| Title | Molybdenum speciation tracking hydrocarbon migration in fine-grained sedimentary rocks |
| |
| Author | Ardakani, O H ;
Hlohowskyj, S R; Chappaz, A; Sanei, H; Liseroudi, M H; Wood, J
M |
| Source | Geochimica et Cosmochimica Acta vol. 283, 2020 p. 136-148, https://doi.org/10.1016/j.gca.2020.06.006  Open Access |
| Image |  |
| Year | 2020 |
| Alt Series | Natural Resources Canada, Contribution Series 20200104 |
| Publisher | Elsevier |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf; html |
| Province | Alberta; British Columbia |
| NTS | 83M/03; 83M/04; 83M/05; 83M/06; 83M/11; 83M/12; 83M/13; 83M/14; 93P/01; 93P/02; 93P/03; 93P/06; 93P/07; 93P/08; 93P/09; 93P/10; 93P/11; 93P/14; 93P/15; 93P/16 |
| Area | Dawson Creek; Peace River |
| Lat/Long WENS | -121.0833 -119.0000 55.8000 55.0000 |
| Subjects | fossil fuels; geochemistry; structural geology; Science and Technology; Nature and Environment; Lower Triassic; petroleum resources; hydrocarbons; hydrocarbon migration; thermal maturation; sedimentary
basins; bedrock geology; lithology; sedimentary rocks; siltstones; shales; structural features; grabens; faults, extension; structural controls; molybdenum geochemistry; concentration; isotope ratios; paleoenvironment; depositional environment;
hydrothermal alteration; dolomitization; diagenesis; paleogeography; spectroscopic analyses; bitumen; wells; organic geochemistry; petrographic analyses; element distribution; pyrite; oxygen; sulphur; Montney Formation; Dawson Creek Graben Complex;
Western Canadian Sedimentary Basin; Pangea; Panthallassic Ocean; Phanerozoic; Mesozoic; Triassic |
| Illustrations | location maps; geoscientific sketch maps; plots; tables; photomicrographs |
| Program | Geoscience for New Energy Supply (GNES) Shale Reservoir Characterization |
| Released | 2020 06 12 |
| Abstract | Molybdenum (Mo) systematics (i.e., total concentration and isotope ratios) are widely used for the reconstruction of paleo-redox conditions in sedimentary records. However, the geochemical processes
affecting the distribution of Mo in carbonaceous fine-grained sedimentary rocks remain unclear. This study investigates how the organic matter type may control Mo concentration and speciation in siltstone/shale strata of the Lower Triassic Montney
Formation in the Western Canadian Sedimentary Basin (WCSB) to identify the effects of hydrocarbon expulsion and migration, fluid/rock interactions, and thermal maturity on Mo geochemistry when used as a paleo-redox proxy.
The bulk Mo concentration
in the studied samples varies from 0.2 to 86ppm (mean = 13 ± 16.7 ppm), with Mo enrichment factors of 22.7 ± 24.4 suggesting an anoxic paleo-depositional setting. The X-ray Absorption Near Edge Spectroscopy (XANES) results show the presence of two
separate Mo species within distinct geographic locations: (1) a group with a higher average Mo oxidation state where Mo is mostly surrounded by oxygen (O) atoms in an octahedral configuration, and (2) a group showing a lower average Mo oxidation
state where Mo is mostly surrounded by sulfur (S) atoms in a tetrahedral configuration.
The reduced Mo species are distributed in the vicinity of fault-related hydrothermal diagenesis/dolomitization zones. In contrast, the oxidized Mo species are
found associated with samples enriched with solid bitumen/pyrobitumen. The results of our study show Mo speciation can significantly help to elucidate complex paleo-redox histories. |
| Summary | (Plain Language Summary, not published)
This study shows how diagenesis and hydrocarbon generation could change paleo-redox proxies in the sedimentary record. |
| GEOSCAN ID | 326399 |
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