鄂尔多斯盆地奥陶系石灰岩岩相及地球化学特征

西安石油大学 地球与工程学院,陕西 西安 710065

碳酸盐岩; 成岩作用; 主微量元素; 同位素; 鄂尔多斯盆地

Lithofacies and geochemical characteristics of Ordovician limestone in Ordos Basin
JIN Cheng-guang,WANG Qi-cong,LIU Jia-wei,SHI Kun,WEI Wei,WANG Yan,LI Bai-qiang,NING Bo,YAN Zuo

(School of Earth Sciences and Engineering,Xi'an Shiyou University,Xi'an 710065,China)

carbonatite; diagenesis; major trace elements; isotope; Ordos Basin

DOI: 10.13800/j.cnki.xakjdxxb.2016.0108

备注

为探讨鄂尔多斯盆地奥陶系石灰岩的岩相和地球化学特征,在露头及岩心观察、岩石薄片鉴定的基础上,确定了石灰岩的主要类型,结合碳、氧稳定同位素、锶同位素、主、微量元素分析等地球化学分析数据,确定了各类石灰岩的地球化学特征。据成岩环境及主要成岩作用,识别出奥陶系主要的石灰岩类型,即泥晶灰岩、海水及淡水亮晶胶结颗粒灰岩、去膏、云化细-粗晶次生灰岩、破裂及紊乱岩溶角砾灰岩; 正常海水环境成因的石灰岩具有高δ13C,δ18O,低87Sr/86Sr,富含Sr,贫Mn,Fe及重金属和稀土元素,受淡水环境影响的石灰岩,具有低δ13C,δ18O,高87Sr/86Sr,贫Sr,富含Mn,Fe及重金属和稀土元素的特征。研究结果表明岩石薄片鉴定以及岩石地球化学分析是开展碳酸盐岩成因研究的有效方法。

The paper discussed the lithofacies of limestone in Ordovician in Ordos,as well as the geochemical characteristics.Based on the observation of outcrops and cores,and the identification of petrographic thin section,the type of limestone lithogenous phase are confirmed.The geochemical characteristics of limestone lithogenous phase are confirmed by geochemistry analytical data,such as carbon and oxygen stable isotopes,strontium isotope,main element and microelement analysis.According to the diagenetic environment and main diageneses,limestone diagenetic facies can be divided into marine phreatic micritic and sparry cementation facies,fresh water vadose sparry cementation facies,degypsification and dolomitization facies,Karst fracture and disorder breccia facies.Diagenetic facies of normal seawater environment is of high δ13C,δ18O,low87Sr/86Sr,and rich of Sr,poor of Mn,Fe,heavy metals and rare earth elements,but diagenetic facies influenced by fresh water is characterized of low δ13C,δ13C,p>18O,high87Sr/86Sr,poor Sr,and rich Mn,Fe,heavy metals and rare earth elements.The research results show that rock slice identification and geochemical analysis are the effective methods for the lithogenous phase researches of carbonate rocks.