Formation of U-rich mineralizing fluids through basinal brine migration within basement-hosted shear zones: A large-scale study of the fluid chemistry around the unconformity-related Cigar Lake U deposit (Saskatchewan, Canada)

Martz, Pierre; Mercadier, Julien; Cathelineau, ‪Michel; Boiron, Marie-Christine; Quirt, David; Doney, Amber; Gerbeaud, O.; Wally, Etienne De; Ledru, Patrick

doi:10.1016/j.chemgeo.2018.05.042

Cited by 44 publications

(40 citation statements)

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“…The replacement of anhydrous minerals (dolomite, feldspars, and plagioclases) by hydrated minerals (talc and chlorite) increases the chlorinity during the alteration of the crystalline basement by fluids. This process has already been suggested in unconformity U-type deposits hosted in the Athabasca Basin in Canada [52,53], in the Modum Complex in Norway [39], and in the Schwarzwald district in Germany [54,55].…”

Section: Discussionmentioning

confidence: 60%

“…t1 ≠ t2 represents the fact that the circulation of the brines derived from the seawater evaporation and derived from the serpentinization should have been temporally disconnected in the deposit. 13 Geofluids ones ( [39,52,54,55,58,80]; Hovland et al, 2018). Carrying this idea a step further, Scribano et al [81] suggested that the formation of a certain subseafloor giant salt deposit in deep marine basins may be genetically related to the serpentinization of ultramafic rocks.…”

Section: What About the Regional Circulation Of Primary Brines?mentioning

confidence: 99%

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Nature and Origin of Mineralizing Fluids in Hyperextensional Systems: The Case of Cretaceous Mg Metasomatism in the Pyrenees

et al. 2019

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During the Albian, the hyperextension of the Pyrenean passive margin led to a hyperthinning of the continental crust and the subsequent subcontinental mantle exhumation. The giant Trimouns talc-chlorite deposit represents the most prominent occurrence of Albian metasomatism in the Pyrenees, with the occurrence of the largest talc deposit worldwide. Consequently, this deposit, which is located on a fault zone and a lithological contact, represents one of the major drains at the scale of the Pyrenees and one of the best geological targets in order to determine the origin(s) of the fluid(s) that circulated during this period. Talc-chlorite ore is characterized by the presence of brines trapped in dolomite, quartz, and calcite fluid inclusions in the vicinity of the talc-rich zone. Considered as being responsible for the formation of talc, these fluids may be interpreted in several ways: (i) primary brines expelled from Triassic evaporites, (ii) secondary brines produced through halite leaching by diagenetic/metamorphic fluids, and (iii) brines derived from seawater serpentinization of mantle rocks. Stable isotope analyses (δ13C, δ18O, δD, and δ37Cl) and Cl/Br ratio measurements in fluid inclusions and their host minerals were carried out in order to determine the origin of the fluid(s) involved in the formation of the ore deposit. The data are consistent with a primary brine origin for the mineralizing fluid, which could have been expelled from the Triassic levels. Other hypotheses have been tested, for example, the production of brines via the seawater concentration during serpentinization. The geochemical proxies used in this study provide equivocal results. The first hypothesis is by far the most realistic one considering the numerous occurrences of Trias formations nearby, their deformation during the extension, and the drainage of the expulsed brines as evidenced by the high-salinity fluid inclusions found all around the deposit. Alternatively, the exhumation of the mantle is considered as a major source of heat and stress that favored brine migration along the major shear zones. Our results fit well with brine circulation in a hyperextensional geodynamic context, which is related to the formation of the talc-chlorite ore, the thinning of the continental crust, and the exhumation of the subcontinental mantle, in accordance with recent works.

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Section: Discussionmentioning

confidence: 60%

Section: What About the Regional Circulation Of Primary Brines?mentioning

confidence: 99%

Nature and Origin of Mineralizing Fluids in Hyperextensional Systems: The Case of Cretaceous Mg Metasomatism in the Pyrenees

et al. 2019

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“…an uplift of the basement, followed by the deposition of the Athabasca Basin (∼ 1.7-1.75 Ga in Whitmeyer and Karlstrom, 2007). The first mineralisation event occurred 120 Ma after the deposition of the Athabasca Basin via the reactivation of the dormant underlying shear zones, triggering the mineralisation of uranium (e.g., Kyser et al, 2000;Mercadier et al, 2010;Martz et al, 2019). The presence of a sedimentary cusp and interconnecting structures would likely facilitate deep crustal hydrothermal fluid transport and circulation up to the surface (Fig.…”

