摘要
对滇中元江地区调查研究发现一套以钙质浊积岩-碎屑浊积岩组合为特征的岩石序列。测制的剖面由2个钙质浊积岩-碎屑浊积岩旋回组成,发育大量不完整的鲍马序列组合及粒序层理、斜层理、包卷层理、槽模构造、透镜状构造等典型浊积沉积构造,且岩石成熟度及分选度都较低。上部还发育一套凝灰质球粒石英岩,粒序层理发育,在其中获得了LA-ICP-MS锆石U-Pb年龄1102±76Ma和1713±48Ma(YJgzn-03),具有明显铅丢失现象;对侵入地层中的石英正长斑岩进行年代学研究,获得了LA-ICP-MS锆石U-Pb年龄349±13Ma和1732±13Ma(YJgzn-02),上部未发生明显铅丢失的平均年龄为1718±30Ma,应为成岩期年龄。两者的锆石都具环带结构,Th/U值都大于0.4,都明显发生了铅丢失,且形成时代相近,应为同期岩浆作用的结果。推测该套地层沉积或受到后期热蚀变年龄为1713±48～1718±30Ma,其沉积年龄应早于古元古代晚期。对比区域昆阳群及前人划分的古元古代地层,认为这套地层下伏于昆阳群之下,应属于早于古元古代晚期(1.7Ga)的碳酸盐前缘-陆棚斜坡浊积岩体系,建议依据地名定义为古元古代"曼林组"(Pt1m)。
In this study, the authors identified a sedimentary sequence of calcareous- clastic turbidites through geological survey in Yuanjiang Couuty of central Yunnan Province. The sedimentary sequence section consists of two calcareous-clastic turbidite forms, and contains a series of sedimentary tectonics, such as Boma sequence, graded bedding, oblique bedding, slump structures and flute marks. These sedimentary rocks show low maturity and sorting under the microscope. At the upper section, there exists about a tufted globular quartzite bed 4m in thickness, whose LA-ICP-MS zircon U-Pb ages are 1102±76Ma and 1713±48Ma（YJgzn-03）, and the zircon exhibits the loss of common Pb ; another sample of quartz-orthophyre that intruded into the turbidite bed has the LA- ICP-MS zircon U-Pb ages 349±13Ma and1732±13Ma（YJgzn-02）, and the sample without loss of common Pb has the mean age of 1718±30Ma, which could be regarded as the intrusive age of quartz-orthophyre. All of the zircons in the two samples that show the same ages are marked by girdle structure in CL images and Th/U 〉 0.4, characterized by loss of common Pb. According to the zircon ages of tuff and intrusive rocks （quartz-orthophyre）, the turbidite bed might have been deposited earlier than 1713±48-1718± 30Ma. Based on correlation with the Proterozoic sedimentary beds and Kunyang Group, the authors hold that the sedimentary sequence of calcareous-clastic turbidite the authors studied in this paper should be formed earlier than Kunyang Group, being products of Proterozoic form or even earlier. The authors suggest that it should be named Proterozoic ＂Manlin Formation＂ because it is near Manlin Village in Yuanjiang County.
作者
刘桂春
李静
胡绍斌
邓仁宏
刘发刚
陈光艳
冯庆来
徐桂香
LIU Guichun;LI Jing;HU Shaobin;DENG Renhong;LIU Fagang;CHEN Guangyan;FENG Qinglai;XU Guixiang(Yunnan Institute of Geological Survey,Kunming 650216,Yunnan,China;Key Laboratory of Sanjiang Metallogeny and Resources Exploration and Utilization,Ministry of Natural Resources,Kunming 650061,Yunnan,China;State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan 430074,Hubei,China)
出处
《地质通报》
CAS
CSCD
北大核心
2018年第11期2007-2014,共8页
Geological Bulletin of China
基金
中国地质调查局项目<云南区域地质调查片区总结与服务产品开发>(编号:DD20160345-02)
<云南1:5万二街
易门
鸣矣河
上浦贝幅区域地质调查>(编号:DD20160017)
国家自然科学基金项目<滇西南原题特斯及其与古特提斯演化关系研究>(批准号:41672222)
云南省科技领军人才培养计划项目<西南"三江"叠合成矿作用与成矿预测>(编号:2013HA001)
关键词
古元古代
浊积岩
沉积特征
沉积时代
滇中元江
Early Proterozoic
turbidite
sedimentary characteristics
deposition period
Yuanjiang County of central Yunnan Province
