利用地球化学标志识别沉积环境——以中扬子台地北缘上震旦统为例

Analyzing sedimentary environment using geochemical indicators—An example from north margin of Middle Yantze platform in Last Sinian.

晚震旦世 ,中扬子台地北缘碳酸盐岩沉积发育 ,可分为浅水台地和深水台盆 2个相区和 7种不同相带。地球化学分析表明 ,该区地球化学特征与沉积环境有密切的关系 :常量元素Mn在局限海湾相中明显偏高 ,而在其它相带中均较低 ;微量元素B在台缘滩相中含量最低 ,仅 0 .82× 1 0 -6 ,而在其它相带中均大于1× 1 0 -6 ,最高可达 6.56× 1 0 -6 ;微量元素Sr和Sr/Ca× 1 0 3 比值与沉积环境密切相关 ,以浅滩相为中心 ,向局限海湾和深水盆地方向明显增加 ,呈双峰分布。因此 ,利用地球化学标志可以判别沉积相。图 4表 1参 7(邹冬平摘 )

During Late Sinian, the north margin of Middle Yantze platform was dominated by carbonate sediments. And it can be divided into shallow water platform and deep water platform and subdivided into seven different facies types. Geochemical analyses indicate that geochemical characteristics are closely related to sedimentary environment in the study area: ①The content of element Mn increases largely in restricted gulf facies, but it is low in other facie types; the content of trace element B is lowest in platform marginal shoal, but it increases in other facie types. ②The ratio of trace element Sr over Sr/Ca×1000 is closely related to sedimentary environment, the Sr/Ca×1000 ratio tends to increase gradually from platform marginal shoal to platform basin. All these evidences show that geochemical characteristic may be a indicator for environment identification.