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  

Geochemical characteristics and geological significance of the Upper Triassic Sanhedong Formation limestone in the Hexi Area of Northwest Yunnan Province

作　　者：杨志娟 朱志军[1] 丁婷 马原驰 王田 周世豪 YANG Zhi-juan;ZHU Zhi-jun;DING Ting;MA Yuan-chi;WANG Tian;ZHOU Shi-hao(School of Earth Sciences,East China University of Technology,Nanchang 330013,China)

机构地区：[1]东华理工大学地球科学学院,江西南昌330013

出　　处：《岩石矿物学杂志》2024年第4期856-870,共15页Acta Petrologica et Mineralogica

基　　金：国家自然科学基金项目(42362018)。

摘　　要：对滇西北河西地区三叠纪三合洞组碳酸盐岩开展了碳、氧同位素及稀土与微量元素地球化学分析,结果表明,三合洞组碳酸盐岩的碳、氧同位素符合正常海相碳酸盐岩碳、氧同位素的数值范围;微量元素Sr、Ba含量高,Co、Cu、Th、U、Ho等含量低,稀土元素总量较低,轻稀土元素相对富集,具有Eu负异常;古盐度参数Z值、Sr/Ba值、Sr/Cu值、Rb/Sr值指示干热气候下的海相咸水环境;Cu/Zn、V/Cr、Ni/Co、U/Th值指示缺氧环境;Y/Ho值、δCe及δEu值反映三合洞组灰岩沉积时受成岩作用影响小。这些特征与四川盆地北部地区须家河组稀土元素地球化学特征、氧化还原环境相似,指示兰坪盆地与上扬子板块四川盆地在晚三叠世时期可能具有相同的构造背景和沉积环境,这些认识可为兰坪-思茅地块古环境与大地构造属性研究提供依据。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 carbonate 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 elements.Paleosalinity parameter Z value,and Sr/Ba,Sr/Cu and Rb/Sr ratios indicate that they deposited in a marine saline water environment with dry-hot climate.The ratios of Cu/Zn,V/Cr,Ni/Co and U/Th indicate an anoxic environment.Y/Ho,δCe andδEu 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 paleoenvironment and tectonic attributes of the Lanping-Simao Block.

关 键 词：兰坪盆地 三合洞组 碳、氧同位素 微量元素 沉积环境 

分 类 号：P588.245[天文地球—岩石学] P595[天文地球—地质学]