苏宏图白垩系黏土岩元素地球化学和黏土矿物特征及其古气候意义

Elemental Geochemistry and Clay Minerals of Cretaceous Clay Rocks in Suhongtu and the Paleoclimatic Significance

为了探究苏宏图地区白垩系苏红图组的古气候环境,应用X射线荧光光谱和电感耦合等离子体质谱方法研究了黏土岩样品的元素地球化学特征,结果表明:P、Mn、Sr/Cu、Mg/Ca、SiO 2/Al 2O 3等元素特征指示白垩系苏红图组总体呈现极度干燥的沉积环境,不同亚相之间沉积环境稍有干湿变化,且扇三角洲相对湿暖;通过XRD和SEM方法研究了全岩矿物组成和黏土矿物类型和组合特征,结果表明:伊利石为主要的黏土矿物,其次为绿泥石、高岭石,黏土矿物的组合类型为伊利石、绿泥石的组合,且绿泥石和高岭石呈现此消彼长的现象,反映了干燥寒冷的沉积环境,并伴随着干湿的气候变化。

To explore the paleoclimatic environment of the Cretaceous Suhongtu Formation(K 1 s)in Suhongtu area,Alxa,Inner Mongolia,NW China.K 1 s is mainly composed of andesite and basalt,and intercalated with siltstone,silty limestone,and pebbly sandstone,and bears the Jehol biota fossils.Elemental geochemical characteristics of clay rock samples were studied using X-ray fluorescence spectroscopy(XRF)and inductively coupled plasma mass spectrometry(ICP-MS).The sedimentology and elemental characteristics of P,Mn,Sr/Cu,Mg/Ca,and SiO 2/Al 2O 3 indicate an overall dry sedimentary environment with slight fluctuations of dry-wet or wet-warm shown in some sedimentary facies.In addition,mineral composition of the whole rock and the types and combination characteristics of clay minerals were analyzed by XRD(X-ray diffraction)and SEM(scanning electron microscope)methods.The results show that illite was the main clay mineral,followed by chlorite and kaolinite.The combination types of clay minerals were illite-chlorite,and chlorite and kaolinite were in inverse proportion,reflecting dry and cold depositional environment and dry-wet climate alternation.