关键词: 地球化学, 构造环境, 下江群, 新元古代, 贵州省

Abstract:

Based on the systematic sampling from the Neoproterozoic Xiajiang Group in the research area and the data analysis of
major elements and rare earth elements, this study shows that rocks had moderate quantities in SiO2, which its value ranged from 57.54×
10-2 to 88.91×10-2 with an average of 68.32×10-2, low content of CaO (generally smaller than 1%), and high concentration in K2O/Na2O
and Al2O3/TiO2 and low amount of TFe2O3+MgO. The ΣREE of total rare earth element is between 46.51×10-6 and 306.29×10-6 and its
average value was 152.46×10-6. ΣLREE/ΣHREE changed in 8.73~21.6, average value was 12.96, which indicated that it was rich in
LREE, loss in HREE. The δEu in each member of Xiajiang group ranged from 0.7 to 0.8, which was Weak negative anomaly. The REE
patterns were slightly to right. LREE had medium fractionation and HREE was low, which demonstated that the REE patterns was high
gradient in LREE and flat in HREE. Through the geochemistry parameter in each formation, it illustrated that it had similar
geochemistry features between Fanzhao and Qingshui formation, also Pinglue and Longli formation. It further illustrated that similar or
transitional structure background. It drew elementary conclusion that it was back-arc basin of active continental margin in Fanzhao and
Qingping stages, and edge marine sedimentary environment of continental margin in Pinglue and Longli stages.

Key words: geochemistry, tectonic setting, Xiajiang Group, Neoproterozoic, Guizhou Province