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勉略构造带新元古代洋盆俯冲作用:来自略阳地区纸房沟岩片火山岩锆石U-Pb年龄和Lu-Hf同位素的证据
投稿时间:2019-11-02  修订日期:2019-12-26  点此下载全文
引用本文:
DOI:10.19762/j.cnki.dizhixuebao.2020049
摘要点击次数: 73
全文下载次数: 71
作者单位E-mail
徐通 陕西省地质调查院 xutong1988819@163.com 
张晓团 陕西省地质调查院  
焦建刚 长安大学地球科学与资源学院  
张红强 陕西省地质调查院  
贾力 长安大学地球科学与资源学院  
基金项目:陕西省自然科学基础研究计划项目(2018JQ4030)和陕西省公益性地质调查科研类项目(201906)
中文摘要:纸房沟岩片位于勉略构造带略阳地区。通过细致的岩石学和地球化学研究,将纸房沟岩片内的火山岩分为拉斑玄武岩系列(Ⅰ类)和钙碱性火山岩系列(Ⅱ类)。Ⅰ类火山岩稀土配分曲线左倾,富Na贫P,整体具有N-MORB特点,形成于洋脊构造环境。相比Ⅰ类火山岩,Ⅱ类火山岩具有更高的SiO2(49.02%~61.86%)和K2O(0.32%~1.55%)含量,相对亏损Nb、Ta、P和Ti,形成于陆缘弧构造环境。Ⅱ类火山岩锆石Lu-Hf同位素测试结果显示,εHf(t)值主体为负值,介于-8.01~+0.77,表明其主要为古老地壳物质熔融成因。Ⅱ类火山岩LA-ICP-MS锆石U-Pb测年结果为854±3Ma(MSWD=0.12, n=30)、844±4Ma (MSWD=0.03, n=15),表明纸房沟岩片火山岩结晶时代为新元古代早中期。综合前人成果认为,纸房沟岩片火山岩为新元古代勉略洋盆俯冲的产物,俯冲作用一直持续到800Ma左右,该俯冲过程很可能是对全球性Rodinia超大陆聚合时间的响应。
中文关键词:勉略构造带  纸房沟岩片  火山岩  新元古代  南秦岭南缘  Rodinia超大陆
 
The subduction of Neoproterozoic ocean in Mianlue tectonic zone: Evidence of zircon U-Pb age and Lu-Hf isotopes from volcanic rocks in Zhifanggou tectonic slice, Lueyang area
Author NameAffiliationE-mail
xutong Shaanxi Institute of Geological Survey xutong1988819@163.com 
zhang xiaotuan Shaanxi Institute of Geological Survey  
jiao jiangang School of Earth Science and Resources, Chang’an University  
zhang hongqiang Shaanxi Institute of Geological Survey  
jia li School of Earth Science and Resources, Chang’an University  
Abstract:Zhifanggou tectonic slice is located in Mianlue tectonic zone, Lueyang area. On the basis of detailed petrological and geochemical studies, we identify that the main rock types in the Zhifanggou tectonic slice are a combination of tholeiite (type Ⅰ) and calc-alkaline volcanic rocks(type Ⅱ). Type Ⅰ volcanic rocks possess the features of normal mid-ocean ridge basalt on the whole, such as left-leaning REE patterns, Na-rich, and P-poor, indicating that they were generated in mid-ocean ridge setting. Type Ⅱ volcanic rocks have higher SiO2(49.02%~61.86%) and K2O(0.32%~1.55%) concentrations than type Ⅰ, negative anomaly of Nb, Ta, P, Ti, suggesting generation in a continental marginal arc setting. The zircon Lu-Hf isotopic composition show that the zircon εHf(t) of type Ⅱ volcanic rocks ranges from -8.01 to +0.77 , suggesting that these melts were derived from old continental crust material. The LA-ICP-MS zircon U-Pb age determined using laser ablation–inductively coupled plasma–mass spectrometry from Type Ⅱ volcanic rocks is 854±3Ma(MSWD=0.12, n=30) and 844±4Ma (MSWD=0.03, n=15), indicating the crystallized age of the volcanic rocks from Zhifanggou tectonic slice in Middle Neoproterozoic. The volcanic rocks from Zhifanggou tectonic slice are considered as the product of subduction of Neoproterozoic Mianlue Ocean, and the subduction did not quit until about ~800Ma. This process was likely to be response to the amalgamation of Rodinia supercontinent.
keywords:Mianlue tectonic zone  Zhifanggou tectonic slice  volcanic rocks  Neoproterozoic  southern margin of the South Qinling Orogen  Rodinia Supercontinent
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