本文選題：哀牢山構(gòu)造帶 + 電氣石B同位素�。� 參考：《中國科學(xué)院研究生院(廣州地球化學(xué)研究所)》2015年碩士論文

【摘要】：滇西三江造山帶(包括昌寧-孟連構(gòu)造帶和哀牢山構(gòu)造帶)位于特提斯-喜馬拉雅構(gòu)造域與濱太平洋構(gòu)造域的復(fù)合部位,兼具印支-思茅和華南陸塊兩大構(gòu)造單元屬性,是研究古特提斯演化歷史的重要地區(qū)之一。目前學(xué)術(shù)界普遍認(rèn)為位于思茅地塊和滇緬泰馬地塊之間的昌寧-孟連構(gòu)造帶是古特提斯多島洋格局的主洋盆遺跡分布區(qū),代表了古特提斯的主縫合帶。哀牢山構(gòu)造帶夾持于印支-思茅地塊與揚(yáng)子地塊之間,沿云南省中西部延伸上千公里。該構(gòu)造帶目前還存在是古特提斯分支洋盆還是弧后盆地的爭(zhēng)論。該構(gòu)造帶對(duì)應(yīng)的縫合帶位置也存在多種觀點(diǎn):第一種觀點(diǎn)認(rèn)為沿哀牢山斷裂分布;第二種觀點(diǎn)認(rèn)為位于哀牢山斷裂以西100千米的李仙江斷裂;第三種觀點(diǎn)認(rèn)為可能沿九甲-安定斷裂分布。同時(shí)哀牢山古特提斯分支洋盆或者弧后盆地的打開時(shí)限也存在分歧。哀牢山構(gòu)造帶及相鄰的揚(yáng)子西緣地區(qū)在古生代發(fā)育了廣泛的碎屑巖沉積,它們記錄了哀牢山洋的演化歷史,通過對(duì)它們進(jìn)行碎屑源區(qū)示蹤研究,可以解決上述相關(guān)問題。本論文以哀牢山構(gòu)造帶及相鄰揚(yáng)子西緣地區(qū)寒武-泥盆系碎屑巖為研究對(duì)象,在詳細(xì)的野外地質(zhì)調(diào)查基礎(chǔ)上,通過巖相學(xué)、碎屑電氣石B同位素和碎屑鋯石U-Pb年代學(xué)及Hf同位素分析等綜合研究,探討了這些碎屑巖的源區(qū)特征及其碎屑物質(zhì)來源,為深入理解哀牢山構(gòu)造帶古特提斯演化、哀牢山古特提斯洋對(duì)應(yīng)的縫合帶位置及打開時(shí)限提供了新的制約。本論文研究所取得的主要進(jìn)展如下:1.哀牢山-藤條河斷裂以東寒武-泥盆系碎屑巖的碎屑物質(zhì)主要來自揚(yáng)子來自哀牢山-藤條河斷裂以東地區(qū)寒武-泥盆系碎屑巖中碎屑電氣石硼同位素組成主要在-13‰~-11‰,同位素組成相對(duì)偏重且較為集中,指示源區(qū)較為單一,可能受到了來自俯沖板片流體或者海相碳酸鹽巖、蒸發(fā)巖的影響。此外,碎屑鋯石年代學(xué)數(shù)據(jù)顯示它們具有相似的年齡譜系,主要年齡區(qū)間為730~900Ma,對(duì)應(yīng)的峰值年齡~828 Ma,εHf(t)值范圍為-29.18~+13.55;其余三個(gè)次級(jí)的年齡區(qū)間為530~650 Ma、1500~1700 Ma和2400~2600 Ma,峰值年齡分別~543Ma、~1570 Ma和~2490 Ma,這樣的年齡分布模式可與前人發(fā)表的來自揚(yáng)子板塊源區(qū)的碎屑鋯石數(shù)據(jù)相對(duì)比,表明這些沉積巖的碎屑物質(zhì)主要來自于揚(yáng)子板塊。2.哀牢山-藤條河斷裂以西志留-泥盆系碎屑巖的碎屑物質(zhì)主要來自印支-來自哀牢山-藤條河斷裂以西地區(qū)思茅一側(cè)哀牢山構(gòu)造帶內(nèi)的碎屑巖中碎屑電氣石硼同位素主要峰值在-13‰~-18‰之間,硼同位素組成相對(duì)偏輕且較為分散,指示源區(qū)較為復(fù)雜,可能受到了非海相蒸發(fā)巖、變質(zhì)流體或者巖漿演化后期強(qiáng)烈的巖漿去氣作用的影響。此外,碎屑鋯石年代學(xué)數(shù)據(jù)顯示它們具有相似的年齡譜系,得到的主要年齡區(qū)間為400~500 Ma和900~1000 Ma,峰值年齡分別~447 Ma和953 Ma,大部分鋯石均具有負(fù)的εHf(t)值。這些年齡區(qū)間的碎屑鋯石可與印支地塊和岡瓦納大陸內(nèi)部找到對(duì)應(yīng)的源區(qū),且可與前人發(fā)表的印支地塊碎屑鋯石數(shù)據(jù)相對(duì)比,表明這些沉積巖的物源主要來自于印支-思茅地塊和岡瓦納大陸。3.哀牢山古特提斯洋對(duì)應(yīng)的縫合帶位置可能沿哀牢山-藤條河斷裂分布。金平地區(qū)志留系碎屑巖源區(qū)特征與揚(yáng)子西緣同時(shí)期碎屑巖相似,而與墨江綠春地區(qū)樣品顯著不同。結(jié)合建水至金平地區(qū)沉積相的變化(海相碎屑巖-灰?guī)r-頁巖及硅質(zhì)巖),可能指示金平地區(qū)位于揚(yáng)子地塊一側(cè),為揚(yáng)子被動(dòng)大陸邊緣沉積;而墨江-綠春地區(qū)志留-泥盆系碎屑巖由思茅地塊一側(cè)沉積形成,并不是前人所認(rèn)為的揚(yáng)子被動(dòng)大陸邊緣的斜坡沉積。由于哀牢山-藤條河斷裂兩側(cè)碎屑沉積物源區(qū)具有不同的板塊屬性,哀牢山-藤條河斷裂可能代表了哀牢山古特提斯洋縫合帶。4.哀牢山古特提斯洋可能于志留紀(jì)已經(jīng)開始打開。揚(yáng)子西緣在寒武奧陶紀(jì)為穩(wěn)定的沉積環(huán)境,主要沉積石英砂巖;從早志留紀(jì)開始揚(yáng)子西緣和哀牢山構(gòu)造帶內(nèi)沉積環(huán)境開始變活躍,主要沉積雜砂巖和砂屑巖。碎屑鋯石U-Pb年齡和Hf同位素以及碎屑電氣石B同位素?cái)?shù)據(jù)表明哀牢山-藤條河斷裂兩側(cè)的碎屑巖自早志留世起就開始具有不同源區(qū):在思茅地塊一側(cè)(哀牢山-藤條河斷裂以西)從志留系到泥盆系所有碎屑巖樣品鋯石U-Pb年齡Hf同位素以及電氣石的B同位素都非常相似,源區(qū)基本上未發(fā)生變化;而在在揚(yáng)子西緣一側(cè)(哀牢山-藤條河斷裂以東)志留-泥盆系碎屑巖源區(qū)特征稍有變化,年輕的碎屑鋯石比例增多。由于哀牢山-藤條河兩側(cè)源區(qū)至少在志留紀(jì)就已經(jīng)開始不同,而且構(gòu)造開始變的活躍,因此我們推斷哀牢山地區(qū)在早志留紀(jì)就已經(jīng)開始裂解,并形成了一個(gè)足夠阻隔碎屑物源運(yùn)移的深水盆地,哀牢山洋可能于志留紀(jì)就已經(jīng)打開。
[Abstract]:The Sanjiang orogenic belt in western Yunnan (including the Changning Meng Lian structural belt and the Ailao Mountain tectonic belt) is located in the compound part of the Tethys Himalaya tectonic domain and the shore Pacific tectonic domain, with the two major tectonic units of the Indo Simao and Southern China blocks, which is one of the most important areas for the study of the evolution history of the ancient Tethys. The Changning Meng Lian tectonic belt between the Mau massif and Yunnan Matai massif is the main