Fluid source and thermal history of an epithermal vein deposit,Owen Lake,central British Columbia: evidence from bitumen and fluid inclusions |
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Authors: | M L Thomson M Mastalerz A J Sinclair R M Bustin |
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Institution: | (1) Department of Geological Sciences, The University of British Columbia, V6T 1Z4 Vancouver, Canada |
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Abstract: | Fluid source and thermal history are determined for the barite and bitumen-bearing, early Eocene (ca. 50 Ma) polymetallic, epithermal veins of the Owen Lake deposit, central British Columbia, Canada. Carbon isotopic values
for the bitumen are highly negative (δ
13 C ca −29%) indicating a probable terrigenous source, which may be 1 no older than Late Cretaceous or, 2 Eocene plant-fossil-bearing
units stratigraphically above the Owen Lake deposit. Heat generated by suspected magmatic activity resulted in downflow of
meteoric water and upflow of hydrothermal water, mixing at the site of deposition.
Aqueous and hydrocarbon fluid inclusions occur within barite; Th of both types of inclusions indicate a temperature range
of approximately 100° to 180 °C. Tm(ice) of aqueous inclusions range from −4.5 to −0.2 °C indicating a range of 7.2 to 0.4
equivalent weight percent NaCl. Parageneticaly younger bitumen has a vitrinite reflectance of 0.6% indicating maturation level
in the temperature range of 80° to 120 °C, strongly suggesting a cooling thermal regime during barite and bitumen deposition,
consistent with a late stage paragenesis. |
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