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Research On The Formation Process Of The Ailaoshan Tectonic Zone In Shuitang-mosha Segment

Posted on:2015-03-27Degree:MasterType:Thesis
Country:ChinaCandidate:M L WangFull Text:PDF
GTID:2250330428969243Subject:Geological Engineering
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The Ailaoshan tectonic zone is an important linear structure and the boundary ofgeological and landforms in southwestern China. In this paper, we selectShuitang-Mosha section of Ailaoshan tectonic belt as the object of study. Through thegeological section which run across the tectonic belt (Malu-Mosha profile,Heping-Shuitang profile and Shuitang street profile) measurement in the field.Combined with observation and analysis in laboratory, we make a comparative studyon the metamorphic and deformation characteristics of the tectonic zone.(focus onthe Ailaoshan group). The Knowledge obtained as follows:①The metamorphicrocks in the tectonic belt can be divided into the eastern high-grade metamorphicrocks and the western low-grade metamorphic rocks. And the both may be the sameset of rock formations(Triassic), just because metamorphic grade is different;②Though the foliated rocks are more developed, bedding or bedding images is stillvisible;③The hypo-metamorphic rock (Ailaoshan rock group) experienced a majorprevious high-temperature plastic deformation and a deuteric brittle or brittle-ductiledeformation which were the sinistral strike-slip movement and right lateral slip;④There are no obvious signs faulted in the outcrops of Ailaoshan fault and Red Riverfault, and the properties of deep fracture is debatable.In this paper we choose the granodioritic gneiss, its synchronic deformationalgranite vein intrusion in the high-grade metamorphic rock series and its proximatemeta-sandstone in the low-grade metamorphic rock series as research objects andpresent new results of zircon U-Pb dating on four samples to do the accuratechronology tests. According to the isotopic dating, we can draw the conclusion that:Firstly, the Ailaoshan Group consists of at least the detrital composition of igneousrocks(722-740Ma) and igneous rocks or sedimentary rocks with an age of235±10Ma,as well as the27-32Ma igneous and metamorphic rocks. The metamorphic rocks inthe study area are unlikely to be the Yangtze Plate; Secondly, the peak metamorphism deformation time of Ailaoshan Group was about27-32Ma(the Late PaleogenePeriod).At last, by observing and recording structural feature and deformation of theAilaoshan tectonic zone in the field, we can preliminarily dividing the stress filedinto two stages: the ductile deformation and brittle deformation.Based on thestructural analysis, it is revealed that the orientation of the maximal principal stress ofthe structurally deformed stress field in the Ailaoshan belt is NE-SW and NW-SEcompression. And the present stress filed sustain the old tectonic stress filed. TheAilaoshan tectonic belt is formed in such a dynamic background.
Keywords/Search Tags:Ailaoshan Tectonic Zone, Ailaoshan Group, Metamorphism anddeformation, Tectonic stress filed, Zircon U-Pb dating
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