SOVETSKAYA GEOLOGIYA (SOVIET GEOLOGY) IN COVER-TO-COVER TRANSLATION, 1961, NO. 8

In the Minusinsk (Siberia) intermontane downwarp, the Devonian-Carboniferous boundary lies within the regional paleomagnetic horizon. This boundary's perfect correlation with the same boundary in the Russian platform (4000 km away) is taken as evidence of the widespread occurrence of the inversely magnetized Upper Fammenian zone, of a certain isochronism between the Devonian-Carboniferous boundaries in Minusinsk and in the northwest of the Russian platform (notwithstanding their tectonic differences, etc.) and of possibilities of such correlations on a worldwide scale.--V.P. Sokoloff.     

SOVETSKAYA GEOLOGIYA (SOVIET GEOLOGY) IN COVER-TO-COVER TRANSLATION, 1962,NO. 6

New data on the stratigraphy of Upper Jurasgic sediments of the central and southern parts of the western Siberia lowland are listed, which have accumulated since the last Stratigraphic Conference in 1960 in Novosibirsk. Present-day paleontological information permits us to clarify views on the age of the Lolcosovskaya suite as a whole, as well as to establish the age volume of each subsuite. – Authors.     

SOVETSKAYA GEOLOGIYA (SOVIET GEOLOGY) IN COVER-TO-COVER TRANSLATION, 1963, NO. 1.

Prognostic estimates of iron ore reserves are discussed on the basis of experience and published theoretical premises. A geologic classification of ore deposits is offered as a basis for prognostication. (Note: The Geological Classification of Iron-Ore Deposits (table 2) may be of interest to American economic geologists.).—C.E. Sears     

SOVESTKAYA GEOLOGIYA (SOVIET GEOLOGY) IN COVER-TO-COVER TRANSLATION, 1961 NO. 1

Parts of certain alkalic intrusive massifs contain up to 63 cc methane per kilogram of rock, with smaller amounts of heavier hydrocarbon gases, bitumen, hydrogen, carbon monoxide and carbon dioxide. The authors argue that the hydrocarbons cannot have come from assimilated limestone, because the igneous rocks contain much more of these gases than do the enclosing limestones. Likewise, the hydrocarbons cannot have been introduced by late solutions because they are much lower in hydrothermal and metasomatic fades than in primary minerals of the high temperature intrusive facies. Hydrocarbons are not stable at magmatic temperatures; the authors conclude that these must have formed in the presence of natural catalysts during slow cooling below 500°C, in accordance with industrial synthesis of hydrocarbons. The C¹²/C¹³ ratio of the bitumens is in the range for ordinary petroleum, suggesting that they formed at relatively low temperature, but the carbon of the gaseous hydrocarbons is lighter, which may indicate that they formed at somewhat higher temperatures. -- E. Ingerson.     

SOVETSKAYA GEOLOGIYA (SOVIET GEOLOGY) IN COVER-TO-COVER TRANSLATION, 1960, NOS. 11 AND 12

The Río Negro-Juruena Province (RNJP) occupies a large portion of the western part of the Amazonian Craton and is a zone of complex granitization and migmatization. Regional metamorphism, in general, occurred in the upper amphibolite facies. The granites and gneisses of the RNJP yield Rb-Sr and Pb-Pb whole-rock isochron dates ranging from 1.8 Ga to 1.55 Ga, with initial ⁸⁷Sr/⁸⁶Sr ratios of ～ 0.703 and a single-stage model μ₁ value of ～ 8.1. In order to improve the geochronological control, SHRIMP U-Pb zircon ages, conventional U-Pb zircon ages, and additional Pb-Pb whole-rock isochron ages were determined for samples of granitoids and gneisses from the Papuri-Uaupés and Guaviare-Orinoco rivers areas (northern part of the province) and Jamari-Machado rivers and Pontes de Lacerda areas (southern part). The granitoids from the northern part of the province yield conventional U-Pb zircon ages of 1709 ± 17 Ma and 1521 ± 31 Ma, and SHRIMP U-Pb concordant zircon results of 1800 ± 18 Ma. Samples of gneissic rocks from the southern part of the RNJP yielded SHRIMP U-Pb concordant ages of 1750 ± 24 Ma and 1570 ± 17 Ma and a Pb-Pb whole-rock isochron age of 1717 ± 120 Ma. These new U-Pb and Pb-Pb results confirm the previous Rb-Sr and Pb-Pb geochronological evidence that the main magmatic episodes within the RNJP occurred between 1.8 and 1.55 Ga, and suggest that this crustal province constitutes a segment of continental crust newly added to the Amazonian Craton at the end of the Early Proterozoic. In the area of the RNJP, there are several anorogenic rapakivi-type granite plutons. Because of the absence of recognized Archean material within the basement rocks, it is reasonable to consider the Early to Middle Proterozoic continental crust as the magmatic source for the rapakivi granite intrusions.