| 青海尕林格矽卡岩铁多金属矿床Fe-Ti氧化物及其热动力学意义 |
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| 关键词:Galinge Fe-Ti oxides spinel geothermometer oxygen barometer oxyexsolution |
| 基金项目:国土资源部公益性行业科研专项(编号: 201411025);青海省地质勘查基金项目(编号: 201304);中国地质调查局地质调查项目(编号: 1212011085528);中国地质调查局高层次地质人才培养计划(编号: 201309);青年地质英才计划(编号: 201112) |
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| The Iron-Titanium Oxides in the Galinge Iron Polymetallic Skarn Deposit of Qinghai Province and Their Thermodynamic Significance |
| The Galinge skarn iron deposit is located at the junction between the Qimantag metallogenic belt in the East Kunlun Mountains and the Qaidam Basin. There are two types of Fe-Ti oxides coexisting assemblages in the Galinge skarn deposit: one is the hydrothermal magnetite-ilmenite coexisting assemblage (HYM) which was discovered in No. 2 Ⅱ ore group, whereas the other one is the igneous magnetite-ilmenite coexisting assemblage (IGM) which is developed in the fresh mafic basaltic andesite. This research aimed to analyze the distinctive composition and significant thermodynamic features of the HYM and IGM. The HYM shows an intergrowth with ferromagnesium spinel, and the crystallographic orientation of growing ilmenite lamellae are parallel to the (111) planes of the magnetite octahedron. Based on the equilibrium of oxidation, the equilibrated temperatures range between 581.8C and 688.9℃, and the oxygen fugacities vary between 10-14.74 and 10-17.94. The IGM is mainly in equilibrium with silicate minerals in the mafic magma. The equilibrated temperatures of the IGM range between 690.73℃ and 740.26℃, and the range of oxygen fugacities is 10-15.44-10-17.30. It is reasonably inferred that the primary metallogenic temperature might have reached 700℃, approaching the crystallographic temperature of water saturated magma. Therefore, the HYM was formed after the primary cooling procedure of the early high-temperature and high-salinity hydrothermal fluid which evolved from the magma. Because of the infiltration metasomatism between the hydrothermal fluid and the mafic igneous rocks, large amounts of metal elements such as Fe, Ti, Al, Mg and Cu were leached out. In the early high temperature setting, Ti and Al were incorporated into the magnetite, and consequently the oxyexsolution of titaniferous magnetite resulted in the intergrowth of magnetite and ilmenite. As the oxyexsolution did not rapidly re-equilibrate under new conditions, the iron-titanium oxide relationship could be preserved and hence could indicate the equilibrium temperature and the oxygen fugacity of the oxidation. |
| YU Miao,FENG Cheng-you,LIU Hong-chuan,LI Ding-wu,WANG Hui,LIU Jian-nan,ZHAO Yi-ming,LI Da-xin.2016.The Iron-Titanium Oxides in the Galinge Iron Polymetallic Skarn Deposit of Qinghai Province and Their Thermodynamic Significance[J].Acta Geoscientica Sinica,37(2):204-214. |
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