• 责任者：Yu Yushuai (Wahan Institute of Geology and Mineral Resources ; Wuhan 430205 ; China) ; Yang Zhusen
• 刊名：Acta Petrologica Sinica
• 出版年：2013
• 卷期：29(11)
• 关键词：铁矿 ; iron ores ; 稳定同位素 ; stable isotopes ; 西藏 ; Tibet
• 页码：p.3815-3827
• 图表：6 illus., 8 tables, 51 refs.
• 分类号：1001
• issnNo：ISSN1000-0569
• isbnNo：CN11-1922/P

     The genetic mineralogy characteristics of garnet, pyroxene, chlorite from Gunjiu iron deposit in Nixiong ore-field, located in the western Gangdise metallogenic belt, are analyzed in this paper, showing that the garnet is mostly andradite, with a certain amount of grossularite existed. The pyroxene belongs to diopside, salite and ferrosalite. The results indicate the ore forming fluid has features of acid, high temperature and high oxygen fugacity. It＇ s concluded that the temperature is decreased and the pH, oxygen fugacity are increased from skarn endocontact to exocontact because of the former is rich in andradite but the latter in grossularite. The chlorites are classified into brunsvigite with enrichment in magnesium and lack of iron, forming at a low temperature of 206 -268℃, low pH and reduced environment. δ^13C ∑c values of metallogenic fluids calculated from calcite C-O isotopes are -2. 6‰ to -0. 7‰, and δ18Ov_sMow values are from ＋ 9. 8‰ to ＋ 12.0‰. 8Dv_sMow values of garnet, magnetite and quartz range from -121‰ to - 105‰, with corresponding δTM OH2o values of 8.7‰ and 11.3‰. The isotopic data suggests the source of ore-forming fluids is mainly magmatic water. The pyrite in magnetite shows the same characteristic with magmatic hydrothermal pyrite, with S/Fe values between 1.05 and 1.07, Co/Ni 〉 1. 6Z4S values of pyrites range from 4. 2‰ to 11.1‰, indicating that sulfur was derived from granite magma. The analysis of pyrite is the favorable evidences that the ore-forming mineral is also derived from granitic magma. Combined with previous research, the high temperature and oxygen fugacity caused the metals poured into magma. The magma intruded above and differentiated a number of ore-forming fluids, which encountered and reacted with country rocks during the migration, causing the formation of skarn and degradation alteration minerals, and finally resulting in changes in physical-chemical properties. Magnetites precipitated under 180℃ to 400℃, weak oxidize to oxidize and kalescent to alkaline conditions.