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Association of large sandstone uranium deposits with hydrocarbons

Article · January 2008

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The user has requested enhancement of the downloaded file. issue 89 Mar 2008 Association of large sandstone uranium deposits with hydrocarbons Canning The geology of uranium deposits in Kazakhstan Basin Bigrlyi Walbiri points to similar deposits in Australia Ngalia Basin Western Angela Subhash Jaireth, Aden McKay and Ian Lambert

Sandstone uranium deposits account for approximately 30% of or through the production of

annual global production, largely through in situ leach (ISL) mining. biogenic hydrogen sulfide (H2S: Most of this production has come from deposits in the western Spirakis 1996). In sandstones United States, Niger and Kazakhstan. In Australia, sandstone-hosted relatively poor in organic material, uranium is being produced from the Beverley deposit in the Frome it has been proposed that the

Embayment of South Australia, and a second ISL mine is under reduction is caused either by H2S development at Honeymoon in the same region. (biogenic as well as nonbiogenic) Such deposits form where uranium-bearing oxidised groundwaters produced from the interaction moving through sandstone aquifers react with reducing materials. of oxidised groundwater with The locations of ore zones and the sizes of mineral deposits depend, pyrite in the sandstone aquifer among other factors, on the abundance and reactive nature of the (thiosulfate produced initially by reductant. Hence, the nature and abundance of organic material in oxidation of pyrite breaks down the ore-bearing sedimentary sequence may be of critical importance to form reduced sulfur), or from for the formation of sandstone uranium deposits. the introduction of reduced fluids/ gases (H S, hydrocarbons or In sandstones rich in organic material (containing debris of fossil 2 plants or layers of authigenic, or in situ generated, organic material) the both) along favourable structures organic matter either reduces uranium directly with bacteria as a catalyst, (Spirakis 1996). This paper outlines the geology of the world-class sandstone Turgai Hydrocarbon 65° E70°E Region uranium deposits in the Chu-

0 200 km Sarysu and Syrdarya basins in the south-central portion of Kazakhstan, which are hosted Chu-Sarysu Lake by sandstones relatively poor Inkai Hydrocarbon Aral Region Sea Chu-Sarysu Basin 45° N in organic matter (figure 1, Kyzl-Orda table 1). We highlight the Kara Moinkum Syrdarya BasinKaramurun tau Mo unta crucial role that hydrocarbons ins appear to have played in the Zarechnoye formation of these and other ? Chimkent ? large sandstone type uranium deposits. Based on the model 07-2553-1 Cenozoic Sedimentary basins Redox front in Uranium mine developed, we conclude that underlain by Palaeozoic Palaeogene sands Mesozoic Oil/gas field sediments Redox front in Upper there is considerable potential Archaean, Proterozoic Cretaceous Gas field and Palaeozoic - upper sands in Australia for the discovery of metasediments Redox front in Upper Outline of and granitoids Cretaceous hydrocarbon - middle sands region large sandstone-hosted uranium mineralisation, including in little Figure 1. Regional geology of Chu-Sarysu and Syrdarya basins, southern Kazakhstan. Geological data plotted from the Generalized Geological Map of the World (1995), Geological Survey of explored regions underlain by Canada Open File 2915d. Boundary of the hydrocarbon basins and location of oil and gas fields basins with known or potential in the underlying Permian rocks from a map produced by Blackbourn Geoconsulting (http://www.blackbourn.co.uk/databases/hydrocarbon/chusarysu.html). hydrocarbons.

Association of large sandstone uranium deposits with hydrocarbons 1 issue 89 Mar 2008

Table 1 Uranium resources, organic carbon and sulfides in basins hosting The ore zones extend for major resources of sandstone uranium deposits 20 to 30 kilometres along the Basin/sub-basin Resources Organic Iron sulfide redox front; in plan, they form (‘000 tonnes carbon (wt%) ribbons 50 to 800 metres wide

