ANSTO :: Browsing by Author "Graham, IT"

Browsing by Author "Graham, IT"

Now showing 1 - 13 of 13

Cemented in time: formation of the 20 000 year old Willandra fossil trackway
(Geological Society of Australia, 2014-07-07) Graham, IT; Whiteside, E; Ward, C; Cendón, DI; Westaway, M; Cupper, ML; Woodhead, JD
The Willandra Lakes system of southwestern NSW is situated within the Murray Basin, and consists of 19 interconnected relict lake basins. In general, the lake sediments within the Willandra Lakes system consist of wellsorted quartz sands (with typical lacustrine shelly fauna), associated with deeper water clays and sandy clays. In 2003, the region was found to host the largest known in-situ tract of Pleistocene human footprints in the world, with the site located on the shoreline of a small, relict lake basin between Lakes Garnpung and Leaghur. Optically Stimulated Luminescence dating revealed that the sediments were deposited between 19 000 and 20 000 years ago. The area is of great cultural value to the local Aboriginal communities (the traditional tribal groups Paakantyi, Mutthi Mutthi and Ngiyampaa), as well as to both the national and international scientific communities. Detailed mineralogical (quantitative XRD), geochemical (XRF, ICP-MS, stable isotopes) and textural (petrography, SEM) analyses of the sediments were undertaken to help determine their origin and provide a basis for their future conservation. The footprints themselves are impressed into a hardpan unit, surrounded by low sand dunes. Approximately 820 m2 of the hardpan has been excavated and explored. The footprint-bearing sediments are composed of a series of thin laminae totalling 150 mm thick, accumulated over repeated cycles of wetting and drying. These sediments are largely composed of pelloids and intraclasts of authigenic clay-sized particles (<2–8 μm) of ferroan magnesite (or hydromagnesite/palygorskite), eolian-derived fractured quartz grains and minor (<10 wt%) kaolinite/illite. There is a large lateral and vertical variation in the modal mineralogy; the NE corner contains 90.5 wt% ferroan magnesite (and minor smithsonite) while the SW and W parts contain 49 wt% ferroan magnesite. The other sediments are largely composed of eolian quartz (up to 85 wt%), kaolinite, illite, rutile, albite, microcline, hematite, goethite and rare dolomite. In terms of stable isotopes, the ferroan magnesite carbonate has a δ13C of –2.5‰ while the hydromagnesite has δ13C of 0.4‰. The magnesite, hydromagnesite and palygorskite appear to have been derived through precipitation within the lake. Although direct precipitation of these phases is rare under surficial conditions, it can occur if there is a high Mg/Ca, only possible if extensive early precipitation of calcite cements occurred before the waters entered into the lake. As the lake dried-out, there was an increase in salinity resulting in a decrease in the activity of water in solution, thereby increasing the hydrated Mg2+ leading to magnesite precipitation.
Deep meteoric leaching and its implications for groundwater residence time in a dissected Hawkesbury sandstone plateau (Kulnura-Mangrove Mountain Aquifier, NSW, Australia)
(Geological Society of Australia, 2014-07-07) Hankin, SI; Cendón, DI; Williams, JP; Graham, IT
In the Kulnura-Mangrove region, groundwater extraction for potable water supply and for industrial activities such as farming and mining, can co-exist provided the main recharge areas are protected, pumping does not exceed recharge, and knowledge of the basic parameters within the aquifer are known through appropriate studies. In this study, groundwater residence time in the Kulnura-Mangrove Mountain aquifers was assessed over multiple years using environmental tracers (H2O stable isotopes, δ13CDIC, 3H, 14C and 87Sr/86Sr) and general hydrogeochemistry. The Kulnura-Mangrove Mountain aquifer is mostly hosted in its upper part by the Hawkesbury Sandstone, where intense and deep sandstone weathering profiles have resulted in enhanced groundwater storage. Weathering reactions favoured by the local geological setting has transformed the original Hawkesbury Sandstone quartz arenite into a semisolid or friable sandstone with variable weathering depths where most of the original carbonate cements have been leached, resulting in higher porosity and permeability. XRD analyses show an upper zone down to ~50 m and even 90 m in some areas where all carbonates and probably feldspars have been dissolved and the derived products goethite and kaolinite have formed. With depth, carbonates, mostly siderite, are present representing fresher or less-weathered sandstone. Isotopic analysis of dispersed carbonates shows consistent values with their depositional environment and devoid of 14C. The study incorporated whole rock analysis from samples recovered during well construction at four sites to better characterise water–rock interactions. Based on hydrogeochemistry, isotopic tracers and mineral phase distribution from whole rock XRD analysis, two main groundwater zones are differentiated in areas not disturbed by groundwater extraction. A shallow zone where oxidising Na–Cl-type waters with low pH and EC contain 3H and 14C activities consistent with very modern groundwater affected by bomb pulse signatures (up to 116.9 pMC). In this shallow zone the original Hawkesbury Sandstone has been deeply weathered, enhancing storage capacity for groundwater down to ~50 m in most areas and up to ~90 m in the Peats Ridge zone. The deeper groundwater zone is also relatively oxidising with a tendency towards Ca–HCO3 type waters, higher pH and EC, no 3H and 14C activities consistent with residence times from 0.9 to 11.8 ka BP, depending on the specific areas. The original sandstone is less weathered with depth, favouring the dissolution of dispersed carbonates and a transition to a fractured-rock flow type aquifer, both impacting on groundwater mean residence times.
