International Geologiical Congress - Oslo 2008


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MRD-13 Ore deposits associated with black shales: from their origin to their environmental impacts


High-carbonaceous non-coeval units - complex mineral resources


N.I. Matvienko, Siberian Research Institute of Geology, Geophysics and Mineral Resources (SNIIGGiMS) (Russian Federation)
F.A. Migursky, Siberian Research Institute of Geology, Geophysics and Mineral Resources (SNIIGGiMS) (Russian Federation)


Commercial oil content of non-coeval black shale formations is proved in many world regions. Formation and post-sedimentary transformations of these units were accompanied by tectonic processes. Due to rupture tectonics organomineral fluids entered into sedimentary basin that promoted development of huge masses of phyto- and zooplankton, being accumulated in sediments during extinction, as well as localization of ore and rare elements, frequently up to commercial concentrations.
Collections of non-coeval black shale units were analyzed by a single technique. Rocks were sampled from deep wells and natural outcrops. Exploration targets are Riphean and Cambrian black shale of Australia and the Siberian Platform, Upper Jurassic Bazhenovo Formation in West Siberia; examined is also a collection of high carbonaceous mud of the Black Sea; numerous reference and fund works by Russian and foreign scientists have been applied. It makes possible to study rock types, their post-sedimentary transformations, OM content, its qualitative composition, distribution in rock types, to locate zones of possible oil reservoirs, to determine anomalies with commercial contents of vanadium, phosphorus, copper, nickel, uranium, and some other microelements.
Reservoir rocks are most completely studied from numerous wells that intersected Bazhenovo formation. However foliated reservoir horizons are found in all strata investigated. Realization of rock reservoir potential occurs under the influence of heat flows OM decomposition increases. This OM volume increase in several times results in rock rupture and fractured localities formation. Mobile OM components move along fractures into weak zones. HCs may localize within sought beds or migrate under pressure into host rocks. Reservoir zone prediction is fulfilled using geological-geochemical and geophysical matters.
Many black shale sections show interbeds of variously preserved volcanic ash and authigenic minerals of hydrothermal origin. It means that sedimentation and further transformation of highly carbonaceous rocks was strongly affected by tectonic processes. Black shale formations are oil -bearing under certain thermodynamic conditions and can be oil and probably gas reservoirs of fractured porous and porous-fractured types. Pyroshale ( TOC >10 %) varieties can serve energy and ore minerals as in many samples commercial concentrations of noble and other metals as well as phophorus are found with exact analytical methods. Thus, highly-carbonaceous non-coeval formations are referred as a whole complex raw materials.


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