川东南地区志留纪稀土元素分布及其地质意义

以川南綦江观音桥志留系剖面为代表,通过48个样品中子活化检测出的8种稀土元素分析,详细讨论了REE在该剖面上的分布演化特点及表现形式;研究了本区早志留世古海洋演化及古环境特点:(1)龙马溪组为滞流浅海盆沉积;(2)从龙马溪组到石牛栏组,其 REE逐渐减少,Ce anom从正异常向负异常演化,海平面趋于上升,至石牛栏组达最高;(3) REE分析结论与用沉积学、大地构造及其它地化分析所得出的结论相吻合,证明REE作为环境演化的“示踪剂”有较大意义。

Distribution and Geological Significance of REE in the Silurian of Southeast Sichuan

Instrument neutron activation analyses ( IN-AA) were carried out on 48 Silurian samples from Guanyinqiao section in Southeast Sichuan, and 8REEs were detected. Based on the analytic results, a detailed discussion is made on the distribution and occurrence pattern of REEs and the characteristics of Early- Silurian oceanic evolution and sedimentaryenvironments in the area. And the following conclu-sion is reached: (1) the Longmaxi Formation was deposited in a shallow euxinic basin; (2) from theLongmaxi Formation to the Shiniulan Formation,∑REE decreases gradually and Ce shifts from negative to positive anomalies, indicating a trend of rise of thesea level. The highest sea level was reached during deposition of the Shiniulan Formation. (3) the con-clusions drawn from REE analyses are consistent with those from sedimentological, tectonic and othergeochemical studies, indicating that REEs can be used as indicators of evolution of sedimentary envi-ronments.