Differentiating recharge mechanisms and groundwater inputs in a carbonate aquifer (NW-Queensland, Australia)
(18th INQUA Congress, 2011-07-21) Van der Ley, M; Cendón, DI; Graham, IT; Spencer, J
The NW of Queensland is a remote pristine and sparsely populated region with minimal groundwater monitoring infrastructure. This is a semi-arid climatic region with monsoonal fronts between December and March being the main source of precipitation. While yearly rainfall averages 580 mm, evaporation can reach 3000 mm. Only a limited number of streams flowing north into the Gulf of Carpentaria sustain flow through the year. These are exclusively maintained by groundwater discharge during the dry season. Furthermore, all perennial streams share the same headwater lithology, consisting of an ∼80 m thick Cambrian marine-platform carbonate sequence. A number of water samples have been collected from perennial spring discharges and available wells downstream. Preliminary results suggest the presence of several aquifer systems operating at different time scales. The shallow system has short residence times as indicated by 35S activities in stream waters. The very low SO4 concentrations of stream waters (∼1 mg/L) suggests that most sulfur in the shallow system is marine derived and related to the last monsoonal rainfalls events. Intermediate systems discharge into perennial springs with longer residence times, where no 3H activity is detected and 14C activities suggest sub-modern groundwater. The comparison of 87Sr/86Sr and REEs of local lithologies and water samples show the interaction between water, carbonates and Proterozic metasediments. This proves intermediate systems either expand into underlying metasedimentary formations or mix with other sources prior to discharging in the springs. The deepest regional system contains palaeowaters (ca. 9000 a) that may have been partially recharged through carbonate lithologies but mostly flow through underlying Proterozoic metasediments, generally increasing in age towards the N but also mixing with younger waters along deep faults and other regional structural controls such as the Riversleigh impact structure.
Exceptional datolite crystals from Albion Park, New South Wales: morphology, chemistry and likely origin
(Mineralogical Society of Victoria, 2018) Graham, IT; Colchester, DM; Cendón, DI; Lay, A; Hergt, JM; Greig, A; Larsen, JR
Large, well-formed, semi-transparent yellow–green crystals up to 5.6 cm were found in cavities within the Late Permian Bumbo Latite Member of the Gerringong Volcanics in the now abandoned Cleary Brothers Quarry, Albion Park, New South Wales. Although labelled by the collector as calcite, these were later identified as datolite, with two distinct habits, occurring on a matrix of crystallized quartz and prehnite. The datolite contains very low concentrations of elements other than the essential calcium, silicon, oxygen and boron. Its distinctive chondrite-normalized, positive europium anomaly, when compared with datolite data from elsewhere, suggests crystallization from postdiagenetic hydrothermal fluids in the temperature range of 200–250°C. These datolite crystals are the finest ever found in Australia and rank highly with those found elsewhere in the world. © 2018 Mineralogical Society of Victoria
Groundwater modernisation and associated chemical changes in a Hawkesbury sandstone acquifer (Kulnura–Mangrove Mountain, NSW, Australia)
(Geological Society of Australia, 2014-07-07) Cendón, DI; Hankin, SI; Williams, JP; Graham, IT
Land and groundwater usage has the potential to influence the groundwater chemistry of an aquifer. Progressive modernisation of groundwater, variation in pH and associated water/rock reactions have been identified in areas of the Kulnura–Mangrove Mountain aquifer (KMMA). Detailed temporal and spatial sampling of groundwater (general hydrogeochemistry, H2O stable isotopes, δ13CDIC 3H, 14C and 87Sr/86Sr) revealed important inter-annual variations driven by groundwater extraction showing a progressive influx of modern groundwater at >100 m depth in some areas. In the Peats Ridge plateau, shallow groundwater samples show high 14C bomb pulse signatures, indicating modern recharged groundwater, while deeper groundwater shows a yearly increase in modern 14C inputs, instead of lower a14C values, as observed in other wells and generally expected. Values evolved from 36.1 pMC (5.2 ka BP) in 2007, to modern values of 103 pMC in 2010 with the latest sample in 2012 failing to graphitise, probably due to the high CO2 generally linked in the