沂沭断裂带及其近区震积岩和地震沉积事件全面系统研究

Yishu fault zone is the most violent segment of tectonic movements and seismic activities in the Tancheng-Lujiang fault zone. There exist plenty of earthquake depositional event records （i.e. seismites ）of different geological times in Yishu fault zone its vicinity. Despite of several earthquake depositional event beds studied by some scholars( including the applicant himself), many stratigraphic horizons with conditions developed and preserved seismites are still waiting to be studied in Yishu fault zone and its vicinity. With the advance of the cognitive level in the related academic circles at home and abroad, it is necessary that those seismic event beds of previous research will be carried out some supplementary investigation and reasarch. Although there are often reports about liquefied and thixotropic deformations of saturated microsparry calcite or lime-mud induced by strong earthquakes， relational data of simulated earthquake vibration test are absent all the time. This project will focus on investigate and research for characteristic ,distribution and seismogenesis mechanism of seismites in new seismic event strata by means of principles and methods of seism-geological survey, sedimentology, petrology, stratigraphy, geochemistry, isotopic dating ，seismology and simulated vibration test. Aiming at seismic event strata studied previously, it is mainly to augment researches of new seismic deformation structures. Though simulated earthquake vibration tests, some experiment data of saturated microsparry calcite triggered by earthquakes will be provided in order to quest for the quiddity of seismic syn-sedimentary deformation of microsparry calcite sediments. By the overall and systematic study above-mentioned, a time-space framework for earthquake depositional events of the study area will be established so as to recover the history of seismic and tectonic activities, and summarize significances for research and application.

沂沭断裂带是郯庐断裂带构造与地震活动最强烈的区段，在其内及其附近区存有丰富的、不同地质时代的地震沉积事件记录，即震积岩。在沂沭带及其近区，尽管有些研究者(包括申请者)已对几个地震沉积事件层做了研究，但尚有许多具备发育和保存震积岩条件的层位仍待研究。随着国内外认识水平提高，对以往研究的那些地震事件层也需做必要的补充研究；关于强震引发饱和微亮晶方解石或灰泥的液化与触变变形，虽然常有报道，但一直缺模拟地震振动试验资料。本项目将运用地震地质调查、岩石学、沉积学、地层学、地球化学、地震学及模拟试验等的原理和方法，重点调研新地震事件地层中的震积岩的特征、分布和地震成因机理。针对研究过的地层，主要补充新发现的震积岩类型。通过模拟地震试验，提供饱和微亮晶方解石震动变形的实验资料，探索其地震同沉积变形的实质。经上述全面、系统的研究，建立研究区的地震沉积事件格架，恢复地震与构造活动历史，总结研究和应用意义。

沂沭断裂带属长期发生构造和地震活动的郯庐断裂带中段。它是郯庐断裂带宽度最大与地震活动最激烈部分。因此，在其内及其近区地震事件记录十分丰富。本项目运用地震地质调查、地震学、岩石学、沉积学、地层学及模拟地震试验等的原理和方法，新发现15个以岩石地层单位(“组”或“段”)命名的主要由震积岩组成的地震事件层，其中，有两个地震事件层含有震火山岩。连同以前研究过地震事件层，研究区内已被鉴别出25个地震事件层。这些地震事件层发育30余种震积岩，包括液化砂脉（墙）、液化灰泥(方解石微粒)脉、液化角砾岩、液化均一层、软硅质触变脉、软硅质触变楔、软泥触变脉、震陷构造、软布丁构造、负载与球-枕构造及同沉积断层等. 另外，还含有震裂与震碎火山岩等数种震火山岩。依据每个地震事件层的形成时代和分布范围，建立了研究区的地震事件层时空格架, 首次形象地再造了该断裂带自形成以来的地震作用历史，揭示了由该断裂带及近区地震事件层所记录的的地震事件节律。地震事件层的时空分布支持该断裂带生成-活动与发展历史分两个阶段：古郯庐断裂带阶段和中-新生代阶段。新元古代初,鲁中至苏皖北部NNE向韧性剪切带的形成、沟通了秦岭大别与苏鲁洋间的NEE走向的转换断层,这可能是沂沭断裂带或古郯庐断裂带的成因机制。. 震积岩的微量元素分析结果表明，震积岩的w（La）/ W（Sc）和W（LA）/w（Th）微量元素比值高于上地壳和正常沉积层的平均比值，而W（Th）/ W（Sc）的比例较低。震积岩的Ni和Cr的含量也高于上地壳和正常沉积层。这些微量元素特点反映了盆地基底的不稳定、快速沉积及来自深源元素混入。该断裂带是长期地震活动的构造带，也是Au、Cu和石油矿床的成矿带。震积岩不仅是石油和天然气的良好储集层，而且是Au、Cu和其它矿产资源的容矿岩。运用“地震泵”原理和震积岩的容矿性来探索地震成矿和找寻矿产资源，具有重要的经济意义。. 模拟地震试验首次验证了由微米级方解石组成的饱和灰泥，受VI度烈度以上的强地震作用会发生液化，形成了液化灰泥火山、液化底辟、液化脉状构造及液化卷曲等变形构造。该试验揭示了困惑学术界已久海底灰泥受强震触动是否会液化之谜，为解释地震产生的饱和灰泥液化变形提供了试验资料,也为臼齿构造（molar tooth structure）的地震成因提供了依据。