oceanic site of the Gut Tis do island ocean, representing the main suture zone of Gut Tis. The Ailao Mountain tectonic belt is held between the Indo Simao block and the Yangtze block, and extends up to 1000 kilometers along the Midwest of Yunnan Province. The Tethys branch basin is still an argument in the back arc basin. There are also many points of view in the position of the corresponding suture zone in this tectonic belt: the first view is that the distribution of the Ailao Mountain fault is distributed; the second viewpoint is considered to be located at the Li Xianjiang fault of 100 kilometers west of the Ailao Mountain fault; the third viewpoint is considered to be distributed along the nine a diazepam fault. There are also differences in the opening time limit of the Sean Gut Tis branch or the back arc basin. The Ailao Mountain tectonic belt and the adjacent western margin of the Yangtze River developed a wide range of clastic rocks in the Paleozoic. They recorded the evolution history of the Ailao Mountain ocean. This paper can solve the above problems by using the tracer study of the debris source area. Based on the study of the Ailao Mountain tectonic belt and the Cambrian Devonian clastic rocks in the western margin of the Yangtze River, based on the detailed field geological survey, the characteristics of the source area and the source of detrital materials are discussed through the comprehensive study of petrography, B isotopes of clastic tourmaline, U-Pb chronology of detrital zircon and Hf isotopes. In order to understand the evolution of the ancient Tethys in the Ailao Mountain tectonic belt, the position of the suture zone and the opening time limit of the Ailao Mountain Paleo Tethys ocean are restricted. The main progress made in this study is as follows: 1. the debris of the Cambrian Devonian clastic rocks from the Ailao Mountain rattan River fault mainly comes from the Yangzi from the Ailao Mountain rattan River The composition of the clastic tourmaline boron isotopes in the Cambrian Devonian clastic rocks in the east of the fault is mainly -13 per 1000 ~-11 per thousand, and the isotopic composition is relatively heavy and concentrated, indicating that the source area is relatively single, and may be influenced by the subduction plate fluid or the marine carbonate rocks and the evaporation rocks. In addition, the data of the detrital zircon chronology show them. The age spectrum has a similar age range, the main age range is 730~900Ma, the corresponding peak age ~828 Ma and the Hf (T) range are -29.18~+13.55; the other three secondary age ranges are 530~650 Ma, 1500~1700 Ma and 2400~2600 Ma. The data of clastic zircons in the source area of the sub plate indicate that the debris of these sedimentary rocks mainly comes from the debris of the Silurian detrital rock of the Silurian Devonian System of the Ailao Mountain,.2., the Yangzi plate, mainly from the Indo branch - clastic rocks in the Ailao Mountain tectonic belt of the Simao side of the Ailao Mountain and the west area of the rattan Creek fault. The main peak of boron isotopes of tourmaline is between -13 per thousand and ~-18 per 1000. The composition of boron isotopes is relatively light and scattered, indicating that the source region is more