地质通报
地質通報
지질통보
GEOLOGICAL BULLETIN OF CHINA
2014年
7期
1041-1054
,共14页
任厚州%裴先治%刘成军%李佐臣%李瑞保%魏博%陈伟男%王元元%胥晓春%刘图杰%陈有炘
任厚州%裴先治%劉成軍%李佐臣%李瑞保%魏博%陳偉男%王元元%胥曉春%劉圖傑%陳有炘
임후주%배선치%류성군%리좌신%리서보%위박%진위남%왕원원%서효춘%류도걸%진유흔
西秦岭%太白岩体%二长花岗岩%LA-ICP-MS锆石U-Pb年龄%后碰撞
西秦嶺%太白巖體%二長花崗巖%LA-ICP-MS鋯石U-Pb年齡%後踫撞
서진령%태백암체%이장화강암%LA-ICP-MS고석U-Pb년령%후팽당
Western Qinling Mountains%Taibai intrusion%monzonitic granite%LA-ICP-MS zircon U-Pb age%post-collision
秦岭造山带南缘勉略构造带北侧发育有近东西向展布的印支期花岗岩带，位于甘肃徽县地区的太白岩体是该花岗岩类的一部分。LA-ICP-MS锆石U-Pb同位素年龄表明，太白岩体的形成时代为221.8Ma±1.5Ma，属于印支期晚期。主要岩石类型为灰白色-肉红色中细粒二长花岗岩和花岗闪长岩。地球化学特征表明，太白岩体属于准铝质-弱过铝质的高钾钙碱性系列；稀土元素总量ΣREE为79.0×10-6~194×10-6，稀土元素配分模式呈轻稀土元素强烈富集、重稀土元素相对亏损的右倾型， Eu负异常明显；高场强元素（HFSE）Nb、P、Ti、Y、Yb和大离子亲石元素Ba、Sr强烈亏损。太白岩体是以中基性岩石为主的壳源物质部分熔融形成的岩浆上升侵位形成的，且处于同碰撞（挤压环境）向后碰撞（伸展环境）转化阶段，为后造山期花岗岩，是扬子板块和华北板块全面碰撞导致增厚下地壳物质部分熔融的产物。
秦嶺造山帶南緣勉略構造帶北側髮育有近東西嚮展佈的印支期花崗巖帶，位于甘肅徽縣地區的太白巖體是該花崗巖類的一部分。LA-ICP-MS鋯石U-Pb同位素年齡錶明，太白巖體的形成時代為221.8Ma±1.5Ma，屬于印支期晚期。主要巖石類型為灰白色-肉紅色中細粒二長花崗巖和花崗閃長巖。地毬化學特徵錶明，太白巖體屬于準鋁質-弱過鋁質的高鉀鈣堿性繫列；稀土元素總量ΣREE為79.0×10-6~194×10-6，稀土元素配分模式呈輕稀土元素彊烈富集、重稀土元素相對虧損的右傾型， Eu負異常明顯；高場彊元素（HFSE）Nb、P、Ti、Y、Yb和大離子親石元素Ba、Sr彊烈虧損。太白巖體是以中基性巖石為主的殼源物質部分鎔融形成的巖漿上升侵位形成的，且處于同踫撞（擠壓環境）嚮後踫撞（伸展環境）轉化階段，為後造山期花崗巖，是颺子闆塊和華北闆塊全麵踫撞導緻增厚下地殼物質部分鎔融的產物。
진령조산대남연면략구조대북측발육유근동서향전포적인지기화강암대，위우감숙휘현지구적태백암체시해화강암류적일부분。LA-ICP-MS고석U-Pb동위소년령표명，태백암체적형성시대위221.8Ma±1.5Ma，속우인지기만기。주요암석류형위회백색-육홍색중세립이장화강암화화강섬장암。지구화학특정표명，태백암체속우준려질-약과려질적고갑개감성계렬；희토원소총량ΣREE위79.0×10-6~194×10-6，희토원소배분모식정경희토원소강렬부집、중희토원소상대우손적우경형， Eu부이상명현；고장강원소（HFSE）Nb、P、Ti、Y、Yb화대리자친석원소Ba、Sr강렬우손。태백암체시이중기성암석위주적각원물질부분용융형성적암장상승침위형성적，차처우동팽당（제압배경）향후팽당（신전배경）전화계단，위후조산기화강암，시양자판괴화화북판괴전면팽당도치증후하지각물질부분용융적산물。
An EW-trending Indosinian granitoide belt extends near northern Mianlue suture zone on the south margin of Qinling orogenic belt. The Taibai intrusion is a part of the Indosinian granitoids located in the Huixian County of Gansu Province. LA-ICP-MS zircon U-Pb dating of the Taibai intrusion indicates that the emplacement age of the Taibai intrusion is 221.8Ma ± 1.5Ma, sug-gesting Late Indosinian. The Taibai intrusion is mainly composed of gray-pale red, medium to fine grained monzonitic granite and granodiorite. According to the geochemical characteristics, it is suggested that Taibai intrusion belongs to the metaluminous to weakly peraluminous high-potassic calc-alkaline series and is characterized by strong depletion of high field strength elements (HFSE) Nb, Ti, P Y, Yb and large ion elements Ba, Sr with obvious negative Eu anomalies. The total amount of rare earth elements ΣREE=79.0 × 10-6~194 × 10-6,the rare earth elements (REE) exhibit right-oblique patterns with strong enrichment of light rare earth ele-ments (LREE) and the relative depletion of heavy rare earth elements (HREE). The rocks of the Taibai intrusion was formed by ris-ing and emplacement of partially melted granitic magma resulting from partial melting of the shell material, belonging mainly to inter-mediate-basic rocks. The Taibai intrusion, formed at the transitional stage from syn-collision (compression environment) to post-collision (extentional environment), is of late-orogenic granitoids and also a product formed by partial melting of thickened lower crust resulting from the collision between the North China plate and the Yangtze plate.
