Russian Geologists Research Articles

Coal inclusions in sedimentary rocks: a geochemical phenomenon. A review

In many coal-bearing basins, there are numerous coalified fragments of ancient plants (coal-precursors) enclosed in host rocks. Such fragments occur in isolated positions out of the coal beds. In the Russian literature, these coal fragments are named coal inclusions. Coal inclusions are mostly the remains of stems, trunks, and branches, as well as the roots of trees. The review presented covers: (a) definition and classification of fossil woods; (b) relations between coalification and mineralization of fossil woods; (c) some special topics dealing with different and even zonal coalification degree of coal inclusions embedded different host rocks; (d) some historical data on geochemistry of coal inclusions; (e) basic empirical regularities in geochemistry, observed world-wide; (f) some data about chemical nature of humin substance—a precursor of lignite and vitrain matter in coalified wood; (g) results of calculations modelling the Ge enrichment in coal inclusions; (h) economic importance of Ge in coal inclusions; and (j) use of coal inclusion geochemistry for indication of some diagenetic and catagenetic processes, and as a tool for stratigraphic correlation. The most part of the above studies performed during 1934–1972 were outlined in the monograph “Geochemistry of coal inclusions in sedimentary rocks” [Yudovich, Ya.E., 1972. Geochemistry of coal inclusions in sedimentary rocks. L.: Nauka [Leningrad: “Science” Pub. House], 84 pp.]. These materials are added to some recent work by Bulgarian and Russian geologists, performed with use of modern analytical methods. It has been shown that: (a) coalified wood may contain very exotic micro-mineral phases, sometimes far unexpected; (b) apart from Ge, coalified wood may contain high concentrations of some other trace elements, which were earlier not detected because of analytical limitations (REE, As, etc.). These special peculiarities can be partly contributed by epigenetic hydrothermal processes. As a summary, the review shows that coal inclusions are unique geochemical phenomenon, sharply different from even neighboring coal beds in trace element content. Among the most extreme elements is germanium, its mean concentration in the ash of coal inclusions being up to 220 times higher than in the ash of coal beds. The most important peculiarity of the coalified wood is the good preservation of the original lignin structures, which may effectively scavenge Ge from solutions, whereas peat-born coals (in beds) contained such structures in far fewer amounts. In addition, a reservoir of dissolved germanium in peat bog waters was of lower concentration than in sediments, which buried the coal inclusions. Finally, the peat bog acidic environment may act as an unfavorable factor. Ge-enrichment can be completed in a time ranging from a few thousand years up to tens of million years. However, if the waters are enriched in Ge, the process can proceed more rapidly and would be completed even under the most unfavorable parameters (compared to the model conditions). This implies that enrichment can take place during the early diagenetic stage. Such a scenario was supported by geologic considerations. Some Canadian and Soviet works performed from 1950 to 1960 along with some recent Russian studies show that Ge in coal inclusions can be of economic interest. Geochemistry and mineralogy of coal inclusions are of great interest and need further detailed study.

Russian geology and the plate tectonics revolution

Abstract The suggestion of the concept of ‘scientific revolution’ by Thomas Kuhn in 1962 was, in itself, a significant event in the history of science, and ‘crucial’ episodes or ‘paradigm shifts’ have come to be of special interest in the history of geology (as in other sciences). The appearance of a new paradigm is commonly associated with attempts by the most talented and well-established practitioners to consolidate or sustain the position of the previously prevailing paradigm. For almost 40 years, global theories in geology have been developing under the influence of mobilist ideas. It is no secret that in Russia the mobilist school initially met with serious opposition, and that even up to the present it has had numerous opponents. However, Western, and especially popular, scientific literature usually exaggerates the intensity of the situation and underestimates the contribution of Russian geologists and geophysicists to the development of mobilism and plate tectonics. The present paper describes some of the debates in Russia concerning mobilist doctrines, the work done in that country in the last three decades of the twentieth century from a mobilist perspective, and various theories that had currency in Russia at the end of that century.

Establishment of Mathematical Geology in Russia: Some Brush Strokes in the Portrait of the Founder of Mathematical Geology, Prof. A. B. Vistelius