complex and may be affected by the effect of non marine evaporite, metamorphic fluid or intense magma degassing in the late stage of magma evolution. The age spectrum is 400~500 Ma and 900~1000 Ma, and the peak age is ~447 Ma and 953 Ma respectively. Most of the zircon has negative e Hf (T) value. These zircon can find the corresponding source area with the Indo and Gondwana continents, and can be compared with the data of the Indosinian block zircon data published by the predecessors. It is indicated that the source of these sedimentary rocks mainly comes from the Indosinian Simao block and the.3. Ailao Sean Gut Tis Jan zone in the island of Gondwana, which may be distributed along the Ailao Mountain rattan Creek fault. The characteristics of the Silurian clastic rocks in the Jinping area are similar to the detrital rocks at the western margin of the western margin of the Yangtze, but not with the samples of Lvchun in Mojiang. The changes in the sedimentary facies of the Jianshui to the Jinping area (marine clastic rock, limestone shale and siliceous rock) may indicate that the Jinping area is located on one side of the Yangtze block and deposited on the passive continental margin of the Yangtze, while the Silurian Devonian clastic rocks in the Mojiang Lvchun region are deposited on one side of the Simao massif and are not considered by the predecessors to be passive large of the Yangtze. Because of the different plate properties on both sides of the Ailao Mountain rattan River fault, the Ailao Mountain rattan River fault may represent the Ailao Mountain Suzhou suture zone,.4. Ailao Mountain ancient trate ocean may have begun to open in the Silurian period. The western margin of the young son in the Cambrian Ordovician period is a stable sedimentary ring. From the Early Silurian, the sedimentary environment in the western margin of the Yangtze and the Ailao Mountain tectonic zone began to become active, mainly sedimentary sandstones and sandstones. The U-Pb age of the detrital zircon and Hf isotopes and the data of the B isotopes of the clastic tourmaline indicate that the clastic rocks on both sides of the Ailao mountain Tsao river broke from the Early Silurian period. The U-Pb age Hf isotopes of zircon from the Silurian to the Devonian system and the B isotopes of the tourmaline are very similar in one side of the Simao massif and from the west of the Ailao Mountain to the Devonian. The source area is basically not changed, but the shredded Devonian system is broken on the one side of the western margin of the Yangtze (Ailao Mountain - rattan River fault). The characteristics of the source area of the debris rock are slightly changed, and the proportion of young detrital zircon is increased. Because the source areas of the Ailao Mountain - vattan river at the two sides of the Silurian period are at least different and the structure begins to become active, we infer that the Ailao Mountain area has started cracking in the Early Silurian period and formed a deep enough detrital source movement. In the basin, Ailao Mountain ocean may have been opened in Silurian.
【學(xué)位授予單位】：中國科學(xué)院研究生院(廣州地球化學(xué)研究所)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P548;P534.4

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