Role of Magmatism and Related-Exsolved Fluids during Ta-Nb-Sn Concentration in the Central Eastern Desert of Egypt:Evidences from Mineral Chemistry and Fluid Inclusions  

作　　者：Mohamed Abd El Monsef Mabrouk Sami Fatma Toksoy‐Köksal Rainer Abart Martin Ondrejka Khaled MAbdelfadil 

机构地区：[1]Geology Department,Faculty of Science,Tanta University,31527 Tanta,Egypt [2]Geology Department,Faculty of Science,Minia University,61519 El-Minia,Egypt [3]Department of Geological Engineering,Middle East Technical University,06800 Ankara,Turkey [4]Department of Lithospheric Research,University of Vienna,1090 Vienna,Austria [5]Department of Mineralogy,Petrology and Economic Geology,Comenius University,Bratislava,Slovakia [6]Department of Geology,Faculty of Science,Sohag University,82524 Sohag,Egypt [7]Department of Physics and Earth Sciences,Jacobs University,28759 Bremen,Germany

出　　处：《Journal of Earth Science》2023年第3期674-689,共16页地球科学学刊（英文版）

基　　金：Ministry of Higher Education of Egypt for supporting his research stay at University of Vienna(Austria)as a postdoctoral fellow。

摘　　要：The rare metals of Abu Dabbab area in the Central Eastern Desert of Egypt have been investigated for their mineralogy and conditions of precipitation using combination of EMPA and fluid inclusions studies,in order to delineate the source,mechanism of formation and evolutionary model for these economic metals.The(Ta-Nb-Sn)-bearing minerals at the Abu Dabbab area include columbite group minerals(CGMs),wodginite and cassiterite.In both granitic intrusion and its enclosed quartz veins,most of zoned CGMs and cassiterite grains are commonly characterized by a well-developed twostage texture.Hence,columbite-(Mn)(CGM-Ⅰ)represents the early formed phase of CGMs that is characterized by high Mn#values(0.64-0.92)with quite low Ta#values(0.13-0.49).It was invaded by Ta-rich phases including tantalite-(Mn)(CGM-Ⅱ;Ta#=0.13-0.49)and wodginite,which contain high Ta_(2)O_(5)and SnO_(2)(17.91 wt.%).In regard to cassiterite,there are distinct compositional differences between the early-phase cassiterite(Cst-Ⅰ)and the late-phase one(Cst-Ⅱ),where the latter is enriched in Ta_(2)O_(5),Nb_(2)O_(5)and FeO.The chemistry and textural criteria of the early stage CGM-Ⅰand Cst-Ⅰ,all are indicative of magmatic origin.While,the latter CGM-Ⅱ,wodginite and Cst-Ⅱwere influenced by the late magmatic Ta-rich fluids.Fluid inclusions microthermometry shows criteria of phase separation represented by both boiling and fluid immiscibility.The initial fluid was supposed to be of magmatic origin(magmatic CH4),that was consequently influenced by fluid mixing/dilution with post-hydrothermal/meteoric water with respect to the decompression process during uplift.Isochore construction gave rise to an estimate P-T conditions(T=330-370℃,P=22-50 MPa).The fluid inclusions’microthermometry supports a transition between magmatic and late to post-hydrothermal activities in addition to surface-derived fluid(meteoric fluid?)in a part as main source for the polymetallic deposits.

关 键 词：columbite-group minerals wodginite CASSITERITE magmatic-hydrothermal fluid inclusion deposits Abu Dabbab 

分 类 号：P618.2[天文地球—矿床学]