本文選題：早古生代 + 花崗巖漿作用��； 參考：《中國科學院研究生院(廣州地球化學研究所)》2016年博士論文

【摘要】：特提斯-喜馬拉雅構造域內,如印度西北部、尼泊爾、藏南以及中國西南部發(fā)育有早古生代巖漿巖和沉積巖(~525-460 Ma),這些區(qū)域在早古生代時期位于岡瓦納大陸北緣,朝向原特提斯洋。目前,不同學者對這些區(qū)域早古生代構造事件主要提出了兩種動力學模型:(1)泛非造山運動。是與Rodinia超大陸裂解以及岡瓦納大陸的聚合相關的造山運動;(2)安第斯型造山運動。隨著岡瓦納大陸的聚合,由原特提斯洋向印度克拉通以及鄰區(qū)相關微陸塊之下俯沖而引起的造山運動。然而,由于晚古生代巖漿作用記錄的缺失、以及受到古特提斯洋關閉和喜馬拉雅造山運動相關的熱構造事件改造,相關區(qū)域的早古生代構造演化以及古地理位置尚未得到較好約束。滇西南地區(qū)是東特提斯構造帶的重要組成部分,位于北西西向展布的喜馬拉雅構造結向南北向伸展的東南亞構造結轉換部位,并保存了大量早古生代巖漿活動和沉積作用證據(jù),是我們研究早古生代原特提斯構造屬性的天然實驗室。本次研究選取研究對象為滇西南地區(qū)騰沖、保山和禪泰地塊內的片麻狀花崗巖、變火山巖以及碎屑巖并對其開展了系統(tǒng)的巖石學、巖相學、鋯石U-Pb年代學、主量及微量元素地球化學和Lu-Hf及Sr-Nd同位素組成研究,以探討滇西南地區(qū)早古生代巖漿巖的巖石成因、沉積物源性質及早古生代構造背景與動力學機制。結合前人研究成果,本文重建了早古生代岡瓦納大陸邊緣微陸塊的地理位置,提出了相關區(qū)域的構造演化模型。主要獲得了以下研究成果和認識:(1)騰沖、保山和禪泰地塊早古生代花崗質巖石鋯石U-Pb年代學、原位Lu-Hf同位素、全巖主微量元素和Sr-Nd同位素數(shù)據(jù)分析表明它們形成于早古生代時期的岡瓦納大陸北緣。十二個樣品厘定出的U-Pb鋯石結晶年齡為492-460 Ma,主要礦物為石英、鉀長石、斜長石和黑云母,次要礦物為白云母和石榴石等,A/CNK值為1.10-1.39,為強過鋁質S型花崗巖。樣品表現(xiàn)出高Si O2(53.57-69.10 wt.%),高Rb/Sr和Rb/Ba比值,低Al2O3(12.4-15.8 wt.%)、Mg O(0.2-1.0 wt.%)、Ti O2(0.02-0.55 wt.%)、Fe Ot(0.5-3.3 wt.%)和Ca O/Na2O比值,富集LILEs,虧損Nb、Sr、P、Eu和Ti。87Sr/86Sr初始比值為0.70839-0.72302,εNd(t)值介于-5.3和-8.1之間,Nd模式年齡為1.7-2.8 Ga,與已發(fā)表的藏南同期花崗質巖石一致。早古生代巖漿巖εHf(t)值變化為-0.37到-14.1,Hf模式年齡為1.49-2.35 Ga。源區(qū)以古老變質泥巖和含有少量比例變質火成巖(新元古代)組分為特征。研究認為滇西南騰沖、保山和禪泰地塊早古生代過鋁質S型花崗巖形成于與增生造山運動有關的活動大陸邊緣背景。(2)騰沖-保山地塊瀾滄群惠民組兩個變火山巖鋯石U-Pb定年獲得了晚奧陶世年齡,分別為462±6 Ma和454±27 Ma。結合同一地區(qū)已發(fā)表的地球化學數(shù)據(jù)表明,惠民組火山巖具有鈣堿性特征,含較高Al2O3(13.04-18.77 wt.%)和較低Ti O2(0.64~1.00 wt.%)。Si O2含量為53.57-69.10 wt.%,mg#值變化于62~50,為高鎂安山質巖石。樣品表現(xiàn)出富集輕稀土元素(LREEs)和大離子親石元素(LILEs),具有明顯的Eu負異常(δEu=0.20~0.33),虧損高場強元素,與弧火山巖相似。初始87Sr/86Sr變化為0.72136~0.72252,εNd(t)值變化為-7.63~-7.62。研究認為滇西南地區(qū)早古生代火山巖形成于島弧背景,為新元古代-早古生代岡瓦納大陸北緣增生造山的產(chǎn)物。(3)對西盟群帕可組三個變質砂巖和瀾滄群七個變質碎屑巖樣品的激光U-Pb測年(394顆)和原位Lu-Hf同位素組成(246顆)研究表明,碎屑鋯石年齡變化范圍為3490-465 Ma,εHf(t)值變化為-35.45~26.3。不同樣品給出的最小年齡分別為515±19 Ma、531±13 Ma、514±14 Ma、480±12 Ma、559±16 Ma、489±5 Ma、548±7 Ma、505±20 Ma、503±14 Ma和465±4 Ma。相應樣品的最小年齡峰值分別為568 Ma、541 Ma、560 Ma、506 Ma、562 Ma、491 Ma、551 Ma、530 Ma、551Ma和614 Ma,約束它們的沉積年齡小于491 Ma。因此滇西南帕可組和瀾滄群應該沉積于491-454 Ma間的晚寒武世-中奧陶世,而非以往所認為的前寒武紀地層。Lu-Hf同位素組成則顯示變質碎屑巖樣品物源為古老地殼物質的再循環(huán)和新生地殼組分,具有東岡瓦納大陸親緣性。(4)滇西南奧陶紀高鎂質巖石和同期鎂鐵質及花崗質巖石為早古生代時期原特提斯洋沿東岡瓦納大陸北緣俯沖的產(chǎn)物,代表了岡瓦納大陸北緣早古生代巖漿巖帶向南的延伸。沿土耳其西北部、伊朗中部、巴基斯坦西北部、印度和尼泊爾西北部到藏南及滇西南存在一個漸進穿時造山運動。(5)研究認為在岡瓦納大陸奧陶紀(約460 Ma)重建圖中,騰沖-保山及禪泰地塊更可能靠近印度板塊而不是澳大利亞板塊。由此提出了滇西南地區(qū)構造演化模型,滇西南地區(qū)原特提斯洋的俯沖至少持續(xù)到450 Ma。
[Abstract]:The early Paleozoic magmatic rocks and sedimentary rocks (~525-460 Ma) developed in the Tethys Himalaya tectonic domain, such as Northwestern India, Nepal, Zangnan, and southwestern China, are located on the northern margin of Gondwana in the early Palaeozoic era and toward the original Tethys ocean. At present, different scholars have mainly raised the early Paleozoic tectonic events in these regions. Two dynamic models: (1) the Pan African orogeny. The orogenic