Geochemistry and fluid inclusions of scheelite-mineralized granodiorite porphyries from southern Anhui Province,China |
| |
| Institution: | 1. South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 Xingang Street, Guangzhou 510301, China;2. Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 511 Kehua Street, Wushan, Guangzhou 510640, China;3. College of Resource and Metallurgy, Guangxi University, Nanning, Guangxi 530004, China;4. University of Chinese Academy of Sciences, Beijing 100049, China;5. Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, China;1. Faculty of Earth Science and Mineral Resources, China University of Geosciences, Beijing 100083, China;2. MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;3. No. 916 Geological Team, Jiangxi Bureau of Geology, Mineral Resources, Exploration and Development, Jiujiang 332000, China;4. Northwestern Geological Team, Jiangxi Bureau of Geology, Mineral Resources, Exploration and Development, Shahe 332100, China;1. MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;2. School of Earth and Environment, University of Western Australia, 35 Stirling Highway, Nedlands, WA 6009, Australia |
| |
| Abstract: | We report petrological, cathodoluminescence (CL), major and trace element analyses and fluid inclusion studies on scheelite (W)-mineralized granodiorite porphyries from Dongyuan and Zhuxiling, southern Anhui Province (China). In Dongyuan, the larger part of the granodiorite porphyry body is mineralized with W concentrations up to 1140 g/t (total WO3 reserves >140 000 tonnes), whereas in Zhuxiling mineralization is spatially more limited. All mineralized rocks are strongly altered, containing abundant calcite and no fresh plagioclase. W-mineralized rocks show higher K, Pb and lower Na, Sr, Ti contents compared to the non-mineralized ones. Co-variations between mobile elements (K, Na, Pb, Sr, Rb, etc.) and W, combined with petrological observations, demonstrate that fluid alteration must have controlled the mineralization. In quartz from both deposits 4 types of fluid inclusions have been recognized, i.e., aqueous-carbonic (WC-type), aqueous (W-type, subdivided into Wm-type containing minor detected CO2 and Wn containing no CO2), carbonic (pure CO2, C-type) and late secondary aqueous inclusions (LW-type). WC- and LW-type inclusions represent the original magmatic fluids and meteoric waters, respectively. The other inclusions represent evolved magmatic fluids which are closely related to alteration and mineralization. WC-, Wm- and Wn-type inclusions show higher salinity and lower homogenization temperatures, indicating fluid immiscibility with CO2 effervescence. Additionally, during plagioclase alteration and precipitation of K-feldspar and sericite the K/Na ratio is lowered and Ca released. The precipitation of scheelite must have been promoted by increasing Ca contents in the fluid and also by increasing pH due to CO2 loss. The present study demonstrates that for granitic rocks without calcareous wall rock, plagioclase breakdown must have been the key factor for scheelite mineralization. The presence of CO2-rich fluid indicates that both deposits formed in the same intracontinental extension setting as those in the Nanling region. Thus, the Yanshanian granites from southern Anhui Province may have a great potential for W mineralization, especially the blind ones in deep levels. |
| |
| Keywords: | Scheelite Plagioclase breakdown Granodiorite porphyry Fluid inclusions |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
