International Geology Review

Sidorenko, A.V.

doi: 10.1080/00206816509474718pmid: N/A

The total area of Precambrian rocks exposed at the surface or covered with a thin veneer of Quaternary deposits is estimated at 25 million km2, or 17 percent of the land surface. Recent development of test-hole drilling is yielding an increasing amount of information on the Precambrian crystalline basement of platforms covered with a thick sedimentary mantle. The picture of the Precambrian that has been built up is one of strongly altered rocks, injected with magmatic material, which have frequently been remelted and have herefore lost their original outlines. Petrographic study of Precambrian shields has been most widely employed and absolute dating has been concerned more with a particular intrusive phase than a particular stratigraphic complex — even though sedimentary-metamorphic rocks occur extensively and magmatic rocks merely breach them. The time has come to construct a stratigraphy of the Precambrian, not by distinguishing phases of rnagmatism and linking them up with stratified rocks, but on the basis of sequence of bedding as expressed in sedimentary-metamorphic complexes. Detailed mapping even in regions where strongly metamorphosed rocks occur and injections of magmatic material are considerable has established that the original sedimentary rocks are on the whole well preserved, that no remelting or displacement of the original material occurs to disturb boundaries between strata, and that the general character of the bedding has been retained. Aims of Precambrian geologic study are summarized and methods are enumerated. — W. D. Lowry.

Kharitonov, L.Ya.

doi: 10.1080/00206816509474719pmid: N/A

The karelides are Karelian volcanic and sedimentary rocks in various stages of metamorphism which form broad northwesterly trending belts. These rocks occur in synclinoria between which are areas of the old granite-gneiss basement of the extensive Karelian massif. Details of the stratigraphic sequence, structure, magmatic and metamorphic events, and geologic history are described. Radioactive age determinations are interpreted within the framework of the inferred geologic history. This is a timely supplement to the recently published Volume 1 of The Precambrian, edited by K. Rankama. — C. G. Tillman.

Vorobyev, B.S.; Lapkin, I.Yu.; Pan'kiv, A.M.; Sterlin, B.P.; Tkhorzhevskiy, S.A.

doi: 10.1080/00206816509474720pmid: N/A

Detailed subsurface data on the south side of the Voronezh Massif near Kharkov have provided a basis for evaluating the structure and stratigraphic relations of the beds below the Cretaceous. In evaluating the oil possibilities of the area, need for an additional line of deep boreholes south of Kharkov has emerged. The absence of Devonian and Lower Permian beds reduces the prospects for oil and gas, but other parts of the succession, notably the Carboniferous and Triassic, may prove a promising zone of exploration. Some traps may be produced by block fault movements in the basement, but most of the possible traps are stratigraphic. — B.N. Cooper.

Lebedev, Yu.S.

doi: 10.1080/00206816509474721pmid: N/A

The chiefly residual, nickel-bearing, weathered “crust” (30 to more than 80 m thick) on the hyperbasites of the South Bug Basin at the southern margin of the Ukrainian shield was formed during the Upper Cretaceous and part of the Tertiary. Compositions for “crusts” on each of the following rocks are given: apoharzburgite-serpentinite, amphibole pyroxenites and peridotites, phlogopite rocks, chlorite rocks, carbonatites, and chrome-spinel rocks. Vertical zoning, present in the weathering products, appears to be related to stages in the weathering processes that reflect changes in the external mediuni, especially in its redox potential and pH. Predictions may be made as to the composition of bedrock on the basis of the composition of the “crust.” — R.V. Dietrich.

Lugov, S.F.

doi: 10.1080/00206816509474722pmid: N/A

The decisive factor in the genesis of a deposit of any particular formation is the development of a mobile folded zone in time and the change in character of the manifestation of intrusive magmatism and mineralization associated with it. The Chukotka deposits provide a convincing illustration of the connection between deposits of a particular stanniferous formation, of diverse composition, and granitoids at certain stages in the development of a mobile Mesozoic zone of folding. The geological-geochernical and structural factors in the Chukotka tin-tungsten province lead to the following classification, starting with: 1) stanniferous pegmatite; 2) stanniferous (tungsteniferous) skarn formation; 3) cassiterite quartz formation; 4) cassiterite-quartz-sulfide formation; 5) cassiterite silicate formation; 6) cassiterite sulfide formation. Each type and its subtype are discussed and details of the individual genetic types of stanniferous deposits are given in a table. Industrial tin mineralization in Chukotka is connected with deposits of cassiterite-silicate and cassiterite-quartz sulfide formations, while tin-tungsten mineralization is associated with cassiterite-quartz formation. — C.E. Sears.

Stankevich, Ye.F.

doi: 10.1080/00206816509474723pmid: N/A

This paper deals with the complex interrelations of regional tilt of the pressure surface, water temperature, density gas saturation, and pressures in determining the direction and rate of flow of water in different hydrologic depth zones. The various ideas of other Soviet authors are analyzed and evaluated. The author points out that the inequality method should not be used to test for flow in or between strata if the heights of reference points are similar or if the density is especially important in understanding long - time movements of occluded water in the so-called ”stagnation zone.“ — B.N. Cooper.

Nechayev, S.V.; Kononov, Yu.V.

doi: 10.1080/00206816509474724pmid: N/A

Rare earth mineralization, in the form of xenotime and monazite, occurs along tear faults at an unidentified locality in the Precambrian terrane of European part U. S. S. R. The petrographic and geologic relationships of the last rocks appear to reflect Mg-Fe metasomatism followed by metasomatisrn. The rare earth mineralization appears to have accompanied the K metasomatism. Chemical analyses are presented for one xenotime and two monazites; emission and X-ray spectroscopic analyses are presented for the xenotime. — R.V. Dietrich.

Sterkin, V.D.

doi: 10.1080/00206816509474725pmid: N/A

This excellent summary of tectonics of the major portion of the Pyongnam Trough, Korea, gives an account of the Archean, Proterozoic, and Paleozoic rocks as affected by orogenic episodes, some of which were Mesozoic in age. Nappe folding related to gravitational tectogenesis is especially prominent. The overthrust zones are parts of the later stages of the Indosinian orogeny. — B.N. Cooper.

doi: 10.1080/00206816509474726pmid: N/A

The committee on the Paleogene of the U. S. S. R. presents a tabulation of the lithologic and faunal characteristics of a complete Paleogene section in the Crimea. The Committee proposes that this section serve as a new type of section for the Paleogene of Europe. — C.G. Tillman.

doi: 10.1080/00206816509474727pmid: N/A

The Committee on Ordovician and Silurian Stratigraphy of the U. S. S. R. defines a number of time-stratigraphic subdivisions of the Russian Ordovician and Silurian Systems. — C.G. Tillman.