摘要
运用LA-ICP-MS方法对湘东南泗洲山地区南华系大江边组上部泥质岩和震旦系（埃迪卡拉系）埃岐岭组底部变泥铁质砂岩碎屑锆石进行U-Pb测年,分别获得了28组和92组U-Pb有效年龄.前者锆石年龄主要集中分布于693 ～ 897 Ma（占67.9％）,1810 ～1916Ma（占17.9％）,1974～2177Ma（占14.2％）三个区间,最年轻的谐和错石年龄为734 ±4Ma（MSWD=1.07,n=4）；后者锆石年龄主要集中分布于570～699Ma（占9.8％）,715～ 774Ma（占7.6％）,882～1272Ma（占67.4％）,1300～ 1681Ma（占7.6％）,1899 ～2490Ma（占7.6％）五个区间,最年轻的谐和锆石年龄为634±7Ma（MSWD=1.09,n=4）.研究认为,大江边组上部地层的形成时代＜734±4Ma,与澄江组顶部、牛牯坪组、岩门寨组、拱洞组及隆里组等地层形成时代相近,揭示“板溪期”地层的顶界年龄及江口冰期开启年龄＜ 734±4Ma；埃岐岭组形成时代＜634 ±7Ma,与陡山沱组及蓝田组等地层形成时代相近,支持南沱冰期结束于635Ma左右的认识.综合研究认为,大江边组和埃岐岭组的物源可能分别主要来源于武夷地块南东部和南岭—云开地块南部的一个Grenville期造山带.推测物源的转换可能与南岭—云开地块、武夷地块在两组沉积时期之间聚合或紧邻有关,其时限约为734～634Ma.
LA-ICP-MS U-Pb dating was carried out on detrital zircons from the argillaceous rocks in upper Dajiangbian Formation of Nanhuan System and the metamorphic mud-ferruginous sandstone in bottom Aiqiling Formation of Sinian （Ediacaran） System, 28 and 92 effective U-Pb ages were obtained respectively. The former detrital zircon U-Pb age populations were at 693 - 897Ma （ account for 67.9% ） , 1810 - 1916Ma （ account for 17.9% ）, 1974 -2177Ma（ account for 14.2% ）, the youngest concordant age was 734 ＋_4Ma（MSWD = 1.07, n = 4）; The latter detrital zircon U-Pb age populations were at 570 -699Ma（ account for 9.8% ）, 715 -774Ma （ account for 7.6% ）, 882 - 1272Ma（ account for 67.4% ）, 1300 ~ 1681Ma（ account for 7.6% ）, 1899 - 2490Ma （ account for 7.6% ）, the youngest concordant age was 634 _＋ 7Ma（MSWD = 1.09, n = 4）. It was confirmed that the age of the upper Dajiangbian Formation was 〈 734 _＋ 4Ma, which can be correlated with the top part of Chengjiang Formation, Niuguping Formaion, Yanmenzhai Formation, Gongdong Formation and Longli Formation, indicated the top boundary age of ＂Banxi Period＂ strata and the start age of Jiangkou iceage should be 〈 734 _＋ 4Ma. The age of the Aiqiling Formation was 〈 634 ＋-TMa, as same as the age of the Doushantuo Formation and Lantian Formation, supported the viewpoint that the end age of Nantuo iceage was at ca. 635Ma. Comprehensive research shows that the main provenance of Dajiangbian Formation and Aiqiling Formaion maybe the southeastern part of the Wuyi terrane and the Grenvillian orogenic belt in south of the Nanling-Yunkai terrane respectively. The transition of provenance was speculated to be related to the coalescence or juxtaposition of the Nanling--Yunkai terrane and Wuyi terrane during the deposited period of above two formations,which maybe 734 -634Ma.
出处
《地质论评》
CAS
CSCD
北大核心
2013年第5期853-868,共16页
Geological Review
基金
国家自然科学基金重点项目(批准号41030315)
国家自然科学基金项目(批准号41072088)
中国地质调查局基础研究项目(编号1212011121111)的成果
关键词
湘东南
南华系大江边组
震旦系（埃迪卡拉系）埃岐岭组
地层时代
物源
碎屑锆石
U-PB年代学
Southeast Hunan Province
Dajiangbian Formaion of Nanhuan System
Aiqiling Formation of Sinian （Ediacaran） System
stratigraphic age
provenance
detrital zircon
U-Pb geochronology
作者简介
伍皓,男,1984年生.硕士研究生,研究方向为沉积学和岩相古地理学,Email：wuhaocgs@sohu.com.
