發(fā)布時間：2018-04-20 16:48

  本文選題：紹村-雄村 + 韌性剪切帶�。� 參考：《中國地質大學(北京)》2017年碩士論文

【摘要】：皖南地處華夏板塊與揚子板塊結合處,屬江南造山帶東段,同時也是欽杭成礦帶東段,區(qū)域上各類礦點數百個,且成礦類型多樣,其中受韌性剪切帶控制占主導地位。皖南地區(qū)除自然地理條件差以外,其地質構造復雜,研究程度較低,尤其是基礎構造研究薄弱。因此更深一步了解韌性剪切帶特征及其演化史與金礦成礦的時空對應關系成為急需解決的問題。本文通過對皖南歙縣紹村-雄村地區(qū)詳細地野外地質調查,發(fā)現研究區(qū)普遍經歷了韌性剪切變形作用,變形程度強弱交替,野外露頭新鮮面可見有明顯的糜棱面理,石英、長石定向拉長以及剪切作用下形成的旋轉碎斑等多種變形特征組合。野外觀測到的多種膝折等小型褶皺現象,以及石英脈的侵入,發(fā)育有硅化現象,指示同期或后期發(fā)生較強的構造運動。通過對鏡下定向薄片的顯微觀察得出:石英顆粒定向排列,具有σ型殘斑,S-C組構,指示方向為右行擠壓剪切,部分為膨凸重結晶及核幔構造,可觀察到由靜態(tài)恢復重結晶作用形成的規(guī)則邊界的新晶體。根據石英重結晶類型及絹云母塑性變形認為該韌性剪切帶為中高溫條件下變形,疊加后期低溫變形。通過EBSD實驗結果得知剖面全程滑移系以菱面a滑移為主,變形條件均為中溫-中低溫,變化幅度不大,部分還經歷晚期的低溫條件下的變形作用。使用極摩爾圓法估算定向樣品的運動學渦度,其數值極大多數低于0.71,因此紹村-雄村剖面主要為純剪切作用。結合韌性剪切帶地化剖面中元素分布以及構造變形強弱關系得出∶在構造變形程度強的位置,金元素富集現象不明顯,在變形程度較弱地方,金礦物富集。分析原因為,構造變形程度強的地方壓力大,致使含礦熱液沿構造斷裂帶流向壓力小的區(qū)域。因此,說明韌性剪切帶更多的是為金元素提供空間及含礦熱液運移的通道,而不是主要的控礦因素。紹村-雄村韌性剪切帶的形成時間為加里東期,與華南地區(qū)加里東期隆升構造有關,基底巖石在地下深處因隆升作用發(fā)生韌性變形,經歷了中溫到低溫作用,之后發(fā)生脆性變形;在燕山期由逆沖推覆構造被推覆至地表。
[Abstract]:The south of Anhui is located at the junction of the Huaxia plate and the Yangtze plate, which belongs to the eastern section of the Jiangnan orogenic belt and is also the eastern section of the Qinghang metallogenic belt. There are hundreds of all kinds of occurrences in the area, and the metallogenic types are various, among which the ductile shear zone dominates. Except for the poor physical and geographical conditions, the geological structure is complex and the research degree is relatively low, especially the basic structure research is weak in the south of Anhui province. Therefore, a deeper understanding of the characteristics of the ductile shear zone and the relationship between the evolution history and the temporal and spatial correspondence between gold mineralization and the ductile shear zone becomes an urgent problem to be solved. Based on a detailed field geological survey of Shaomun-Xiongcun area in Shexian County, southern Anhui Province, it is found that the study area generally experienced ductile shear deformation, the degree of deformation was alternately strong and weak, and the fresh surface of outcrop in the field could be seen to have obvious surface texture and quartz. There are many kinds of deformation characteristic combinations, such as directional stretching of feldspar and rotating debris formed by shear. A variety of small fold phenomena, such as knee fold, and the intrusion of quartz veins, have been observed in the field, which indicate the occurrence of strong tectonic movement in the same period or later period. Through the microscopic observation of the directional thin slices under the microscope, it is found that the quartz particles are arranged in a directional direction, with 蟽 -shaped macular S-C fabric, indicating a right compression shear direction, and some of them are expanded convex recrystallization and core-mantle structure. A new crystal with regular boundary formed by static recovery recrystallization can be observed. According to the type of quartz recrystallization and the plastic deformation of sericite, the ductile shear zone is deformed at medium and high temperature and deformed at low temperature in the late superimposed period. The results of EBSD experiment show that the whole slip system of the profile is mainly rhombohedral a slip, and the deformation conditions are medium temperature to medium low temperature, with little change, and some of them also undergo late deformation at low temperature. The kinematic vorticity of the directional samples is estimated by using the polar molar circle method. The maximum value of the vorticity is less than 0.71, so the Shaomun-Xiongcun section is mainly pure shearing. In combination with the distribution of elements in the geochemistry section of the ductile shear zone and the relationship between the tectonic deformation and the intensity of the tectonic deformation, it is concluded that the enrichment of gold elements is not obvious in the position of strong tectonic deformation, but the gold is enriched in the area of weak deformation. The reason is that the local pressure with strong tectonic deformation is high, which leads to the flow of ore-bearing hydrothermal fluid along the structural fault zone to the area with low pressure. Therefore, the ductile shear zone provides more space for gold elements and channels for hydrothermal migration of ore-bearing elements than the main ore-controlling factors. The forming time of the Shaocun-Xiongcun ductile shear zone is Caledonian, which is related to the Caledonian uplift structure in South China. Then brittle deformation occurred, and the thrust nappe structure was pushed to the surface during the Yanshanian period.
【學位授予單位】：中國地質大學(北京)
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：P618.51

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