滇西北河西地区上三叠统三合洞组灰岩地球化学特征及其地质意义OA北大核心CSTPCD

This article conducts carbon and oxygen isotopes,rare earth,and trace element geochemical analyses of carbonate samples from the Triassic Sanhedong Formation in the Hexi Area of the northwest Yunnan Province.The analyzed results demonstrate that their carbon and oxygen isotope values are consistent with the normal marine car-bonate rocks.Samples from the Sanhedong Formation have a high Sr and Ba content,low Co,Cu,Th,U,Ho and total rare earth element content,and a negative anomaly of Eu,but they are slightly enriched in light rare earth ele-ments.Paleosalinity parameter Z value,and Sr/Ba,Sr/Cu and Rb/Sr ratios indicate that they deposited in a ma-rine saline water environment with dry-hot climate.The ratios of Cu/Zn,V/Cr,Ni/Co and U/Th indicate an anox-ic environment.Y/Ho,δCe and δEu values indicate that the limestone of the Sanhedong Formation is less affected by diagenesis during sedimentation.These characters are similar to that of the Xujiahe Formation in the northern part of the Sichuan Basin,indicating that the Lanping Basin and the Sichuan Basin in the Upper Yangtze Plate probably have a similar tectonic and sedimentary environment during Late Triassic,which can help to study the paleoenviron-ment and tectonic attributes of the Lanping-Simao Block.