哀牢山构造带及邻区古生代碎屑沉积物源示踪及其大地构造意义

发布时间：2018-05-30 18:40

本文选题：哀牢山构造带 + 电气石B同位素　；参考：《中国科学院研究生院(广州地球化学研究所)》2015年硕士论文

【摘要】：滇西三江造山带(包括昌宁-孟连构造带和哀牢山构造带)位于特提斯-喜马拉雅构造域与滨太平洋构造域的复合部位,兼具印支-思茅和华南陆块两大构造单元属性,是研究古特提斯演化历史的重要地区之一。目前学术界普遍认为位于思茅地块和滇缅泰马地块之间的昌宁-孟连构造带是古特提斯多岛洋格局的主洋盆遗迹分布区,代表了古特提斯的主缝合带。哀牢山构造带夹持于印支-思茅地块与扬子地块之间,沿云南省中西部延伸上千公里。该构造带目前还存在是古特提斯分支洋盆还是弧后盆地的争论。该构造带对应的缝合带位置也存在多种观点:第一种观点认为沿哀牢山断裂分布;第二种观点认为位于哀牢山断裂以西100千米的李仙江断裂;第三种观点认为可能沿九甲-安定断裂分布。同时哀牢山古特提斯分支洋盆或者弧后盆地的打开时限也存在分歧。哀牢山构造带及相邻的扬子西缘地区在古生代发育了广泛的碎屑岩沉积,它们记录了哀牢山洋的演化历史,通过对它们进行碎屑源区示踪研究,可以解决上述相关问题。本论文以哀牢山构造带及相邻扬子西缘地区寒武-泥盆系碎屑岩为研究对象,在详细的野外地质调查基础上,通过岩相学、碎屑电气石B同位素和碎屑锆石U-Pb年代学及Hf同位素分析等综合研究,探讨了这些碎屑岩的源区特征及其碎屑物质来源,为深入理解哀牢山构造带古特提斯演化、哀牢山古特提斯洋对应的缝合带位置及打开时限提供了新的制约。本论文研究所取得的主要进展如下:1.哀牢山-藤条河断裂以东寒武-泥盆系碎屑岩的碎屑物质主要来自扬子来自哀牢山-藤条河断裂以东地区寒武-泥盆系碎屑岩中碎屑电气石硼同位素组成主要在-13‰~-11‰,同位素组成相对偏重且较为集中,指示源区较为单一,可能受到了来自俯冲板片流体或者海相碳酸盐岩、蒸发岩的影响。此外,碎屑锆石年代学数据显示它们具有相似的年龄谱系,主要年龄区间为730~900Ma,对应的峰值年龄~828 Ma,εHf(t)值范围为-29.18~+13.55;其余三个次级的年龄区间为530~650 Ma、1500~1700 Ma和2400~2600 Ma,峰值年龄分别~543Ma、~1570 Ma和~2490 Ma,这样的年龄分布模式可与前人发表的来自扬子板块源区的碎屑锆石数据相对比,表明这些沉积岩的碎屑物质主要来自于扬子板块。2.哀牢山-藤条河断裂以西志留-泥盆系碎屑岩的碎屑物质主要来自印支-来自哀牢山-藤条河断裂以西地区思茅一侧哀牢山构造带内的碎屑岩中碎屑电气石硼同位素主要峰值在-13‰~-18‰之间,硼同位素组成相对偏轻且较为分散,指示源区较为复杂,可能受到了非海相蒸发岩、变质流体或者岩浆演化后期强烈的岩浆去气作用的影响。此外,碎屑锆石年代学数据显示它们具有相似的年龄谱系,得到的主要年龄区间为400~500 Ma和900~1000 Ma,峰值年龄分别~447 Ma和953 Ma,大部分锆石均具有负的εHf(t)值。这些年龄区间的碎屑锆石可与印支地块和冈瓦纳大陆内部找到对应的源区,且可与前人发表的印支地块碎屑锆石数据相对比,表明这些沉积岩的物源主要来自于印支-思茅地块和冈瓦纳大陆。3.哀牢山古特提斯洋对应的缝合带位置可能沿哀牢山-藤条河断裂分布。金平地区志留系碎屑岩源区特征与扬子西缘同时期碎屑岩相似,而与墨江绿春地区样品显著不同。结合建水至金平地区沉积相的变化(海相碎屑岩-灰岩-页岩及硅质岩),可能指示金平地区位于扬子地块一侧,为扬子被动大陆边缘沉积;而墨江-绿春地区志留-泥盆系碎屑岩由思茅地块一侧沉积形成,并不是前人所认为的扬子被动大陆边缘的斜坡沉积。由于哀牢山-藤条河断裂两侧碎屑沉积物源区具有不同的板块属性,哀牢山-藤条河断裂可能代表了哀牢山古特提斯洋缝合带。4.哀牢山古特提斯洋可能于志留纪已经开始打开。扬子西缘在寒武奥陶纪为稳定的沉积环境,主要沉积石英砂岩;从早志留纪开始扬子西缘和哀牢山构造带内沉积环境开始变活跃,主要沉积杂砂岩和砂屑岩。碎屑锆石U-Pb年龄和Hf同位素以及碎屑电气石B同位素数据表明哀牢山-藤条河断裂两侧的碎屑岩自早志留世起就开始具有不同源区:在思茅地块一侧(哀牢山-藤条河断裂以西)从志留系到泥盆系所有碎屑岩样品锆石U-Pb年龄Hf同位素以及电气石的B同位素都非常相似,源区基本上未发生变化;而在在扬子西缘一侧(哀牢山-藤条河断裂以东)志留-泥盆系碎屑岩源区特征稍有变化,年轻的碎屑锆石比例增多。由于哀牢山-藤条河两侧源区至少在志留纪就已经开始不同,而且构造开始变的活跃,因此我们推断哀牢山地区在早志留纪就已经开始裂解,并形成了一个足够阻隔碎屑物源运移的深水盆地,哀牢山洋可能于志留纪就已经打开。
[Abstract]:The Sanjiang orogenic belt in western Yunnan (including the Changning Meng Lian structural belt and the Ailao Mountain tectonic belt) is located in the compound part of the Tethys Himalaya tectonic domain and the shore Pacific tectonic domain, with the two major tectonic units of the Indo Simao and Southern China blocks, which is one of the most important areas for the study of the evolution history of the ancient Tethys. The Changning Meng Lian tectonic belt between the Mau massif and Yunnan Matai massif is the main oceanic site of the Gut Tis do island ocean, representing the main suture zone of Gut Tis. The Ailao Mountain tectonic belt is held between the Indo Simao block and the Yangtze block, and extends up to 1000 kilometers along the Midwest of Yunnan Province. The Tethys branch basin is still an argument in the back arc basin. There are also many points of view in the position of the corresponding suture zone in this tectonic belt: the first view is that the distribution of the