This paper presents a concise historic overview of the establishment and pathways of development of mathematical geology. Its very existence is largely due to the activity of Russian geologist Prof. Vistelius (1915–1995) who was the first president of the International Association of Mathematical Geology. Presented are important facts of biography of A. B. Vistelius, as well as the history of his scientific investigations. It is elucidated that in the USSR, mathematical geology, like genetics or cybernetics, was hardly accepted by the ideology that dominated at that time from its very appearance in the 40s. Both mathematical geology and its creator could not be squeezed into the tight limits of the Soviet ideology. But the difficulties only benefited his bright individuality and hardened his style of scientific reasoning, leadership, and fight for purity of science. Vistelius believed that mathematical geology would be the paradigm for geoscience in the 21st century. It is ascertained that the scientific ideology of conceptual modeling of geologic processes and objects suggested by Vistelius has totally proved itself. However, its further propagation is impeded by those geologists whose thinking is traditional and whose paradigm is old. This situation must be changed to enter the coming century equipped with economically reliable concepts ensuring sustainable development. It could be unprofitable and even dangerous to ignore the concepts developed by Prof. Vistelius. This paper focuses on the principal ideas of Prof. Vistelius and detailed large-scale program of development of mathematical geology in the foreseeable future. This program is fulfilled in the Institute of Mathematical Geology (IMAG) of the Russian Academy of Natural Sciences, founded by Prof. Vistelius.

Ultrahigh‐pressure metamorphism and decompressional P–T paths of eclogites and country rocks from Weihai, eastern China: Reply

We welcome the constructive comment by Enami on our suggested in situ model for coeval UHP metamorphism of coesite-bearing eclogite, garnet amphibolite, and country rock gneisses at Weihai in the northeastern tip of the Su-Lu UHP terrane (20). Establishment of UHP metamorphism for this region was based on the occurrence of coesite relics (17; 14; 20) from a single eclogitic block at a beach locality. We have recently identified two additional coesite-bearing eclogite localities in the vicinity of Weihai (15). We agree with Enami that the evidence for UHP metamorphism preserved in the country rock gneisses is `far less convincing'. In this area, we described several small garnet amphibolite layers or pods and calc–silicate layers concordant with the surrounding granitic gneisses. The amphibolites preserve mineral aggregates after omphacite and show ghost eclogitic textures (Fig. 2f, Zhang et al. 1995a). Moreover, plagioclase in some garnet-bearing clinopyroxene gneisses is clearly a retrograde phase (Fig. 3a, 20); a P–T estimate of the peak metamorphism was not made, but these rocks were assumed to have experienced similar P–T histories to the less thoroughly overprinted coesite-bearing eclogite block. We used the term `calc–silicate rock' but not `calc–silicate gneiss'; the calc–silicate rocks are not `similar to typical skarns' which tend to occur at the contact between carbonate wall rocks and granitic intrusives. The assemblage of the calc–silicate rocks described in our paper (20) consists of Grt + Cpx ± Qtz + Ttn (Fig. 1) rather than Pl + Scp + Grt + Cpx + Ep. As shown in Fig. 1, garnet, clinopyroxene, and quartz constitute up to 95–97 vol% of the rock; minor secondary anhedral plagioclase and zoisite rim garnet and clinopyroxene (Fig. 2). Garnet and clinopyroxene contain titanite and apatite inclusions. The plagioclase contains inclusions of relict garnet and titanite, and ranges in An content from 19 to 65; these anhedral plagioclase grains are not in equilibrium with the precursor garnet and clinopyroxene, and appear to be a retrograde phase. Photomicrograph showing retrograde zoisite after clinopyroxene in calc-silicate rock (SL91-6E). Crossed polars, width of view = 0.75 mm. Cpx, clinopyroxene; Zo, zoisite; Grt, garnet. (b) A Schematic diagram granoblastic texture and a typical assemblage Grt + Cpx + Ttn + Qtz for (a) a calc-silicate rock (SL91-6B) from Weihai (width of view = 1.5 mm). Grt, garnet; Cpx, clinopyroxene; Ttn, titanite; Qtz, quartz. Lack of plagioclase sets the minimum P for the peak metamorphism at 14 kbar. As described in detail in our original paper (20), the calculated maximum P could be as high as 30–35 kbar. Such a P–T estimate is consistent with the occurrence of high-Al titanite which contains 5–6 wt% Al2O3 (Table 3, 20), and is similar to high-Al titanite in the Donghai coesite-bearing eclogite of the Su-Lu region (21), in the Shuanghe carbonate-bearing eclogite in the Dabie Mountains (1), and in UHP eclogite of the Western Gneiss Region (11). These observations indicate the eclogitic and country rocks at Weihai share the same P–T path (20). Both we and Enami recognize an upper amphibolite-to-granulite facies overprint for the Weihai occurrence. We agree with him that the lack of relict coesite in the country rock gneisses means that the assignment of UHP conditions remains questionable. Our interpretation, however, is plausible, based on concordant layering, high-Al titanite, and P–T computations. For kinetic reasons, with the influx of minor amounts of fluid into the gneissic rocks, any earlier formed coesite grains would have been entirely transformed to quartz at such high-T conditions unless the coesite relics were stored in rigid crystals such as zircon. It took more than half a century for European and Russian geologists to discover tiny inclusions of diamond and coesite in strong, chemically resistant container grains of garnet, clinopyroxene, and zircon from UHP metamorphic rocks in collision belts within Eurasia and Africa (567a; 2). With new appreciation and sophisticated instrumentation, the UHP record in felsic gneisses of the Dabie–Su-Lu region have been increasingly recognized. This includes the additional finding of tiny coesite inclusions in zircons from Dabie felsic gneisses (12; 13), in dolomite and garnet from calc–silicate rocks and dolomite-bearing eclogite (10; 19), and in garnet and jadeite from jadeite-bearing quartzite (21; 8O values have been determined for UHP minerals from country rock gneiss, quartzite, and eclogite in the Qinglongshan of the Su-Lu terrane (9). Aegirine as a retrograde phase after jadeite and garnet in garnet–jadeite–quartz rocks have been reported (18; 21, 8); it has been increasingly recognized in country gneiss of the Su-Lu terrane (16; 21; 4) and in the Dabie Mountains (3). The identification of additional UHP indicators will require further studies; the debate regarding the in situ versus foreign origin for eclogitic rocks will continue. We look forward to further discoveries of phenomena constraining the P–T conditions attending UHP metamorphism of the Weihai rocks.

