藏南萨迦拉轨岗日淡色花岗岩特征及与变质核杂岩的关系

张金阳; 廖群安; 李德威; 张雄华; 袁晏明

藏南萨迦拉轨岗日淡色花岗岩特征及与变质核杂岩的关系

中国地质大学地球科学学院, 湖北武汉 430074

基金项目:

中国地质调查局"1∶25万定结幅、陈塘区幅(国内部分) 区域地质调查" 20001300009231

详细信息

作者简介:
张金阳(1977-), 男, 现正攻读岩浆岩石学专业硕士学位

中图分类号: P58
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出版历程
- 收稿日期: 2003-05-15
- 刊出日期: 2003-11-25

Laguigangri Leucogranites and Its Relation with Laguigangri Metamorphic Core Complex in Sajia, South Tibet

Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China

摘要

摘要: 藏南拉轨岗日带展布着串珠状变质核杂岩, 其内出露的淡色花岗岩体构成北喜马拉雅淡色花岗岩带.岩体既有在变质核杂岩内核中分布的, 亦有在滑脱系分布的, 岩体均表现出强力主动侵位的特征.淡色花岗岩可分为两期: 早期黑云母淡色花岗岩和晚期白云母淡色花岗岩.岩石高硅富铝, 含白云母±电气石±石榴石特征富铝矿物, 为S型花岗岩.北喜马拉雅淡色花岗岩结晶年龄为17~10Ma, 源岩为MCT上部基底副变质岩.当挤压体制与伸展体制转换时, 降压作用导致了岩浆的生成, 同时, 由于压力骤减, 年轻造山带更为塑性的下地壳物质与软层隆起导致上地壳伸展, 从而形成变质核杂岩, 岩浆对内核的上隆起到促进作用.
- 变质核杂岩 /
- 淡色花岗岩 /
- 拉轨岗日 /
- 西藏萨迦
Abstract: Laguigangri metamorphic core complexes (MCC) occurred in paternoster shape in south Tibet. Leucogranites, distributed in the core or detachment of the MCC, form the famous northern Himalayan leucogranites belt. They actively emplaced and occurred in two periods: early biotite leucogranites and late muscovite leucogranites. With high SiO₂ and Al₂O₃, the leucogranites have muscovite±tourmaline±garnet aluminous minerals and so do S-type granites. The crystalline of the northern Himalayan leucogranites is dated 17-10 Ma, whose source is the para-metamorphical rocks in the high Himalayan crystalline basement on top of the MCT. The magma resulted from decompression during the conversion of the structural mechanism. Simultaneously, the pressure decompression caused more plastic lower crust and the liquid layer in younger orogen to rise to the upper crust and formed the MCC. It is found that the magma speeds the formation of the MCC.
- metamorphic core complex /
- leucogranites /
- Laguigangri /
- Sajia of Tibet

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图 1 藏南地区构造格架

YZS.雅江缝合带; DFG.定日-岗巴逆冲断层; STD.藏南拆离断层

Fig. 1. Structure of Dingjie region, southern Tibet

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图 2 阿马变质核杂岩地质简图

1.定日-岗巴断裂; 2.拆离断层; 3.白云母淡色花岗岩; 4.黑云母淡色花岗岩; AnZl.拉轨岗日变质核杂岩、花岗质片麻岩与表壳变质岩; AnZk.片岩组合; C_1-2s-P₂b.低级变质岩; T₁₊₂l.吕村组; T₃n.涅如组; Q.第四系

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图 3 拉轨岗日淡色花岗岩稀土元素配分(a) 及微量元素蛛网图(b)

Fig. 3. Leedy-chondrite normalized rare earth elements (a) and ocean ridge granite normalized trace element spider diagrams (b) for leucogranites

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表 1 拉轨岗日淡色花岗岩主量元素分析结果

Table 1. Chemical compositions of the leucogranites

表 2 拉轨岗日淡色花岗岩稀土元素和微量元素分析结果

Table 2. REE and trace element compositions of the leucogranites

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