduction island arc rift formed by marine volcanic deposit, the Langlike copper polymetallic deposit is a island arc porphyry Cu polymetallic deposit; the discovery of Porphyry copper deposit is the first case in the North Qilian area.4. With LA-ICP-MS zircon U-Pb dating, the results demonstrate that the basalt and rhyolite in Yincan copper polymetallic mine are separately age of 457.0 ± 9.1 Ma and 467.8 ±6.7 Ma; while the andesite and quartz diorite Langlike copper polymetallic mine are separately age of 479.2 ± 9.9 Ma and 461.5 ± 7.3 Ma, ore molybdenite Re-Os isochron age of469.3 ± 2.9Ma, indicating that the mineralization in this area is mainly concentrated in theMiddle Ordovician.5. Ore-forming material source of typical deposit shows that the sulfur in Yincan copper polymetallic deposits is mainly derived from mantle magma, and it mixes reduced sulfur(δ34S average 6.42 ‰) in sulfate from seawater; the sulfur in Langlike copper polymetallic deposits is only stemmed from mantle(δ34S average 2.67 ‰), significantly different from the Yincan marine volcanic type copper.6. Through the research on typical deposits in this ore field, we have confirmed the predictive factors of its type and established two prospecting model: 1) the ore prediction factors and prospecting model of marine volcanic rock type copper polymetallic; 2) the ore prediction factors and prospecting model of porphyry Cu polymetallic; and have determined the further prospecting directions of marine volcanic type and porphyry Cu polymetallic deposits.