【摘要】：奇臺達(dá)坂位于新疆西昆侖新藏公路540km處,在其周圍分布有小規(guī)模的中酸性侵入巖,巖體嚴(yán)格受郭扎錯—金沙江縫合帶控制呈北西向展布,巖性主要為英云閃長巖、石英閃長巖和花崗閃長巖。鋯石環(huán)帶結(jié)構(gòu)明顯,Th/U值介于0.15~0.73之間,為典型的巖漿鋯石。LA-ICP-MS鋯石U-Pb同位素測年結(jié)果表明,其形成年齡分別為214.7±2.0 Ma、211.3±3.3 Ma和210.6±2.8 Ma,時代為晚三疊世。主微量元素英云閃長巖→石英閃長巖→花崗閃長巖,巖石中SiO_2(58.96%~67.52%)含量逐漸增高,Al_2O_3(14.79%~16.37%)、CaO(3.41%~5.25%)和Mg O(1.47%~3.42%)逐漸降低;里特曼指數(shù)1.03~1.79,K_2O+Na_2O全堿含量為4.36%~6.4%,屬鈣堿性系列。稀土元素中等(∑REE=101.27×10-6~271.04×10-6),輕重稀土分異明顯(LaN/YbN平均為10.69),Eu異常明顯(δEu平均值0.60)。大離子親石元素(LILE)Rb、K、Th富集、相對虧損Ba,高場強(qiáng)元素(HFSE)Nb、Zr、Hf、Sr、P、Ti虧損。對研究區(qū)侵入巖進(jìn)行投圖分析,認(rèn)為它是形成于大陸邊緣弧環(huán)境的未分異I型花崗巖,物質(zhì)來源主要為巖漿弧地殼的角閃巖相變玄武巖,并卷入少量的地幔物質(zhì)。根據(jù)巖體的成因類型并結(jié)合區(qū)域構(gòu)造環(huán)境演化認(rèn)為,在晚三疊世末,古特提斯洋南緣局限洋盆(巴顏喀拉中生代邊緣裂陷海洋盆)發(fā)生自NE向SW的持續(xù)俯沖消減,洋—陸轉(zhuǎn)換開始,該套中酸性侵入巖侵入就位。
[Abstract]:Qitaidaban is located at the 540km of Xin-Tibet Highway in West Kunlun, Xinjiang, and has a small scale of intermediate-acid intrusive rocks around it. The rock mass is strictly controlled by the Guozhai-Jinshajiang suture zone and distributes in the north-west direction, and the lithology is mainly composed of quartz diorite. Quartz diorite and granodiorite. The U-Pb isotopic dating of zircon 路LA-ICP-MS shows that the age of zircon formation is 214.7 鹵2.0 Ma 211.3 鹵3.3 Ma and 210.6 鹵2.8 Ma, respectively, and the age is late Triassic. The content of SiO_2 (58.96%, 67.52%) in the main trace element Yingyun diorite and quartz diorite is gradually increasing. The content of Al2O3 (14.7920%) Cao (3.41%) and Mg O (1.470.42%) decreases gradually, and the whole alkali content of the Richman index 1.031.79 K2O Na_2O is 4.366.40.It belongs to the calc-alkaline series. The rare earth elements are moderate (鈭，

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