| 高喜马拉雅变质岩“夕线石带”的地质意义 |
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| 引用本文： | 任留东,陈炳蔚.高喜马拉雅变质岩“夕线石带”的地质意义[J].地球科学进展,2004,19(5):715-721. |
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| 作者姓名： | 任留东 陈炳蔚 |
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| 作者单位： | 中国地质科学院地质研究所,北京,100037 |
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| 基金项目： | 国土资源部青藏高原专项基金,国土资源部青年地质学家基金,200101020405,,, |
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| 摘 要： | 通过对聂拉木高喜马拉雅结晶岩系石榴子石带-十字石带-蓝晶石带-夕线石带倒转变质的研究,认为除夕线石带以外的其它变质带主要由固相变质反应形成。夕线石的出现并非蓝晶石或十字石带递增变质所致。"倒转变质"不应包括所谓的夕线石带。实际上,夕线石化与深熔作用之后的溶液（或熔体）活动更为密切。时间顺序上应是递增变质作用及分带→深熔作用→夕线石化,夕线石的出现不是深熔作用的开始,而是深熔作用的结束。夕线石的形成主要与变形作用过程中黑云母和／或钾长石的分解及碱（土）金属组分的迁移有关,关键在于溶液（或熔体）组分沿裂隙迁移过程中发生的组分逐步沉淀,最早沉凝的Al、Si组分形成夕线石和石英,之后陆续有其它的组分的结晶;细夕线石粗粒化即进一步转化形成柱状夕线石的同时形成蠕英结构和斜长石生长边。夕线石化可能与深熔花岗（片麻）岩的上升过程有关。
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| 关 键 词： | 高喜马拉雅变质岩 聂拉木 夕线石化 形成机制 |
| 文章编号： | 1001-8166(2004)05-0715-07 |
| 修稿时间： | 2003年7月4日 |
THE IMPLICATION OF THE "SILLIMANITE ZONE" IN THE HIGH HIMALAYAN CRYSTALLINE ROCKS |
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| REN Liu-dong,CHEN Bing-wei.THE IMPLICATION OF THE "SILLIMANITE ZONE" IN THE HIGH HIMALAYAN CRYSTALLINE ROCKS[J].Advance in Earth Sciences,2004,19(5):715-721. |
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| Authors: | REN Liu-dong CHEN Bing-wei |
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| Institution: | Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China |
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| Abstract: | The inversion metamorphic zones, garnet zone to starolite, kyanite, and sillimanite zones in the High Himalayan crystalline rocks at the Nyalam profile have been reinvestigated. Except for the sillimanite zone, the other metamorphic zones are brought about by the solid state reactions under regional dynothermal metamorphism. The presence of sillimanite is not resulted from the prograde metamorphism of kyanite or starolite zone, i.e., sillimanitization has no relations with the Ky-St-Grt zonation. The so-called sillimanite zone here is not an independent metamorphic one and therefore cannot be included in the inversion metamorphism. In fact,Sillimanitization is closely related to the solution or melt after anatexis. Temporally the sequence is prograde metamorphism and zonation→anatexis→sillimanitization. The occurrence of sillimanite in the High Himalayan crystalline rocks marks the waning, not the beginning period of anatexis. Genesis of sillimanite is mainly associated with the decomposition of biotite and/or potassium feldspar and the subsequent migration of alkaline and alkaline earth metals in the deformation process. The step segregation is crucial in the formation of sillimanite in the migration of solution or melting through the fissure. The Al, Si components condensed at early stage formed sillimanite and quartz, and other components precipitation, successively. Contemporaneously with the coarsening of fibrolite to prismatic sillimanite, the myrmekite texture and albitic plagioclase rim occurred. Sillimanitization may be related with the doming and uplift of the anatexitic granitic gneisses. |
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| Keywords: | High Himalayan crystalline rocks Inversion metamorphic zones Nyalam profile Sillimanitization Formation mechanism |
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