| 西藏过铝花岗岩副矿物特征及岩石成因意义 |
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| 关键词:peraluminous granite accessory mineral petrogenesis Tibet |
| 基金项目:国家重点基础研究发展规划项目(编号:2002CB412609,G1998040800); 中国地质调查局“青藏高原南部空白区基础地质综合研究”项目(编号:200313000025); 中国地质大学“岩石圈构造、深部过程及探测技术”教育部重点实验室开放课题(编号:2003003) |
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| Characteristics of the Accessory Minerals from the Peraluminous Granites in Tibet and Their Implications |
| The behaviors of accessory minerals can directly indicate the geochemical process of the magmatic system. In order to discuss petrogenesis as well as mineralogical, petrological and accessory mineral characteristics of of peraluminous granites, the authors studied in detail zircon content and crystal form of the peraluminous granites in Tibet. It is shown that the rocks contain abundant muscovite, tourmaline and plagioclase. These rocks belong to muscovite type of strongly peraluminous granites (MPG-type) in Barbarin′s classification. 26 accessory minerals were recognized. They can be assigned to 6 accessory mineral associations, with the main type being zircon+phosphorite. Five zircon crystal forms have been distinguished. In the cathodoluminescence images, the zircons show good crystal morphology and clear oscillatory zoning, as is the case of magmatic zircon. The peraluminous granites in Tibet are of magmtic petrogenesis. Magma originated from partial melt of the crust material. The graphs of accessory minerals show three petorgenetic types: high aluminum crust source, crust source and crust-mantle mixed source. The crystallization temperature of the Gandese belt is higher than that of the Himalayan belt. The features of zircon groups in different tectonic belts show different types of petrogenetic information. The Himalayan belt is regarded as of crust source petrogenesis, whereas the Gandese belt has the participation of mantle source composition in addition to crust source petrogenesis. These differences show inhomogeneity of lithospheric composistion and evolution in Tibet plateau. |
| LIAO Zhong-li,MO Xuan-xue,PAN Gui-tang,ZHU Di-cheng,WANG Li-quan,ZHAO Zhi-dan,JIANG Xin-sheng.2006.Characteristics of the Accessory Minerals from the Peraluminous Granites in Tibet and Their Implications[J].Acta Geoscientica Sinica,27(2):115-122. |
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