International Geology Review

Vinogradov, V.I.; Chernyshev, I.V.; Shanin, L.L.

doi: 10.1080/00206817109475590pmid: N/A

Iron and zinc sulfides, deposited by petroleum brines, are believed to have been derived from terrigenic sedimentary rocks, judging by the isotopic composition of their sulfur, and not from any deposits of these metals in the depths. This view is supported by isotopic analysis of sulfur in brines inside and outside the oil field and in waters of mud volcanoes. Isotopic composition of native (and apparently young) lead, deposited in two of the wells, may likewise represent an epigenetic concentration of the originally dispersed metals in the brines.

Bogdanov, Yu.V.; Golubchina, M.N.

doi: 10.1080/00206817109475591pmid: N/A

Striking preponderance of the light isotopes and a very wide range of variation (δS34 from +13.5 to -21.8) are typical of the isotopic composition of sulfidic sulfur in copper ore deposits of the area, even as they are in the case of analogous ore deposits elsewhere. Fluctuations in the isotopic composition of sulfur in profiles of cupriferous rocks and parts thereof are explainable by specificities in physicochemical environments of the sediment-water-organic substance system. -- Authors.

Grinenko, L.N.; Grinenko, V.A.; Zagryazhskaya, G.D.; Stolyarov, Yu.M.

doi: 10.1080/00206817109475592pmid: N/A

Isotopic composition of sulfur was determined in more than 150 samples of sulfides and sulfates from the Levikha ore field. On the basis of the results so obtained, we are discussing the sources of sulfur in the sulfide ores and in sulfates of the ore deposits, physicochemical conditions of their deposition, and their genetic connections with sulfides in the overburden. -- Authors.

Chukhrov, F.V.

doi: 10.1080/00206817109475593pmid: N/A

Enrichment of S32 in sulfidic sulfur and large variations in δS34 content of certain minerals are characteristic of the ores. It is possible therefore that their sulfur was derived from sedimentary rocks and that bacterial reduction of sedimentary sulfates had a part in the process. The isotopic composition of sulfidic sulfur in cupriferous sandstones and in the veinlets therein is about the same. Consequently, a borrowing a sulfur by the veinlets from the sandstones appears to be a reasonable assumption. A biogenic-sedimentary origin of the sulfides does not preclude accessions of copper and other metals from the magma. -- Author.

Khlestov, V.V.

doi: 10.1080/00206817109475594pmid: N/A

Relatively high geothermal gradient and greater depths of the erosion plane may account for certain distinctions of the Lower Archean metamorphic complexes. Their granulites and amphibolites could not have been formed at depths shallower than 15-16 and 10 km, respectively, as indicated by review of the available data. The granulite fades of metamorphism is not restricted to Precambrian rocks, but is found also in younger complexes, some of which outcrop on the surface of the ground, although they were subjected to intensive autodiaphthoresis, which usually accompanied crystallization of anatectic melts within the amphibolitic range of the temperature.

Mel'nik, Yu.P.; Yaposhchuk, M.A.

doi: 10.1080/00206817109475595pmid: N/A

Mineral equilibria in magnesial rocks undergoing metamorphosis in closed systems at different H2O content but at constant pressures and temperatures may be interpreted as follows: a) if H2O is excessive, as in pelitic rocks, the metamorphic zonation (an orderly sequence of dehydrations) correctly represents changes in the temperature during the progressive metamorphism; b) if H2O is deficient, as in the ortho-rocks, the metamorphic zonation may not always be representative of the temperature; however, when H2O itself is zoned in the rock and the metamorphism is isothermal, the metamorphic zonation may become entirely analogous to the zonation in the presence of excessive H2O; c) presence of metastable associations and rapid alternations of mineral parageneses, as in certain magmatic rocks, represent variations in H2O content of the rocks rather than different facies of the metamorphism.

Semenov, A.S.

doi: 10.1080/00206817109475596pmid: N/A

The generalized popular image of conductivity structure of the crystalline as a tripartite section (high-low-high conductivity of top, middle, and bottom of the base, respectively) is disqualified significantly by recent soundings, in the USSR and elsewhere, by too many exceptions to the rule. The most plausible explanation of such three-dimensional exceptions is the presence of electron-conducting minerals and formations in different positions at great depths, which may affect conductivities of the entire profile.

Burshtar, M.S.; Nazarov, D.A.

doi: 10.1080/00206817109475597pmid: N/A

A method of mapping which essentially combines isopachs and estimated degrees of compaction of sediments (e.g. in six spans of geological time, in the Neocomian complex, Caucasian piedmont), proves serviceable in many qualitative-semiquantitative derivations. Among these are directions, volumes, and rates of migration of sedimentational waters, the carriers of hydrocarbons, inside and outside the test area; the optimum compaction depths for the sediments; positions of pressure-heads in the evolving artesian basin; zones of oleogenesis and positions of probable accumulations of hydrocarbons.

Azizbekov, S.A.; Dzotsenidze, G.S.

doi: 10.1080/00206817109475598pmid: N/A

Place-time expressions of volcanism in the Caucasus and parts of the adjacent territories suggest migration of the centers of magmatism from region to region, in the dimension of time (Precambrian-Quaternary). In general, a weakening of tectonic-magmatic activity in a region runs concurrently with its intensification in some other region (not necessarily adjacent to the former). Deep-seated controls of such shifts may be reasonably suggested.

Geodekyan, A.A.

doi: 10.1080/00206817109475599pmid: N/A

Large accumulations of oil and gas in shelf zones under the sea are definitely indicated, on consideration of the geochemistry of organic substance in such environments, modern ideas on geochemistry, genesis and migrations of hydrocarbons, and exploration-production experience in different parts of the world. However, truly scientific prognosis and exploration are contingent upon further comprehensive research, basic as well as applied.