干旱区生态环境知识资源中心(Arid): Orogenic gold formation in an evolving, decompressing hydrothermal system: Genesis of the Samut gold deposit, Eastern Desert, Egypt

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DOI	10.1016/j.oregeorev.2018.12.030
	Orogenic gold formation in an evolving, decompressing hydrothermal system: Genesis of the Samut gold deposit, Eastern Desert, Egypt
	Zoheir, Basem 1,2; Steele-MacInnis, Matthew 3; Garbe-Schoenberg, Dieter 2
通讯作者	Zoheir, Basem
来源期刊	ORE GEOLOGY REVIEWS
ISSN	0169-1368
EISSN	1872-7360
出版年	2019
卷号	105 页码:236-257
英文摘要	Samut is a vein-type gold mineralization in the Eastern Desert of Egypt, which shares many geologic features with other orogenic deposits in this region. The deposit has a long history of mining activity dating back to ancient times, but so far has received little attention from the standpoint of geologic study. Here, we present new field, petrographic, microthermometric and microanalytical data from the Samut gold deposit to evaluate its genesis and fluid evolution. Vein quartz at Samut shows abundant evidence of precipitation coinciding with early phases of ductile deformation that show transitions to increasing brittle fracturing and fragmentation through time. In some samples, brecciation of the vein quartz is intense and shows evidence of repeated episodes of fragmentation. This brittle style of deformation culminates with latest-stage brittle opening and loss of confining pressure, resulting in open-space filling textures. Backscattered electron images and electron microprobe analysis reveal three varieties of pyrite in the mineralized quartz veins (Py I, Py II and Py III). Laser ablation ICPMS analysis of pyrites from mineralized quartz veins reveals that the earlier Py I is low in arsenic and gold, whereas Py II and Py III are enriched in both elements. Anhedral Py II is particularly gold-rich, and gives way to blocky, euhedral Py III that is rich in arsenic but not as rich in gold compared to Py II. Fluid inclusions in the least brittle deformed vein quartz indicate that the veins formed at minimum temperatures of similar to 300 degrees C, early in the hydrothermal system. The calculated fluid pressures at homogenization of the aqueous-carbonic inclusions furnish a wide range throughout the paragenesis, perhaps on the order of similar to 1 to 3 kbar. The delta S-34 values of pyrites imply sulfur isotopic composition of the mineralizing fluid on the order of +0.6 to +4.9%, overlapping with the broad range of delta S-34 values calculated for ore fluids in orogenic gold deposits worldwide. Together, these results support a general model in which gold and sulfide deposition was coinciding with an ongoing syn-deformational vein formation, and tending towards the late stages of vein growth prior to loss of confinement. Free-milling gold appears to be mostly related to the later stages of brittle fracturing and re-sealing of the veins during repeated fluid release, as the background fluid pressure evolved from earlier dominantly lithostatic to later fully hydrostatic conditions.
英文关键词	Orogenic gold Decompressing hydrothermal system LA-ICPMS data of pyrite Fluid inclusions Au depositional model
类型	Article
语种	英语
国家	Egypt ; Germany ; Canada
收录类别	SCI-E
WOS记录号	WOS:000459949300016
WOS关键词	ORE-FORMING FLUIDS ; HIGH CO2 CONTENT ; RE-EQUILIBRATION ; SULFUR ISOTOPES ; ASHANTI BELT ; MICROTHERMOMETRIC DATA ; NATURAL PROCESSES ; PHASE-EQUILIBRIA ; INCLUSION DATA ; QUARTZ VEINS
WOS类目	Geology ; Mineralogy ; Mining & Mineral Processing
WOS研究方向	Geology ; Mineralogy ; Mining & Mineral Processing
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/217821
作者单位	1.Benha Univ, Dept Geol, Fac Sci, Banha 13518, Egypt; 2.Univ Kiel, Inst Geosci, Ludewig Meyn Str 10, D-24118 Kiel, Germany; 3.Univ Alberta, Dept Earth & Atmospher Sci, Edmonton, AB T6G 2E3, Canada
推荐引用方式 GB/T 7714	Zoheir, Basem,Steele-MacInnis, Matthew,Garbe-Schoenberg, Dieter. Orogenic gold formation in an evolving, decompressing hydrothermal system: Genesis of the Samut gold deposit, Eastern Desert, Egypt[J],2019,105:236-257.
APA	Zoheir, Basem,Steele-MacInnis, Matthew,&Garbe-Schoenberg, Dieter.(2019).Orogenic gold formation in an evolving, decompressing hydrothermal system: Genesis of the Samut gold deposit, Eastern Desert, Egypt.ORE GEOLOGY REVIEWS,105,236-257.
MLA	Zoheir, Basem,et al."Orogenic gold formation in an evolving, decompressing hydrothermal system: Genesis of the Samut gold deposit, Eastern Desert, Egypt".ORE GEOLOGY REVIEWS 105(2019):236-257.