本文關鍵詞： 磁性地層學 古地磁學 白堊紀 車拉盆地 西秦嶺　出處：《西北大學》2017年碩士論文　論文類型：學位論文

【摘要】：自晚三疊世秦嶺造山帶完成其主體拼合過程以來,西秦嶺發(fā)育了眾多的陸相山間沉積盆地,其中,晚中生代山間盆地記錄秦嶺造山帶陸內(nèi)演化階段淺部地殼調(diào)整的詳細信息,其盆地性質(zhì)及構造—沉積演化過程日漸成為中外學者關注的熱點。本文對隴南宕昌地區(qū)白堊紀車拉盆地進行了高精度的磁性地層學、巖石磁學和構造古地磁研究。車拉—寺麻剖面(N:34°5.5",E:104028.3M)位于車拉盆地北部,厚約1450m,代表性樣品的巖石磁學實驗(飽和等溫剩磁和磁化率隨溫度變化曲線)結果表明:車拉—寺麻剖面主要的磁性礦物為磁鐵礦和赤鐵礦。通過系統(tǒng)地逐步熱退磁技術進行剩磁測試,633塊磁性地層定向樣品產(chǎn)生穩(wěn)定的特征剩磁,部分樣品可分離出雙分量特征,其低溫分量方向在地理坐標系下十分接近現(xiàn)今地磁場偶極子場方向,可能由現(xiàn)今地磁場方向的粘滯剩磁產(chǎn)生;大部分樣品具有單分量特征,與雙分量樣品的高溫分量的地磁場方向基本一致。結合該剖面的磁極性序列與沉積速率變化特征,車拉—寺麻剖面的沉積時代可追溯到145～76Ma。通過該剖面19個構造古地磁采點,231塊定向樣品的熱剩磁測試分析,能夠產(chǎn)生穩(wěn)定特征剩磁的182塊定向樣品的古地磁研究表明:以白堊紀歐亞板塊的古地磁極為參考極,車拉盆地存在約18°的順時針旋轉(zhuǎn),且早白堊世其旋轉(zhuǎn)速率約為0.69°/Ma,略小于晚白堊世的0.89°/Ma。白堊紀車拉盆地的旋轉(zhuǎn)可能是塊體沿盆地西南緣岷縣—宕昌左行走滑斷裂東向旋轉(zhuǎn)擠出引起的,或疊加白堊紀羌塘—昌都地塊和拉薩地塊匯聚碰撞背景下中國西部的區(qū)域走滑作用。
[Abstract]:Since the late Triassic Qinling orogenic belt completed its main assembly process, many continental intermountain sedimentary basins have been developed in the West Qinling Mountains. Among them, the late Mesozoic intermountain basin records the detailed information of the shallow crustal adjustment in the evolution stage of the Qinling orogenic belt. The nature of the basin and the process of tectonic-sedimentary evolution have become the focus of attention of Chinese and foreign scholars. In this paper, the Cretaceous Cretaceous Cretaceous Chela Basin in Longnan is studied in this paper. Petromagnetism and tectonic paleomagnetism. The Chela-Simma section N: 34 擄5.5 "E: 104028.3M) is located in the northern part of the Chela basin. The results of rock magnetic experiments (saturation isothermal remanence and magnetic susceptibility curves with temperature) show that the main magnetic minerals in Chela-Sima section are magnetite and hematite. Demagnetization Technology for remanence testing: 633 directional samples of magnetic strata produce stable characteristic remanence. Some samples can be separated with two-component characteristics, and the direction of low-temperature component is very close to the direction of the dipole field of the present geomagnetic field in geographical coordinate system, which may be produced by the viscous remanent magnetic field in the direction of the present geomagnetic field, and most of the samples have the characteristics of single component. The direction of geomagnetic field of the high-temperature component of the two-component sample is basically the same. The sedimentary epoch of the Chela Sima section can be traced back to 145U 76 Ma.The thermal remanence test and analysis of 231 directional samples from 19 tectonic paleomagnetic mining sites in this section were carried out. Paleomagnetic studies of 182 directional samples capable of producing stable characteristic remanence show that the paleomagnetic pole of the Cretaceous Eurasian plate is used as the reference pole, and that there is a clockwise rotation of about 18 擄in the Cretaceous Eurasian plate. The rotation rate in early Cretaceous is about 0.69 擄/ Ma, which is slightly smaller than that in late Cretaceous 0.89 擄/ Ma.The rotation of Cretaceous Cretaceous Cretaceous Chela basin may be caused by the rotating extrusion of the block along the eastward direction of Minxian-Dangchang left strike-slip fault in the southwestern margin of the basin. Or stacking the Cretaceous Qiangtang-Changdu block and Lhasa block converging in the background of the regional strike slip in western China.
【學位授予單位】：西北大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：P539.3;P318.44
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本文編號：1496822