Unravelling sources of solutes in groundwater of an ancient landscape in NW Australia using stable Sr, H and O isotopes

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    Abstract

    © 2014 Elsevier B.V. The Precambrian meta-sedimentary fractured rock aquifers of the Hamersley Basin in northwest Australia are some of the oldest water-bearing formations on the planet and host enormous iron ore deposits. Groundwater is the only permanent source of water in the basin, therefore understanding the hydrological processes that effect water quality and quantity is a pre-requisite for sustainable water management. We used a combination of major dissolved ion concentrations, including Sr and Ca, in combination with δ2H, δ18O and δ87Sr in flood water and groundwater as tracers to constrain the processes affecting groundwater chemistry. The δ87Sr composition of groundwater in three major aquifer types ranges from 11.8‰ to 40.6‰ and reflects the mineralogy of altered Precambrian dolomite (15.1‰ to 55.4‰) rather than the host iron ore formations (22.5‰ to 46.5‰ >95% iron oxides) or highly radiogenic shale bands and clay minerals (200‰ to 2322.5‰). Groundwater in the terminal Fortescue Marsh wetland of the basin has a rather constant δ87Sr signature of 36.6±1.4‰ irrespective of variations in TDS, δ18O and Sr concentration. This groundwater is considered to be mature in a geochemical sense, representing the final stage of water evolution on a basin scale. Mixing calculations utilising δ87Sr and Ca/Sr data demonstrate contributions of salts from three major sources: on average >92% from precipitation, ~7% from carbonate rocks and
    Original languageEnglish
    Pages (from-to)67-78
    Number of pages12
    JournalChemical Geology
    Volume393-394
    DOIs
    Publication statusPublished - 30 Jan 2015

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