U3O8) (wt%) (rarely, 1.7 kilometres). In cross- Chu-Sarysu and 1340a < ~ 0.03–0.05b 0.1c section, the zones are asymmetric Syrdarya roll-fronts, tabular bodies and Callabonna (Frome 41.2d < 0.05 to 0.5e Tracese lenses. Thickness varies from five Embayment) metres to more than 25 metres. Wyoming 320f 0.5c 1 to 4c Uranium mineralisation occurs as South Texas 45 to 80g <0.16h 0.5 to 4h coffinite and pitchblende, which a Fyodorov (1999); b Petrov (1998); c Fyodorov (1996); d Ozmin database, Geoscience are finely dispersed in the clay Australia (2007); e Heathgate Resources (1998); f after de Voto (1978); g Dhalkamp (1993); matrix and also infill cavities in h Goldhaber et al (1978) sandstone (Petrov 1998). The depth of uranium ore varies from 100 metres to more than 800 The geological setting in Kazakhstan metres (Fyodorov 1996). The Chu-Sarysu and Syrdarya basins of Kazakhstan are components The source of uranium in the of a large artesian basin that was split into two main components deposits is not clear. It could have following the Pliocene uplift of the Karatau Mountain Range (figure been derived from Ordovician 1). The basins are filled with thick sandstone aquifers capped by and Silurian metasediments impermeable shaly beds. Mineralisation, often as roll fronts, is hosted and granites exposed in the by sands of Upper Cretaceous and Palaeocene–Eocene age. Tyan-Shan Ranges along the The Chu-Sarysu Basin is more mineralised than the Syrdarya Basin southeastern flanks of the basin, and contains larger uranium deposits, which are hosted by a Late which also provided the detrital Cretaceous – Palaeogene age multicoloured clay–gravel–sandstone material for the sedimentary sequence deposited in a continental environment. The large deposits sequence hosting mineralisation. include Inkai, Moinkum, Karamurun and Zarechnoye. In the Uranium-bearing hydrothermal Syrdarya Basin, the host is a grey clay – sandstone sequence formed in vein deposits hosted in pre- coastal-marine and continental conditions (Petrov 1998). Mesozoic metasediments along The roll fronts display mineral and geochemical zoning typical of the northeastern flanks of the oxidation–reduction fronts associated with sandstone uranium deposits Chu-Sarysu Basin could also elsewhere. Hydroxides of iron dominate the oxidation zone, whereas have been a source (Petrov 1998). the reduced zones are dominated by iron sulfides (pyrite and marcasite). Further uranium could have been The uranium zone is enriched in rhenium, zinc, copper, silver, cobalt, contributed from devitrification molybdenum, nickel and vanadium. Significant enrichments of of volcanic tuff interbedded with selenium occur towards the contact with the zone of reduction. Palaeocene/Eocene sands. Lead–lead isotope model ages suggest that mineralisation “Based on the model developed, we occurred in three more or less continuous stages starting conclude that there is considerable potential from Late Oligocene – Middle Miocene and continuing into in Australia for the discovery of large Late Pliocene to Quaternary time (Mikhailov and Petrov 1998). sandstone-hosted uranium mineralisation.” Tectonic reactivation during

Association of large sandstone uranium deposits with hydrocarbons 2 issue 89 Mar 2008

the Late Oligocene – Middle Miocene created palaeogeographic thick containing oil and gas conditions favourable for large-scale groundwater flow from the (figure 2; Bykadorov et al 2003). palaeo Tyan-Shan region in the southeastern flanks of the basin. The Chu-Sarysu hydrocarbon The regional extent and general distribution of the redox fronts in basin is made up of two the basins suggests that the palaeo-groundwater flow direction was sequences: lagoonal to marginal- predominantly from the southeast to the northwest. Groundwaters marine salt-bearing strata of probably entered permeable aquifers adjacent to the Tyan-Shan Famenian – Early Carboniferous uplands (Petrov 1998) and flowed towards discharge zones in the age; and alluvial-lacustrine red- general region of the Aral Sea. beds of Middle Carboniferous Late Pliocene – Quaternary ages of mineralisation coincide with – Permian age. The latter include intensive tectonic activity associated with orogenic movements in the Tyan-Shan and the uplift of the Karatau Mountains, along a 500 metres of Permian evaporites. pre-existing regional fault, which created the present-day Visean and Early (pre-salt) hydrodynamic regime. Groundwater flows associated with the Permian sandstones host minor Karatau uplift only caused minor changes in the configuration of volumes of gas. The southeastern the mineralised regional redox fronts created in the Late Oligocene – part of the basin contains Middle Miocene (Petrov 1998). hydrocarbon source rocks and Although organic material in the ore-bearing grey sandstones is also hosts the principal oil and quite low (generally <0.03–0.05%; table 1), Petrov (1998) believes gas fields. Famenian – Early that it was enough (with a minor contribution from iron sulfides) to Carboniferous marls and black produce large sandstone uranium deposits. Petrov ascribes the lack of shales and Permian bituminous direct correlation between uranium and the concentration of organic marls with high total organic material to coalification of organic material, which caused loss of carbon may be an additional active organic reductants such as waxy bitumen and humic acids. source, with Permian salts acting as a regional cap (Bykadorov Chu-Sarysu oil and gas basins et al 2003). The Late Cretaceous to Palaeogene continental and marine Aubakirov (1998) suggested sedimentary sequence that hosts world-class sandstone uranium that the uranium mineralisation deposits is underlain by a Palaeozoic sequence up to five kilometres formed at a geochemical trap created by an influx of reduced

