| 南岭东段龙头寨群南迳组的建立及其地质时代厘定 |
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| 引用本文： | 丁辉,巫建华,劳玉军,刘帅.南岭东段龙头寨群南迳组的建立及其地质时代厘定[J].地质通报,2017,36(9):1645-1655. |
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| 作者姓名： | 丁辉 巫建华 劳玉军 刘帅 |
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| 作者单位： | 1. 东华理工大学地球科学学院, 江西 南昌 330013;2. 东华理工大学核资源与环境国家重点实验室培育基地, 江西 南昌 330013 |
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| 基金项目： | 国家自然科学基金项目《赣南-粤北相邻区河口-南迳加里东期火山岩研究与铀成矿关系》（批准号：41662006）和中国核工业集团公司项目《中国中—新生代铀成矿作用研究》（编号：中核地计［2008］74号） |
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| 摘 要： | 南岭带东段晚奥陶世广泛发育一套浅变质岩系,称为龙头寨群。以南迳乔子山剖面和中寨剖面为层型剖面建立南迳组,并置于龙头寨群顶部。用SHRIMP法测得南迳盆地南迳组安山岩样品14个锆石U-Pb年龄数据,其~(206)Pb/~(238)U年龄变化范围为460~425Ma,年龄加权平均值为442.1±3.9Ma(MSWD=0.75);英安岩15个锆石~(206)Pb/~(238)U年龄变化范围为450~420Ma,年龄加权平均值为439.9±3.7Ma(MSWD=0.50)。结合司前河口破火山口碎斑熔岩的SHRIMP锆石U-Pb年龄(443.6±5.4Ma(MSWD=1.3)),可将南迳组的地质时代归于晚奥陶世末期—早志留世初期。龙头寨群南迳组的建立和地质时代的厘定,不仅为龙头寨群的地质时代归入晚奥陶世—早志留世初期提供了可靠的依据,而且为南岭带东段晚奥陶世—早志留世浅变质岩系属含有火山岩的优地槽型沉积提供了证据。
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| 关 键 词： | 火山岩 SHRIMP锆石U-Pb年龄 晚奥陶世晚期-早志留世初期 南迳组 龙头寨群 |
| 修稿时间： | 2017/2/14 0:00:00 |
The establishment of the Nanjing Formation in Longtouzhai Group in eastern Nanling Re-gion and the determination of its age |
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| DING Hui,WU Jianhu,LAO Yujun and LIU Shuai.The establishment of the Nanjing Formation in Longtouzhai Group in eastern Nanling Re-gion and the determination of its age[J].Geologcal Bulletin OF China,2017,36(9):1645-1655. |
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| Authors: | DING Hui WU Jianhu LAO Yujun and LIU Shuai |
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| Institution: | 1. Collage of Earth Science, East China Institute of Technology, Nanchang 330013, Jiangxi, China;2. State Key Laboratory Breeding Base of Nuclear Resources and Environment, East China Institute of Technology, Nanchang 330013, Ji-angxi, China |
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| Abstract: | The epimetamorphic rock series well developed in eastern Nanling Region is a suite of Late Ordovician epimetamorphic rock series called Longtouzhai Group that consists of dark gray, gray, celadon fine grained feldspar quartz sandstone, sericite slates, silty slate and phyllites intercalated with lenticular carbonate and sandstone. They can be subdivided upwards into Bankeng Formation, Guting Formation and Huangzhudong Formation. It is found that the original Late Jurassic Yutian Group is a suite of dark gray andes-ite, light grey dacite, porphyroclastic lava intercalated with gray dacitic tuff, volcanic brecciated tuff, celadon fine grained feldspar quartz sandstone, sericite slates, silty slate, phyllites in Siqian, Shixing (northern Guangdong) and Nanjing, Quannan (southern Jiangxi) areas. It is in conformable contact with the Huangzhudong Formation and is underlain unconformably by Middle Devonian Yunshan Formation. The volcanic rock association in the Nanjing basin is developed considerably well and the boundaries between the roof and the bottom are clearly distinguishable. The Nanjing Formation is established based on the Qiaozishan section and Zhongzhai sec-tion, and the Zhongzhai section serves as its stratotype section. The results of the SHRIMP zircon U-Pb dating indicate that the 206Pb/238U age range of fourteen analytical points of the rhyolite is 460~425Ma with the weighted average of 442.1 ±3.9Ma and MSWD of 0.75; the analytical points of the fifteen rhyolite porphyry samples show ages of 450~425 Ma with the weighted average of 439.9±3.7Ma and MSWD of 0.50. In combination with the zircon U-Pb age of 443.6±5.4Ma (MSWD=1.3) for porphyroclastic la-va in the Hekou (Siqian) caldera SHRIMP, the Nanjing Formation should belong to the Latest Ordovician-Early Silurian. The estab-lishment of the Nanjing Formation in Longtouzhai Group in eastern Nanling Region and the determination of its age not only pro-vide the basis for the argument that Longtouzhai Group belongs to the Late Ordovician-Early Silurian, but also offer the evidence for the opinion that the epimetamorphicd rock series of Late Ordovician-Early Silurian include volcanic miogeosynclinal type sediments in eastern Nanling Region |
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| Keywords: | volcanic rock SHRIMP zircon U-Pb age Late Ordovician-Early Silurian Nanjing Formation Longtouzhai Group |
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