Trace-element geochemistry and S–O isotopes in the fluorite-barite mineralization of Merguechoum,Moroccan eastern Meseta:insights into ore genesis to the Pangea rifting  

作　　者：Mohammed Cherai Larbi Rddad Fouad Talbi Benjamin F.Walter 

机构地区：[1]Faculte´des Sciences,Laboratoire de Geosciences,Geo-Environnement et Prospection Miniere et Hydrique,BP 717,60000 Oujda,Maroc [2]Earth and Planetary Science Division,Physical Science Department,Kingsborough Community College of the City University of New York(CUNY),2001 Oriental Boulevard,Brooklyn,NY 11235–2398,USA [3]Chair of Economic Geology and Geochemistry,Karlsruhe Institute of Technology(KIT),Adenauerring 20B,76131 Karlsruhe,Germany [4]Laboratory for Environmental and Raw Material Analyses(LERA),Adenauerring 20B,76131 Karlsruhe,Germany

出　　处：《Acta Geochimica》2023年第3期435-452,共18页地球化学学报（英文）

摘　　要：The Merguechoum fluorite-barite mineralization,located in the Eastern Meseta of Morocco,is hosted in the Late Hercynian granite.The ore consists of fine crystals of fluorite 1,massive barite 1,euhedral crystals of fluorite 2,and barite 2 with calcite and minor quartz and sulfides.The Merguechoum ore deposits have never been investigated.This study was the first contribution that studied the genesis of fluorite and barite.The ore occurs as dissemination within granite intrusion and also fills the NE-SWtrending meter-sized fractures and faults.The values of the total Rare Earth Elements and Yttrium(REY)and the ratios of LREY/HREY,Y/Ho,Tb/Ca,and Tb/La indicate that the Merguechoum fluorite precipitated from hydrothermal fluids,likely basinal brines,which interacted with the Hercynian granite.The REY data indicate that the ore-forming fluids of the early stage have intensely interacted with the Hercynian granite compared to those of the late ore stage.The gradual decrease in the europium(Eu/Eu^(*)),yttrium(Y/Y^(*)),and cerium(Ce/Ce^(*))anomalies and a low concentration ofΣREY observed in the second ore stage compared to the first ore stage suggest an increase in p H and fO_(2)and by inference a decrease in temperature during the evolution of the hydrothermal system.This evolution could be explained by fluid mixing between the ascending basinal hydrothermal fluids and the diluted sulfate-rich meteoric water barite separates from selected samples reveal that the dissolved sulfates(SO_(4)^(2-))were derived from Permian–Triassic sulfates and/or coeval poreseawater sulfates.The proposed fluid mixing triggered the precipitation of an early-stage F-Ba assemblage followed by the second-stage F-Ba mineralization.Geologic fieldwork,REY inventories,and isotope data point to the ore genesis during the Permian–Triassic extensional tectonic activity concerning the Pangea rifting.This extensional tectonic environment is likely the driving force that mobilized a large amount of the ore-forming basinal brines along the available

关 键 词：Fluorite-barite veins Geochemistry of REY and trace elements O–S isotopes Late hercynian granite Pangea rifting Merguechoum Eastern Meseta of Moroccan 

分 类 号：P619.2[天文地球—矿床学]