摘要
前人研究表明石墨化作用与变质温度具有良好的相关性,同时室内摩擦实验研究认为少量石墨就能够有效地降低断层摩擦阻力,进而被认为对断层弱化起着重要的固体润滑作用而开始受到大家的关注。但是由于技术手段的限制,我们对天然断裂带中含石墨岩石的宏观-微观构造、变形机制、变形-变质环境以及对岩石流变行为的贡献仍然还不是很清楚。本文在详细的野外地质观测的基础上结合室内实验分析,对新生代红河-哀牢山走滑断裂带内哀牢山深变质杂岩东南侧边界发育的含石墨岩石开展了深入的研究。其中主要侧重利用光学显微镜(OM)、扫描电镜(SEM)、电子背散射衍射(EBSD)以及拉曼光谱(Raman Spectra)技术方法和手段,对宏观及显微构造变形行为、石墨拉曼温度、矿物晶格优选定向(LPO)以及其变形-变质环境进行了综合分析。结果表明,含石墨岩石显微构造特征表现为典型的塑性到超塑性流动构造特征,通过石墨拉曼光谱地质温度计,获得了哀牢山杂岩东部边界与上盘未变质岩石接触的含石墨岩石变形-变质的石墨拉曼温度为462~505℃;而靠近深变质岩含石墨岩石的石墨拉曼温度在511~529℃。基质中强烈细粒化的石墨、石英及长石具有明显的晶格优选定向,其中石墨和石英均表现出强烈的(0001)<a>方向上的滑移系。细粒化的石墨滑移系的发育与长石、石英共同对岩石整体的晶质塑性变形起着重要的流变弱化作用。
Previous studies have shown that graphitization has a good correlation with metamorphic temperature conditions.The laboratory friction experiments also indicate that even a small amount of graphite can effectively reduce the friction resistance of faults.Therefore,it is considered as a solid lubricator,which plays an important role in fault weakening.However,due to limitation of technical methods,their macro-and microscopic structure,deformation-metamorphic environment and their contribution to the rheological behavior of graphite-bearing rocks in the natural fault zone remain unclear.On the basis of detailed field geological observations,this study focuses on the graphite-bearing rocks in the southeastern part of the Ailaoshan complex in the Cenozoic Ailaoshan-Red River(ASRR)fault zone.The technical methods of optical microscope(OM),scanning electron microscope(SEM),electron backscatter diffraction(EBSD)and Raman spectra are mainly used to comprehensively analyze the deformation behavior of macro-and microstructure,the graphite Raman temperature,the mineral lattice preferred orientation(LPO)and the deformation-metamorphic conditions.Graphite Raman spectra geothermometer results show that the Raman peak temperature of graphite-bearing rocks in the study area is 530~460℃.Graphite,matrix quartz and plagioclase developed obvious lattice preferred orientations.The graphite and quartz show strong slip system in the direction of(0001)<a>.The development of fine-grained graphite slip system together with feldspar and quartz plays an important role in the plastic flow deformation of the whole rock and rheological weakening.
作者
吕美霞
曹淑云
李俊瑜
程雪梅
Lü Meixia;CAO Shuyun;LI Junyu;CHENG Xuemei(State Key Laboratory of Geological Processes and Mineral Resources,School of Earth Sciences,China University of Geosciences,Wuhan,430074)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2020年第2期491-510,共20页
Acta Geologica Sinica
基金
国家重点研发计划(批准号2017YFC0602401)
优秀青年基金项目(批准号:41722207)
国家自然科学基金面上项目(批准号:41472188,41430211)联合资助.
关键词
哀牢山-红河剪切带
变形显微构造
变形石墨
石墨拉曼光谱地质温度计
晶格优选定向
流变弱化
Ailaoshan-Red River shear zone
deformation microstructure
deformed graphite
graphite Raman spectra geothermometer
lattice preferred orientation(LPO)
rheological weakening
