辽西义县盆地下白垩统义县组大康堡层纹泥地球化学特征及其古气候意义  

Geochemical Characteristics and Their Paleoclimatic Significance of the Varve from Dakangpu Layer of Lower Cretaceous Yixian Formation in Yixian Basin of the Western Liaoning,China

作　　者：王铁晖[1] 巩恩普[1] 陈晓红 许江 黄文韬 

机构地区：[1]东北大学资源与土木工程学院,辽宁沈阳110819 [2]东北大学秦皇岛分校资源与材料学院,河北秦皇岛066004

出　　处：《地球科学与环境学报》2018年第1期49-60,共12页Journal of Earth Sciences and Environment

基　　金：国家自然科学基金项目(41172003);国家重点基础研究发展计划("九七三"计划)项目(2012CB821905);中央高校基本科研业务费专项资金项目(N120601001)

摘　　要：辽西义县盆地义县组大康堡层剖面(辅助标准地层剖面)纹泥发育,占沉积层的60%~70%,为沉积期古环境研究提供了良好素材。通过对湖相纹泥进行岩石学及地球化学研究,探讨了大康堡层沉积期古气候、物源及湖水盐度变化。结果表明:纹泥化学蚀变指数多在65~67之间,变化幅度较小,对气候变化不敏感;w(Rb)/w(Sr)值较低,由下至上逐渐增大,大康堡层沉积期气候较温暖、湿润,存在寒冷、干燥向温暖、湿润变化的趋势;纹泥层偶厚度由下至上逐渐减小,降水量逐渐减少;成分变异指数在1.3~11.6之间,均大于1,代表了初始沉积产物及活动的构造环境;大康堡层物源以偏酸性火山岩为主,如义县组主期火山岩;稀土元素w(La)n/w(Yb)n值大于1,稀土元素在湖水滞留时间较长,沉降速率较慢;稀土元素w(La)n/w(Yb)n值由下至上逐渐减小,在垂向序列上沉积物沉降速率有逐渐增加的趋势,湖水盐度逐渐升高。The varves are well developed in Dakangpu layer profile（auxiliary standard stratigraphic profile）of Yixian Formation in Yixian Basin of the western Liaoning,and cover60%-70% of the deposition layer,which provide a good material for the study of palaeoenvironment during the depositional period.Based on the study on the petrology and geochemistry of varves,the paleoclimate,source and change of salinity of Dakangpu depositional period were discussed.The results show that the chemical index of alteration（CIA）is between 65 and 67 within a small range,and is insensitive to climate changes;w（Rb）/w（Sr）is low and increases gradually from bottom to top,suggesting the climate in Dakangpu depositional period is warm and moist with the trend from dry-cold to warm-humid;the couplet thickness of varve decreases gradually from bottom to top,and the precipitation gradually decreases;the index of component variability（ICV）changes from 1.3 to 11.6,more than 1,representing the existence of initial depositional product and active tectonic setting during the depositional period;the source of Dakangpu layer is dominated by partial acid volcanic rocks,such as the primary volcanic rocks of Yixian Formation;w（La）n/w（Yb）nis greater than 1,and the retention time of REE is longer in the lake with a low sedimentation rate;w（La）n/w（Yb）ndecreases gradually from bottom to top,and the sedimentation rate and the lake salinity are gradually increased.

关 键 词：地球化学 纹泥 义县组 物源 化学蚀变指数 成分变异指数 构造环境 沉降速率 

分 类 号：P595[天文地球—地球化学]