| 西藏过铝花岗岩副矿物特征及岩石成因意义 |
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| 引用本文：廖忠礼,莫宣学,潘桂棠,朱弟成,王立全,赵志丹,江新胜.2006.西藏过铝花岗岩副矿物特征及岩石成因意义[J].地球学报,27(2):115-122. |
| DOI：10.3975/cagsb.2006.02.03 |
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| 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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| 中文摘要:副矿物的行为可以更直接地用来指示岩浆体系的地球化学过程,为了探讨过铝花岗岩的成因,对西藏过铝花岗岩体中的岩性、矿物组成、副矿物特征和锆石含量、晶体形态分布特征进行了研究,矿物岩石特征表明西藏过铝花岗岩富含白云母、电气石和钠质斜长石,属典型的含白云母过铝质花岗岩(MPG)。副矿物见有26种,副矿物组合主要有6种类型,其中主要为锆石 磷灰石 钛铁矿型,尤以锆石 磷灰石最为常见。结果表明,可明显分出5种锆石晶体形态;阴极发光图像中,锆石具有较好的晶形,并显示出清晰的岩浆锆石韵律环带结构。离子探针分析表明锆石具有高的Th/U值。西藏过铝花岗岩为岩浆成因,岩浆主要是由地壳物质部分熔融而成。副矿物组合曲线图的曲线形态可分为3种成因类型:壳源高铝型、壳源型和壳幔混合源型(壳幔同熔型),主要为壳源高铝型。不同构造岩浆带副矿物特征反映的成因信息不同,喜马拉雅带为壳源成因,而冈底斯带除了壳源成因之外,还有幔源成分的加入,反映了青藏高原岩石圈组成和演化的不均一性。 |
| 中文关键词:过铝花岗岩 副矿物 岩石成因 西藏 |
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| Characteristics of the Accessory Minerals from the Peraluminous Granites in Tibet and Their Implications |
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| Abstract: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. |
| keywords:peraluminous granite accessory mineral petrogenesis Tibet |
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