Processes of ore genesis at the world-class Yuchiling molybdenum deposit, Henan province, China

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• 作者：Juan Zhang ; Hui-shou Ye ; Ke Zhou ; Fang Meng
• 关键词：Fluid inclusions ; Stable isotopes ; Re&ndash ; Os geochronology ; Porphyry Mo ; Yuchiling ; Qinling
• 刊名：Journal of Asian Earth Sciences
• 出版年：5 January, 2014
• 年：2014
• 卷：79
• 期：Complete
• 页码：666-681
• 全文大小：7112 K

文摘

The Yuchiling molybdenum deposit is one of the most significant porphyry molybdenum systems in the eastern Qinling of central China. The mineralization is mainly hosted by a porphyritic granite and associated cryptoexplosive breccia. Hydrothermal alteration minerals include K-feldspar, sericite, pyrite, chlorite, epidote, carbonate, kaolinite, fluorite, and gypsum. Ore minerals are dominated by molybdenite and pyrite, with lesser amounts of chalcopyrite, galena, scheelite, wolframite, ilmenite, leucoxene, native gold, sphalerite, and hematite. The 未³⁴S compositions of sulfide minerals range from 鈭?.0鈥?to +4.0鈥? The deposit is characterized by four hydrothermal stages: quartz-K-feldspar (stage I), molybdenite-quartz (stage II), pyrite-sericite-quartz (stage III), and quartz-carbonate (stage IV). Microthermometric studies of fluid inclusions show that the fluids evolved gradually during the ore-forming process. Homogenization temperatures, salinities, and minimum pressure estimates for the inclusions from each mineralization stage evolved as follows: (1) stage I: homogenization temperatures = 203.7-525.8 掳C, salinities = 2.96-10.49 and 29.66 wt.% NaCl equiv., and minimum pressures = 101.9-196.2 MPa; (2) stage II: homogenization temperatures = 173.6-448.6 掳C, salinities = 1.81-9.74 wt.% NaCl equiv., and minimum pressures = 93.1-172.0 MPa; (3) stage III: homogenization temperatures = 130.1-386.0 掳C, salinities = 1.40-9.73 and 34.07 wt.% NaCl equiv., and minimum pressures = 95.5-142.5 MPa; (4) stage IV: homogenization temperatures = 170-230 掳C and salinities = 0.18-5.71 wt.% NaCl equiv. Various fluid inclusions were observed to contain H₂O, CO₂, CH₄, SO₂, C₂H₂, C₂H₄, C₂H₆, and (or) H₂S, as well as solids that include halite, sylvite, anhydrite, chalcopyrite, hematite, molybdenite, and jamesonite. The 未¹⁸O and 未D of the hydrothermal fluids vary from 鈭?.4鈥?to +8.5鈥?and 鈭?1鈥?to 鈭?1鈥? respectively. Microthermometric and stable isotope data indicate that the ore-forming fluids for the Yuchiling molybdenum deposit evolved from early magmatic, to a mixture of meteoric and magmatic water, and finally to a principally late stage meteoric water. A molybdenite Re-Os age of 131.2 卤 1.4 Ma coincides with the early part of the 131-112 Ma period of magmatic and related ore-forming events that are widely recognized in eastern Qinling.