浙江安吉上奥陶统钾质斑脱岩特征  

CHARACTERISTICS OF KATIAN(LATE ORDOVICIAN)K-BENTONITES FROM ANJI,ZHEJIANG PROVINCE

作　　者：汪隆武 张建芳 陈津华 张元动[2] 陈小友 朱朝晖 刘健 胡艳华 马譞 

机构地区：[1]浙江省地质调查院,浙江杭州311203 [2]资源地层学与古地理学重点实验室,中国科学院南京地质古生物研究所,江苏南京210008

出　　处：《地层学杂志》2015年第2期155-168,共14页Journal of Stratigraphy

基　　金：中国地质调查局地质大调查项目(No.1212011220527)资助

摘　　要：在浙江安吉杭垓地区的上奥陶统黄泥岗组和长坞组分别发现42层和5层钾质斑脱岩夹层,对其中部分斑脱岩开展的X衍射分析显示,其主要成分为石英、伊利石、蒙脱石、高岭石和极少量钠长石;该套斑脱岩具有高钾特征,为钾玄岩系列;稀土元素成分分析显示具有高∑REE含量,轻、重稀土分异明显,具较强负铕异常,球粒陨石标准化稀土配分曲线具有右倾的特征;富集Rb、Th、U、K,亏损Ba、Sr、P等。SHRIMP锆石U-Pb测年值为453±4~444.7±3.3 Ma。成因地球化学分析显示,这些斑脱岩主要形成于板内构造环境,为晚奥陶世凯迪期广西运动构造—岩浆事件的产物。A total of 47 bentonite layers have been discovered from the Huangnekang and Changwu formations（Late Ordovician）in the Hanggai area,Anji,northern Zhejiang Province.X-ray diffraction analysis of these bentonites shows that they are mainly composed of quartz,illite,montmorillonite,kaolinite,and small amounts of sodium feldspars.Element geochemical analysis indicates that：1）the bentonites are characterized by high potassium contents,suggesting that they belongs to the shoshonite series;2）they have high contents of∑REE,with a strong fractionation between LREE and HREE,and a strong negative Eu anomaly.The chondrite-normalized REE distributuin is right-biased.The bentonites are enriched in Rb,Th,U and K,but are depleted in Ba,Sr,and P.SHRIMP U-Pb zircon analyses give ages ranging from 453±4 Ma to 444.7±3.3Ma,i.e.approximately Katian to early Hirnantian age.Geochemical data of these bentonites indicate that they were likely to have formed in an intraplate tectonic activities,and were probably related to the tectonic and magmatic activities during the initial Kuangsian Orogeny（Late Ordovician）.

关 键 词：化学地层 钾质斑脱岩 SHRIMP测年 晚奥陶世 广西运动 安吉 浙江 

分 类 号：P534.42[天文地球—古生物学与地层学]