Salt as a fluid driver, and basement as a metal source, for stratiform sediment-hosted copper deposits

Koziy, Lyudmyla; Bull, SW; Large, Ross R.; Selley, D

doi:10.1130/g30380a.1

Cited by 38 publications

(13 citation statements)

References 19 publications

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“…Although the permeability of the basement rocks is significantly lower than that of the overlying sedimentary basin, basin-derived brine percolations have been documented down hundreds of meters within the proximal clay-rich basement rocks surrounding the U deposits, and also in distal, macroscopically fresh samples . These observations, along with mineralization and an alteration halo >400 m below the unconformity at the Eagle Point deposit (Cloutier et al, 2011;Mercadier et al, 2011a), are well documented and clearly indicate large-scale brine percolations and interactions within the basement, as demonstrated for other metal deposits (Ag, Pb-Zn, Cu) located close to basement cover interfaces (Essaraj et al, 2005;Koziy et al, 2009;Boiron et al, 2010).…”

Section: Introductionmentioning

confidence: 78%

“…The development of massive and deep (>400 m below the unconformity) clay-rich alteration halos in the basement rocks near major fault systems and deposits (Alexandre and Kyser, 2005;Jefferson et al, 2007) demonstrates the capability of the basinal brines to percolate into the basement rocks. This was proposed previously for the formation of some basin-and unconformity-hosted Cu and Pb-Zn deposits (Koziy et al, 2009;Boiron et al, 2010). Recent numerical modeling of brine flow for the Athabasca Basin at the time of unconformity-related deposit formation clearly demonstrates the possibility of downward brine percolations in basement rocks during tectonic reactivation (Cui et al, 2012).…”

Section: Hudsonian Uranium Oxides: a Uranium Source For The Unconformmentioning

confidence: 91%

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Magmatic and Metamorphic Uraninite Mineralization in the Western Margin of the Trans-Hudson Orogen (Saskatchewan, Canada): A Uranium Source for Unconformity-Related Uranium Deposits?

et al. 2013

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The genetic model for the giant unconformity-related uranium deposits of the Athabasca Basin is still being debated, with one of the main issues being the source of the uranium concentrated by Mesoproterozoic era (ca. 1.60-1.00 Ga) diagenetic-hydrothermal events at the interface between the Athabasca Basin and the underlying Archean/Paleoproterozoic basement rocks. Currently, accessory minerals like monazite, zircon, and/or apatite from the sedimentary basin and basement rocks are proposed as the primary uranium source for these high-grade uranium deposits. Numerous occurrences of U mineralization of Hudsonian age have been documented for decades all around the Athabasca Basin; however, so far these have not been regarded as viable U sources. Here, a systematic and detailed study of two areas of basement rocks near the eastern part of the Athabasca Basin is presented (i.e., the Way Lake property, lying outside the current margin of the basin, and the Moore Lakes property, currently covered by the basin). This study highlights the significant and widespread occurrence of Hudsonian (ca. 1.81-1.76 Ga) uranium oxide (UO2) mineralization in these zones. Two types of mineralization are identified and documented here: magmatic uranium oxides related to granitic pegmatites and leucogranites, which are more common, and high-temperature, vein-hosted uranium oxides, which have the highest grades. The two types were formed during the peak (1.82-1.81 Ga) and/or postthermal peak (1.81-1.72 Ga) events related to the evolution of the Trans-Hudson orogeny. The magmatic uranium oxides formed by partial melting of Wollaston Group metasedimentary rocks. The origin of the vein-type occurrences is unclear, but their high thorium and rare earth element (REE) contents suggest a high-temperature process associated with Ca and/or Na metasomatism. The uranium oxides are associated with other U-, Th-, and REEbearing accessory minerals like U-rich thorite, thorite, zircon, and/or monazite, adding to the exceptional U contents (100-2,460 ppm) of these UO2-bearing rocks (up to 200 times more primarily enriched in U than other basement or basin rock types). A 3-D model of a 1,300 × 630 × 200-m basement zone from the Way Lake property indicates that uraninite-bearing granitic pegmatites and leucogranites represent 7% of the total volume of crystalline rock. Within this rock volume are approximately 8,121 (assuming a mean U content of 250 ppm) to 16,242 (assuming a mean U content of 500 ppm) tonnes U. The U tonnage of this limited rock volume, contained mainly by the Hudsonian-age UO2, corresponds to between 4% (for McArthur River) and 103% (for Rabbit Lake) of the U tonnage of known unconformity-related U deposits of the basin.Some of the studied rock samples, even macroscopically fresh and located far away from any known unconformity-related U deposit, present clear evidence of alteration, including clay minerals, aluminophosphatesulfate (APS) minerals, and UO2 dissolution, indicating the percolation of the brines associated with the formation ...

