六盘山地区下白垩统红色绿色泥岩地球化学特征及气候环境  

The Geochemistry of the Early Cretaceous Red and Green Mudstones,Liupanshan Group,Liupanshan Area and Its Implications on the Climate

作　　者：张文防[1] 戴霜[1] 刘海娇[1] 陈世强[1] 张永全[1] 张莉莉[1] 张瑞[1] 汪禄波[1] 

机构地区：[1]兰州大学西部环境教育部重点实验室&西部环境与气候变化研究院,甘肃兰州730000

出　　处：《地球科学进展》2012年第11期1236-1244,共9页Advances in Earth Science

基　　金：国家自然科学基金项目"陇中盆地白垩系磁性地层年代与古地磁数据"(编号:40972025);"我国内陆干旱区山系-盆地环境系统的多尺度形成演化"(编号:41021091)资助

摘　　要：白垩纪是距今最近的"温室地球"时期,研究其气候演变对认识现今气候环境格局形成及演变具有重要意义。通过对六盘山地区下白垩统六盘山群李洼峡组中段红色、绿色泥岩的元素地球化学特征研究,发现2种泥岩中大部分元素变异趋势相似;化学风化指数(CIA)相当(红色泥岩平均为66.3%,绿色泥岩平均为65.5%),反映中—低化学风化强度;A-CN-K图解显示源岩单一。利用CaCO3质量百分含量,(CaO+Na2O+K2O)/Al2O3,TFeO/Mn,Ti/Sr,Rb/Sr,Sr/Ba比值等指标分析显示泥岩颜色差异与气候背景有关,红色泥岩形成时气候较为稳定,表现为相对湿润且氧化的环境,而绿色泥岩形成时气候波动较大,表现为相对干旱且还原的环境。Cretaceous is a typical ＂greenhouse＂ period close to the present day.Therefore,it is of great significance to carry out research on its climate change for understanding today＇s pattern of climate and environment.In this study,analysis of the elements geochemistry of the Early Cretaceous red and green mudstones of the middle segment of Liwaxia formation,Liupanshan Group in the Liupanshan basin,shows that a majority of the elements are almost concordantly varied between two kinds of mudstones when compared with that of the global average shale.In addition,the Chemical Index of Alteration（CIA） are slightly low（CIA averaged for red and green mudstone is 66.3% and 65.5%,respectively）,indicating that both their weathering degree are approximately in low-intermediate level.The result of the A-CN-K diagram plot suggests that both their original rock was the same（largely Hercynian granite）.The color differences between the two kinds of mudstones are predominately controlled by the climate change.The variation of the proxies such as CaCO3（wt%）,（CaO＋Na2O＋K2O）/Al2O3,TFeO/Mn,Ti/Sr,Rb/Sr and Sr/Ba proposes that the red mudstone form in the relative wet and oxidation circumstances,whereas the green mudstone in the relative dry and reduction.

关 键 词：泥岩颜色 元素地球化学 风化作用 气候环境 六盘山群 

分 类 号：P595[天文地球—地球化学]