下扬子砂岩物源分析提供东南沿海晚古生代大陆弧新证据

发布时间：2018-05-08 09:54

本文选题：物源分析 + 砂岩岩石学　；参考：《科学通报》2017年25期

【摘要】：运用碎屑组分统计、锆石U-Pb年代学、锆石Hf同位素分析等方法,对下扬子巢湖-南京地区古生代碎屑岩进行沉积岩石学和物源分析.下扬子地区志留系坟头组砂岩为长石石英砂岩,岩屑以火成岩岩屑和低级变质岩岩屑为主;泥盆系五通组砂岩为石英砂岩,岩屑含量少,以变石英岩岩屑为主.五通组和坟头组具有相似的碎屑锆石年龄分布模式,主峰为465~420和838~812 Ma,表明泥盆纪沉积继承了志留纪沉积的物源特征.早古生代下扬子巢湖-南京地区的碎屑来自其南侧的华夏地块武夷地体.巢湖-南京地区二叠系龙潭组砂岩分别为岩屑石英砂岩和长石石英砂岩,成熟度低,岩屑均以中酸性喷出岩岩屑为主,巢湖地区龙潭组具有指示武夷地体古元古代基底的1866 Ma峰值年龄,南京地区龙潭组具有与早古生代砂岩相似的445和970 Ma峰值年龄.结合前人岩相古地理和地球物理资料,认为下扬子地区龙潭组物源区仍位于南侧的华夏地块武夷地体.此外,下扬子地区龙潭组具有341~254 Ma(石炭纪-二叠纪)碎屑锆石,其e_(Hf)(t)值分布在-19.80~+14.90之间,代表碎屑物源区一次新的岩浆事件,该事件具有影响范围大、活动持续频繁、中酸性火成岩为主、岩浆来自古老地壳与新生地壳混合熔融等特征.结合区域地质资料,推测华南板块武夷地体在石炭纪-二叠纪(341~254 Ma)的构造背景为大陆弧.
[Abstract]:By means of clastic component statistics, zircon U-Pb chronology, zircon HF isotope analysis, sedimentary petrology and provenance analysis of Paleozoic clastic rocks in Chaohu-Nanjing area of Lower Yangtze were carried out. The sandstone of Silurian Cemetery formation in Lower Yangtze area is feldspar quartz sandstone with igneous lithic and low grade metamorphic lithic lithology, and Devonian Wutong sandstone is quartz sandstone with less lithic content and metamorphic quartzite lithology. The Wutong formation and the Cemetery formation have a similar age distribution pattern of detrital zircon, the main peaks of which are 465 ~ 420 and 838 ~ 812 Ma, indicating that the Devonian sedimentary inherited the characteristics of Silurian sedimentary provenance. The detritus of the Lower Yangtze Chaohu-Nanjing area in the early Paleozoic came from the Wuyi terrane of the Huaxia block in the south of the area. The sandstone of Longtan formation of Permian in Chaohu-Nanjing area is lithic quartz sandstone and feldspar quartz sandstone respectively. The Longtan formation in Chaohu area has a peak age of 1866 Ma indicating the ancient basement of Wuyi terrane Gu Yuan, and the Longtan formation in Nanjing area has a peak age of 445 Ma and 970 Ma similar to that of the early Paleozoic sandstone. Based on previous lithofacies paleogeography and geophysical data, it is considered that the source region of the Longtan formation in the Lower Yangtze area is still located in the Wuyi terrane of the Huaxia block in the south. In addition, the Longtan formation in the Lower Yangzi area has 341Li 254Ma (Carboniferous Permian) detrital zircon, and its EW value is between -19.80 ~ 14.90, which represents a new magmatic event in the source region of the clastic material, which has a wide range of influence and frequent activity. The intermediate-acid igneous rocks are mainly derived from the mixing and melting of the ancient crust and the new crust. Based on the regional geological data, it is inferred that the tectonic setting of Wuyi terrane in the Carboniferous and Permian period is continental arc.
【作者单位】：南京大学地球科学与工程学院内生金属矿床成矿机制研究国家重点实验室;
【基金】：国家杰出青年科学基金(41525007) 国家自然科学基金(41272085)资助
【分类号】：P534.4;P588.21

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