Karatau Mountains Diagrammatic - not to scale fluids/gases (hydrocarbons and

H2S) along relatively deeply Syrdarya Chu-Saryssu Basin Basin penetrating structures. Chemical analyses of drill core samples through the ore zones show that hydrocarbon gases have accumulated along the redox Uranium deposits front. Some authors consider 07-2553-2 Neogene and Quaternary Late Cretaceous Palaeozoic that this accumulation of Alluvium and Shale, sandstone sediment Clay/silt limestone; locally hydrocarbon gases facilitated hydrocarbons-bearing Palaeogene Medium and fine grained sands Jurassic- Early Cretaceous large-scale ore formation over Clay/silt - thick aquitard Coarse grained sand/gravel Granite extensive redox boundaries Sand (Fyodorov 1999), although the Figure 2. Cross-section of Chu-Sarysu and Syrdarya basins (looking northwest) (Yazhikov 1996). detailed geochemical (including

Association of large sandstone uranium deposits with hydrocarbons 3 issue 89 Mar 2008

In other roll-front systems Hydrocarbon-bearing Basins Darwin Producing (such as in the Wyoming Basin), With flows oxidised waters encounter McArthur Basin With shows reducing materials distributed With more than 3 exploration wells

Felsic igneous rocks through the aquifer and the

Northern Sandstone uranium deposits redox roll front migrates Carpentaria and (Phanerozoic) Territory Karumba Basin Georgina Basin progressively down dip. Under these conditions, the potential for Canning Basin Bigrlyi Walbiri Queensland very large deposits is considered Ngalia Basin lower and the deposits tend to Western Angela Australia Eromanga Basin occur within about 60 kilometres Galilee Basin Cooper Basin of the margins of the sandstone South Bowen Basin Australia uranium basins. Warburton Basin Clarence- Officer Basin Eromanga Basin Surat Basin Morton Eromanga Basin Basin Brisbane Frome Beverley Embayment* 4 Mile Warrior Oban Examples in China Goulds Dam Honeymoon and Texas New South Wales

0 500 km The close spatial association Adelaide Sydney

* Frome Embayment has Mesozoic/Cenozoic between sandstone uranium sediments of Callabonna Sub-Basin overlying felsic igneous rocks Victoria 07-2553-3 deposits and hydrocarbon- Figure 3. Maps showing hydrocarbon-bearing onshore basins of Australia and Archaean/ bearing basins observed in the Proterozoic terranes with uranium-rich felsic rocks. Data for hydrocarbon-bearing basins from Geoscience Australia’s dataset of Sedimentary basins. Outcropping felsic rocks (NSW, Northern Chu-Sarysu Basin is not unique. Territory, Queensland, Tasmania, Victoria) from Geoscience Australia’s 1:1 000 000 Surface Geology of Australia map. Felsic rocks in SA and WA extracted from the solid geology maps of In recent years, sandstone SA and WA (Solid Geology of South Australia, 2006 and 1:500 000 Interpreted Geology Map uranium deposits closely of Western Australia, June 2001) respectively. associated with hydrocarbon- bearing basins have been sulfur and carbon isotopic) studies required to define more precisely identified in the Ordos and the role of hydrocarbons and/or H2S in the Chu-Sarysu and Syrdarya Songlio basins in China (for basins have not been conducted. example, Huang Xian-fang et al Based on the observed features, we propose that the one condition 2005). conducive to formation of the large Kazakhstan sandstone uranium Further afield, in the Texas deposits (table 1) is the organic-poor nature of the highly permeable Uranium Region (Texas Coastal sands in the large Cretaceous and younger artesian basin, which Plain), uranium mineralisation in ensured sustained flow of uranium-bearing oxidised groundwater in organic-poor sandstones has been the aquifers. The other favourable condition would have been the attributed by several researchers to localised availability of active reductants in the form of hydrocarbon the influx of 2H S along faults from gases (including H2S) leaking from Permian hydrocarbon reservoirs hydrocarbon reservoirs at depth (figure 1). A rapid and localised reduction might be critical to form (Reynolds and Goldhaber 1978). relatively large deposits, and tectonic activation of faults in the Late Oligocene – Middle Miocene could have facilitated ingress of the necessary hydrocarbon gases, particularly at the margins of Implications for the hydrocarbon reservoir where the seal was less effective. These Australia conditions resulted in the location of roll fronts at distances of 300 Australia holds roughly 30% to 350 kilometres from the uranium basin margin. of global uranium resources

Association of large sandstone uranium deposits with hydrocarbons 4 issue 89 Mar 2008

recoverable at

Diagrammatic - not to scale sections, as is the case in the

Oxidised waters Vulcan sub-basin. Other datasets dissolved U Roll front useful for the exploration of bodies CH4 & H 2 S Tabular bodies sandstone uranium systems U-rich Playa Lake source include oxidation state of rocks Mudstone groundwaters and sandstones Gas Oil from hydrogeochemistry; Caprock colour of sandstone (and other indicators of oxidation state); distributions of hydrocarbon cap 07-2553-4 rocks; porosity and permeability Figure 4. Diagrams showing proposed model. Uranium is carried in oxidised groundwaters of sandstone aquifers; and active and reduced by hydrocarbons and/or H2S released from the underlying oil and/or gas field. Both roll-front and tabular ore bodies can result from the process. During ore deposition structures. hydrocarbons are often oxidised to form carbonates.

