Geochemistry and sedimentology of sediments in a short fluvial system,NW China:implications to the provenance and tectonic setting  

作　　者：Ling GUO Huanmeng ZHANG Xiaoxia PENG 

机构地区：[1]State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi’an 710069,China [2]Shandong Provincial Key Laboratory of Depositional Mineralization&Sedimentary Mineral,Shandong University of Science and Technology,Qingdao 266590,China

出　　处：《Journal of Oceanology and Limnology》2023年第5期1706-1728,共23页海洋湖沼学报（英文）

基　　金：Supported by the National Natural Science Foundation of China (Nos.42130206,41302076);the MOST Special Fund awarded by the State Key Laboratory of Continental Dynamics,Northwest University (No.201210128);the Shandong Provincial Key Laboratory of Depositional Mineralization&Sedimentary Mineral,Shandong University of Science and Technology (No.DMSM2017033)。

摘　　要：Six outcrop sections in Fenghe River,Northwestern China,were sampled and analyzed.This study aims to determine provenance,tectonic setting,and source-area paleoweathering of the sediments of Fenghe River in combination of lithofacies analysis and bulk-rock geochemical data.The lithofacies in the studied area were classified as gravel,sand,and fine-grained clastic lithofacies,reflecting generally channel fill deposits,channel bar deposits,and over-bank deposits,respectively.The Chemical Index of Alteration(CIA),Plagioclase Index of Alteration(PIA),and Chemical Index of Weathering(CIW)values ranged 50.10–62.29,50.13–66.35,56.52–71.12,respectively,together with element ratios such as Rb/Sr,K/Na,Rb/K,Th/K,Rb/Ti,and Cs/Ti indicate that the source area was under a low to moderate chemical weathering condition probably in cold and semi-arid climates.Moreover,plot of SiO_(2)vs.(Al_(2)O_(3)+K_(2)O+Na_(2)O)suggests that the sediments were deposited in a semi-arid climate.Plots of Cr/Th vs.Th/Sc,TiO_(2)vs.Zr,La/Yb vs.rare earth element(REE),and La-Th-Sc ternary diagrams,along with the lithology,indicate that the sediments in Fenghe River were mainly originated from felsic igneous rocks.Major elements-based discrimination diagrams and Th-Sc-Zr/10 and La-Th-Sc ternary diagram of the samples indicates that the source rocks of Fenghe River developed in a composite active continental margin and continental island arc field.

关 键 词：GEOCHEMISTRY lithofacies SEDIMENTS PROVENANCE PALEOWEATHERING Fenghe River 

分 类 号：P512.2[天文地球—地质学] P597.3