Geochemical characteristics of Huanhe formation sandstones in Yihewusu area of Ordos basin and the indications to provenance area and tectonic setting
In order to explore the tectonic background and material sources of the sandstones of Lower Cretaceous Huanhe formation,the petrological and geochemical characteristics of the sandstones of Huanhe formation in Yihewusu area of Ordos basin were analyzed mainly through microscopic identification and petrographic and mineralogical tests.The main components of the sandstone of Huanhe formation in Yihewusu area are quartz,feldspar and mica,with small amounts of dark minerals such as pyrite and charcoal fragments.The grains are rounded and sub-angular,poorly sorted,and have the characteristics of near-source deposition.The elemental geochemical analysis on the sandstones are characterized by high SiO2 content(71.69% on average),medium Al2O3 content(12.39%on average)and low content of other elements.The average chemical alteration index(CIA)of the rocks and minerals is 60.92 and the average chemical weathering index(CIW)is 68.47,indicating that the source rocks of the provenance area have experienced moderate intensity weathering.The standardized spider-web diagram of trace element spheroidal meteorites shows that Huanhe formation in the study area enriched in elements such as Ba,Th,La and U,and deficient in elements such as Nb,Zr,Ho and Er.The Rare Earth Element(REE)pattern shows that the sandstones of Huanhe formation in the study area bears negative anomalies in Eu,with an average of 10.23 for LREE/HREE,16.27 for La/Yb,and 11.65 for LaN/YbN.The tectonic background of the sandstones deposition in Yihewusu area was the active continental margin,and the main source area is the felsic igneous rock.It is believed that the original provenance area of the sandstones of Huanhe formation in the Yihewusu area mainly come from the Wolf Mountain and Wulashan diserict.
sandstone geochemistrytectonic settingprovenance analysisHuanhe formationYihewusu area
国家科技期刊平台
NSTL
万方数据