Association of large sandstone uranium deposits with hydrocarbons 5 issue 89 Mar 2008

Conclusions Technical Meeting, Vienna, June 1999. IAEA-TECDOC 1425: We propose that potentially large sandstone uranium mineralisation is 95–112. most likely to occur where three criteria are met: Heathgate Resources. 1998. Beverley • hydraulic connections to uranium-enriched source rocks Uranium Mine. Environmental Impact Statement. Unpublished. • presence of permeable sandstone aquifers, with impermeable rocks Huang Xian-fang, Liu De-chang, above and below that seal the aquifer Du Le-tian & Zhao Ying-jun. 2005. • hydrocarbon accumulations in the sequence underlying the aquifers A new sandstone type uranium together with features that could have facilitated migration of metallogenetic type—‘structure—oil, gas type’. In: Jingwen Mao & hydrocarbon gases into the uraniferous aquifer, in particular areas Bierlein FP (eds), Mineral Deposit at the margins of hydrocarbon cap-rocks and where there has been Research: Meeting the Global reactivation of structures. Challenge. Proceedings of the Eighth Biennial SGA meeting, Beijing, This model has been applied to Australia at regional scale, leading China, August 2005, 265–268. to the conclusion that there is considerable scope for discovery of Mikhailov VV & Petrov NN. 1998. major sandstone uranium mineralisation of the general type being Age of exogene uranium deposits mined in Kazakhstan. in south and south-east Kazakhstan according to the lead-isotope study. Geology of Kazakhstan 2(354): For more information 63–70. phone Subhash Jaireth on +61 2 6249 9419 O’Brien GW & Woods EP. 1995. email [email protected] Hydrocarbon-related diagenetic zones (HRDZs) in the Vulcan sub- basin, Timor Sea: Recognition and Acknowledgments exploration implications. APEA Journal 220–251. We thank Lynton Jaques, Graham Logan, Yanis Miezitis and Roger Skirrow who reviewed this paper and Neale Jeffery who provided Petrov NN. 1998. Epigenetic stratified-infiltration uranium cartographic and drafting support. deposits of Kazakhstan (in Russian). Geology of Kazakhstan 2(354): References 22–39. Aubakirov KhB. 1998. On the deep origin of ore-forming solutions in the uranium deposits in platform sequence of depressions (with Chu-Sarysu Reynolds RL & Goldhaber MB. Province as an example). Geology of Kazakhstan 2(354):40–47. 1978. Origin of a South Texas roll- type uranium deposit: I. Alteration Bykadorov VA, Bush VA, Fedorenko OA, Filipova IB, Miletenko NV, of iron – titanium oxide minerals. Puchkov VN, Smirnov AV, Uzhekenov BS & Volozh AV. 2003. Ordovician– Economic Geology 73:1677–1689. Permian palaeogeography of Central Eurasia: Development of Palaeozoic petroleum-bearing basins. Journal of Petroleum Geology 26:325–350. Spirakis CS. 1996. The roles of organic matter in the formation of Dahlkamp F J. 1993. Uranium Ore Deposits. Berlin, Springer–Verlag. uranium deposits in sedimentary de Voto RH. 1978. Uranium Geology and Exploration. Lecture Notes and rocks. Ore Geology Reviews References. Colorado School of Mines 11:53–69. Yazhikov, V. 1996. Uranium raw Fyodorov GV. 1996. A comparative description of the geological- material base of the Republic technological characteristics of the sandstone-hosted uranium deposits in of Kazakhstan and prospects of Wyoming and Southern Kazakhstan. In: In Situ Leach Uranium Mining. using in situ leach mining for its Proceedings of International Atomic Energy Agency Technical Committee development. In: In Situ leach Meeting, Almaty, Kazakhstan, September 1996. uranium Mining. Proceedings Fyodorov GV. 1999. Uranium deposits of the Inkai–Mynkuduk ore field, of IAEA Technical Committee Kazakhstan. In: Developments in Uranium Resources, Production, Demand Meeting, Almaty, Kazakhstan, and the Environment. Proceedings of International Atomic Energy Agency September 1996.

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