藏北羌塘中西部紅脊山蛇綠巖的巖石學(xué)、地球化學(xué)、年代學(xué)特征及構(gòu)造意義
發(fā)布時(shí)間：2018-10-18 18:35
【摘要】：紅脊山蛇綠巖是筆者等厘定出的各單元出露齊全的巖石組合，前人對(duì)這套蛇綠巖的研究幾乎是一片空白，尤其缺少蛇綠巖年代學(xué)和地球化學(xué)的資料，這嚴(yán)重制約了龍木錯(cuò)-雙湖-瀾滄江板塊縫合帶在羌塘中西部的深入研究。紅脊山蛇綠巖的巖石學(xué)、年代學(xué)、地球化學(xué)特征及構(gòu)造意義等一系列問題均有待解決，針對(duì)這些問題，本文從蛇綠巖的巖石學(xué)、年代學(xué)和地球化學(xué)特征等方面進(jìn)行了詳細(xì)的研究，以期解決這些問題。 巖石學(xué)研究結(jié)果顯示，該套蛇綠巖總體呈NW-SE向帶狀斷續(xù)展布，長(zhǎng)約30km，寬約5km，由變質(zhì)橄欖巖，變質(zhì)堆晶輝長(zhǎng)巖，變質(zhì)基性巖墻，變質(zhì)玄武巖，放射蟲硅質(zhì)巖和斜長(zhǎng)花崗巖組成。 蛇綠巖鋯石U-Pb年代學(xué)研究結(jié)果顯示，變質(zhì)堆晶輝長(zhǎng)巖21個(gè)測(cè)點(diǎn)得出的加權(quán)平均年齡為274.8±2.6Ma（MSWD=0.21）；斜長(zhǎng)花崗巖12個(gè)測(cè)點(diǎn)得出的加權(quán)平均年齡值為271.7±2.3Ma（MSWD=0.38）；紅脊山變質(zhì)堆晶輝長(zhǎng)巖和斜長(zhǎng)花崗巖兩個(gè)年齡值非常接近，代表了紅脊山蛇綠巖的形成時(shí)代，即紅脊山蛇綠巖形成于早二疊世。 本文以變質(zhì)橄欖巖、變質(zhì)堆晶輝長(zhǎng)巖、變質(zhì)基性巖墻和變質(zhì)玄武巖為研究對(duì)象，對(duì)紅脊山蛇綠巖進(jìn)行了詳細(xì)的巖石學(xué)和地球化學(xué)研究，其地化特征分析結(jié)果表明，各蛇綠巖單元主量元素含量與典型的N-MORB非常相似，稀土元素總量較低，具有輕稀土略虧損的近平坦左傾型配分型式，銪異常不顯著，各蛇綠巖單元微量元素蛛網(wǎng)圖總體也與N-MORB相似，表明變質(zhì)基性巖源于N-MORB型虧損地幔源區(qū)。但是，與典型的大洋中脊玄武巖相比，各蛇綠巖單元微量元素蛛網(wǎng)圖上都顯示了部分大離子親石元素（Ra、Ba、U）的明顯富集和部分高場(chǎng)強(qiáng)元素（Nb、Ta）的明顯虧損，尤其是Nb的虧損較為明顯，這又與典型的大洋中脊MORB型玄武巖有明顯區(qū)別，，顯示紅脊山蛇綠巖兼具N-MORB和IAB特征，表明本區(qū)蛇綠巖受到了俯沖帶物質(zhì)的影響，很可能形成于俯沖帶之上的弧后盆地次級(jí)擴(kuò)張的大地構(gòu)造背景，是特提斯大洋巖石圈在俯沖過程中引發(fā)弧后盆地次級(jí)擴(kuò)張的產(chǎn)物，屬于SSZ型蛇綠巖范疇。 綜合以上研究結(jié)果，筆者認(rèn)為二疊紀(jì)古特提斯大洋演化已經(jīng)進(jìn)入了弧后拉張階段，由于弧后拉張，二疊紀(jì)紅脊山地區(qū)出現(xiàn)了一個(gè)小洋盆，而紅脊山蛇綠巖就是這一期構(gòu)造運(yùn)動(dòng)的記錄。本文對(duì)紅脊山蛇綠巖的研究為龍木錯(cuò)-雙湖-瀾滄江板塊縫合帶中西段的構(gòu)造演化研究提供了重要依據(jù)和基礎(chǔ)資料，進(jìn)而為探討青藏高原特提斯演化以及岡瓦納和歐亞大陸的界線提供了新的資料和認(rèn)識(shí)。
[Abstract]:The Hongjishan ophiolite is a fully exposed rock assemblage of various units determined by the author and the previous study of the ophiolite is almost blank, especially the lack of information on the geochronology and geochemistry of the ophiolite. This seriously restricted the deep study of Longmu-Shuanghu-Lancang River plate suture zone in the central and western Qiangtang. A series of problems such as petrology, geochronology, geochemical characteristics and tectonic significance of ophiolite in Hongji Mountain need to be solved. The geochronology and geochemical characteristics are studied in detail in order to solve these problems. The petrological results show that the ophiolite is distributed in a NW-SE zonal pattern, about 30km long and 5km wide, consisting of metamorphic peridotite, metamorphic heap pyroxenite, metamorphic basalt dike, metamorphic basalt, radiolarian siliceous rock and plagioclase granite. The results of U-Pb chronological study on zircon from ophiolite show that the weighted average age of metamorphic pyroxene is 274.8 鹵2.6Ma (MSWD=0.21), that of clinopyroclase is 271.7 鹵2.3Ma (MSWD=0.38), that of clinopyroxenite is 271.7 鹵2.3Ma (MSWD=0.38), that of metamorphic pyroxene is 274.8 鹵2.6Ma (MSWD=0.21), that of amphiolite is 271.7 鹵2.3Ma. The two ages of Hongjishan metamorphic heap pyroxenite and clinopyranite are very close, which represents the formation age of Hongji mountain ophiolite, that is, Hongjishan ophiolite was formed in early Permian. In this paper, metamorphic peridotite, metamorphic heap pyroxene, metamorphic basic rock dike and metamorphic basalt are taken as the objects of study. The detailed petrology and geochemistry of Hongjishan ophiolite are studied in detail. The main element contents of each ophiolite unit are very similar to those of typical N-MORB, the total amount of