摘要
总结我国扬子地块南缘新元古代—早中生代沉积岩目前已发表的Nd同位素资料发现,这些沉积岩具有随时间变化而其Nd同位素组成发生漂移的现象。在绝大多数时间里,它们具有2000Ma左右的Nd模式年龄,但在1000~700Ma的新元古代和<400Ma的晚古生代—早中生代时间段中,Nd同位素模式年龄急剧降低,反映在此时间段内,新生地幔物质已经进入沉积物的物源区。1000~700Ma期间的Nd同位素变化归因于晋宁期的碰撞造山作用而晚古生代-早中生代沉积岩的Nd同位素变异起因于海盆发育阶段洋壳的出现。即扬子地块南缘在晚古生代—早中生代期间曾经存在过洋壳,且该洋盆可能是古特提斯大洋分支的一部分。
The systematic Nd isotopic analysis of Neo Proterozoic Early Mesozoic sedimentary rocks from Southern margin of Yangtze Block show that these rocks have the feature of Nd isotopic shift with their ages. In most of their deposit time, these rocks have Nd model age of about 2000Ma.However, at stages of 1000-700Ma and <400Ma, the Nd model age decreased rapidly, which suggests that the juvenile mantle derived material had become one of the source components of these sedimentary rocks. The variation of Nd isotope in sedimentary rocks of 1000 ̄700Ma resulted from the Jinning orogenesis and that of Late Plaeozoic Early Mesozoic originated from the newly developed oceanic crust, which could be one of the branches of Plaeo Tethys Ocean.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
1998年第1期22-33,共12页
Acta Petrologica Sinica
基金
地质矿产部"九五"重点科技攻关项目
关键词
扬子地块
晚古生代
洋壳
沉积岩
钕同位素
Nd isotope
Sedimentary rocks
Oceanic crust
Late Paleozoic
Southern margin of Yangtze Block