Cementation characteristics of saline lacustrine clastic rock and control of water salinity on cementation
To clarify the types of cement in clastic reservoirs of saline lake basins and explore the controlling effect of water salinity on cement strength,we use the Paleogene of the Qaidam Basin as a case study.Experimental tests and analyses,such as casting thin-section,whole rock minerals,clay minerals,cathodoluminescence,and scanning electron microscopy,trace elements,were conducted.The study investigated the types of cement in the basin and the influence of ancient water salinity on cement types and strength,establishing a correlation formula between the total amount of carbonate and anhydrite cement and ancient salinity.The results indicate that six types of cement materials,including calcite,dolomite,anhydrite,zeolite,quartz overgrowth,and feldspar overgrowth,developed in the saline lake Basin of the Qaidam Paleogene,shedding light on the formation mechanism of anhydrite and calcite cementation.The distribution of carbonate and anhydrite cement is controlled by the paleosalinity of the water body.Anhydrite cement is dominant near the salt lake center,while calcite and anhydrite transition toward the basin's edge,with decreasing bonding strength and reduced cement content.The study iden-tifies key salinity thresholds:below 9‰,carbonate cementation dominates;between 9‰ and 15‰,both carbonate and an-hydrite cementation occur;above 15‰,anhydrite cementation prevails.Additionally,for every 1.0‰ increase in paleosalin-ity,the average total cement content increases by more than 0.5%,while for every 1.0 km increase in distance from the lake center,the cement content decreases by 0.68% .
Qaidam BasinPaleogenesaline lake basinclasticscement
万方数据
维普