study area with modern groundwater. The 3H activities have also evolved from values below the quantification limit in 2007 and 2008 to values of ~1.1 TU in 2012. The minimal buffering capacity of the quartzose sandstone aquifer, at least in its upper zone where dispersed carbonates have long been dissolved, means that shallow groundwater generally has a low pH. Limited historical data (1998) shows higher pH for all samples compared to the same wells analysed for this work. However, it is in the central area where pH changes are most evident. During 2007, groundwater pH was similar to that expected for samples at similar depths with consistent groundwater residence times; however, successive samples show a shift to lower pH similar to those found in much shallower samples, as well as modern groundwater ages. Groundwater extraction is therefore causing an inflow of modern waters at depth with associated acidification. An important consequence of acidification is the capacity to mobilise trace metals. Of particular interest is aluminium as it has been linked to enhanced risks of cognitive decline for subjects with a high daily intake from drinking water (≥ 3.7 μM·day−1). Shallow samples in the Mangrove Mountain area and some of the deeper samples with Al concentrations of ~3.45 μM are a risk for average drinking water intakes. The movement of low pH shallow groundwater is causing an increase in Al concentrations, particularly in the central area of the KMMA, and this may be affecting groundwater for local consumption or that recovered in bottling plants. © Geological Society of Australia Inc
Groundwater residence time in a dissected and weathered sandstone plateau: Kulnura–Mangrove Mountain aquifer, NSW, Australia
(Taylor Francis Online, 2014-04-14) Cendón, DI; Hankin, SI; Williams, JP; Van der Ley, M; Peterson, MA; Hughes, CE; Meredith, KT; Graham, IT; Hollins, SE; Levchenko, VA; Chisari, R
Groundwater residence time in the Kulnura–Mangrove Mountain aquifer was assessed during a multi-year sampling programme using general hydrogeochemistry and isotopic tracers (H2O stable isotopes, δ13CDIC, 3H, 14C and 87Sr/86Sr). The study included whole-rock analysis from samples recovered during well construction at four sites to better characterise water–rock interactions. Based on hydrogeochemistry, isotopic tracers and mineral phase distribution from whole-rock XRD analysis, two main groundwater zones were differentiated (shallow and deep). The shallow zone contains oxidising Na–Cl-type waters, low pH, low SC and containing 3H and 14C activities consistent with modern groundwater and bomb pulse signatures (up to 116.9 pMC). In this shallow zone, the original Hawkesbury Sandstone has been deeply weathered, enhancing its storage capacity down to ∼50 m below ground surface in most areas and ∼90 m in the Peats Ridge area. The deeper groundwater zone was also relatively oxidised with a tendency towards Ca–HCO3-type waters, although with higher pH and SC, and no 3H and low 14C activities consistent with corrected residence times ranging from 11.8 to 0.9 ka BP. The original sandstone was found to be less weathered with depth, favouring the dissolution of dispersed carbonates and the transition from a semi-porous groundwater media flow in the shallow zone to fracture flow at depth, with both chemical and physical processes impacting on groundwater mean residence times. Detailed temporal and spatial sampling of groundwater revealed important inter-annual variations driven by groundwater extraction showing a progressive influx of modern groundwater found at >100 m in the Peats Ridge area. The progressive modernisation has exposed deeper parts of the aquifer to increased NO3− concentrations and evaporated irrigation waters. The change in chemistry of the groundwater, particularly the lowering of groundwater pH, has accelerated the dissolution of mineral phases that would generally be inactive within this sandstone aquifer triggering the mobilisation of elements such as aluminium in the aqueous phase. © 2020 Informa UK Limited
Groundwater systems in northern Australia – are they suitable for a northern food bowl: evidence from residence times and geochemical analyses of ground and surface waters in the Lawn Hill region, northwest Queensland
(Geological Society of Australia, 2014-07-07) Van der Ley, M; Cendón, DI; Graham, IT
