方维萱, 郑小明, 方同辉, 倪杰才, 郭玉乾, 李建旭. 甘肃红石山地区泥盆纪—石炭纪有限洋盆重建与蛇绿混杂岩深部结构[J]. 地质通报, 2021, 40(5): 649-673.
    引用本文: 方维萱, 郑小明, 方同辉, 倪杰才, 郭玉乾, 李建旭. 甘肃红石山地区泥盆纪—石炭纪有限洋盆重建与蛇绿混杂岩深部结构[J]. 地质通报, 2021, 40(5): 649-673.
    FANG Weixuan, ZHENG Xiaoming, FANG Tonghui, NI Jiecai, GUO Yuqian, LI Jianxu. Restoration of the Devonian-Carboniferous limited ocean basin and deep structure of ophiolitic melange in the Hongshishan area of Gansu Province[J]. Geological Bulletin of China, 2021, 40(5): 649-673.
    Citation: FANG Weixuan, ZHENG Xiaoming, FANG Tonghui, NI Jiecai, GUO Yuqian, LI Jianxu. Restoration of the Devonian-Carboniferous limited ocean basin and deep structure of ophiolitic melange in the Hongshishan area of Gansu Province[J]. Geological Bulletin of China, 2021, 40(5): 649-673.

    甘肃红石山地区泥盆纪—石炭纪有限洋盆重建与蛇绿混杂岩深部结构

    Restoration of the Devonian-Carboniferous limited ocean basin and deep structure of ophiolitic melange in the Hongshishan area of Gansu Province

    • 摘要: 采用构造岩相学和构造-古地理单元恢复、AMT、地面高精度磁法等综合方法,对甘肃红石山和邻区泥盆纪—石炭纪有限洋盆进行重建,对红石山蛇绿混杂岩带进行构造岩相学解剖和深部探测。划分出5个构造层,前华里西期、华里西期、印支期、燕山期和喜山期。北部构造带为四顶黑山-雀儿山晚古生代岩浆弧相,中部构造带红石山蛇绿混杂岩带恢复为泥盆纪—石炭纪有限洋盆相+洋壳残片相,南部构造带为白山-狼娃山晚古生代岛弧相。蛇绿岩套从下到上的垂向单元为晚泥盆世—早石炭世变质超镁铁杂岩→堆晶超镁铁-镁铁岩→均质辉长岩和少量的辉绿岩墙→早石炭世扫子山期深水相硅质岩和含炭硅质细碎屑岩(有限洋盆相)。陆缘海相岛弧地体南北两侧为早石炭世扫子山期和白山期浅海相火山岛弧带。哈萨克斯坦板块南缘南向俯冲碰撞在敦煌地块北缘增生楔构造背景下,形成SSZ型蛇绿岩套。红石山构造-蛇绿混杂岩带与周缘地质体具有不同的构造岩相学边界,从北向南具有明显的4个构造岩相学水平分带,中心部位为超基性岩构造岩块单元,以糜棱岩相辉长岩和蛇纹石片岩为包络面的构造岩片(基质单元),蛇绿混杂岩带总体为无根状大型透镜体。红石山构造-蛇绿混杂岩带将两侧地质体卷入混杂岩带内,这种复杂镶嵌结构的构造岩相体有利于形成大型-超大型斑岩型金铜钼矿床、浅成低温热液金矿床和造山型金矿床。

       

      Abstract: Based on the comprehensive studies of tectonic lithofacies, restorations of tectonic paleogeographic units, AMT, and high-precision ground magnetic survey, the Devonian-Carboniferous limited ocean basin in the Hongshishan area of Gansu province was reconstructed.Furthermore, the depth structures of ophiolitic melange were detected by the means of AMT and tectonic lithofacies.It is classified into five tectospheres, namely, Pre-Variscan tectosphere, Variscan tectosphere, Indosinian tectosphere, Yanshanian tectosphere and Himalayan tectosphere.The northern tectonic belt is the Siding Heishan-Quershan Late Paleozoic magmatic arc facies, the central tectonic belt is the Hongshishan ophiolite melange belt which is restored to the Devonian-Carboniferous limited oceanic basin facies + oceanic crust remnant facies, and the southern tectonic belt is the Baishan-Langwashan Late Paleozoic island arc facies.The Hongshishan ophiolitic units from the lower to the top are the Devonian-Carniferous metamorphized ultramafic complex→cumulate ultramafic to mafic complex→homogeneize gabbro and diabase dikes→cherts and carbonic fine-clastic rocks formed from the deep water environment in the Early Carniferous Saozishan period(the limited oceanic facies).The north and south sides of the continental margin marine island arc terrain are Early Carboniferous Saozishanian and Baishanian shallow marine volcanic island arc belts.As a result of southward subduction of the Kazakhstan plate, the Hongshishan SSZ-type ophiolitic melange might be formed on the accretionary wedge on the northern margin of the Dunhuang terrain.Hongshishan ophiolitic melange belt and its peripheral terrain are defined by different tectonic petrography boundaries, which obviously show four tectonic petrography zones from north to south.The center is ultramafic rocks characterized by gabbro and serpentine schist mylonite.The ophiolite melange belt is generally a large rootless lens.The Hongshishan tectonic-ophiolite melangite belt involved the geological terrains on its both sides to form a complex mosaic structural lithofacies conducive to the formation of large-super-large porphyry Au, Cu, Mo deposits, epithermal gold deposits and orogenic gold deposits.

       

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