青海循化盆地晚渐新世沉积物中坡缕石的特征及其古气候指示意义  

Characteristics of Clay Mineralogy of Late Oligocene Sediments in Xunhua Basin,Qinghai Province and Their Implications for Palaeoclimate

作　　者：殷科[1] 洪汉烈[1,2] 李荣彪[1] 强泰[1] 张克信[1,2] 王锦荣[1] 

机构地区：[1]中国地质大学地球科学学院,湖北武汉430074 [2]中国地质大学地质过程与矿产资源国家重点实验室,湖北武汉430074

出　　处：《现代地质》2010年第1期187-194,共8页Geoscience

基　　金：中国地质调查局项目(1212010610103);中国地质大学(武汉)地质过程与矿产资源国家重点实验室开放课题基金(GPMR200910);国家自然科学基金项目(40872038)

摘　　要：采用X射线衍射和扫描电子分析方法,对青海循化盆地晚渐新世沉积物的矿物组成、坡缕石的矿物学特征以及古气候指示作用进行了深入的研究。结果表明,晚渐新世循化盆地沉积物中粘土矿物组成主要有蒙脱石、伊利石、坡缕石和绿泥石等;坡缕石一般呈纤维状或者针状,沿片状蒙脱石的边缘及表面交代生长,为典型自生成因的坡缕石。坡缕石是干旱-半干旱气候条件的特征矿物,其出现表明循化地区晚渐新世气候特征较为干旱,与粘土矿物组合及伊利石结晶度所反映的气候环境信息相吻合;沉积物中坡缕石相对含量及有序度自下而上逐渐增大,说明循化地区的干旱化逐渐加剧。循化地区晚渐新世（-23 Ma）的干旱化可能与青藏高原隆升或者全球气候变冷事件密切相关。Mineral compositions and palaeoclimatic indicator of palygorskite of the Late Oligocene sediments in Xunhua basin,Qinghai,were investigated using X-ray diffraction（XRD） and scanning electron microscopy（SEM） methods.The results show that mineral compositions of the sediments are smectite,illite,palygorskite and chlorite,and the fibrous or acicular palygorskites are typically authigenic,which grew along the edges or the surfaces of platy smectite,respectively.Palygorskite is a characteristic clay mineral under semi-arid and arid climate conditions,the occurrence of palygorskite in the Late Oligocene sediments in Xunhua basin is indicative of an arid palaeoclimate condition,which is consistent with the clay mineral assemblage and illite crystallinity.The relative content and crystallinity of palygorskite show an continuous increase from the lower to the upper portion,reflecting the increasing aridity.The arid palaeoclimate probably resulted from the uplift of Qinghai-Tibet Plateau or the global cooling event.

关 键 词：坡缕石 结晶度 有序度 古气候 循化盆地 晚渐新世 

分 类 号：P588.2[天文地球—岩石学]