部分熔融与高级变质岩流变机制_以内蒙古大青山高级变质岩为例

第15卷第3期2008年5月

地学前缘(中国地质大学(北京);北京大学)

Earth Science Frontiers (Chin a University of Geosciences,Beijing;Peking University)Vol.15No.3M ay 2008

收稿日期:2007 09 20;修回日期:2008 01 14

基金项目:国家自然科学基金资助项目(40572117);中国地质调查局项目(200113000021)作者简介:刘正宏(1960 ),男,博士,教授,从事构造地质研究。E mail:zh liu@jlu edu cn

部分熔融与高级变质岩流变机制 以内蒙古大青山高级变质岩为例

刘正宏, 徐仲元, 杨振升

吉林大学地球科学学院,吉林长春130061

Liu Zhenghong, Xu Zhongy uan, Yang Zhensheng

S ch ool of E arth Sc ienc es,J ilin Univ er sity ,Changc hun 130061,Ch ina

Liu Zhenghong ,Xu Zhongyuan,Yang Zhensheng Partial m elting and the rheologic mechanism o f high grade meta morphic ro ck a case study on D aqingshan high grade metam orphic rock in Inner M ongolia .Earth Science Frontiers ,2008,15(3):168 177

Abstract:T here is a restr icted relatio nship betw een t he par tial melting and the defo rmation o f hig h g rade meta mo rphic ro ck;the deformat ion enhances the deg ree of r ock partial melt ing and decreases the partial melt ing

temper ature.M elt influences r ock str eng th and deformat ion mechanism.T he Daqingshan hig h gr ade met amor phic ro cks wer e mo dified by metamo rphism,defo rmatio n and anatex ite in the lo wer cr ust,and developed a complex assemblag e o f st ructur al elements.T he characterist ics o f macr ostr uctures and micro tectonics show that the ma in defor matio n mechanism of high g rade metamo rphic rock is t he melt enhanced g rain side diffusion and the gr ain flow ,w hich caused a larg e scale plastic flo w of r ock.So me macr ostructural elements,such as a sy mmetry flo w fo lds,melted lineations,ro ck and miner al bands,intr ast ratal diapiric folds and a larg e do me,wer e for med in partially melt ed high g rade metamo rphic r ocks.T he microfabr ics features of ro ck are equilibri um tex tures of tr iple sides,similar to the metafabr ics of ro cks by stat ic cr ystalline metamo rphism;the deform at ion of miner al g rain is not obvio us and the intracr ystalline deformat ion tex tures did not dev elo p;the meta mo rphic tectonite of low er cr ustal tect onic level,the tectonic g neiss,was for med.

Key words:Daqing shan;hig h gr ade metamo rphic rock;rheolo gic mechanism;partial melting

摘 要:部分熔融作用与高级变质岩变形作用是相互制约,变形作用能够提高岩石部分熔融程度,降低熔融温度。熔体存在影响和制约岩石强度和变形机制。大青山高级岩经历了下部地壳构造层次变质变形和深熔作用改造,形成了复杂构造要素组合。宏观与微观构造特点表明:高级变质岩变形机制主要为熔体增强颗粒边界扩散和颗粒流动,使岩石发生大规模的塑性流动。在宏观上形成了不对称流动组构、熔融线理、岩石和矿物条带、层内底辟褶皱和大型穹窿构造。但是,在微观上矿物颗粒变形不明显,晶内变形组构不发育,表现为三边平衡结构,与静态结晶变质岩结构相似,形成了地壳深部构造层次上变质构造岩 构造片麻岩。关键词:大青山;高级变质岩;流变机制;部分熔融

中图分类号:P 588 3 文献标识码:A 文章编号:1005 2321(2008)03 0168 10

大青山高级变质岩位于华北克拉通北缘,以广泛发育高级变质的麻粒岩系和孔兹岩系为特征,其总体上呈东西向线形构造带产出。前人对这些高级

变质岩的原岩建造、形成构造背景和变质变形的演化历史进行了深入的研究,取得许多新的进展[1 12]

。

高级变质岩普遍经受了角闪岩相 麻粒岩相变质变