| The guoluolongwa gold deposit hosts in the Wanbaogou Group in the Eastern Kunlun orogenic belt, is a mesothermal quartz-vein type gold deposit related to Variscan-Indosinian-Yanshanian intermediate-fesic magmatism.Based on the review of previous data, and through detailed field geological investigation and laboratory analysis, we suggested that the Wanbaogou Group low-grade metamorphiosed volcanic-sedimentary rocks are the host rocks of the gold-bearing quartz veins, whose direct wall rocks are chlorite-quartz-phyllite rocks and siliceous rocks. Gold deposits in this area are controlled by multi-order structural systems, controlled by NW-trending East-Kunzhong deep regional faults and located in secondary fault systems. The mineralization is mainly pyrite-dominant sulfide quartz vein type and subordinate sulfide alteration type. Ore bodies are distributed as various-shape veins, with the strike 170°-190°and dip 62°-85°,the incline to west is the main trend of these ore bodies. The main ore minerals are pyrite and chalcopyrity, with minor sphalerite, galena, and limonite. Gold occurs as electrum and native gold, mainly in pyrite, and quartz is the main gangue minerals. Wall-rock alteration includes chloritization, sericitization, and carbonatization (calcite, siderite). The gold deposit-forming process experienced four metallogenic epochs, represented by the sedimentary-metamorphose, hydrothermal-mineralize, structure-rupture and supergene leaching-enrichment.Theδ34S of pyrite in gold orebodies is from 0.2‰5 to 3.88‰5, averaging 2.208‰, of galena from -2.03‰5 to -5.95‰5, averaging -3.463‰, which are less than the valued commonly observed in mesothermal-hydrothermal gold deposit and magmatic sulfide deposit, while slightly richer in 32S than aerolite, showing that the source of the ore-forming fluid is not simply derived from magmatic water, but a mixture of meteoric water and magmatic water.Lead isotopes are homogeneous relatively. The ratios 206Pb/204Pb,207Pb/204Pb and 208Pb/204Pb in phyrite are in the range of 18.057-18.135, 15.524-15.585 and 37.962-38.110 respectively, and for galena are 18.093-18.106, 15.542-15.563 and 37.901-37.919 respectively. According to Doe and Zartman's Pb isotopic scheme, most Pb isotope data are plot in the area between mantle evolutiona-trend line and upper-crustal evolution-trend, indicating that the deposit formed in a typical orogenic belt.Rare-earth-element(REE) contents of pyrite monominerals ranges from 0.77×10-6 to 58.79×10-6. Some parameters related to REE are:∑LREE/∑HREE ratios between 10 to 28; 5Eu between 0.36 to 0.85, and (Gd/Yb) N from 0.54 to 2.30, showing weak negative Eu anomaly, and right inclineing patterns. Cobalt and nickel contents in pyrite are between 1.365×10-6 to 1016×10-6 (418.3×10-6 in average) and 6.325×10-6 to 515.5×10-6(201.2×10-6 in average) respectively, with Co/Ni ratios is from 1 to 7 and 2.1 in average, indicating that the Co and Ni were derived from mafic-intermediate volcanic rocks.Trace elements analysis show that there are high contents of Au, Ag, As and Pb in metavolcanic rocks and Cu, Zn and Mo in metasediments. Both R type cluster analysis and factor analysis indicate that gold metallogenesis was relatively independent. Components of fluid inclusions in gold-bearing quartz show that ore-forming fluid is alkalescent, rich in sulfur, and Na+> K+, same as the rock mass in the east Kunlun orogenic belt.According to this research, combined with the deposit geological characters in this area which had been found, we regarded the genesis of the Guoluolongwa gold deposit as a typical orogenic belt mesothermal quartz-vein gold deposit. In the end of this thesis, the mineralization regularity was summarized and mineralization model was established. |
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