Alteration Spatially Associated With The Phoenix Unconformity Related Uranium Deposit Athabasca Basin Saskatchewan Canada

Author : Kewen Wang
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (133 download)

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Download or read book A Study of Petrography, Fluid Inclusions and Graphite Alteration of the Phoenix Uranium Deposit, Athabasca Basin, Northern Saskatchewan, Canada written by Kewen Wang and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Phoenix unconformity-related uranium (URU) deposit, located in the southeastern Athabasca Basin, is associated with a NE-trending, moderately SE-dipping reverse fault crosscutting the unconformity between the Proterozoic Athabasca Group and the Archean - Paleoproterozoic basement. The mineralisation occurs mainly along the faulted graphite zones or at the intersection of the faults and unconformity and is associated with pervasively developed tourmaline alteration. Primary aqueous fluid inclusions were studied in post-diagenetic, pre- to syn-mineralisation quartz overgrowths and vug-filling drusy quartz in sandstone (QBSN2), and syn- to post-mineralisation, veinfilling coarse-grained drusy quartz in both sandstone (QBSN3) and basement (QBSM4). Only a few liquid-dominant biphase aqueous fluid inclusions were found in QBSN2, while four types of aqueous fluid inclusions, including liquid-dominant biphase (liquid + vapour), vapour-dominant biphase (vapour + liquid), monophase (vapour-only) and triphase (liquid + vapour + solid) inclusions, were recognized in QBSN3 and QBSM4. The coexistence of multiple types of inclusions within individual fluid inclusion assemblages is interpreted to indicate fluid immiscibility and heterogeneous trapping. Microthermometric and cryogenic Raman spectroscopic analyses reveal that the highsalinity fluids in QBSN2, QBSN3 and QBSM4 belong to the H2O-NaCl-CaCl2 ± MgCl2 fluid system. The liquid-dominant inclusions in QBSN2 are interpreted to represent homogeneous trapping of the liquid phase show a high salinity of 27.9 wt% (NaCl+CaCl2; same for all the salinity values unless otherwise specified) and a moderate temperature of 128 °C, whereas those in QBSN3 indicate a wide range of salinities from 1.2 to 33.0 wt% and temperatures from 80 to 157 C for QBSN3. The inclusions of QBSM4 yielded high salinities from 26.0 to 30.1 wt% and low to moderate temperatures from 90 to 130 °C. Bulk fluid inclusion volatile analysis by mass spectrometry indicates H2O as the dominant species, with less than 1 mole% non-aqueous volatiles. The Raman spectroscopic study of the metamorphic graphite in metapelites (Gr1) suggests gradual structural disordering towards the mineralisation, reflected by an increasing percentage of disordered spectra (D1 and D2 bands at ~1350 cm-1 and ~1620 cm-1 other than prominent G band at ~1580 cm-1). Surficial defects appearing as hollow points were observed near the mineralisation zone and interpreted to be caused by oxidizing acidic brines. Secondary methane-dominant vapour inclusions associated with biphase aqueous inclusions in the pegmatitic or massive quartz in the basement (QBSM2) are considered to represent the basement derived C-O-H fluids, which may have served as reducing agents for U precipitation. The new data obtained in this study about fluid inclusions and graphite in the Phoenix uranium deposit are generally consistent with those from other unconformity-related uranium deposits in the Athabasca Basin. However, our mineralising fluid temperatures are considerably lower than those reported in previous studies, and the depth of mineralisation, inferred from fluid immiscibility and pressure calculations, is significantly shallower than invoked in the conventional deep-burial hydrothermal model. Furthermore, the spatial association of graphite dissolution and structural disordering with mineralisation confirm the important role of graphite in mineralisation through fluid-graphite reaction and generation of hydrocarbons.