| 扬子东南缘两界河组碎屑锆石U-Pb年龄及其对Sturtian冰川作用的启示 |
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| 引用本文： | 高永娟,张予杰,安显银,刘石磊,郑杰,桑永恒.扬子东南缘两界河组碎屑锆石U-Pb年龄及其对Sturtian冰川作用的启示[J].地球科学,2020,45(8):3070-3081. |
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| 作者姓名： | 高永娟 张予杰 安显银 刘石磊 郑杰 桑永恒 |
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| 作者单位： | 1.中国地质调查局成都地质调查中心, 四川成都 610081 |
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| 基金项目： | 国家自然科学基金项目41503025国家自然科学基金项目41802137中国地质调查局项目DD20190054中国地质调查局项目DD20160018中石油西南油气田分公司项目XNS14JS2018-076 |
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| 摘 要： | 扬子东南缘两界河组的岩性以岩屑砂岩和石英砂岩为主，代表了长安冰期和古城冰期之间的间冰期沉积，其沉积时限的厘定对认识华南Sturtian冰期地层的时空分布特征具有重要意义.对黔东地区两界河组碎屑锆石进行了系统的形态学和U-Pb年代学研究，大多数锆石为典型的岩浆锆石，锆石U-Pb年龄主要分布于740~900 Ma，另有少量古元古代和太古宙年龄，主要峰值为~760 Ma、~780 Ma、~800 Ma、~820 Ma和880~900 Ma.在两界河组底部获得最年轻的单颗粒锆石年龄为708±15 Ma，在上部获得最年轻的单颗粒锆石年龄为703±22 Ma，结合区域上相当地层渫水河组的顶部年龄（~690 Ma），认为黔东地区两界河组的沉积时代应在708~690 Ma之间.两界河组碎屑锆石U-Pb年龄谱记录了扬子陆块新元古代幕式岩浆事件及早期地壳演化的信息，结合锆石形态认为其物质来源可能包括下伏新元古代岩浆岩及沉积地层、扬子西北缘和西南缘的基底岩石.研究区两界河组底部碎屑锆石年龄约束了江口间冰期沉积晚于~708 Ma，考虑到南华纪早期地层分布在一定程度上受控于盆地构造活动，不排除长安冰期沉积物在黔东地区局部存在的可能性.
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| 关 键 词： | 扬子陆块 两界河组 碎屑锆石 江口冰期 间冰期 地质年代学 |
| 收稿时间： | 2020-03-23 |
Detrital Zircon U-Pb Ages of Liangjiehe Formation in East Guizhou Province and Its Implications for Sturtian Glaciation |
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| Abstract: | The Liangjiehe Formation is the interglacial stratum between Chang'an and Gucheng glaciations in the southeastern Yangtze Block, and the lithology is dominated by detrital sandstone and quartz sandstone. For a better understanding of the temporal and spatial distribution of the Sturtian glacigenic strata in South China, it is important to determine the depositional age of the Liangjiehe Formation. In this study, systematical morphology and zircon U-Pb dating were carried out on detrital zircons from the Liangjiehe Formation in the eastern Guizhou. Most of the detrital zircons are of magmatic origin, and have a main 206Pb/238U age range of 740-900 Ma and minor populations of Paleoproterozoic-Archean ages, with peaks at~760 Ma, ~780 Ma, ~800 Ma, ~820 Ma and 880-900 Ma. The youngest single-grain zircon obtained at the bottom of the Liangjiehe Formation gives the age of 708±15 Ma, and the youngest single-grain zircon from the upper part gives the age of 703±22 Ma. Taking into account the topmost age~690 Ma of the contemporary stratum (Xieshuihe Formation), it is suggested that the Liangjiehe Formation was most likely deposited at 708-690 Ma. The detrital zircon U-Pb age spectrum of the Liangjiehe Formation records the Neoproterozoic episodic tectonic-magmatic events and the information for the early crustal evolution of Yangtze Block. The zircon morphology indicates that the provenances of the Liangjiehe Formation may include the underlying Neoproterozoic magmatic and sedimentary strata, and the basement rocks from the northwestern and southwestern Yangtze Block. The detrital zircon U-Pb dating at the bottom of the Liangjiehe Formation constrained the interglacial deposition later than~708 Ma. Considering that the stratigraphic distribution in the early Nanhua period is partly controlled by basin tectonic activities, the Chang'an glacial deposit may exist locally in eastern Guizhou. |
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