扬子地块西、北缘中元古代地层的划分与对比

发布时间：2018-04-14 03:25

本文选题：中元古代早期 + 中元古代晚期　；参考：《地质学报》2017年10期

【摘要】：广泛分布于扬子地块西缘和北缘的中元古代地层经历了强烈的变形和绿片岩相的变质改造。根据形成时代,该区的中元古代可以识别出两个阶段,中元古代早期(1.8~1.4Ga)和中元古代晚期(1.4~1.0Ga)。中元古代早期的地层包括大红山群、东川群、河口群和通安组(1~4段),中元古代晚期的地层主要由分布在扬子地块西南缘的昆阳群、会理群和分布于扬子地块北缘的神农架群和打鼓石群组成。新的锆石原位定年结果表明,通安组的凝灰岩形成于1744±14Ma左右,河口群角斑岩形成于1659±23Ma左右,侵入会理群天宝山组的辉长辉绿岩形成于1026±7Ma左右。根据岩石组合、形成环境以及年代学资料,中元古代早期的大红山群、东川群、河口群和通安组(1~4段)形成时代相近,地层组成基本相同,它们都含有与岩浆热液有关的铁氧化物铜金(IOCG)矿床或层状铜矿床(SSC),都在1.75~1.45Ga期间形成于大陆裂解环境。扬子地块北缘的火地垭群也可能属于中元古代早期地层。中元古代晚期地层在扬子地块西缘北缘均有分布,其中的昆阳群和会理群大体形成于1.2~1.0Ga,神农架群和打鼓石群形成于1.4~1.0Ga,它们的顶界可能延伸到新元古代早期。在中元古代晚期的地层中含有大量叠层石,表明它们形成于温暖潮湿的浅海环境。除上述的中元古代晚期地层之外,云南元谋地区的苴林群、川西的登相营群、通安组五段等也属于中元古代晚期的地层。
[Abstract]:The Mesoproterozoic strata widely distributed in the western and northern margin of the Yangtze block experienced strong deformation and metamorphic transformation of greenschist facies.According to the age of formation, two stages can be identified in the Middle Proterozoic, I. e., the early Middle Proterozoic (1.8Ga1.4Ga) and the late Middle Proterozoic (1.4Ga-1.0Ga).The early Middle Proterozoic strata include the Dahongshan Group, the Dongchuan Group, the Estuary Group and the Tong'an formation, and the late Middle Proterozoic strata are mainly composed of the Kunyang Group, which is distributed in the southwest margin of the Yangtze Block.The Huili Group and the Shennongjia Group and the Dagu Stone Group distributed in the northern margin of the Yangtze block.The results of zircon dating in situ indicate that tuff of Tongan formation formed at about 1744 卤14Ma, the diagonal porphyry of estuarine group formed at about 1659 卤23Ma, and the pyroxenite intruding into Tianbaoshan formation of Huili group was formed at 1026 卤7Ma.According to the rock assemblage, formation environment and chronological data, the early Middle Proterozoic Dahongshan Group, Dongchuan Group, Estuary Group and Tongan formation (No. 1) were formed in a similar time and the stratigraphic composition was basically the same.They all contain iron oxide copper gold IOCGs related to magmatic hydrothermal solution or layered copper deposits. They were formed in continental pyrolysis environment during 1.75~1.45Ga.The Huodiya Group in the northern margin of the Yangtze Block may also belong to the early Middle Proterozoic strata.The late Middle Proterozoic strata were distributed in the northern margin of the western margin of the Yangtze block, in which the Kunyang Group and Huili Group were formed in 1.210Ga, the Shennongjia Group and the Dagu Stone Group were formed in 1.4 ~ 1.0Ga. their top boundary may extend to the early Neoproterozoic.A large number of stromatolites were found in the late Middle Proterozoic strata, indicating that they were formed in warm and humid shallow sea environments.In addition to the late Middle Proterozoic strata mentioned above, the late Middle Proterozoic strata of Lin Qun in Yuanmou area, Dengfangying Group in western Sichuan and the fifth member of Tongan formation also belong to the late Middle Proterozoic strata.
【作者单位】：中国地质科学院地质研究所;
【基金】：国家自然科学基金(41472082) 国家重点研发计划深地资源勘查开采重点专项(No.2016YFC0601001) 中国地质调查局项目(12120115068901)资助的成果
【分类号】：P534.3

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