movement associated with the Rodinia supercontinental cracking and the polymerization of the Gondwana continent; (2) the Andean orogeny. With the polymerization of the Gondwana continent, the orogenic movement caused by the subduction of the original Tethys ocean to the India Craton and the adjacent area. The lack of magmatism in the late Paleozoic, as well as the transformation of the thermal tectonic events related to the closure of the Paleo Tethys ocean and the Himalaya orogenic movement, has not been well constrained by the early Paleozoic tectonic evolution and palaeogeographic position in the related regions. The Himalaya tectonic knot extends to the North-South extension of the Southeast Asian tectonic junction, and preserves a large number of Early Paleozoic magmatic activities and depositional evidences. It is a natural laboratory for our study of the early Paleozoic original Tethys structural properties. This study selected the study object in Tengchong, Baoshan and Zen land block in southwestern Yunnan. The lithology, petrography, zircon U-Pb chronology, principal and trace element geochemistry, and Lu-Hf and Sr-Nd isotopic compositions of the main and trace elements are carried out to explore the petrogenesis of the early Paleozoic magmatic rocks in southwestern Yunnan, in order to explore the early Paleozoic tectonic background and motive force. Based on the previous research results, this paper reconstructs the geographical location of the continental margin of the gwana continental margin in the early Paleozoic and proposed the tectonic evolution model of the related regions. The main achievements are as follows: (1) the zircon U-Pb chronology of the early Paleozoic granitic rocks in Tengchong, Baoshan and Zen thay massif, in situ Lu-Hf isotopes and whole rocks The main trace elements and Sr-Nd isotopic data indicate that they formed in the northern margin of the Gondwana continent in the early Paleozoic era. The U-Pb zircon crystallization age of twelve samples is 492-460 Ma, the main minerals are quartz, potassium feldspar, plagioclase and biotite, and the secondary minerals are muscovite and garnet, and the A/CNK value is 1.10-1.39, which is a strong peralmite. The sample shows high Si O2 (53.57-69.10 wt.%), high Rb/Sr and Rb/Ba ratio, low Al2O3 (12.4-15.8 wt.%), Mg O. The age of 1.7-2.8 Ga is the same as that of the published granitic rocks in Zangnan. The epsilon Hf (T) value of the early Paleozoic magmatic rocks changed from -0.37 to -14.1, and the Hf mode age was 1.49-2.35 Ga. source area with ancient metamorphic mudstone and a small proportion of metamorphic igneous rocks (Neoproterozoic) components. It was considered that Tengchong, Baoshan and Chan Tai massif in southwestern Yunnan. The early Paleozoic peraluminous S type granites were formed in the active continental margin associated with the hyperplastic orogeny. (2) the U-Pb zircon U-Pb of the Huimin group of the Lancang group, Tengchong - Baoshan block, obtained the age of the late Ordovician, and the geochemical data of 462 + 6 Ma and 454 + 27 Ma. in the same area showed that the Huimin group fire The high Al2O3 (13.04-18.77 wt.