本文關(guān)鍵詞： 牦牛山組 火山巖 地球化學(xué)特征 構(gòu)造事件 LA-ICP-MS鋯石U-Pb測(cè)年　出處：《地質(zhì)通報(bào)》2017年Z1期 　論文類(lèi)型：期刊論文

【摘要】：利用巖石地球化學(xué)分析和LA-ICP-MS鋯石U-Pb定年方法,對(duì)阿木尼克山地區(qū)牦牛組火山巖進(jìn)行了系統(tǒng)的地球化學(xué)特征和鋯石U-Pb年代學(xué)研究。其地球化學(xué)特征為,SiO_2含量介于53.94%~64.69%之間,全堿含量介于5.38%~9.86%之間,范圍較大,里特曼指數(shù)介于1.45~4.54之間,屬于堿性巖和鈣堿性巖,鋁飽和指數(shù)A/CNK均大于1.1,具有S型花崗巖的特征;稀土元素總量為68×10~(-6)~372×10~(-6),LREE/HREE值介于4.51~18.25之間,輕稀土元素富集,重稀土元素虧損,稀土元素配分曲線右傾;微量元素中不相容元素Rb、Ba、Th富集,Ta、Nb虧損明顯,蛛網(wǎng)曲線呈現(xiàn)峰谷迭起的曲線形式。鋯石CL圖像和U-Pb同位素分析結(jié)果顯示,牦牛山組火山巖鋯石自形程度好,均有巖漿振蕩環(huán)帶的特征,Th/U值介于0.4~1.3之間,屬于巖漿成因鋯石。測(cè)得該火山巖中2件樣品的鋯石~(206)Pb/~(238)U年齡介于371~399Ma之間,年齡加權(quán)平均值分別為374.8±3.1Ma和392.4±3.3Ma,表明火山巖形成時(shí)代為中—晚泥盆世。結(jié)合區(qū)域特征,認(rèn)為牦牛山組火山巖的形成與柴達(dá)木盆地北緣的演化有關(guān),其是后碰撞階段伸展作用的產(chǎn)物。
[Abstract]:Geochemistry analysis and LA-ICP-MS zircon U-Pb dating method are used. The geochemical characteristics and zircon U-Pb chronology of the yak volcanic rocks in the Amunicia Mountain area have been systematically studied. The geochemical characteristics of the volcanic rocks are as follows. The content of SiO_2 was between 53.94 and 64.69%, and the content of total alkali was between 5.384.86% and 9.86%, and the Ritman index was between 1.45 and 4.54. It belongs to alkaline rock and calc-alkaline rock, and the Al saturation index A / CNK is higher than 1.1, which is characterized by S-type granite. The total amount of rare earth elements is 68 脳 10 ~ (10) ~ (-6) ~ (6) ~ 372 脳 10 ~ (10) ~ (-1) ~ (-1) LREE / HREE = 4.51 ~ 18.25, which is enriched in light rare earth elements. Loss of heavy rare earth elements, right deviation of the distribution curve of rare earth elements; The enrichment of Th in trace element RbsBaTh is characterized by obvious depletion of Th, and the curve of cobweb appears to be a curve with peaks and valleys. The results of CL zircon images and U-Pb isotopic analysis show that the trace elements are depleted. The zircon of the volcanic rocks of the Yaniushan formation is of good shape, and the characteristics of the magmatic oscillating ring zone range from 0.4 to 1.3. Zircon of magmatic origin. Two samples of zircon from this volcanic rock were measured, and the ages of zircon / Zircon / B / B / B _ (238U) are between 371- 399Ma and 371m ~ 399Ma. The average age weighted values are 374.8 鹵3.1 Ma and 392.4 鹵3.3 Ma, respectively, indicating that the volcanic rocks were formed in the Middle to late Devonian epoch and combined with regional characteristics. It is considered that the formation of volcanic rocks in Yaniushan formation is related to the evolution of the northern margin of the Qaidam basin and is the product of extension in the post-collision stage.
【作者單位】： 成都理工大學(xué)地球科學(xué)學(xué)院;
【基金】：中國(guó)地質(zhì)調(diào)查局項(xiàng)目《柴達(dá)木周緣及鄰區(qū)成礦帶地質(zhì)礦產(chǎn)調(diào)查評(píng)價(jià)》下屬研究項(xiàng)目《青海省都蘭縣阿木尼克山地區(qū)J47E017001、J47E018001、J47E018002、J47E019003四幅1∶5萬(wàn)區(qū)域地質(zhì)礦產(chǎn)調(diào)查》(編號(hào):1212011221146)
【分類(lèi)號(hào)】：P588.14
【正文快照】： 青海省地礦局石油普查大隊(duì)1962年在《祁連山、阿爾金山、昆侖山地質(zhì)概況》[1]一書(shū)中于柴達(dá)木盆地東北緣創(chuàng)名“牦牛山統(tǒng)”。原義指“系盆地東北緣牦牛山一帶,由紫紅色礫巖、砂巖、泥板巖、火山巖組成”。牦牛山統(tǒng)上部與石炭系為不整合接觸,下與地槽相的奧陶系不整合接觸,產(chǎn)植物

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