Petrology and Geochemical Characteristics of Sandy Dolomite in the Central Yunnan Water Diversion Project
The thin section identification method,scanning electron microscope(SEM),energy dispersive spec-trometer(EDS),and CT tests,along with the examination of chemical elements and carbon and oxygen isotopes are utilized to analyze meticulously the petrology and geochemical characteristics of dolomite with varying sandifi-cation degrees along the route in Yuxi section of the Central Yunnan Water Diversion Project.The present paper concludes as follows:within diverse diagenetic environments encompassing recrystallization,cementation,dolomiti-zation,and dolomite dissolution,it is observed that the higher the degrees of sandification are,the more both pore development and void occurrence are.During the process of sandification,a distinct elemental migration is wit-nessed,characterized by the loss of calcium(Ca)and magnesium(Mg),alongside the enrichment of silicon(Si)and aluminum(Al).The characteristics of migration and evolution patterns of major elemental constituents exhibit a discernible correlation with the sandification process of dolomite.The content of ∑LREE,∑HREE,and ∑REE gradually decreased from severely to weakly sandy dolomite,indicating that dolomite experienced a certain degree of leaching loss during the sanding process;the concentration of rare earth elements decreases,and the degree of fractionation increases with the enhancement of sandification degrees.The average Marine-Terrestrial environmental indicator values(Z)value is 143.0‰,the average salinity(S)value is 30.0％,and the average temperature(T)of 35.5 ℃ are calculated out through the content of δ13CPDB and δ18OPDB in the carbon and oxy-gen isotopes.It proved that the formation of sandy dolomite is of marine origin without the impact of meteoric wa-ter in the research area,and both the environmental salinity and seawater temperature are higher during the for-mation of dolomite.The result has shown that the geochemical behaviors of major and trace elements during the process of dolomite sandification are well correlated.
Central Yunnan Water Diversion Projectsandy dolomitepetrologygeochemistry
万方数据
维普
