本文選題：青藏高原　切入點(diǎn)：羌塘中部　出處：《吉林大學(xué)》2015年碩士論文　論文類(lèi)型：學(xué)位論文

【摘要】：羌塘地塊處于青藏高原中北部，龍木錯(cuò)－雙湖－瀾滄江板塊縫合帶將其劃分為羌南和羌北兩大塊體，羌南具有親岡瓦納大陸的特點(diǎn)，而羌北具有親歐亞大陸的特點(diǎn)。兩側(cè)的基底性質(zhì)與構(gòu)成、古生代沉積建造和生物地理區(qū)系、巖漿活動(dòng)與變質(zhì)作用、構(gòu)造運(yùn)動(dòng)分期存在著顯著差異。近年來(lái)龍木錯(cuò)－雙湖－瀾滄江板塊縫合帶研究取得了突破性進(jìn)展，許多關(guān)鍵地質(zhì)問(wèn)題集中在羌塘地區(qū)，無(wú)人區(qū)的神秘面紗逐漸被揭開(kāi)，李才教授將其比喻為打開(kāi)青藏高原地學(xué)皇冠上的明珠。 在龍木錯(cuò)－雙湖－瀾滄江板塊縫合帶中段的岡瑪錯(cuò)－日灣茶卡地區(qū)，近東西向展布著一條富含暖水型生物化石的早石炭世地層－日灣茶卡組（C1r），出露面積約100平方公里。日灣茶卡組是羌塘中部少有的具有化石時(shí)代依據(jù)的沉積地層，且含有揚(yáng)子型Guizhouphyllum－Yuanophyllum珊瑚等化石組合，一直是眾多學(xué)者關(guān)注的熱點(diǎn)。然而由于其位處羌塘無(wú)人區(qū)，條件極其艱苦，淡水缺乏，無(wú)道路通行，其研究程度并不高。近年來(lái)我們發(fā)現(xiàn)日灣茶卡組南北兩側(cè)均分布著典型的岡瓦納相冷水型沉積地層－展金組（C2P1z），二者呈構(gòu)造接觸。含有揚(yáng)子型生物化石的暖水型沉積夾持于典型的岡瓦納相冷水型沉積之中，這一特殊地質(zhì)現(xiàn)象的解答對(duì)該區(qū)乃至整個(gè)龍木錯(cuò)－雙湖－瀾滄江板塊縫合帶的演化具有重要意義。 本文在大量野外工作的基礎(chǔ)之上，充分利用前人的研究資料和成果，，綜合運(yùn)用巖石學(xué)、同位素年代學(xué)及構(gòu)造地質(zhì)學(xué)等多學(xué)科知識(shí)對(duì)日灣茶卡組進(jìn)行了全方位研究。日灣茶卡組砂巖和礫巖樣品LA－ICP－MS鋯石U-Pb測(cè)年分析結(jié)果存在325～400M（a主要峰值為360Ma），400～500Ma（峰值為437和454Ma），500～600Ma（極少），800～1100Ma和1200Ma五個(gè)年齡區(qū)間。最年輕碎屑鋯石年齡在320Ma左右，與古生物化石組合反映時(shí)代一致，印證了其時(shí)代為早石炭世維憲期；碎屑鋯石中360Ma、437Ma、454Ma年齡峰值最為明顯，為龍木錯(cuò)－雙湖－瀾滄江洋島弧消減事件和加里東運(yùn)動(dòng)的年齡記錄，表明碎屑巖的物源區(qū)主要來(lái)自揚(yáng)子大陸周緣。結(jié)合古生物化石資料可知，日灣茶卡組屬于歐亞大陸揚(yáng)子型石炭紀(jì)沉積地層，為島弧環(huán)境下的一套淺水臺(tái)型沉積。
[Abstract]:The Qiangtang block is located in the central and northern part of the Qinghai-Xizang Plateau, and the Longmu-Shuanghu-Lancangjiang plate suture zone divides it into two blocks: the southern Qiang and the northern Qiang. The southern Qiang is characterized by a pro-Gondwana continent. On the other hand, the north of Qiang Dynasty has the characteristics of being pro-Eurasian, the properties and composition of the basement on both sides, the Paleozoic sedimentary formation and biogeographic fauna, magmatic activity and metamorphism. In recent years, great progress has been made in the study of the suture zone of the Longmu-Shuanghu-Lancang River plate. Many key geological problems are concentrated in the Qiangtang area, and the mysterious veil of the no-man 's land has been gradually unravelled. Professor Li Cai likened it to opening the crown of the Qinghai-Xizang Plateau. In the Gangma Chaka area of the middle section of the Longmu-Shuanghu-Lancang River plate suture zone, Near the east to west, there is an early Carboniferous strata rich in warm water type biofossils, the Jiwan Chaka formation, with a exposed area of about 100 square kilometers. The Riwan Chaka formation is one of the few sedimentary strata with fossil age basis in the middle of Qiangtang. The fossil assemblage containing Yangtze type Guizhouphyllum-Yuanophyllum coral has always been a hot topic for many scholars. However, due to its location in no man's land in Qiangtang, the conditions are extremely difficult, fresh water is scarce, and there is no road passage. In recent years, we have found that there are typical cold water sedimentary strata of Gondwana facies on the north and south sides of the Jiwan Chaka formation, and the two are tectonic contacts. Warm water sedimentation with Yangtze type biofossils is also found. Trapped in a typical Gondwana cold water deposit, The solution of this special geological phenomenon is of great significance to the evolution of the suture zone of the Longmujiao-Shuanghu-Lancang River plate in this area. On the basis of a great deal of field work, this paper makes full use of previous research materials and achievements, and synthetically applies petrology. Isotopic geochronology and tectonic geology were used to study the Jiwan Chaka formation in an all-round way. The LA-ICP-MS zircon U-Pb dating of sandstone and conglomerate samples of the Jiwan Chaka formation shows that the main peak value of zircon U-Pb dating is 360 Ma, 400 Ma, 500 Ma (the peak values are 437 and 454 Ma, 500600 Ma) (P < 0.05). Very few of the five ages range from 800 Ma to 1200 Ma. The youngest age of the clastic zircon is about 320 Ma. Consistent with the age of paleontological fossil assemblage, it is confirmed that its age is the early Carboniferous Shiwei constitutional period, and the peak age of 360 Ma, 437 Ma and 454 Ma in the zircon is the most obvious, which is the age record of the island arc subduction event and Caledonian movement in Longmu Duo-Shuangghuang-Lancangjiang Ocean. The results show that the source region of the clastic rocks is mainly from the margin of Yangtze continent. According to the paleontological fossil data, the Jiwan Chaka formation belongs to the Yangtze type Carboniferous sedimentary strata in Eurasia, which is a set of shallow water platform deposits under the island arc environment.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：P534.45

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