rare earth elements is relatively low, and the ophiolite unit has a near-flat left-dip distribution pattern with slight depletion of light rare earth elements, and europium anomaly is not significant. The trace element cobweb map of each ophiolite unit is similar to that of N-MORB, indicating that the metamorphic basic rocks originated from the N-MORB type depleted mantle source region. However, compared with the typical basalt in the mid-oceanic ridge, the trace element cobwebs of each ophiolite unit show the obvious enrichment of some large ion lithophile elements (Ra,Ba,U) and the obvious depletion of some high field strength elements (Nb,Ta), especially the depletion of Nb. This is obviously different from the typical MORB basalt in the mid-oceanic ridge, which indicates that the ophiolite in Hongji Mountain possesses both N-MORB and IAB characteristics, indicating that the ophiolite in this area is affected by subduction zone material. It is very likely that the tectonic setting of the secondary extension of the back-arc basin over the subduction zone is the product of the secondary expansion of the back-arc basin caused by the Tethys oceanic lithosphere during the subduction and belongs to the category of SSZ ophiolite. Based on the above results, the authors believe that the evolution of the Permian PaleoTethys ocean has entered the post-arc extensional stage. As a result of the back-arc extension, a small oceanic basin appeared in the Red Ridge Mountains of the Permian period. The Hongji Mountain ophiolite is the record of this period of tectonic movement. In this paper, the study of ophiolite in Hongji Mountain provides important basis and basic data for the study of tectonic evolution in the western segment of the Longmao-Shuanghu-Lancangjiang plate suture zone. It provides new data and understanding for the Tethys evolution of the Qinghai-Tibet Plateau and the boundary between Gondwana and Eurasia.
【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
【分類號(hào)】：P597.3;P588
本文編號(hào)：2280016
[Abstract]:The Hongjishan ophiolite is a fully exposed rock assemblage of various units determined by the author and the previous study of the ophiolite is almost blank, especially the lack of information on the geochronology and geochemistry of the ophiolite. This seriously restricted the deep study of Longmu-Shuanghu-Lancang River plate suture zone in the central and western Qiangtang. A series of problems such as petrology, geochronology, geochemical characteristics and tectonic significance of ophiolite in Hongji Mountain need to be solved. The geochronology and geochemical characteristics are studied in detail in order to solve these problems. The petrological results show that the ophiolite is distributed in a NW-SE zonal pattern, about 30km long and 5km wide, consisting of metamorphic peridotite, metamorphic heap pyroxenite, metamorphic basalt dike, metamorphic basalt, radiolarian siliceous rock and plagioclase granite. The results of U-Pb chronological study on zircon from ophiolite show that the weighted average age of metamorphic pyroxene is 274.8 鹵2.6Ma (MSWD=0.21), that of clinopyroclase is 271.7 鹵2.3Ma (MSWD=0.38), that of clinopyroxenite is 271.7 鹵2.3Ma (MSWD=0.38), that of metamorphic pyroxene is 274.8 鹵2.6Ma (MSWD=0.21), that of amphiolite is 271.7 鹵2.3Ma. The two ages of Hongjishan metamorphic heap pyroxenite and clinopyranite are very close, which represents the