滇西凤庆“澜沧岩群”变质作用特征及其变质变形序列

发布时间：2018-09-11 17:52

【摘要】：昌宁-孟连带的演化历史一直是中外地质学者和专家研究的热点。“澜沧岩群”位于昌宁-孟连带南段的东缘,其地层划分、岩石特征及变质特征,以及地质演化等方面,仍有诸多存疑。通过对滇西凤庆地区“澜沧岩群”野外剖面及路线地质调查,室内岩石薄片研究及成分测试,经综合对比认为:“澜沧岩群”的主要岩性以石榴石黑云母片岩、黑云母片岩、黑云母石英片岩、白云母片岩、千枚岩为主,其内部夹少量经过后期变质变形改造的花岗质糜棱岩和构造片岩,有华力西-印支期的二叠纪石英闪长花岗岩脉侵入。岩石化学特征表明其原岩为长英质岩类和富铝泥质岩类的沉积岩。“澜沧岩群”具有长期、复杂的变质变形演化史。共分为三期变形三期变质作用:第一期同变质变形(D1M1)以顺层挤压作用为主,形成了尖棱-顶厚-紧闭褶皱,区域性面理S1形成;变质较强,主要为低角闪岩相的区域动热变质作用。该幕变质作用是“澜沧岩群”片岩的主期变质作用。形成的主要变质矿物共生组合为:(片岩类):石榴石(Gar)+斜长石(Pl)+黑云母(Bi)+石英(Q);(千枚岩类):绢云母1(Ser)+钠长石(Act)+石英(Q)。第二期同变质变形(D2M2)以水平收缩作用为主,形成区域性的轴面褶劈理和滑劈理S2,变质程度较弱主要形成低角闪岩相向绿片岩相的区域动热退变质作用,形成的主要变质矿物共生组合为:(片岩类):钠长石(Act)+白云母(Mus)+绿泥石(Chl)+石英(Q);(千枚岩类):绢云母2(Ser)+绿泥石(Chl)+石英(Q)。第三期先变形后变质(D3M3)以基底滑脱韧性变形为主,变形具有浅-表构造层次的特征,小型叠加褶皱和皱纹线理十分发育,剪切面理S3具有非透入性特点。变质程度不均,断裂带以脆性-韧性动力变质为主,主要形成低绿片岩相,主要变质矿物共生组合为:绢云母3(Ser)+石英(Q)。根据区域地质背景和构造特征,推测“澜沧岩群”第一期变质变形作用发生在华力西期-印支期,昌宁-孟连洋洋壳俯冲期;第二期演化为华力西期-印支期昌宁-孟连洋洋壳俯冲完成后,冈瓦纳地块与扬子地块陆-陆碰撞期;第三期发生在喜山期澜沧江断裂带隆升,断裂带发生脆-韧性剪切造山运动为中。
[Abstract]:The evolutionary history of the Changning-Menglian belt has been a hot spot for geologists and experts both at home and abroad. Lancang rock group is located in the eastern margin of the southern section of Changning-Menglian belt. Its stratigraphic division, rock characteristics and metamorphic characteristics, as well as geological evolution are still doubtful. Based on the field profile and route geological investigation of Lancang rock group in Fengqing area, western Yunnan, the author considers that the main lithology of "Lancang rock group" is garnet biotite schist, through the laboratory research and composition test. Biotite quartz schist, Muscovite schist, phyllite are dominant, with a small amount of granitic mylonite and tectonic schist which were transformed by late metamorphism and deformation, and the Permian quartz diorite vein intruded in the Permian period. The petrochemical characteristics indicate that the source rocks are feldspar and aluminum-rich argillaceous sedimentary rocks. Lancang Group has a long and complicated history of metamorphic deformation and evolution. It is divided into three stages of deformation and three stages of metamorphism: the first stage of synmetamorphic deformation (D1M1) is dominated by bedding compression, resulting in the formation of sharp ridge-top thick-tight fold, regional plane S1 formation, strong metamorphism, strong metamorphism, It is mainly regional dynamic thermal metamorphism of low amphibolite facies. The metamorphism is the main metamorphism of Lancang Group schist. The main metamorphic mineral symbiotic assemblages formed are: (schist): garnet (Gar) plagioclase, (Pl) biotite, (Bi) quartz, (Q); (phyllite): sericite 1 (Ser) albite (Act) quartz (Q). The second stage of synmetamorphic deformation (D2M2) is mainly horizontal shrinkage, forming regional axial fold cleavage and slip cleavage S _ 2, and the weak metamorphism mainly forms the regional dynamic retrograde metamorphism of low-amphibolite facies to greenschist facies. The main metamorphic mineral symbiotic assemblages formed are: (schist): albite (Act) Muscovite, (Mus) chlorite, (Chl) quartz, (Q); (phyllite): sericite 2 (Ser) chlorite (Chl) quartz (Q). In the third stage, the first deformation and later metamorphism (D3M3) are dominated by the ductile deformation of the basement, which is characterized by shallow-surface tectonics, small superimposed folds and wrinkles, and shear plane S3, which is not permeable. The metamorphic degree is uneven, the fault zone is mainly brittle and ductile dynamic metamorphism, mainly forming low green schist facies, and the main metamorphic mineral symbiotic assemblage is sericite 3 (Ser) quartz (Q). According to the regional geological background and structural characteristics, it is inferred that the first stage of metamorphic deformation of Lancang Group occurred during the Varissian-Indosinian period and the subduction period of Changning Menglian oceanic crust. The second stage evolved into the continental-continental collision period between the Gondwana block and the Yangtze block after the subduction of the Changning-Menglian oceanic crust during the Varissian-Indosinian period, and the third stage occurred in the uplift of the Lancang River fault zone in the Himalayan period. The brittleness ductile shear orogeny occurred in the fault zone.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P588.3

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