本文選題：果可山 + 石英閃長(zhǎng)巖��； 參考：《地質(zhì)學(xué)報(bào)》2017年01期

【摘要】：柴達(dá)木盆地北緣果可山地區(qū)石英閃長(zhǎng)巖LA-ICP-MS鋯石U-Pb定年獲得的206 Pb/238 U加權(quán)平均年齡為247±3 Ma。石英閃長(zhǎng)巖由斜長(zhǎng)石(55%~60%)、石英(15%~20%)、角閃石(10%~15%)和黑云母(5%~10%)組成,屬準(zhǔn)鋁質(zhì)-弱過鋁質(zhì)系列(A/CNK=0.95~1.02),具有I型花崗巖特征。樣品富集輕稀土元素和大離子親石元素(K、Rb、Cs、Ba、Th等),相對(duì)虧損重稀土元素和高場(chǎng)強(qiáng)元素(Nb、Ta、P、Ti等),類似弧巖漿巖。樣品中MgO含量(2.04%~2.44%)和Mg#值(48.9~51.9)均高于變玄武巖/變泥巖在1~4GPa壓力下部分熔融形成的熔體,且包含大量暗色包體,這暗示它們可能是由角閃巖相下地殼部分熔融產(chǎn)生的巖漿和富集地幔來(lái)源的巖漿發(fā)生混合而成。低的鋯石Ti溫度和高Ce~(4+)/Ce~(3+)比值,表明其結(jié)晶自低溫、高氧逸度巖漿,巖漿形成過程中可能有富水熔體/流體的加入。在花崗巖構(gòu)造環(huán)境判別圖解上,樣品均落在火山弧環(huán)境;同時(shí),樣品La/Nb比值(2.27~2.64)與活動(dòng)大陸邊緣區(qū)高La/Nb比值(2.0)特征相吻合。結(jié)合區(qū)域地質(zhì)背景分析,我們認(rèn)為果可山石英閃長(zhǎng)巖形成于古特提斯洋向北俯沖的活動(dòng)大陸邊緣弧環(huán)境。
[Abstract]:The weighted mean age of 206 Pb/238 U obtained from LA-ICP-MS zircon dating of quartz diorite in Guokeshan area, northern margin of Qaidam Basin, is 247 鹵3 Ma. Quartz diorite is composed of plagioclase (55) and plagioclase (55), quartz (15), hornblende (10) and biotite (10). It is a quasialuminum-weakly peraluminous series (A / CNK _ (0.95N) 1.02) and is characterized by I-type granite. The samples are enriched with light rare earth elements and large ion lithophile elements, such as K ~ (2 +) Rb ~ (2 +) C ~ (1) ~ (1) ~ (1) ~ (1) ~ (2) ~ (2 +), etc., and are similar to arc-magmatic rocks. The contents of MgO and Mg# in the samples are higher than that of melts formed by partial melting of metamorphic rocks / metamorphic rocks under the pressure of 1~4GPa, and contain a large number of dark inclusions, the content of which is 2.04 ~ 2.44) and the value of Mg# is 48.9% ~ 51.9%, which is higher than that of melts formed by partial melting of metamorphic rocks under 1~4GPa pressure. This suggests that they may be a mixture of magma derived from the partial melting of the lower crust of amphibolite facies and magma enriched from the mantle. The low zircon Ti temperature and the high Ce~(4 / ce ~ (3) ratio indicate that the crystallization of the zircon is derived from low temperature, high oxygen fugacity magma and the addition of water-rich melts / fluids during magma formation. In the judging diagram of granite tectonic environment, the samples all fall in volcanic arc environment, and the La/Nb ratio of the samples is 2.272.64) which is consistent with the high La/Nb ratio 2.0 in the active continental margin. Based on the analysis of regional geological background, we think that the quartz diorite of Guokeshan was formed in the active continental margin arc environment of the PaleoTethys ocean subducting northward.
【作者單位】： 合肥工業(yè)大學(xué)資源與環(huán)境工程學(xué)院;
【基金】：國(guó)家自然科學(xué)基金項(xiàng)目(編號(hào):41272221,41372207) 中國(guó)地質(zhì)調(diào)查局地質(zhì)調(diào)查項(xiàng)目(編號(hào):12120115069401,1212011120159)資助的成果
【分類號(hào)】：P597.3;P588.122

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