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Section: Introductionmentioning

confidence: 78%

Section: Hudsonian Uranium Oxides: a Uranium Source For The Unconformmentioning

confidence: 91%

Magmatic and Metamorphic Uraninite Mineralization in the Western Margin of the Trans-Hudson Orogen (Saskatchewan, Canada): A Uranium Source for Unconformity-Related Uranium Deposits?

et al. 2013

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“…2010). The role of basement as the main metal reservoir, the sedimentary cover being insufficient to account for the mass of metal deposited, has been put forward also for other metals such as copper, on the basis of mass and heat transfer modelling (Koziy et al. 2009).…”

Section: Discussionmentioning

confidence: 99%

Fluid flows and metal deposition near basement /cover unconformity: lessons and analogies from Pb–Zn–F–Ba systems for the understanding of Proterozoic U deposits

Boiron¹,

Cathelineau²,

Richard³

2010

Geofluids

105

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Fluid circulation at basement ⁄ cover unconformities is of first importance for metal transfer and especially the formation of Pb-Zn, F, Ba and U-deposits. This is typically the case for world-class Proterozoic U deposits (Canada, Australia, Gabon) in basins, which show many similarities with younger Pb-Zn-F-Ba systems (Irish Paleozoic Pb-Zn deposits, F-Pb-Zn-Ba deposits related to extensional tectonics from Spain, western France and Silesia and fluid movements related to continental rifting in the Rhine graben). As fluid mixing near the basement ⁄ cover unconformity is one of the key factors for ore formation, a series of parameters have been considered for both systems: the time gap between basin formation and metal deposit, the origin and nature of the ore fluids, the temperature of fluid end members and the style of migration. Results show great similarities in all fluid systems: (i) a wide range of fluid salinity indicating the lack of homogeneity of fluid chemistry at the scale of the reservoirs, (ii) the deep penetration of brines through faults and dense networks of microfractures within the basement below the unconformity, (iii) local fluid-rock interaction leading to porosity increase and significant fluid changes in fluid chemistry, (iv) a pulsatory fluid regime during fluid trapping, (v) anisothermal fluid mixing revealed by a systematic temperature gap between brines and recharge fluids, (vi) stages of fluid movements facilitated by discontinuous opening related to later tectonic ⁄ telogenetic stages linked to major geodynamic events, typically without related sedimentation and burial (exception in a few cases characterized by the synchronous production and penetration of surface brines and ore genesis). By analogy with younger systems, the conditions of burial and penetration of brines in the Archean basement suggest that thermal convection drove the brine movements, and was possibly linked to extensional tectonics in a part of the giant mid-Proterozoic U-deposits.

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“…; Koziy et al . ). However, considering the uncertainties of salinity distribution at the time of mineralization in the Athabasca Basin (e.g.…”

Section: Study Methods and Inputsmentioning

confidence: 97%

The effects of basement faults on thermal convection and implications for the formation of unconformity‐related uranium deposits in the Athabasca Basin, Canada

Chi

Bethune

2016

Geofluids

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The formation of the world‐class, high‐grade unconformity‐related uranium deposits in the Athabasca Basin (Canada) requires circulation of large amounts of fluids, the mechanisms for which are still not well understood. Recent studies advocate thermal convection as a possible driving force for the fluid flow related to uranium mineralization; however, little is known regarding how basement faults, which are spatially associated with most unconformity‐related uranium deposits, influence fluid convection and how this may affect the localization of mineralization. This study addresses these questions through simulations of thermal convection with various configurations of basement faults using the FLAC3D software. Modelling results indicate that the location, spacing, orientation and thermal conductivities of basement faults influence the size and location of thermally driven fluid convection. In a model with a single isolated fault, the fault coincides with an upwelling plume and the dip angle of the fault does not affect the fluid flow pattern; when the fault is moved laterally, the upwelling plume shifts accordingly. In the case of two vertical faults, the faults may either coincide with upwelling flow between two convection cells or be located below individual convection cells, depending on fault spacing. In the latter case, fluid may flow into and out of individual fault zones. Similar results were also obtained for models with two nonvertical (i.e. dipping) faults. Convective flow can penetrate the uppermost basement when the permeability is less than two orders of magnitude lower than that of the overlying sandstone. In this case, the basement faults not only can control the location of ascending flow, but also can passively act as fluid conduits of either flow from the basin into the basement (ingress), or flow from the basement into the basin (egress), depending on their thermal conductivities and relative locations in the models.

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Salt as a fluid driver, and basement as a metal source, for stratiform sediment-hosted copper deposits

Cited by 38 publications

References 19 publications

Magmatic and Metamorphic Uraninite Mineralization in the Western Margin of the Trans-Hudson Orogen (Saskatchewan, Canada): A Uranium Source for Unconformity-Related Uranium Deposits?

Magmatic and Metamorphic Uraninite Mineralization in the Western Margin of the Trans-Hudson Orogen (Saskatchewan, Canada): A Uranium Source for Unconformity-Related Uranium Deposits?

Fluid flows and metal deposition near basement /cover unconformity: lessons and analogies from Pb–Zn–F–Ba systems for the understanding of Proterozoic U deposits

The effects of basement faults on thermal convection and implications for the formation of unconformity‐related uranium deposits in the Athabasca Basin, Canada

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