Abstract
In the Kiggavik area (Nunavut, Canada), major fault zones along, or close to, where uranium deposits are found are often associated with occurrence of thick quartz breccia (QB) bodies. These bodies formed in an early stage (~1750 Ma) of the long-lasting tectonic history of the Archean basement, and of the Proterozoic Thelon basin. The main characteristics of the QB are addressed in this study; through field work, macro and microscopic observations, cathodoluminescence microscopy, trace elements, and oxygen isotopic signatures of the quartz forming the QB. Faults formed earlier during syn- to post-orogenic rifting (1850–1750 Ma) were subsequently reactivated, and underwent cycles of cataclasis, pervasive silicification, hydraulic brecciation, and quartz recrystallization. This was synchronous with the circulation of meteoric fluids mixing with Si-rich magmatic-derived fluids at depth, and were coeval with the emplacement of the Kivalliq igneous suite at 1750 Ma. These processes led to the emplacement of up to 30 m thick QB, which behaved as a mechanically strong, transverse hydraulic barrier that localized later fracturing, and compartmentalized/channelized vertical flow of uranium-bearing fluids after the deposition of the Thelon Basin (post 1750 Ma). The development and locations of QB control the location of uranium mineralization in the Kiggavik area.
Highlights
Fault zones are often associated with enhanced, focused, repeated fluid circulations in the earth’s crust [1,2,3,4,5,6,7]
Occurrence of quartz breccia (QB) has been recognized along various segments of the major faults within the Kiggavik area (e.g., Andrew Lake Fault (ALF), Judge Sisson fault (JSF), Figure 1C,D and Figure 2A)
Fault zones outlined by the QB are presumably better preserved in the field due to the silicification process that increases their resistance to erosion
Summary
Fault zones are often associated with enhanced, focused, repeated fluid circulations in the earth’s crust [1,2,3,4,5,6,7]. These fluids may have different origins: Meteoric, magmatic, metamorphic or basinal, and possibly transport metals to a favorable area of deposition [8,9]; that will allow for the formation of potential economic ore deposits. Quartz-cemented breccias can have an economic interest, being possibly associated with ore deposits such as epithermal (Au-Ag-Cu-Pb-Zn-Sb, [16,17]), orogenic gold (Au, [18]), and porphyric (Cu-Mo-Au-Ag, [19,20])
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