Ailao Mountain fault is distributed; the second viewpoint is considered to be located at the Li Xianjiang fault of 100 kilometers west of the Ailao Mountain fault; the third viewpoint is considered to be distributed along the nine a diazepam fault. There are also differences in the opening time limit of the Sean Gut Tis branch or the back arc basin. The Ailao Mountain tectonic belt and the adjacent western margin of the Yangtze River developed a wide range of clastic rocks in the Paleozoic. They recorded the evolution history of the Ailao Mountain ocean. This paper can solve the above problems by using the tracer study of the debris source area. Based on the study of the Ailao Mountain tectonic belt and the Cambrian Devonian clastic rocks in the western margin of the Yangtze River, based on the detailed field geological survey, the characteristics of the source area and the source of detrital materials are discussed through the comprehensive study of petrography, B isotopes of clastic tourmaline, U-Pb chronology of detrital zircon and Hf isotopes. In order to understand the evolution of the ancient Tethys in the Ailao Mountain tectonic belt, the position of the suture zone and the opening time limit of the Ailao Mountain Paleo Tethys ocean are restricted. The main progress made in this study is as follows: 1. the debris of the Cambrian Devonian clastic rocks from the Ailao Mountain rattan River fault mainly comes from the Yangzi from the Ailao Mountain rattan River The composition of the clastic tourmaline boron isotopes in the Cambrian Devonian clastic rocks in the east of the fault is mainly -13 per 1000 ~-11 per thousand, and the isotopic composition is relatively heavy and concentrated, indicating that the source area is relatively single, and may be influenced by the subduction plate fluid or the marine carbonate rocks and the evaporation rocks. In addition, the data of the detrital zircon chronology show them. The age spectrum has a similar age range, the main age range is 730~900Ma, the corresponding peak age ~828 Ma and the Hf (T) range are -29.18~+13.55; the other three secondary age ranges are 530~650 Ma, 1500~1700 Ma and 2400~2600 Ma. The data of clastic zircons in the source area of the sub plate indicate that the debris of these sedimentary rocks mainly comes from the debris of the Silurian detrital rock of the Silurian Devonian System of the Ailao Mountain,.2., the Yangzi plate, mainly from the Indo branch - clastic rocks in the Ailao Mountain tectonic belt of the Simao side of the Ailao Mountain and the west area of the rattan Creek fault. The main peak of boron isotopes of tourmaline is between -13 per thousand and ~-18 per 1000. The composition of boron isotopes is relatively light and scattered, indicating that the source region is more complex and may be affected by the effect of non marine evaporite, metamorphic fluid or intense magma degassing in the late stage of magma evolution. The age spectrum is 400~500 Ma and 900~1000 Ma, and the peak age is ~447 Ma and 953 