本文選題：班公湖-怒江縫合帶西段 + 中酸性侵入巖�。� 參考：《成都理工大學》2015年碩士論文

【摘要】：在野外地質調查基礎上,對班公湖-怒江縫合帶西段納屋錯地區(qū)的中酸性侵入巖及早白堊世去申拉組中基性火山巖進行了詳細的巖石學、巖石地球化學、鋯石U-Pb測年等研究工作,查明了主要巖石類型、巖石組合及其時空分布規(guī)律;分析并探討了該區(qū)的巖漿活動及構造環(huán)境,討論了該區(qū)班-怒特提斯洋的俯沖極性�？p合帶內中酸性侵入巖以閃長玢巖為主,石英閃長玢巖、石英二長閃長巖、石英斜長(斑)巖、斜長花崗斑巖、花崗閃長斑巖零星出現(xiàn),均屬鈣堿性和高鉀鈣堿性系列。具有LREE富集而HREE虧損的右傾模式,微弱的Eu負異常,表明巖漿分異程度較低,斜長石分離結晶作用不明顯。富集大離子不相容元素(HFSE)Rb、K、Ba,虧損高場強元素(LILE)Nb、Ta、Ti、P,曲線總體呈平坦型,顯示出島弧鈣堿性系列巖體特征和演化趨勢。在構造環(huán)境判別圖解上顯示既有火山弧花崗巖,也有同碰撞花崗巖的特征,說明其形成于班公湖-怒江特斯洋殼的俯沖階段�？p合帶南側鹽湖復式巖體中酸性侵入巖屬于高鉀鈣堿性和鈣堿性系列。稀土元素配分顯示輕稀土較富集的右傾型,Eu異常不明顯,顯示殼幔型物源特點。原始地幔標準化圖解呈向右緩傾的模式,具俯沖帶巖漿作用島弧型特征。在構造判別圖解上均落入火山弧花崗巖VAG區(qū)域,島弧型特征明顯,說明其形成于班公湖-怒江特提斯洋殼南向俯沖階段的活動大陸邊緣。縫合帶內和鹽湖復式巖體的巖石學、巖石地球化學特征相似,其巖石成因均來自俯沖帶地幔鍥的部分熔融,并受到來自俯沖板片沉積物熔體的交代。鋯石U-Pb定年結果表明縫合帶內石英閃長玢巖年齡值為104.5Ma,鹽湖復式巖體的鉀長花崗巖年齡值為100.7Ma,石英二長閃長巖年齡值為108.3Ma。結合區(qū)域地質資料,可知其它們的成巖地質時代主要為早白堊世晚期到晚白堊世,說明其形成于俯沖巖漿弧環(huán)境,為巖漿弧花崗巖類巖石。早白堊世去申拉組火山巖主要為一系列的中基性火山巖,其稀土元素分布型式為輕稀土弱富集型的右傾型,Eu呈現(xiàn)弱異常;微量元素整體上富集Rb、Ba、Th、U等大離子親石元素(LILE),虧損Nb、Ta等高場強元素(HFES),具有明顯島弧火山巖特點。說明其形成于班公湖-怒江特提斯洋殼南向俯沖的消減過程。
[Abstract]:On the basis of field geological investigation, the intermediate-acid intrusive rocks of the Nawuso area in the western section of Bangong Lake-Nujiang suture zone were studied in detail in petrology, petrogeochemistry, and petrochemistry of the Middle and basic volcanic rocks of the early Cretaceous Cretaceous Cretaceous Gesheng-La formation. The main rock types, rock assemblages and their temporal and spatial distribution are identified, magmatic activity and tectonic environment in the area are analyzed and discussed, and the subduction polarity of the Ban-Nutertes Ocean in this area is discussed. The intermediate-acid intrusive rocks in the suture zone are mainly diorite porphyrite, quartz diorite, quartz plagioclase (porphyry), plagioclase porphyry and granodiorite porphyry, all of which belong to calc-alkaline and high-potassium calc-alkaline series. The weak EU negative anomaly with LREE enrichment and hree depletion shows that the magmatic differentiation is low and the crystallization of plagioclase is not obvious. The enrichment of large ion incompatibility element (HFSE) RbSe Kni-Bai, depleted high field strength element (Lile) NbPe Tajiao TiTiP.The curve is flat in general, showing the characteristics and evolution trend of the island arc calc-alkaline series rock mass. Both volcanic arc granite and syncollision granite are shown in the tectonic environment discriminant diagram, which indicates that they were formed in the subduction stage of Bangonghu-Nu Jiangtes oceanic crust. The acidic intrusive rocks in the salt lake complex on the southern side of the suture zone belong to the high potassium calc-alkaline and calc-alkaline series. The REE partition shows that the REE distribution is not obvious in the right dip type EU which is rich in LREE and shows the characteristics of the crust-mantle type provenance. The normalized diagram of the primitive mantle shows a rightward gentle dip pattern, which is characterized by the island arc of magmatism in the subduction zone. All of them fall into the VAG area of volcanic arc granite on the tectonic discriminant diagram, and the island arc type is obvious, which indicates that it was formed in the active continental margin of the southern subduction stage of Bangong Lake-Nu River Tethys oceanic crust. The petrology and geochemistry of the suture zone are similar to those of the salt lake complex. The petrogenesis of the suture zone is derived from the partial melting of the mantle of the subduction zone and from the metasomatism of the subduction plate sediment melt. The results of zircon U-Pb dating show that the age of quartz diorite porphyrite in suture zone is 104.5 Ma. the age of potassium feldspar in salt lake complex is 100.7 Ma, and the age of quartz diorite is 108.3 Ma. In combination with regional geological data, their diagenetic geological ages are mainly from the late early Cretaceous to the late Cretaceous, indicating that they were formed in the subduction magmatic arc environment and are magmatic arc granitic rocks. The volcanic rocks of the early Cretaceous Cretaceous are mainly of a series of meso-basic volcanic rocks, and the REE distribution pattern is the LREE enriched weakly enriched right-dip type EU shows weak anomaly. The trace elements are enriched in large ion lithophile elements (lie), such as RbBX, BaTiThU, etc., and depleted in high field strength elements (HFES), such as NB, Ta, etc., and have obvious characteristics of island arc volcanic rocks. It was formed in the course of subduction of Tethys oceanic crust in Bangong Lake-Nu River.
【學位授予單位】：成都理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P588.1

【參考文獻】

相關期刊論文 前2條

1 常承法,鄭錫瀾;中國西藏南部珠穆朗瑪峰地區(qū)地質構造特征以及青藏高原東西向諸山系形成的探討[J];中國科學;1973年02期

2 翟慶國,李才,李惠民,王天武;西藏岡底斯中部淡色花崗巖鋯石U-Pb年齡及其地質意義[J];地質通報;2005年04期

相關碩士學位論文 前1條

1 關俊雷;西藏唐古拉巖漿巖帶西段晚三疊世花崗巖體的成因研究[D];成都理工大學;2014年

，

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