南秦岭勉略构造带黑沟峡火山岩年代学及地球化学特征——新元古代勉略洋盆存在及俯冲的记录
发布时间：2019-04-02 10:08
【摘要】：黑沟峡火山岩位于南秦岭勉(县)略(阳)构造带略阳地区,由拉斑玄武岩及少量钙碱性安山岩组成。对黑沟峡火山岩进行了LA-ICP-MS锆石U-Pb年代学和岩石地球化学研究。结果显示,黑沟峡安山岩LA-ICP-MS U-Pb测年结果为807±13Ma(MSWD=3.6,n=14),限定其形成时代为新元古代中期。玄武岩SiO_2含量为43.54%~54.51%,富Na贫P,稀土配分曲线整体左倾,整体表现出N型洋脊玄武岩地球化学特征,其源区受到再循环物质的改造。安山岩SiO_2含量较高(57.92%~60.71%),Na_2O和K_2O含量变化大,Nb、Ta、P、Ti等负异常明显,La/Yb、Sc/Ni、Th/Yb等微量元素特征表现出大陆边缘弧火山岩地球化学特征;较高的Mg~#值(40.40~60.72)以及变化较大的Cr、Ni含量、A/CNK值(0.58~1.62),表明安山岩为壳幔混合成因。本文研究表明,黑沟峡火山岩并非前人认为的晚古生代"双峰式火山岩",而是新元古代勉略洋盆存在及俯冲作用的产物。结合区域资料,认为勉(县)略(阳)地区存在新元古代早中期弧—盆体系,且洋盆北向俯冲作用持续到800 Ma左右,该过程很可能是对Rodinia超大陆聚合事件的响应。
[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.
【作者单位】： 陕西省地质调查院;长安大学地球科学与资源学院;西部矿产资源与地质工程教育部重点实验室;中国地质大学(北京)地球科学与资源学院;
【基金】：中国地质调查局地质调查项目(编号:1212011120161) 国家自然科学基金资助项目(编号:41472191,41172186,40972136,40572121) 高等学校博士学科点专项科研基金资助项目(编号:20110205110004) 中央高校基本科研业务专项基金资助项目(编号:CHD2011TD020,2013G1271092,2013G1271091)的成果~~
【分类号】：P548;P588.14
[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.
【作者单位】： 陕西省地质调查院;长安大学地球科学与资源学院;西部矿产资源与地质工程教育部重点实验室;中国地质大学(北京)地球科学与资源学院;
【基金】：中国地质调查局地质调查项目(编号:1212011120161) 国家自然科学基金资助项目(编号:41472191,41172186,40972136,40572121) 高等学校博士学科点专项科研基金资助项目(编号:20110205110004) 中央高校基本科研业务专项基金资助项目(编号:CHD2011TD020,2013G1271092,2013G1271091)的成果~~
【分类号】：P548;P588.14
【参考文献】
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1 徐通;裴先治;刘成军;陈有p，
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