Geochronology and fluid inclusion study of the Yinjiagou porphyry-skarn Mo-Cu-pyrite deposit in the East Qinling orogenic belt, China

详细信息    查看全文

• 作者：Guang Wu ; Yuchuan Chen ; Zongyan Li ; Jun Liu ; Xinsheng Yang ; Cuijie Qiao
• 关键词：Molybdenite Re&ndash ; Os age ; Sericite 40Ar&ndash ; 39Ar age ; Fluid inclusion ; Porphyry&ndash ; skarn deposit ; Yinjiagou Mo&ndash ; Cu&ndash ; pyrite deposit ; East Qinling orogenic belt
• 刊名：Journal of Asian Earth Sciences
• 出版年：5 January, 2014
• 年：2014
• 卷：79
• 期：Complete
• 页码：585-607
• 全文大小：9954 K

文摘

The Yinjiagou Mo-Cu-pyrite deposit of Henan Province is located in the Huaxiong block on the southern margin of the North China craton. It differs from other Mo deposits in the East Qingling area because of its large pyrite resource and complex associated elements. The deposit鈥檚 mineralization process can be divided into skarn, sulfide, and supergene episodes with five stages, marking formation of magnetite in the skarn episode, quartz-molybdenite, quartz-calcite-pyrite-chalcopyrite-bornite-sphalerite, and calcite-galena-sphalerite in the sulfide episode, and chalcedony-limonite in the supergene episode. Re-Os and ⁴⁰Ar-³⁹Ar dating indicates that both the skarn-type and porphyry-type orebodies of the Yinjiagou deposit formed approximately 143 Ma ago during the Early Cretaceous. Four types of fluid inclusions (FIs) have been distinguished in quartz phenocryst, various quartz veins, and calcite vein. Based on petrographic observations and microthermometric criteria the FIs include liquid-rich, gas-rich, H₂O-CO₂, and daughter mineral-bearing inclusions. The homogenization temperature of FIs in quartz phenocrysts of K-feldspar granite porphyry ranges from 341 掳C to >550 掳C, and the salinity is 0.4-44.0 wt% NaCl eqv. The homogenization temperature of FIs in quartz-molybdenite veins is 382-416 掳C, and the salinity is 3.6-40.8 wt% NaCl eqv. The homogenization temperature of FIs in quartz-calcite-pyrite-chalcopyrite-bornite-sphalerite ranges from 318 掳C to 436 掳C, and the salinity is 5.6-42.4 wt% NaCl eqv. The homogenization temperature of FIs in quartz-molybdenite stockworks is in a range of 321-411 掳C, and the salinity is 6.3-16.4 wt% NaCl eqv. The homogenization temperature of FIs in quartz-sericite-pyrite is in a range of 326-419 掳C, and the salinity is 4.7-49.4 wt% NaCl eqv. The ore-forming fluids of the Yinjiagou deposit are mainly high-temperature, high-salinity fluids, generally with affinities to an H₂O-NaCl-KCl 卤 CO₂ system. The 未¹⁸O_H2O values of ore-forming hydrothermal fluids are 4.0-8.6鈥? and the 未D_V-SMOW values are between 鈭?4鈥?and 鈭?2鈥? indicating that the ore-forming fluids were primarily magmatic. The 未³⁴S_V-CDT values of sulfides range between 鈭?.2鈥?and 6.3鈥?with a mean of 1.6鈥? sharing similar features with deeply sourced sulfur, implying that the sulfur mainly came from the lower crust composed of poorly differentiated igneous materials, but part of the heavy sulfur came from the Guandaokou Group dolostone. The ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb values of sulfides are in the range of 17.331-18.043, 15.444-15.575, and 37.783-38.236, respectively, which is generally consistent with the Pb isotopic signature of the Yinjiagou intrusion, suggesting that the Pb chiefly originated from the felsic-intermediate intrusive rocks in the mine area, with a small amount of lead from strata. The Yinjiagou deposit is a porphyry-skarn deposit formed during the Mesozoic transition of a tectonic regime that is EW-trending to NNE-trending, and the multiepisode boiling of ore-forming fluids was the primary mechanism for mineral deposition.