干旱区生态环境知识资源中心(Arid): Mantle-derived fluids in the continental-scale Nubian aquifer

Arid

DOI	10.1016/j.chemgeo.2022.121023
	Mantle-derived fluids in the continental-scale Nubian aquifer
	Mohammed, Abdel Mawgoud; Crossey, Laura J.; Karlstrom, Karl E.; Krishnamurthy, R. V.; Kehew, Alan E.; Darrah, Thomas H.; Emry, Erica L.
通讯作者	Mohammed, AM
来源期刊	CHEMICAL GEOLOGY
ISSN	0009-2541
EISSN	1872-6836
出版年	2022
卷号	608
英文摘要	The Nubian aquifer of northeastern Africa is one of the largest confined fossil-water aquifer systems in the world. It is central for ongoing water needs and future development goals of Egypt, Libya, Sudan and Chad. Groundwater extraction and consumptive use over the past 40 years have led to a continuous decline of water level and to the reduction and/or cessation of natural flow in artesian wells and springs. This study introduces new noble gas and stable isotope geochemical data from deep groundwater supply wells of the main oases of the Western Desert of Egypt (Bahariya, Farafra, Dahkla, and Kharga) and places these data in the context of a regional compilation of published hydrological and hydrochemical data. Helium isotopes, stable isotope compositions for water (delta H-2; delta O-18) and dissolved inorganic carbon (delta C-13), salt compositions, and [CO2] suggest deeply derived fluid inputs. Highly variable groundwater temperatures (20-56 degrees C) also suggest the presence of geothermal inputs that mix with aquifer water. Nubian water displays high P-CO2 (up to three orders of magnitude higher than atmosphere) and hydrochemical analysis using delta C-13 suggests up to similar to 30% of the CO2 is derived from deep geologic sources. Helium isotope (He-3/He-4) ratios of samples obtained from the Nubian aquifer range from crustal values of 0.02R(A) (where R-A reflects the He-3/He-4 in air or 1.384 x 10(-6)) to values of up to 0.36R(A) (2.5% mantle helium) in Dahkla Oasis of Egypt and up to 1.4R(A) (17% mantle helium) in Libya. Correlations among excess heat, increases in [CO2], delta C-13, and He-3/He-4 indicate that small volumes of deeply sourced fluids carrying mantle-derived volatiles are leaking into the Nubian aquifer. Geothermal water apparently ascend along faults and shear zone conduits and mix with regional groundwater. The origin of these volatiles may be partial melts in low velocity upper mantle beneath the aquifer and young magmatism surrounding the Nubian aquifer. Fluid-rock interactions along flowpaths can explain variable associations and correlations among the tracers. Variability of composition and temperature suggest complex fluid mixing within the Nubian aquifer, the existence of fault-bounded hydrologic sub-basins, and a connection between tectonics and water quality. Better understanding of the sources and admixtures of deep geothermal fluid inputs is needed for informed water management.
英文关键词	Nubian aquifer Helium isotopes Hydrochemcial tracers Mantle-derived volatiles Stable isotopes
类型	Article
语种	英语
收录类别	SCI-E
WOS记录号	WOS:000844871700001
WOS关键词	HELIUM ISOTOPE RATIOS ; NOBLE-GASES ; WESTERN DESERT ; RED-SEA ; SANDSTONE AQUIFER ; STABLE-ISOTOPE ; RADIOGENIC HELIUM ; DEUTERIUM EXCESS ; SHALLOW AQUIFERS ; CARBON-DIOXIDE
WOS类目	Geochemistry & Geophysics
WOS研究方向	Geochemistry & Geophysics
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/392131
推荐引用方式 GB/T 7714	Mohammed, Abdel Mawgoud,Crossey, Laura J.,Karlstrom, Karl E.,et al. Mantle-derived fluids in the continental-scale Nubian aquifer[J],2022,608.
APA	Mohammed, Abdel Mawgoud.,Crossey, Laura J..,Karlstrom, Karl E..,Krishnamurthy, R. V..,Kehew, Alan E..,...&Emry, Erica L..(2022).Mantle-derived fluids in the continental-scale Nubian aquifer.CHEMICAL GEOLOGY,608.
MLA	Mohammed, Abdel Mawgoud,et al."Mantle-derived fluids in the continental-scale Nubian aquifer".CHEMICAL GEOLOGY 608(2022).