Development of Sulfuric Acid Speleogenetic Deposits within Cavernous Middle Eocene Beds:Inference on Hydrocarbon Gas Seepages,Giza Pyramids Plateau,Egypt  

作　　者：Hanan S.BADAWY 

机构地区：[1]Geology Department,Faculty of Science,Beni-Suef University,Beni-Suef,Egypt

出　　处：《Acta Geologica Sinica(English Edition)》2021年第3期946-961,共16页地质学报（英文版）

基　　金：This work is supported by the Faculty of Science,Beni-Suef University(BSU-FSC-0805699).

摘　　要：Development of sulfuric acid speleogenetic mineral deposits within cavernous middle Eocene beds of the Pyramids plateau is linked to hydrocarbon gas seepages.The work carried out field observations,binocular,polarizing,scanning and transmitted electron microscopy investigation,X-ray diffraction and X-ray fluorescence analyses.The morphological and petrographic features and chemical composition of the studied mineral deposits reveal a hypogene sulfuric acid speleogenesis.A model comprised of the following stages can be used to explain the presence of these features.(1)Ascent of hydrogen sulfide(H_(2)S)gas associated with hydrocarbon seepages from the Cretaceous reservoirs under reducing conditions followed by oxidation to sulfuric acid(H_(2)SO_(4)),(2)descent of carbonic acid(H_(2)CO_(3))-rich solution generated from surface sources,(3)reaction of H_(2)SO_(4)and H_(2)CO_(3)with the calcareous and argillaceous host rocks,(4)formation of H_(2)SO_(4)speleogenetic by-products represented by natroalunite,aluminium-phosphate-sulfate,hydrated halloysite and Fe/Mn oxides within the replacive gypsum,and(5)subsequent stresses due to the formation of nearby stratiform cavities gave rise to the development of fractures/veinlets filled with displacive fibrous satinspar gypsum.The study sets the paleokarst features of the Giza Pyramids plateau within a hypogene sulfuric acid karst system developed by the action of groundwater containing H_(2)S,H_(2)SO_(4)and H_(2)CO_(3).

关 键 词：KARSTIFICATION natroalunite aluminium-phosphate-sulfate hydrated halloysite enterolithic growth satinspar gypsum 

分 类 号：P611[天文地球—矿床学]