云南保山栗柴坝组碳酸盐岩地球化学特征及环境意义

Geochemical Characteristics and Environmental Significance of Carbonate Rock in Lichaiba Formation in Baoshan Region,Yunnan

云南保山熊洞村栗柴坝组地层(S_(2-3)l)其底部与早志留世仁和桥组(S_1r)整合接触,顶部与早泥盆世向阳寺组(D_1x)整合接触,地层沉积较连续,整体表现出混合沉积的特征。以此剖面为基础,连续采集碳酸盐岩样品24个,根据其显微特征、元素相关性、组份含量及相关元素的比值特征,探讨了研究区碳酸盐岩沉积地球化学特征与古环境意义。研究表明:①样品中Sr与CaO、SiO_2、Al_2O_3和K_2O等氧化物之间,以及各氧化物相互之间具有密切相关性,反映了栗柴坝组不同沉积阶段陆源组份与方解石矿物之间的相互作用关系。②通过对碳酸盐岩中元素含量以及相关元素比值的垂向分布特征分析,如Sr/Ba、Mn/Fe和V/Ni等,对栗柴坝组不同沉积阶段进行了古水深、古盐度和古气候等方面的研究,数据表明栗柴坝组各时期沉积环境差异显著。③岩石微观特征和元素地球化学特征所反映的沉积环境具有一致性。对岩石地球化学特征的研究有益于古沉积环境恢复和古气候的判别与重建。

The bottom of Lichaiba formation in xiongdong village is conformable contact with early Silurian Renheqiao group, the top is conformable contact with early Devonian Xiangyangsi group, and the stratum in this area is continuous, shows mixed sedimentary characteristic. This study discussed the depositional geochemistry characteristics and the palaeo sedimentary environment significance of carbonate rock in the Silurian Lichaiba formation, in Baoshan region. Based on the study of microscopic characteristics, regional geological background and the geochemical analyses of 24 carbonate rock samples, the results indicated： ①Sr and CaO in carbonates positively correlated with each other; CaO remarkably negatively correlated with A1203, K20, SiO2, V, ZiO2; It reflects the interaction between the terrestrial component and the mineral calcite at different stages of deposition;② Through the analysis of element content and ratio in the vertical direction,for example Sr/Ba,Mn/Fe and V/Ni, we have done some research on ancient seawater deep, ancient salinity and ancient climate in different deposition phase of Lichaiba group;③What the microscopic features and geochemical characteristics of the rocks reflect have good consistency. The study on the geochemical characteristics is beneficial to the identification and reconstruction of palaeoenvironment and palaeoclimate.