本文選題：羌南地塊 + 日灣擦卡組�。� 參考：《西北大學》2015年碩士論文

【摘要】：羌塘地塊對于青藏高原的演化及動力學等問題的研究至關重要。羌塘地塊曾被認為是一個整體,直到雙湖-龍木錯縫合帶的發(fā)現(xiàn),羌塘地塊被劃分為羌北和羌南兩個塊體,同時,也將岡瓦納大陸和歐亞大陸界線問題的分歧集中到班公湖—怒江縫合帶及雙湖—龍木錯縫合帶二者之間,因此,羌南地塊之北的雙湖—龍木錯縫合帶在晚古生代到底是不是歐亞大陸的南緣,也即在晚古生代羌南和羌北是否已拼合這一問題至關重要。那么,羌南以及羌北塊體晚古生代的古地磁數(shù)據(jù)對研究這一問題就顯得十分重要。但是目前只有羌北地塊獲得的古地磁數(shù)據(jù)比較充分,而羌南地塊的古地磁數(shù)據(jù)特別是晚古生代的數(shù)據(jù)十分稀少,這使得龍木錯一雙湖縫合帶演化時限的確定比較困難。針對這一問題,本文選擇羌南地塊下石炭統(tǒng)的日灣擦卡組地層進行古地磁研究,以期獲得早石炭世羌南地塊的古地磁極位置及古緯度,為青藏高原大地構造演化研究提供依據(jù)。在羌南地塊改則地區(qū)下石炭統(tǒng)的日灣擦卡組地層設置12個采樣點,共采集167塊野外古地磁定向樣品,室內(nèi)加工后對其進行巖石磁學研究和退磁處理。巖石磁學結果顯示巖石中載磁礦物主要包括磁鐵礦和針鐵礦,還有少量磁黃鐵礦。由此,對于實驗樣品采用熱退磁、交變退磁以及混合退磁方法進行磁清洗,采用主分量分析方法進行分析并用Fisher統(tǒng)計法對樣品的剩磁進行統(tǒng)計,分別獲得低溫分量和高溫分量的平均方向。其低溫分量方向與現(xiàn)代地磁場方向近于相同,可能是現(xiàn)代地磁場重磁化的結果；高溫分量結果則通過了嚴格的褶皺檢驗,很可能代表了原生剩磁。本文獲得下石炭統(tǒng)日灣擦卡組地層校正后的高溫分量平均方向為：Ds=242°, Is=18.8°,Ks=19.9,a95=10°:對應的古地磁極位置為：γp=16.9°,ψp=199.1°, dp/dm=10.4/5.4；古緯度西古一9.7。。通過與羌北地塊同時代的古地磁極位置對比可以得知：石炭紀時,羌南地塊處于南半球,并且和羌北地塊處于分離狀態(tài),沒有拼合,因此可以認為在石炭紀時特提斯洋位于羌北地塊和羌南地塊之間。結合前人資料分析可以推斷羌南地塊和羌北地塊在晚二疊世拼合形成整體的羌塘地塊,雙湖-龍木錯縫合帶不再是歐亞大陸的南緣,羌塘塊體之南的班公湖-怒江帶成為新的歐亞大陸南緣。羌南塊體在石炭紀到三疊紀的運動趨勢總體北移并伴隨有旋轉(zhuǎn)。
[Abstract]:The Qiangtang block is very important for the study of the evolution and dynamics of the Qinghai-Tibet Plateau. The Qiangtang block was once considered as a whole until the discovery of the Shuanghu-Longmu dislocation suture zone. The Qiangtang block was divided into two blocks, the northern Qiang and the southern Qiang, and at the same time, The differences between Gondwana and Eurasia are also concentrated between the Bangong Lake-Nujiang suture zone and the Shuanghu-Longmu fault suture zone. Whether the Shuanghu-Longmu fault suture belt in the northern part of the southern Qiang block is the southern edge of Eurasia in the late Paleozoic, that is, whether the southern Qiang and the northern Qiang in the late Paleozoic have been combined or not is of great importance. The paleomagnetic data of the late Paleozoic in the southern Qiang and northern Qiang blocks are very important for the study of this problem. But at present, only the paleomagnetic data obtained from the northern Qiang block are quite sufficient, and the paleomagnetic data of the southern Qiang block are very rare especially in the late Paleozoic, which makes it difficult to determine the time limit for the evolution of the Longmu dislocation Shuanghu suture zone. In order to obtain the paleomagnetic pole position and paleolatitude of the early Carboniferous Qiangnan block, this paper chooses the lower Carboniferous strata of the Lower Carboniferous to study paleomagnetism in order to provide the basis for the study of tectonic evolution of the Qinghai-Xizang Plateau. A total of 167 field paleomagnetic directional samples were collected at 12 sampling points in the lower Carboniferous strata of the Lower Carboniferous in the Changzi area of the Qiang Nan Block. The rock magnetics and demagnetization were studied and demagnetized after laboratory processing. The results of petromagnetism show that there are mainly magnetite and goethite, and a small amount of pyrrhotite. Therefore, the experimental samples were cleaned by thermal demagnetization, alternating demagnetization and mixed demagnetization. Principal component analysis (PCA) and Fisher statistics were used to analyze the remanence of the samples. The average directions of the low temperature component and the high temperature component are obtained respectively. The direction of the low-temperature component is similar to that of the modern geomagnetic field, which may be the result of the gravity magnetization of the modern geomagnetic field, while the high-temperature component results pass the strict fold test, which probably represents the primary remanence. In this paper, the average direction of high temperature component after stratigraphic correction in the Lower Carboniferous Zhiwan Zaika formation is found to be: 1: Dsn 242 擄, Iso 18.8 擄KS ~ (19. 9) a 95 ~ 10 擄: the corresponding paleomagnetic pole position is 緯 p ~ (16. 9) 擄, 蠄 ~ (p) 199.1 擄, DP / D ~ (m) 10.4 / 4, and paleolatitude is 9. 7. 7. By comparing the paleomagnetic pole position of the same age with the northern Qiang block, it can be concluded that the southern Qiang block was in the southern hemisphere during the Carboniferous, and it was separated from the northern Qiang block, and there was no combination. Therefore, the Tethys Ocean was located between the northern Qiang block and the southern Qiang block during the Carboniferous. Based on the analysis of previous data, it can be inferred that the southern Qiang block and the northern Qiang block combined to form a whole Qiangtang block in the late Permian, and the Shuanghu-Longmu fault suture zone is no longer the southern margin of Eurasia. The Bangong Lake-Nujiang belt to the south of the Qiangtang block became the southern edge of the new Eurasian continent. The movement trend of the southern Qiang block from Carboniferous to Triassic generally moved northward and was accompanied by rotation.
【學位授予單位】：西北大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P318.44;P534.45

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