Water resources in the northern regions of Australia have become increasingly important with the possible development of a northern ‘food-bowl’. Understanding the chemistry, flow systems, and mean residence time (MRT) of groundwater systems in this region is therefore essential. The Lawn Hill region of northwest Queensland is subjected to a semi-arid monsoonal climate with an average of 542 mm/a – the majority falling in the warmer months through November–March. Due to the polarity of rainfall, most streams run dry during the dry season. However, four major perennial streams are maintained by groundwater discharge, highlighting the importance of groundwater–surface water interaction and our understanding of such systems. The regional geology is dominated by the Barkly Tableland, an expansive Cambrian carbonate plateau, or siliciclastic formations of the Proterozoic Mount Isa Inlier. The carbonate and siliciclastic lithologies exhibit variable influences on groundwater chemistry and flow. There are distinct differences in chemical signatures whereby the carbonate-hosted groundwater was found to be strongly influenced by carbonate dissolution with little evidence of evapotranspirative enrichment as indicated by both Cl concentrations and stable water isotopes (SWI). Conversely, major ion chemistry and SWI composition of the siliciclastic-hosted groundwaters suggest they are strongly influenced by evapotranspirative enrichment and less by later water–rock interactions (though these do impart a signature on groundwater chemistry). Importantly, the limited influence of evapotranspiration on carbonate-hosted groundwater with TDS values ranging 540–611 mg/L means these waters are classified as freshwater and represent a low–medium irrigation salinity risk. Comparatively, the siliciclastic-hosted groundwaters have much higher TDS values (599–7204 mg/L), which spans the fresh–brackish–saline classifications and represents a medium–high salinity risk. These differences highlight the fact that suitability of groundwater for irrigation purposes greatly depends on the geological controls through water–rock interactions and influence on groundwater infiltration. The mean residence time (MRT) of groundwater is an important indicator for groundwater sustainability. Again, there is a clear distinction between carbonate and siliciclastic hosted groundwaters. Both tritium and radiocarbon analyses of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) indicate a modern age for carbonate groundwaters with fast recharge indicating the carbonate groundwater is less susceptible to depletion but more susceptible to anthropogenic influences. Comparatively, measurable tritium concentrations in siliciclastic groundwaters indicate a modern system; however, DIC and DOC radiocarbon analyses indicate a much older groundwater up to ca 10 000 a (depending on the flow model applied). The differences between tritium and radiocarbon MRT may indicate more complex mixing between young and old groundwater and slower recharge, suggesting siliciclastic groundwaters may be susceptible to depletion.
Hydrogeochemical processes in a monsoon dominated karst environment, NW Queensland
(Australian Geosciences Council, 2012-08-05) Van der Ley, M; Cendón, DI; Graham, IT; Spencer, J
The Lawn Hill region, NW Queensland Australia, is host to perennial streams fed by springs from a large karstic aquifer with sub-modern (>50 y) groundwater, developed in Cambrian carbonate lithologies. NW Queensland is subject to semi-arid monsoon climates, and consequently the modern ground and surface waters and their interactions are greatly dependent on seasonal variability of rainfall. We have used a range of techniques to evaluate hydrogeochemical processes including geochemical analysis of host rocks, and a range of isotopic and chemical analyses of ground and surface waters. Samples were collected over multiple sampling campaigns, including during the wet season. Surface waters and groundwaters from carbonate terrains were found to be similarly Ca(Mg) HCO3 type waters as expected from interactions with the karst carbonates, which were found to be composed of primarily dolomite and minor chert. However, there are many indicators (14C, 3H and others) of a more complex system with different temporal scales. Surface waters, while showing dolomitic interactions, have compositions which suggest interaction with underlying silicic lithologies before forming springs. Also, variability in the strength and timing of the monsoon appears to have an effect on activation of different springs and groundwater flow. Additionally, there are groundwaters with much longer residence times (∼6000 a) and chemistries indicative of interaction with silicic and underlying Proterozoic sedimentary units.
