Geology topics
Source-linked reports with geographic coverage including Kazakhstan, Russia.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean resources of 84.5 trillion cubic feet of continuous gas in the North Caspian Basin Province of Kazakhstan and Russia.
A probabilistic mineral resource assessment of metal resources in undiscovered porphyry copper deposits of the Ural Mountains in Russia and Kazakhstan was done using a quantitative form of mineral resource assessment. Permissive tracts were delineated on the basis of mapped and inferred subsurface distributions of igneous rocks assigned to tectonic zones that include magmatic arcs where the occurrence of porphyry copper deposits within 1 km of the Earth's surface are possible. These permissive tracts outline four north-south trending volcano-plutonic belts in major structural zones of the Urals. From west to east, these include permissive lithologies for porphyry copper deposits associated with Paleozoic subduction-related island-arc complexes preserved in the Tagil and Magnitogorsk arcs, Paleozoic island-arc fragments and associated tonalite-granodiorite intrusions in the East Uralian zone, and Carboniferous continental-margin arcs developed on the Kazakh craton in the Transuralian zone. The tracts range from about 50,000 to 130,000 km 2 in area. The Urals host 8 known porphyry copper deposits with total identified resources of about 6.4 million metric tons of copper, at least 20 additional porphyry copper prospect areas, and numerous copper-bearing skarns and copper occurrences. Probabilistic estimates predict a mean of 22 undiscovered porphyry copper deposits within the four permissive tracts delineated in the Urals. Combining estimates with established grade and tonnage models predicts a mean of 82 million metric tons of undiscovered copper. Application of an economic filter suggests that about half of that amount could be economically recoverable based on assumed depth distributions, availability of infrastructure, recovery rates, current metals prices, and investment environment.
The Uralides—the late Precambrian and Paleozoic orogenic terrane between the Russian and Siberian Platforms—in part are exposed in the Ural Mountains, in the central Soviet Arctic, along the west edge of the Siberian Platform, and in southern Siberia and Kazakhstan, and in part are buried beneath the fill of the West Siberian Lowlands and other basins. Paleomagnetic orientations suggest that the Russian and Siberian Platforms were far apart during the early Paleozoic, converged during the middle Paleozoic, and collided in the Permian or Triassic. The geology of the Uralides accords with the concept that the two subcontinents approached and collided as the intervening oceanic plate slid beneath them along subduction (Benioff) zones. The medial eugeosyncline of the Uralides consists largely of what may be oceanic material scraped off against the edges of the opposed subcontinents. Basalt-and-spilite belts may represent ocean-floor abyssal tholeiite, and the manganiferous cherts and other sediments upon them may be pelagic oozes. Andesite belts may have formed as island arcs within the ocean, swept subsequently against the continents. Fossil subduction zones are recorded by great faults soled by, or containing tectonic injections of, mafic and ultramafic rocks from the lower oceanic crust and upper mantle, and containing high-pressure metamorphic rocks. Granitic and silicic-volcanic rocks may have formed above the subduction zones in the accreted parts of the continental plates. Both these continental-margin magmatic rocks and the island-arc complexes display ratios of potassium to silicon that vary across strike and so indicate the directions of dip of the subduction zones. From the distribution of such indicators of various ages, a history of the continental margins can be deduced. An active subduction zone dipped beneath the Siberian Platform during at least parts of late Precambrian and early, middle, and late Paleozoic time. The late Precambrian and Cambrian history of the Russian side is unclear, but in the Ordovician and Silurian the Russian continental margin was stable, while somewhere offshore an island arc was present whose trench was on the Russian side; the last of the intervening oceanic plate vanished down the subduction zone in about the Early Devonian, and the island arc became part of the continental margin. During the remainder of the Devonian and during the Carboniferous and Early Permian, a subduction zone was present along the margin of the enlarged Russian continent and dipped beneath it. Each subcontinent grew oceanward as oceanic material was accreted against it, and the subduction zones stepped oceanward correspondingly. The continental magmatic zones migrated oceanward behind the accreting edges of the continental plates, so the tectonic and magmatic progression with time at any one place is analogous to the variations present across the entire orogenic belt at any one time. Severe right-lateral deformation of the Uralides, the Russian side having moved northward relative to the Siberian side during Mesozoic and early Cenozoic time, is inferred from structural and magnetic-anomaly patterns. The deformation was accomplished by oroclinal folding, strike-slip faulting, and tensional thinning of the crust. The Uralides may have been continuous in early Mesozoic time with the Ellesmerides of North Greenland and the Canadian Arctic islands. The Cenozoic (and late Mesozoic?) opening of the Arctic Ocean was accomplished by spreading of the Eurasia Basin, and by opening of the Canada Basin behind a counterclockwise-rotating Alaska.