黔东松桃地区大塘坡组LA-ICP-MS 锆石U-Pb年龄及其地质意义
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本文为中国地质调查局 “上扬子地块东南缘锰矿成矿地质背景研究”(编号: 12120114016701)和国土资源部公益性行业科研专项经费“上扬子地块东南缘锰矿国家级整装勘查区成矿系统与深部找矿关键技术研究及示范”(编号:201411051) 的成果。


LA-ICP-MS Zircon U-Pb Dating from the Nanhuan Datangpo Formation in Songtao Area, East Guizhou and Its Geological Significance
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    摘要:

    南华裂谷盆地在南华纪出现地垒区与地堑区的明显沉积分异。在对黔东松桃地区将军山剖面南华系地层进行实测的基础上,与地堑区南华系地层进行了对比。发现地垒区与地堑区的沉积分异主要表现在铁丝坳组与大塘坡组的岩性与厚度变化上。在此基础之上,对将军山剖面大塘坡组底部凝灰层进行LA-ICP-MS锆石U-Pb年代学研究,得到年龄值为664.2±2.4 Ma。通过该年龄与前人在地堑区所获得的对应地层年龄进行对比,可将南华裂谷盆地地垒区Sturtian冰期结束时间限定在不晚于663~667 Ma范围内,这证明Sturtian冰期消退事件在黔东地区范围内具有等时性,整个Sturtian—Marinoan间冰期持续时间约为10 Ma。与此同时,通过与世界范围内各古板块上Sturtian冰后期沉积的最新定年结果进行对比工作,得出全球Sturtian冰期结束时间同样具有等时性的结论。

    Abstract:

    A remarkable sedimentary differentiation arises in the horst and graben areas within the Nanhua Rift Basin during Nanhuan. Based on the detailed fieldwork on the Nanhuan sequences in the Jiangjunshan Profile, Songtao Area, East Guizhou Province, South China, a stratigraphic correlation is carried out with the Nanhuan Sequences in the graben and horst areas in the Nanhua Basin. The sedimentary differentiation is showed in the lithological and thickness changes of the Tiesiao Formation and the first Member in the Datangpo Formation. In the graben area, the Tiesiao Formation is composed of the glacial—marine diamictites and sandstone with the thickness of ~10m, the 1st Member of the Datangpo Formation is composed of 0.5 to 15 m massive Mn carbonate (rhodochrosite) interbedded with Mn bearing shale. In the horst area, the thickness of the Tiesiao Formation decreases to several meters and its lithology changes to glacial—marine diamictites and carbonates, the Mn rich deposit vanishes. LA ICP MS zircon U Pb dating results from the tuff layer at the bottom of the Datangpo Formation gives an age of 664.2±2.4 Ma which constrains of the Sturtian Glaciation ending time in the Nanhua Basin horst area. Compared with the ages from the sedimentary sequences in the garben area, we can constrain the ending time of the Sturtian Glaciation to 663~667 Ma. This result proves that the ending time of the Sturtian Glaciation in East Guizhou Province is synchronic. Meanwhile, according to the latest geochronological data collected world widely, we find that the Sturtian Glaciation in global scale is also synchronic

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余文超,杜远生,周琦,王萍,袁良军,徐源,潘文,谢小峰,齐靓,焦良轩.2016.黔东松桃地区大塘坡组LA-ICP-MS 锆石U-Pb年龄及其地质意义[J].地质论评,62(3):539-549,[DOI].
YU Wenchao, DU Yuansheng, ZHOU Qi, WANG Ping, YUAN Liangjun, XU Yuan, PAN Wen, XIE Xiaofeng, QI Liang, JIAO Liangxuan.2016. LA-ICP-MS Zircon U-Pb Dating from the Nanhuan Datangpo Formation in Songtao Area, East Guizhou and Its Geological Significance[J]. Geological Review,62(3):539-549.

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  • 收稿日期:2015-07-30
  • 最后修改日期:2016-03-23
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  • 在线发布日期: 2016-05-19
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