Hydrogeochemistry of modern streams in the Riversleigh area (QLD-Australia): relationship with local carbonate lithologies-preliminary results
(University of New South Wales, 2006) Cendón, DI; Graham, IT; Price, I; Hankin, SI; Chivas, AR
Not available
The Kulumadau epithermal breccia-hosted gold deposit, Woodlark Island, Papua New Guinea
(AusIMM, 2015-03-18) Burkett, D; Graham, IT; Spencer, L; Lennox, P; Cohen, D; Zwingmann, H; Lau, F; Kelly, BFJ; Cendón, DI
The Kulumadau deposit represents an intermediate-sulfidation epithermal gold deposit (3.8 Mt at 2.3 g/t, Ag:Au = 1). Mineralisation is primarily confined to hydrothermal breccias within preexisting fault zones, where it is disseminated throughout a hydrothermal matrix comprising chlorite-quartz-adularia-illite-I/S clays-calcite-pyrite. The host sequence represents numerous mid-Miocene pyroclastic flow eruptions within a tectonically active emergent shallow marine to subaerial depositional setting. Subsequent growth faulting was responsible for debris avalanches, which were subsequently cut by reverse faults. Faults were exploited by hydrothermal fluids, with the heightened porosity at the juncture between faults and debris material facilitating boiling of the ore constituents. Fluid inclusion studies suggest that fluid mixing between meteoric fluids and magmatic fluids, accompanied by boiling, were the primary mechanisms for gold deposition. The occurrence of anhydrite/gypsum as late-stage veins and their sulfur and oxygen isotopic values indicate post-mineralisation mixing of sea water with hydrothermal fluids.
Radiocarbon analysis of bulk and fractionated dissolved organic carbon from ground and surface waters in remote NW Queensland
(Australian Geosciences Council, 2012-08-05) Van der Ley, M; Cendón, DI; Graham, IT
Radiocarbon analysis of dissolved inorganic carbon (DIC) is prone to dilution by radiocarbon-free DIC from older hosts, particularly in carbonate-rich areas. Dissolved organic carbon (DOC) can provide a source of carbon less affected by water-rock interactions, but is rarely utilised due to more complex sample processing and potential residence time differences for specific fractions. We have developed and applied 14C methods of bulk and fractionated DOC to waters in the Lawn Hill region, remote NW Queensland. As groundwater chemistry here is largely controlled by interactions with Cambrian carbonates, analysis of 14CDIC required uncertain geochemical corrections. Additional samples were analysed from the Greater Sydney region, NSW, with greater variety of residence times and chemistries, to test the methodology. Bulk DOC was pre-concentrated in the field using a weak and non-selective resin, followed by extraction in the lab and fractionation into different DOC groups based on ultrafiltration and selective resin adsorption techniques. All samples were characterised using liquid chromatography and fluorescence to monitor the characteristics of different fractions. Comparisons of 14C activities of DIC and DOC highlight the effect of carbonate dissolution and the usefulness of DOC in radiocarbon analyses. DIC activities were consistently lower than those of DOC, particularly in carbonate-rich regions. Additionally, comparison of fractionated DOC samples showed varying 14C activities, indicating that fractionation may be required for reliable residence times.
Stratigraphy and age-dating of the Kiriwina Formation,Woodlark Island, Papua New Guinea
(Australian Geosciences Council, 2012-08) McGeeney, D; Graham, IT; Cohen, DD; Spencer, L; Jacobsen, GE; Williams, A
The Upper-Pleistocene Kiriwina Formation (KFm) of Woodlark Island, Papua New Guinea, is a complex, largely transitional shallow marine to near-shore terrestrial sedimentary unit. This study provides the first detailed analysis of the KFm on any KFm hosting island of the Solomon Sea. Highly elevated Au contents (up to 10 ppm) occur within various sub-units. The KFm covers most of the island’s surface, has a thickness of 0–90m, and unconformably overlies the mid-Miocene Okiduse Volcanics that host carbonate-base metal-Au epithermal mineralization. The formation has undergone rapid horizontal and vertical changes in the sedimentary environment and style; individual units and subunits occur as repeated lenses of conglomerates, gritstones, beach sands, silts, lagoonal clays, and mixed clays/carbonates. The KFm is capped by porous and permeable shallow marine limestones, which in places have undergone karst development. Detailed mapping indicates previously unknown near-shore terrestrial subunits that may comprise a large part of the sequence. Andesitic fragments are widely dispersed throughout each member and subunit. The main clay in the Talpos Marine Clay Member is nontronite, an Fe-rich smectite. New C14 radiometric age-dating has determined the KFm to be 47,130–60,300 yrs BP at Kulumadau and > 70,000 yrs BP at Busai. These ages were used as a basis to determine an average uplift rate of 1.06m/1000 years.
Understanding Riversleigh’s geology: what we know in 2006, and where to next
(University of New South Wales, 2006) Graham, IT; Price, E; Cendón, DI; Woodhead, JD
Not available

Browsing by Author "Graham, IT"

Results Per Page

Sort Options