摘要
湘东北地区与赣西北地区共同组成江南造山带中段,是探讨江南造山带大地构造演化的关键区域。采用LA-ICP-MS定年方法厘定湘东北地区栗山片麻状黑云母花岗闪长岩的锆石U-Pb年龄为(838.6±5.6)Ma(MSWD=3.2,n=21),表明其成岩于新元古代,证实幕阜山岩体范围内存在新元古代岩浆活动;相应的锆石Lu-Hf同位素分析显示εHf(t)为5.8~13.8,一阶段模式年龄T_(DM1)为1 169~841Ma,二阶段模式年龄T_(DM2)为1 357~845Ma,fLu/Hf值为-0.97^-0.9,推测岩浆源区以中新元古代新生地壳物质为主。结合江南造山带东、中、西段最新岩浆岩年代学和锆石Hf同位素研究成果,认为造山带东、中、西段广泛存在近同期(830~820 Ma)新元古代岩浆活动,且岩浆源区地幔物质贡献程度以东段最高,中段次之,西段最低,推测湘东北地区在新元古代时期可能具有与造山带东段类似的岛弧构造环境。
The northeast area of Hunan Province, together with the northwest of liangxi Province, consti- tuting the middle part of the Jiangnan orogenic belt, is the key region of the magmatism and tectonic evolu- tion research. Based on the geological characteristics investigation, we determined the forming age of the Lishan gneissic biotite granodiorite magma, （838. 6± 5.6） Ma（MSWD= 3. 2, n= 21）, which means the Neoproterozoic period, by the zircons LA-ICP-MS U-Pb testing, and verified the existence of the Neoprot- -820 Ma in the whole Jiangnan orogen, and the highest contribution degree to the mantle material of mag- matic source to the magma origin is the eastern, the second the middle part, and the lowest the western one. We then speculated that the island arc tectonic environment in northeastern of Hunan in the middle part, similar to the eastern of the orogenic belt.
出处
《地质科技情报》
CSCD
北大核心
2017年第6期32-42,共11页
Geological Science and Technology Information
基金
中国地质调查局地质矿产调查评价专项项目(DD20160031)
