【摘要】：黑溝峽火山巖位于南秦嶺勉(縣)略(陽)構(gòu)造帶略陽地區(qū),由拉斑玄武巖及少量鈣堿性安山巖組成。對(duì)黑溝峽火山巖進(jìn)行了LA-ICP-MS鋯石U-Pb年代學(xué)和巖石地球化學(xué)研究。結(jié)果顯示,黑溝峽安山巖LA-ICP-MS U-Pb測(cè)年結(jié)果為807±13Ma(MSWD=3.6,n=14),限定其形成時(shí)代為新元古代中期。玄武巖SiO_2含量為43.54%~54.51%,富Na貧P,稀土配分曲線整體左傾,整體表現(xiàn)出N型洋脊玄武巖地球化學(xué)特征,其源區(qū)受到再循環(huán)物質(zhì)的改造。安山巖SiO_2含量較高(57.92%~60.71%),Na_2O和K_2O含量變化大,Nb、Ta、P、Ti等負(fù)異常明顯,La/Yb、Sc/Ni、Th/Yb等微量元素特征表現(xiàn)出大陸邊緣弧火山巖地球化學(xué)特征;較高的Mg~#值(40.40~60.72)以及變化較大的Cr、Ni含量、A/CNK值(0.58~1.62),表明安山巖為殼幔混合成因。本文研究表明,黑溝峽火山巖并非前人認(rèn)為的晚古生代"雙峰式火山巖",而是新元古代勉略洋盆存在及俯沖作用的產(chǎn)物。結(jié)合區(qū)域資料,認(rèn)為勉(縣)略(陽)地區(qū)存在新元古代早中期弧—盆體系,且洋盆北向俯沖作用持續(xù)到800 Ma左右,該過程很可能是對(duì)Rodinia超大陸聚合事件的響應(yīng)。
[Abstract]:The Hegouxia volcanic rocks are located in the Lianyang area of the Mianxiao (Yang) tectonic belt in the South Qinling Mountains and are composed of tholeiite and a small amount of calc-alkaline andesite. The LA-ICP-MS zircon U-Pb chronology and petrogeochemistry of the Heigouxia volcanic rocks have been studied. The results show that the LA-ICP-MS U-Pb dating results of the Heigou Gorge andesite are 807 ~ 13 Ma (MSWD=3.6,n=14), which is limited to the middle Neoproterozoic age. The SiO_2 content of basalt is 43.54% ~ 54.51%, rich in Na and poor in P, the REE distribution curve is left-leaning as a whole, showing the geochemical characteristics of N-type oceanic ridge basalt as a whole, and the source area of basalt is reformed by recycled materials. The content of SiO_2 in andesite is higher (57.92% / 60.71%), the content of Na_2O and K _ 2O varies greatly, Nb,Ta,P,Ti and other negative anomalies are obvious, and La/Yb,Sc/Ni,. The characteristics of trace elements such as Th/Yb show geochemical characteristics of continental margin arc volcanic rocks. The higher Mg~# value (40.40 / 60.72), the higher Cr,Ni content, and the A / CNK value (0.58 / 1.62) indicate that the andesite is of crust-mantle mixing origin. It is shown in this paper that the Heigouxia volcanic rocks are not the late Paleozoic "bimodal volcanic rocks", but are the products of the existence and subduction of the Mianliao oceanic basin in the Neoproterozoic. Based on the regional data, it is believed that there exists an arc-basin system in the early and middle Neoproterozoic, and the northward subduction of the ocean basin continues to about 800 Ma. This process is likely to be a response to the aggregation event of Rodinia supercontinent.
【作者單位】： 陜西省地質(zhì)調(diào)查院;長(zhǎng)安大學(xué)地球科學(xué)與資源學(xué)院;西部礦產(chǎn)資源與地質(zhì)工程教育部重點(diǎn)實(shí)驗(yàn)室;中國(guó)地質(zhì)大學(xué)(北京)地球科學(xué)與資源學(xué)院;
【基金】：中國(guó)地質(zhì)調(diào)查局地質(zhì)調(diào)查項(xiàng)目(編號(hào):1212011120161) 國(guó)家自然科學(xué)基金資助項(xiàng)目(編號(hào):41472191,41172186,40972136,40572121) 高等學(xué)校博士學(xué)科點(diǎn)專項(xiàng)科研基金資助項(xiàng)目(編號(hào):20110205110004) 中央高校基本科研業(yè)務(wù)專項(xiàng)基金資助項(xiàng)目(編號(hào):CHD2011TD020,2013G1271092,2013G1271091)的成果~~
【分類號(hào)】：P548;P588.14

【參考文獻(xiàn)】

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