Ma respectively. Most of the zircon has negative e Hf (T) value. These zircon can find the corresponding source area with the Indo and Gondwana continents, and can be compared with the data of the Indosinian block zircon data published by the predecessors. It is indicated that the source of these sedimentary rocks mainly comes from the Indosinian Simao block and the.3. Ailao Sean Gut Tis Jan zone in the island of Gondwana, which may be distributed along the Ailao Mountain rattan Creek fault. The characteristics of the Silurian clastic rocks in the Jinping area are similar to the detrital rocks at the western margin of the western margin of the Yangtze, but not with the samples of Lvchun in Mojiang. The changes in the sedimentary facies of the Jianshui to the Jinping area (marine clastic rock, limestone shale and siliceous rock) may indicate that the Jinping area is located on one side of the Yangtze block and deposited on the passive continental margin of the Yangtze, while the Silurian Devonian clastic rocks in the Mojiang Lvchun region are deposited on one side of the Simao massif and are not considered by the predecessors to be passive large of the Yangtze. Because of the different plate properties on both sides of the Ailao Mountain rattan River fault, the Ailao Mountain rattan River fault may represent the Ailao Mountain Suzhou suture zone,.4. Ailao Mountain ancient trate ocean may have begun to open in the Silurian period. The western margin of the young son in the Cambrian Ordovician period is a stable sedimentary ring. From the Early Silurian, the sedimentary environment in the western margin of the Yangtze and the Ailao Mountain tectonic zone began to become active, mainly sedimentary sandstones and sandstones. The U-Pb age of the detrital zircon and Hf isotopes and the data of the B isotopes of the clastic tourmaline indicate that the clastic rocks on both sides of the Ailao mountain Tsao river broke from the Early Silurian period. The U-Pb age Hf isotopes of zircon from the Silurian to the Devonian system and the B isotopes of the tourmaline are very similar in one side of the Simao massif and from the west of the Ailao Mountain to the Devonian. The source area is basically not changed, but the shredded Devonian system is broken on the one side of the western margin of the Yangtze (Ailao Mountain - rattan River fault). The characteristics of the source area of the debris rock are slightly changed, and the proportion of young detrital zircon is increased. Because the source areas of the Ailao Mountain - vattan river at the two sides of the Silurian period are at least different and the structure begins to become active, we infer that the Ailao Mountain area has started cracking in the Early Silurian period and formed a deep enough detrital source movement. In the basin, Ailao Mountain ocean may have been opened in Silurian.
【学位授予单位】：中国科学院研究生院(广州地球化学研究所)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P548;P534.4

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