Petrographic and Raman spectroscopic study of graphite alteration in the Phoenix uranium deposit, southeastern Athabasca Basin, northern Saskatchewan
Petrographic and Raman spectroscopic study of graphite alteration in the Phoenix uranium deposit, southeastern Athabasca Basin, northern Saskatchewan
Abstract ID#: 36619
English Abstract:
The Phoenix unconformity-type uranium (U) deposit, located in the southeastern Athabasca Basin, is associated with a NE-trending, moderately SE-dipping reverse fault crosscutting the unconformity between the Athabasca basin and the Archean – Paleoproterozoic basement. Graphite is well developed in metapelite and locally in pegmatitic rocks in the basement, and is spatially associated with U mineralization; however, as in most other unconformity-related U deposits, its role in mineralization is still unclear. It is uncertain whether graphite acted as a direct reductant to precipitate uraninite, or as the precursor of hydrocarbons that caused uraninite precipitation. It is also unclear whether fluid – graphite interactions left a signature in the graphite that may be used as a mineralization indicator. In this study, a series of graphitic metapelite samples were collected from the alteration zones hosting mineralization near the unconformity down to the unaltered basement. Petrographic study of the graphite was undertaken and followed by Raman spectroscopic analysis. Preliminary petrographic observations indicate that graphite flakes near the mineralization zone are relatively discontinuous and locally have a corroded crystal shape. The Raman spectra of all samples show a prominent G band (~1580 cm-1) in the first-order region. However, graphite in samples closer to the mineralization has more obvious D1 and D2 bands (~1350cm-1 and 1620 cm-1), attributed to defects in the graphite. The spectra in the second-order region are similar among the samples, but the samples closer to the U mineralization have stronger S2 bands than those farther away from it. These observations indicate that there is a gradual loss of the structural ordering of graphite toward the U mineralization zone, which may be related to increasing reactivity between fluids and graphite.