关键词: 羌塘盆地, 角木日地区, 二叠系, 碳酸盐岩, 地球化学特征, 古沉积环境

Abstract:

In order to study the Permian paleoenvironment of the Jiaomuri area (Qiangtang Basin), geochemical analysis were taken
from the dolomite samples of Lower Permian Zhanjin Formation and limestone samples of Middle Permian Longge Formation. Our data
show that the average of the Y/Ho ratio is 45.14 while element Gd shows light positive anomaly, suggesting normal marine carbonate
characteristics. The contents of SiO2 and Al2O3 are low indicating relatively limited terrestrial input. The low total REE contents
（ΣREE） and the different LREE and HREE values of the samples indicate that REE were removed and LREE were fractionated more
easily than HREE. The samples have obviously negative Ce and Eu anomalies showing an oxidizing paleoenvironment, which further
supported by the analysis of V/Cr, V/(V+Ni), Sr/Ba and Sr/Ca ratios. Up-section, the Permian samples showed higher salinity and
oxidbillity, which was supposed to be related to water depth shallowing related to a local compression tectonic trend.

Key words: Qiangtang Basin, Jiaomuri area, Permian, carbonate, element geochemistry, paleoenvironment