鲜水河断裂带炉霍段北部断裂岩特征与变形行为研究  

Fault rock characteristics and deformation behavior along the northern Luhuo segment of the Xianshuihe fault zone

作　　者：白明坤 李海兵[2,3] 郑勇 吴琼 CHEVALIER Marie-Luce 潘家伟 任治坤[1] BAI MingKun;LI HaiBing;ZHENG Yong;WU Qiong;CHEVALIER Marie-Luce;PAN JiaWei;REN ZhiKun(State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China;MNR Key Laboratory of Continental Dynamics,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;Jiangsu Donghai Continental Deep Hole Crustal Activity National Observation and Research Station,Donghai 222300,China)

机构地区：[1]中国地震局地质研究所,地震动力学国家重点实验室,北京100029 [2]中国地质科学院地质研究所,自然资源部大陆动力学重点实验室,北京100037 [3]江苏东海大陆深孔地壳活动国家野外科学观测研究站,东海222300

出　　处：《岩石学报》2024年第12期3998-4019,共22页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(42402221、42020104007、42230312);中国地震局地质研究所基本科研业务费项目(IGCEA2303);国家科技基础资源调查专项(2021FY100103)联合资助。

摘　　要：鲜水河断裂带是中国陆内活动性最强、强震频率最高的活动断裂之一,断裂岩以及大地测量学研究发现该断裂带可能具有广泛的蠕滑变形。研究该断裂带几何结构和变形行为有助于认识蠕滑与粘滑机制,并为评估其强震危险性提供关键科学依据。本文以鲜水河断裂带炉霍段北部断层剖面及其中的断裂岩为研究对象,通过野外地质调查、显微构造观察、扫描电镜以及X射线衍射(XRD)分析等方法,对断裂带的几何结构、断裂岩物理特征与矿物组成等开展了详细分析。结果显示,炉霍段北部的最新主断面位于断裂变形带东部边界,走向N110°,倾向北东,倾角约50°,具有左行走滑兼正断的运动学特征;主断面附近的断层泥相对发育,上盘以棕色为主,宽约3cm,下盘以黑色为主,宽约20~30cm,成分主要为粘土矿物和石英。靠近主断面强矿物含量达70%以上,矿物颗粒均以棱角状、长条状为主,存在矿物颗粒被截切形成平直截切面的现象,指示其应以粘滑变形行为为主;断裂带内的断层泥透镜体则显示,粘土矿物含量极高(>60%),定向明显且面理发育,Al和K元素富集等现象,指示可能存在前期蠕滑变形行为。上述结果指示,鲜水河断裂带炉霍段可能经历了从蠕滑到粘滑变形行为的转变。以上研究结果与鲜水河断裂带以高角度左行走滑,广泛存在蠕滑变形的认识不同,表明断裂带变形行为存在明显的空间分布不一致的特征,除了围岩性质和流体作用以外,断裂的空间几何结构也是重要的控制因素。新的研究结果可以为更深入了解大型走滑断裂带变形行为、孕震机制以及未来强震危险性提供科学依据。The Xianshuihe fault is one of the most active intra-continental fault in China with high frequency of large earthquakes.However,fault rocks and geodetic studies have shown that it has extensively creeping behavior.Understanding the geometrics and deformation behavior along and within the Xianshuihe fault is essential to investigate its deformation mechanism and assess its earthquake hazard.Here,we focus on the geometrics,fault rock physical characteristics within the northern Luhuo segment of the fault.Optical microscopy,scanning electron microscopy,and powder X-ray diffraction(XRD)are used to analyze the mineral composition and deformation behavior.There,the current location of the fault plane is located along the eastern boundary of the fault deformation zone with N110°-striking,~50°-dipping(to the NE)and sinistral/normal motion.Fault gouge in the fault core is mostly brown(3cm-thick)and black(20~30cm-thick)upstream and downstream from the main fault,respectively.It mainly consists of clay minerals and quartz,as well as>70%of strong minerals.The gravels in the fault gouge are mainly angular and long with the phenomenon of being sliced to form flat,straight planes,suggesting that the fault is dominated by stick-slip deformation due to large earthquakes.What s more,the fault gouge lenticle in fault zone is mainly consists of clay minerals(>60%)with dense foliations,clearly oriented and the enrichment of Al and K elements,which indicate the creeping behavior.Then we got that the northern Luhuo segment of the Xianshuihe fault has obvious stick-slip deformation after creeping.Our results are different with those previously published,which argued that the Xianshuihe fault is a steeply dipping sinistral fault with extensive creeping deformation.Our new data show that the spatial distribution of deformation behavior varies along various segments of the Xianshuihe fault.It can be due to the host rocks and fluid,as well as the geometry of fault branches.Our new results help to better understand the deformation behavio

关 键 词：鲜水河断裂带炉霍段 断裂几何结构 变形行为 蠕滑/粘滑 断层泥 

分 类 号：P542.3[天文地球—构造地质学] P588.33[天文地球—地质学]