Section: Determining the Reference Model For The Wmtz In The Hearne Cmentioning

confidence: 99%

Precambrian deformation belts in compressive tectonic regimes: A numerical perspective

et al. 2020

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This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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“…The deposition of uranium is associated with massive hydrothermal alteration in both basin and basement, dominated by the development of an illite-chlorite clay zone and major desilicification (Bruneton, 1993). Large-scale circulations of NaCl-and CaCl2-rich basinal brines at the basin-basement interface favoured massive fluid-rock interactions leading to the formation of the hydrothermal alteration and U mineralization (Derome et al, 2005;Mercadier et al, 2010;Richard et al, 2016;Martz et al, 2019a). The Cigar Lake uranium deposit is also marked by the presence in the U ore of arsenide and sulpharsenide minerals of potential economic importance as by-products: rammelsbergite (NiAs2), nickeline (NiAs), maucherite (Ni11As8), löllingite (FeAs2), skutterudite (NiAs3), gersdorffite (NiAsS) and cobaltite (CoAsS) (Reyx and Rulhmann,1993;Kaczowka;2017).…”

Section: Introductionmentioning

confidence: 99%

Evaluation of rammelsbergite (NiAs2) as a novel mineral for 187Re-187Os dating and implications for unconformity-related U deposits

Chernonozhkin

Reisberg

Luais

et al. 2020

Geochimica et Cosmochimica Acta

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Rammelsbergite (NiAs2) is often present in ore deposits worldwide in association with other arsenides, sulphides and sulfarsenides. This work demonstrates the value of the application of the Re-Os isotopic system to the dating of rammelsbergite. Using the example of the Cigar Lake uranium deposit (Athabasca Basin, Saskatchewan, Canada), our results show that rammelsbergite concentrates significant and variable amounts of Re when crystallizing, up to 1.6 µg g-1 , while incorporating minimal common Os. Such characteristics make this mineral an ideal target for Re-Os isotopic dating, by both isochron and model age methods. Remarkable agreement of the Re-Os age of the rammelsbergite with the U-Pb age of the uranium oxide grains found inside one of the massive rammelsbergite veins confirms the applicability of the method. The selected rammelsbergite samples from the Cigar Lake uranium deposit yield a 187 Re-187 Os isochron age of 1239 +33/-20 Ma. These results challenge a longstanding petrogenetic model which postulates contemporaneous U oxide and Ni-Co-arsenide deposition in unconformity-related uranium deposits. The new Re-Os age of rammelsbergite veins indicates that arsenide crystallization postdated the deposition of the primary uranium oxides at 1461-1341 Ma, implying that uranium oxides and nickel arsenides, as well as other sulphides and sulfarsenides, were not precipitated contemporaneously during a single hydrothermal event as previously proposed. The 187 Re-Os data suggest that crystallization of rammelsbergite and co-genetic sulphides, arsenides and sulfarsenides was linked to the ca. 1270 Ma Mackenzie magmatic event, marked by the emplacement of mafic dikes throughout the Canadian Shield, including in the area of the Athabasca Basin. This study therefore suggests a new hypothesis for the origin of nickel, cobalt, sulfur and arsenic in unconformity-related U deposits of the Athabasca Basin. More broadly, the successful application of the 187 Re-187 Os rammelsbergite chronometer in this geological context suggests that its application in other ore deposit environments worldwide is likely to provide similar insights. In this respect, the 187 Re-187 Os chronometer applied to rammelsbergite, and potentially to other arsenides and sulfarsenides, represents a valuable complement to molybdenite dating because it can be used in systems that lack molybdenite.

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Formation of U-rich mineralizing fluids through basinal brine migration within basement-hosted shear zones: A large-scale study of the fluid chemistry around the unconformity-related Cigar Lake U deposit (Saskatchewan, Canada)

Cited by 44 publications

References 92 publications

Nature and Origin of Mineralizing Fluids in Hyperextensional Systems: The Case of Cretaceous Mg Metasomatism in the Pyrenees

Nature and Origin of Mineralizing Fluids in Hyperextensional Systems: The Case of Cretaceous Mg Metasomatism in the Pyrenees

Precambrian deformation belts in compressive tectonic regimes: A numerical perspective

Evaluation of rammelsbergite (NiAs2) as a novel mineral for 187Re-187Os dating and implications for unconformity-related U deposits

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