formation age of Hongji mountain ophiolite, that is, Hongjishan ophiolite was formed in early Permian. In this paper, metamorphic peridotite, metamorphic heap pyroxene, metamorphic basic rock dike and metamorphic basalt are taken as the objects of study. The detailed petrology and geochemistry of Hongjishan ophiolite are studied in detail. The main element contents of each ophiolite unit are very similar to those of typical N-MORB, the total amount of rare earth elements is relatively low, and the ophiolite unit has a near-flat left-dip distribution pattern with slight depletion of light rare earth elements, and europium anomaly is not significant. The trace element cobweb map of each ophiolite unit is similar to that of N-MORB, indicating that the metamorphic basic rocks originated from the N-MORB type depleted mantle source region. However, compared with the typical basalt in the mid-oceanic ridge, the trace element cobwebs of each ophiolite unit show the obvious enrichment of some large ion lithophile elements (Ra,Ba,U) and the obvious depletion of some high field strength elements (Nb,Ta), especially the depletion of Nb. This is obviously different from the typical MORB basalt in the mid-oceanic ridge, which indicates that the ophiolite in Hongji Mountain possesses both N-MORB and IAB characteristics, indicating that the ophiolite in this area is affected by subduction zone material. It is very likely that the tectonic setting of the secondary extension of the back-arc basin over the subduction zone is the product of the secondary expansion of the back-arc basin caused by the Tethys oceanic lithosphere during the subduction and belongs to the category of SSZ ophiolite. Based on the above results, the authors believe that the evolution of the Permian PaleoTethys ocean has entered the post-arc extensional stage. As a result of the back-arc extension, a small oceanic basin appeared in the Red Ridge Mountains of the Permian period. The Hongji Mountain ophiolite is the record of this period of tectonic movement. In this paper, the study of ophiolite in Hongji Mountain provides important basis and basic data for the study of tectonic evolution in the western segment of the Longmao-Shuanghu-Lancangjiang plate suture zone. It provides new data and understanding for the Tethys evolution of the Qinghai-Tibet Plateau and the boundary between Gondwana and Eurasia.
【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
【分類號(hào)】：P597.3;P588
【參考文獻(xiàn)】
相關(guān)期刊論文 前10條
1 李才;龍木錯(cuò)-雙湖-瀾滄江板塊縫合帶與石炭二疊紀(jì)岡瓦納北界[J];長(zhǎng)春地質(zhì)學(xué)院學(xué)報(bào);1987年02期
2 李才，程立人，胡克，洪裕榮;西藏羌塘南部地區(qū)的冰海雜礫巖及其成因[J];長(zhǎng)春地質(zhì)學(xué)院學(xué)報(bào);1995年04期
3 梁定益,聶澤同,郭鐵鷹,張宜智,許寶文,王為平;西藏阿里喀喇昆侖南部的岡瓦納——特提斯相石炭二疊系[J];地球科學(xué);1983年01期
4 潘桂棠,朱弟成,王立全,廖忠禮,耿全如,江新勝;班公湖—怒江縫合帶作為岡瓦納大陸北界的地質(zhì)地球物理證據(jù)[J];地學(xué)前緣;2004年04期
5 李才;黃小鵬;翟慶國(guó);朱同興;于遠(yuǎn)山;王根厚;曾慶高;;龍木錯(cuò)—雙湖—吉塘板塊縫合帶與青藏高原岡瓦納北界[J];地學(xué)前緣;2006年04期
6 李日俊,吳浩若,李紅生,孫東立;藏北阿木崗群、查桑群和魯谷組放射蟲的發(fā)現(xiàn)及有關(guān)問題討論[J];地質(zhì)論評(píng);1997年03期
7 沈渭洲,高劍峰,徐士進(jìn),李惠民,周國(guó)慶,楊鑄生,楊七文;四川石棉蛇綠巖的地球化學(xué)特征及其構(gòu)造意義[J];地質(zhì)論評(píng);2003年01期
8 黃汲清;陳國(guó)銘;陳炳蔚;;特提斯-喜馬拉雅構(gòu)造域初步分析[J];地質(zhì)學(xué)報(bào);1984年01期
9 鄧萬明,尹集祥,咼中平;羌塘茶布-雙湖地區(qū)基性超基性巖和火山巖研究[J];中國(guó)科學(xué)(D輯:地球科學(xué));1996年04期
10 李才;翟慶國(guó);董永勝;黃小鵬;;青藏高原羌塘中部榴輝巖的發(fā)現(xiàn)及其意義[J];科學(xué)通報(bào);2006年01期
本文編號(hào)：2280016
本文鏈接：http://sikaile.net/kejilunwen/diqiudizhi/2280016.html
最近更新
教材專著
