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Geoscience ›› 2017, Vol. 31 ›› Issue (02): 267-277.

• Mineralogy, Petrology and Mineral Deposit • Previous Articles     Next Articles

Mineralization Characteristics and Indication Significance of Biotite-Rutile from the Gabbro Intrusions in the Yinmin Iron-Copper District, Yunnan Province

SUN Zijian1(), FANG Weixuan2(), LU Jia2,3, WANG Tongrong4, GUO Yuqian2, SONG Lihong2   

  1. 1. Beijing Institute of Geology for Mineral Resources, Beijing 100012, China
    2. China Non-ferrous Metals Resource Geological Survey, Beijing 100012, China
    3. Faculty of Land Resource Engineering, Kunming University of Science and Technology, Kunming, Yunnan 650093, China
    4. Kunming Fengjing Mineral Co.Ltd, Kunming, Yunnan 654102, China
  • Received:2016-03-12 Revised:2016-12-28 Online:2017-04-10 Published:2017-04-25

Abstract:

In order to discuss the metallogenetic and diagenetic environment of iron oxide-copper-gold type deposit, the mineral-geochemical characteristics of biotites, rutiles, chlorites and ankerites of gabbro intrusions in the depth of Yinmin iron-copper district, Yunnan Province were analysed. Rutiles were derived from magmatic crystallization and multiple-stages alteration. The crystallization temperature of rutiles ranged from 820 to 1,082 ℃, and the multi-phases alteration temperature of rutiles ranged from 444 to 730 ℃. Rutiles had a symbiotic relationship with biotites. The biotites were divided into three types: Ti-rich magnesial biotites crystallised from magma, magnesial biotite and ferruginous biotite due to hydrothermal alteration. The crystallization temperature of the primary Ti-rich magnesial biotites ranged from 653 to 750 ℃, the alteration temperature of hydrothermal magnesial biotites ranged from 525 to 619 ℃, and that of hydrothermal ferruginous biotites ranged from 551 to 577 ℃. The oxygen fugacity of all the biotites was near Ni-NiO, indicating that biotites formed in the high oxygen fugacity environment, which was conducive to the formation of rutiles. In conclusion, both of biotites and rutiles formed in the environment with high temperature and oxygen fugacity. Ankerite-siderite alteration was developed in the later stage, forming in the strongly reduced and alkaline environment, playing a corrosive role to rutiles. The alteration temperature of chlorites, which were altered from ferromagnesian, such as biotites, hornblende and pyroxene, ranged from 174 to 243 ℃. The oxygen fugacity was from -44.68 to -51.42, and the sulphur fugacity was from -14.42 to -19.76, showing that chlorites formed in an environment with low-medium temperature, low oxygen fugacity and high sulphur fugacity, which was benefit to the formation of metal sulfide. In sum, the stages of magmatic crystallization, biotitization and rutiles mineralization were characterized by geochemical lithofacies with high temperature and strong oxidization, which was benefit to the Ti-Fe mineralization. Strong reducing geochemical lithofacies followed, which was favorite for the formation of metal sulfide. Above all, the superposition and evolution of geochemical lithofacies were benefit to the iron oxide-copper-gold type deposit mineralization.

Key words: Yinmin iron-copper district, gabbro intrusion, biotitization, rutile mineralization, Yunnan

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