本文關(guān)鍵詞：岡底斯造山帶新生代以來剝露歷史的熱年代學(xué)約束及沉積響應(yīng)　出處：《中國地質(zhì)大學(xué)(北京)》2016年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 岡底斯造山帶 低溫?zé)崮甏鷮W(xué) 裂變徑跡 盆地分析 剝蝕

【摘要】：低溫?zé)崮甏鷮W(xué)數(shù)據(jù)能記錄地殼淺部數(shù)公里至十幾公里的剝露歷史,地球內(nèi)部作用(構(gòu)造)和外部作用(剝蝕作用)對(duì)地貌景觀的塑造發(fā)揮著強(qiáng)烈的控制作用。為探索他們之間的相互關(guān)系,本研究對(duì)岡底斯造山帶不同地貌和構(gòu)造背景的地區(qū)進(jìn)行系統(tǒng)采樣,應(yīng)用鋯石、磷灰石裂變徑跡法和(U-Th)/He方法,對(duì)藏南岡底斯造山帶新生代剝露歷史進(jìn)行系統(tǒng)研究。同時(shí)結(jié)合岡底斯礫巖沉積學(xué)工作及前人已發(fā)表的熱年代學(xué)數(shù)據(jù),揭示岡底斯造山帶中段新生代以來的剝露過程及其對(duì)應(yīng)的動(dòng)力學(xué)機(jī)制,并對(duì)岡底斯不同區(qū)域的剝蝕差異進(jìn)行探討,理清岡底斯造山帶最南緣晚漸新世至早中新世的剝蝕與沉積作用之間的耦合關(guān)系。岡底斯造山帶不同地貌或地質(zhì)背景下熱年代學(xué)數(shù)據(jù)差異較大,體現(xiàn)在岡底斯北部受河流下切和斷層影響較小地區(qū)磷灰石裂變徑跡年齡主要大于25Ma;岡底斯造山帶南部磷灰石裂變徑跡年齡主要小于28Ma;而南部網(wǎng)狀河谷區(qū)域磷灰石裂變徑跡年齡主要集中在21-14Ma,(U-Th)/He為9-11Ma;斷層帶附近樣品磷灰石裂變徑跡年齡在8-18Ma。熱模擬結(jié)果顯示岡底斯不同地貌或構(gòu)造背景地區(qū)經(jīng)歷了不同的剝蝕歷史,晚始新世至早漸新世岡底斯北部發(fā)生快速剝蝕,該期剝蝕與拉薩地殼增厚有關(guān),之后岡底斯造山帶北部保持相對(duì)穩(wěn)定且緩慢的剝蝕速率。而岡底斯南部經(jīng)歷了多期剝蝕事件,晚漸新世至早中新世快速剝蝕與岡底斯逆沖斷裂或與岡底斯逆沖斷裂不相容的伸展抬升有關(guān)。斷裂帶附近20-8Ma的局部快速剝蝕事件受到同期南北正斷裂或東西向的走滑斷裂帶作用,或與岡底斯南部網(wǎng)狀河流的發(fā)育有關(guān)。根據(jù)岡底斯礫巖野外及前人的地質(zhì)資料表明岡底斯礫巖沿岡底斯最南緣1300km具有相似的下粗上細(xì),退積序列沉積特點(diǎn)。熱年代學(xué)數(shù)據(jù)和模擬結(jié)果揭示18-14Ma岡底斯礫巖發(fā)生了快速剝蝕事件,但岡底斯礫巖下段與上段存在明顯的不整合接觸關(guān)系,即由深湖相突變過渡為沖積扇的變化,表明18-14Ma剝蝕事件之前區(qū)域已經(jīng)發(fā)生了快速抬升。該期快速剝蝕僅沿岡底斯礫巖和岡底斯南部網(wǎng)狀河谷區(qū)域發(fā)育表明該期快速剝蝕可能與岡底斯南部的網(wǎng)狀河流形成有關(guān),與之前發(fā)生的區(qū)域隆升可能存在著時(shí)滯關(guān)系或無明顯直接關(guān)系。20-18Ma岡底斯礫巖迅速埋藏至4-7km,主要受大反沖斷裂的影響,不支持盆地由于快速沉降埋藏的觀點(diǎn)。
[Abstract]:The low-temperature thermochronological data can record the history of the shallowness of the crust, ranging from several kilometers to more than ten kilometers. The Earth's interior (structure) and external (denudation) play a strong controlling role in shaping the landscape. In this study, systematic sampling of different landforms and tectonic backgrounds of the Gangdis orogenic belt was carried out, and zircon, apatite fission track method and U-ThU / he method were used. A systematic study of the Cenozoic denudation history of the Gangdis orogenic belt in southern Tibet is carried out. At the same time, combined with the sedimentology of the Gangdese conglomerate and the previous published thermochronological data. This paper reveals the denudation process and its corresponding dynamic mechanism since the Cenozoic in the middle segment of the Gangdis orogenic belt, and probes into the denudation differences in different regions of the Gangdis orogenic belt. The coupling relationship between late Oligocene and early Miocene denudation and sedimentation in the southernmost margin of the Gangdis orogenic belt is clarified. The fission track age of apatite is more than 25 Main in the north of Gangdis, which is influenced by river undercutting and fault. The fission track age of apatite in the southern Gangdis orogenic belt is less than 28 Ma. The age of apatite fission track in the southern reticular valley is mainly 9-11 Ma. The fission track age of apatite in the vicinity of the fault zone is 8-18 Ma.The thermal simulation results show that different geomorphological or tectonic backgrounds of Gangdese have undergone different denudation history. From the late Eocene to the early Oligocene, rapid denudation occurred in the northern part of Gangdis, which was related to the thickening of the Lhasa crust. After that, the northern part of the Gangdis orogenic belt maintained a relatively stable and slow denudation rate, while the southern Gangdis experienced several denudation events. The rapid denudation from late Oligocene to early Miocene is related to the Gangdis thrust fault or to the incompatible extensional uplift of the Gangdis thrust fault. The local rapid denudation event of 20-8 Ma near the fault zone was subjected to the synchronic north-south normal fault. Or east-west strike-slip fault zone. According to the field data of Gangdese conglomerate and previous geological data, it is shown that Gangdese conglomerate has similar thickness along the southernmost margin of Gangdis, 1300km. Thermal chronological data and simulation results show that rapid denudation occurred in the Gangdis conglomerate at 18-14 Ma, but there is an obvious unconformity contact relationship between the lower Gangdis conglomerate and the upper member. That is, the transition from deep lacustrine facies to alluvial fan. The rapid denudation occurred only along the Gangdese conglomerate and the grid valley in the south of Gangdese, indicating that the rapid denudation may be associated with the south of Gangdes. The formation of a network of rivers. There may be a time-delay relationship or no obvious direct relationship between the uplift and the previous regional uplift. The Gangdis conglomerate of 20-18 Ma is rapidly buried to 4-7 km, which is mainly affected by the large recoil fault. It does not support the view that the basin is buried due to rapid subsidence.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：P542

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