%) and lower Ti O2 (0.64~1.00 wt.%).Si O2 content is 53.57-69.10 wt.%, and the mg# values are high magnesium an mountain rock. The samples show the enrichment of light rare earth elements and large ionic stone elements, which have obvious negative anomaly (delta) and high loss field. The strong element is similar to the arc volcanic rocks. The initial 87Sr/86Sr change is 0.72136~0.72252, and the change of Nd (T) value is -7.63~-7.62.. The early Paleozoic volcanic rocks in Southwest Yunnan are formed in the island arc background, which are the product of the hyperplastic orogeny in the northern margin of the Neoproterozoic Early Paleozoic Gondwana continent. (3) three metamorphic sandstone and Lancang group in the Ximeng group Palac group. The study of laser U-Pb dating (394) and in situ Lu-Hf isotopic composition (246) of seven metamorphic clastic rocks showed that the age range of detrital zircon was 3490-465 Ma, and the minimum age of Hf (T) values was 515 + 19 Ma, 531 + 13 Ma, 514 + 14 Ma, 480 + 12 Ma and 559 + Ma. The minimum age peaks of 5 + 20 Ma, 503 + 14 Ma and 465 + 4 Ma. respectively are 568 Ma, 541 Ma, 560 Ma, 506 Ma, 562 Ma, 491 Ma, 551 Ma, Ma, 551Ma, and Ma, which restrict their deposition age to be deposited in the late Cambrian Middle Ordovician between the Southwest Yunnan and Lancang The.Lu-Hf isotopic composition of the Precambrian strata shows that the metamorphic clastic rock samples were derived from the ancient crustal material recirculation and the new crustal component, and had the relationship between the East Gondwana continent. (4) the Ordovician high magnesia rocks in southwestern Yunnan and the same period of the mafic and granitic rocks were the north of the early Paleozoic to the north of the eastern Gondwana continent. The product of the marginal subduction represents the extension of the early Paleozoic magmatic rocks in the northern margin of the Gondwana. Along the northwestern part of Turkey, central Iran, northwest Pakistan, India and Nepal to Zangnan and southwestern Yunnan, there is a progressive orogenic orogenic movement. (5) the study was identified in the Ordovician (about 460 Ma) reconstruction of the Gondwana continent. Tengchong Baoshan and Chan Tai block are more likely to be near the India plate rather than the Australian plate. Thus the tectonic evolution model in southwestern Yunnan was put forward. The subduction of the original Tethys ocean in southwestern Yunnan lasted for at least 450 Ma..

【學位授予單位】：中國科學院研究生院(廣州地球化學研究所)
【學位級別】：博士
【學位授予年份】：2016
【分類號】：P542
，

本文編號：1871632