| 贺兰山地区中奥陶统樱桃沟组物源及构造背景分析 |
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| 引用本文： | 王振涛,周洪瑞,王训练,景秀春.贺兰山地区中奥陶统樱桃沟组物源及构造背景分析[J].沉积学报,2014,32(2):205-217. |
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| 作者姓名： | 王振涛 周洪瑞 王训练 景秀春 |
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| 作者单位： | 中国地质大学(北京)地球科学与资源学院; |
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| 基金项目： | 国家重点基础研究发展计划(973计划)项目(编号:2011CB403001)资助 |
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| 摘 要： | 鄂尔多斯盆地西缘贺兰山地区的樱桃沟组发育一套夹有碳酸盐滑塌重力流沉积的陆源碎屑岩。由于缺少可靠的物源数据，对早古生代鄂尔多斯盆地西缘的构造背景尚未有定论。本文对樱桃沟组碎屑岩进行了地球化学及岩石学分析，砂岩碎屑组分特征表明，该组源区大地构造背景为再旋回造山带。常量元素和微量元素地球化学特征表明樱桃沟组的物源呈现双物源的特点。更进一步，樱桃沟组的稀土元素配分模式对比表明了樱桃沟组碎屑岩的物源来自阿拉善古陆和/或北祁连造山带。综合分析砂岩的常量元素、微量元素和稀土元素的地球化学特征，经构造判别图解，认为樱桃沟组物源区主要为主动大陆边缘，也有来自被动大陆边缘的信息，表明贺兰山地区业已受到北祁连早古生代造山带的影响。樱桃沟组与研究区周缘造山带稀土元素配分模式对比研究显示，前者与其北西部阿拉善古陆和南西部北祁早古生代连造山带花岗岩露头稀土元素配分模式一致，均表现为轻稀土富集，重稀土亏损的右倾模式，具有轻微的Eu负异常和明显的Tm负异常，结合中奥陶世鄂尔多斯西缘古水流和碎屑锆石年龄分布特征，认为樱桃沟组的物源主要来自祁连造山带，部分来自阿拉善古陆。
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| 关 键 词： | 鄂尔多斯盆地 贺兰山地区 樱桃沟组 构造背景 物源 |
Provenance and Tectonic Settings Analysis of Yingtaogou Formation of Middle Ordovician in Helan Mountain Area |
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| Abstract: | Yingtaogou Formation in the Helan Mountain area, located in the western margin of Ordos basin, consists of a set of terrigenous detrital rocks, with carbonate slump gravity flow deposits. The Early Paleozoic tectonic setting of Ordos basin is still in debate due to the lack of reliable material source data. In this paper, the petrologic and geochemical characteristics have been researched systematically. The characteristics of debris composition of sandstone show that Yingtaogou Formation comes from recycling orogeny area. The geochemical signatures of major and trace elements of sandstone from Yingtaogou Formation indicate its double provenance supply feature. More specifically, comparison study on REE distribution patterns shows clastic rocks from Yingtaogou Formation derive from Alashan and/or North Qilian orogenic belt. The geochemical signatures of major and trace elements and REEs, in Combination with the discrimination diagrams for tectonic settings have mirrored that the study area when Yingtaogou Formation deposited was surrounded by the active and passive continental margin, which means it is affected by both Helan aulacogen and North Qilian Early Paleozoic orogenic belt. REE patterns between Yingtaogou Formation and its adjacent areas display the former is in accordance with Alashan paleolandmass to the northwest and granite from North Qilian Early Paleozoic orogenic belt, and the REE distribution pattern show they are rich in LREE and lack of HREE and exhibit slightly Eu anomalies and marked negative Tm anomalies. After comprehensive consideration of the middle Ordovician palaeocurrents in the western Ordos and detrital zircon age features, this paper suggests that the provenance of Yingtaogou Formation was mainly the North Qilian orogenic belt and the Alashan paleolandmass as a minor one. |
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