地学前缘 ›› 2018, Vol. 25 ›› Issue (4): 86-98.DOI: 10.13745/j.esf.yx.2017-12-19

• 岩（矿）石、地层特征及地质意义 • 上一篇    下一篇

湘赣中、上奥陶统烟溪组、对耳石组硅质岩成因

郑宁，李廷栋，程木伟   

  1. 1. 中国地质科学院 地质研究所, 北京 100037
    2. 中国石油勘探开发研究院 亚太研究所, 北京 100083
  • 收稿日期:2017-09-11 修回日期:2017-10-19 出版日期:2018-07-15 发布日期:2018-07-15
  • 作者简介:国家自然科学青年科学基金项目(41402100)；中国地质调查局全国地质构造区划与区域地质调查综合集成项目及子项目(DD20160345，1212011120117，121201102000150012-32)；中国地质调查局中东亚跨境成矿带对比与综合编图项目(DD20160102)

Origin of siliceous rocks in the MiddleUpper Ordovician Yanxi Formation, Hunan Province and Duiershi Formation, Jiangxi Province in South China.

ZHENG Ning,LI Tingdong,CHENG Muwei   

  1. 1. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China
    2. AsiaPacific Department, PetroChina Research Institute of Petroleum Exploration ＆ Development, Beijing 100083, China
  • Received:2017-09-11 Revised:2017-10-19 Online:2018-07-15 Published:2018-07-15

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摘要： 华南地区中—上奥陶统浅海半深海环境中广泛发育了一套高硅岩石，主要分布于湖南烟溪组和江西对耳石组。该套硅质岩呈东西条带状发育于扬子板块与华夏板块之间，地层厚度从东南到西北逐渐减薄，岩层多呈薄层状，含放射虫Protoentactinia sp.，部分岩样放射虫含量超过50%。分析结果表明，生物Si和陆源Si为本区硅质岩Si的重要来源，生物化学成因特征明显。硅质岩Al/(Al+Fe+Mn)比值＞0.45，K2O/Na2O比值范围为1.55~42.11，由微量元素Ni、V、B、Cr与Al2O3关系图来看，二者关系表现为部分线性、部分离散，U/Th比值为0.72。湘赣中部地区硅质岩中稀土元素含量偏高，东南部Ce元素略呈负异常，研究区∑LREE≈∑HREE，表明衡阳到赣州一带受一定火山、热水活动的影响。

关键词: 湘赣, 奥陶系, 放射虫, 硅质岩, 地球化学

Abstract: High siliceous rocks are extensively developed in the neriticbathyal environment of South China during the MiddleUpper Ordovician. These rocks are mainly distributed throughout the Yanxi and Duiershi Formations in Hunan and Jiangxi provinces, respectively, generally between the Yangtze and Cathaysian Plates in the EW strip. The stratum thickness gradually decreases from SE to NW, and the layers are mostly thin. Radiolarian Protoentactinia sp. is found in the rocks, sometimes more than 50% in sample content. Analysis results showed that biological and terrigenous Si is the main silicon source—a clear indication of rocks biochemical origin. It was found that the Al/(Al+Fe+Mn) ratio is greater than 0.45, and K2O/Na2O ratio ranges between 1.55 and 42.11. The Al2O3Ni, V, B, Cr diagram showed both discrete and linear relationships and a U/Th ratio of 0.72. Lastly, our study revealed that REE contents in central Hunan and Jiangxi provinces are relatively high, while element Ce in chert in the southeast area showed slightly negative anomaly. In the research area, ∑LREE≈∑HREE, this suggests that the areas from Hengyang to Ganzhou are affected by volcanic and hydrothermal activities.

Key words: Hunan and Jiangxi provinces, Ordovician, Radiolarian, siliceous rock, geochemistry

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