Fluid inclusions and H-O-S-Pb isotope systematics of the Chalukou giant porphyry Mo deposit, Heilongjiang Province, China

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• 作者：Jun Liu ; Jing-Wen Mao ; Guang Wu ; Feng Wang ; Da-Feng Luo ; Yan-Qing Hu ; Tie-Gang Li
• 关键词：Fluid inclusion ; Isotope ; Porphyry Mo deposit ; Chalukou ; Great Xing'an Range
• 刊名：Ore Geology Reviews
• 出版年：June, 2014
• 年：2014
• 卷：59
• 期：Complete
• 页码：83-96
• 全文大小：4195 K

文摘

The Chalukou giant porphyry Mo deposit, located in the northern Great Xing'an Range, is the largest Mo deposit in the Xing'an-Mongolia orogenic belt. This deposit's ore bodies are mainly hosted in an intermediate-felsic complex and Jurassic volcanic sedimentary rocks, of which Late Jurassic granite porphyry, quartz porphyry and fine grained granite are closely associated with the Mo mineralization. Three types of fluid inclusions (FIs) are present in the quartz associated with oxide and sulphide minerals, i.e., liquid-rich two-phase, gas-rich two-phase and daughter mineral-bearing multiphase FIs. The FIs in the quartz phenocrysts of the granite porphyry contain liquid-rich two-phase, gas-rich two-phase and daughter mineral-bearing multiphase FIs. The homogenization temperatures vary from 230 掳C to 440 掳C and 470 掳C to 510 掳C, and their salinities vary from 0.7% to 53.7% NaCl eq. and 6.2% to 61.3% NaCl eq., respectively. The FIs of K-feldspar-quartz-magnetite veins of the early stage are composed of liquid-rich two-phase, gas-rich two-phase and daughter mineral-bearing multiphase FIs with homogenization temperatures and salinities of 320 掳C to 440 掳C and 4.2% to 52.3% NaCl eq., respectively. The FIs of quartz-molybdenite veins and breccia of the middle stage are composed of liquid-rich two-phase, gas-rich two-phase and daughter mineral-bearing multiphase FIs with homogenization temperatures and salinities of 260 掳C to 410 掳C and 0.4% to 52.3% NaCl eq., respectively. FIs of quartz-fluorite-galena-sphalerite veins of the late stage are liquid-rich two-phase FIs with homogenization temperatures and salinities of 170 掳C to 320 掳C and 0.5% to 11.1% NaCl eq., respectively. The ore-forming fluids of the Chalukou deposit are characterised by high temperature, high salinity and high oxygen fugacity, belonging to an F-rich H₂O-NaCl 卤 CO₂ system. The 未¹⁸O_W values vary from 鈭?#xA0;4.5鈥?to 3.2鈥? and the 未D_W values vary from 鈭?#xA0;138鈥?to 鈭?#xA0;122鈥? indicating that the ore-forming fluids were a mixture of magmatic and meteoric water. The 未³⁴S values range from 鈭?#xA0;1.9鈥?to + 3.6鈥?with an average of + 1.6鈥? The ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb values of the metallic minerals are in the ranges of 18.269-18.501, 15.524-15.567 and 38.079-38.264, respectively. Both the S and Pb isotopic systems indicate that the ore metals and fluids came primarily from a deep-seated magma source from the juvenile lower crust. The Mo mineralization in the Chalukou deposit occurred at a depth of 0.5 to 1.3 km, and multiple stages of phase separation or immiscibility of ore-forming fluid was critical for the formation of the Chalukou deposit.