Plate tectonics in Russia

ABSTRACTAfter a short period of propagation of Wegener's continental drift ideas in Russia in the twenties and first half of the thirties of this century, there came a much longer period (1935–1960) of fixist reaction', when vertical tectonic movements were regarded as primary and most important and horizontal ones as secondary and subsidiary. In the sixties, interest in the manifestation of horizontal movements on strike‐slip faults, overthrusts and nappe formation began to grow, and at the verge of sixties and seventies ideas of plate tectonics began to penetrate into Russia. But at the begining they met strong resistance mainly from the older generation of scientists. In spite of this, these ideas finally gained the support of the majority of Earth scientists in this country. Russian geologists and geophysicists made a significant contribution to the development of the plate tectonics theory as well as in its regional, global and theoretical aspects.

Geoscience Education in Old and New Russia

At the beginning of this century, the subject called “natural history” was taught in all types of Russian schools. Approximately one-third of that course was geology. The first decades after the October Revolution of 1917 became a sort of “golden age” in the history of geoscience education in Russia. After the second world war, geology disappeared from school curricula and some of its topics were integrated into courses called “science” and “physical geography.” Today the goal of many Russian geologists would be to return geology to Russian schools as an independent discipline. It is also important to organize and present teachers' refresher courses in the geosciences and, of course, to improve teacher training.

Charles Bénard's first expedition to Novaya Zemlya, 1908

ABSTRACTIn the summer of 1908 the Mission Océanographique Arctique Française sailed from Dunkirk aboard the ketchJacques Cartier. Sponsored by the Société d'Océanographie du Golfe de Gascogne and led by Charles Bénard, its major aims were to study the fisheries potential of the Barents Sea, to explore Gusinaya Zemlya on the south island of Novaya Zemlya, to chart and sound the bays and straits of that area, to carry out geological investigations, and to make a traverse of Matochkin Shar, which bisects Novaya Zemlya. The expedition established itself at Belush'ya Guba, from where Bénard and his companions explored much of Gusinaya Zemlya and surveyed, sounded and charted the adjacent waters. An attempt at crossing the south island, made by the medical officer Candiotti, was unsuccessful. Later, accompanied by the Russian geologist Vladimir Aleksandrovich Rusanov, Candiotti sailed through Matochkin Shar and made the first crossing of the north island, from Neznayemyy Zaliv to Krestovaya Guba. The expedition ended on rather a sour note: Bénard abandoned his ship and crew at Arkhangel'sk, leaving the organizing committee with the problems of unravelling the mess and repatriating the crew.

New Soviet gas field

According to a Reuter report, the Soviet Communist party daily Pravda has stated that Russian geologists have found a new natural gas field in western Siberia. Gas was reported to have been found about 3.2 km beneath the new Yevo‐Yakhinsky field, but the size of the strike was not disclosed. The new field is located near the large, established Urengoi field.

The biostratigraphic potential of Precambrian stromatolites

The morphology of stromatolites is controlled partly by the biological composition of algal mats and partly by the direct action of environmental factors. Both trapping of detrital grains and precipitation of carbonate in algal mats are important processes in stromatolite formation. Precambrian stromatolites were probably not subject to the environmental restrictions of Recent stromatolites. Stromatolites can be classified on the basis of a number of morphological features, some of which relate directly to the biological characteristics of algal mats (lamina shape and microstructure) and some of which have at least partial environmental control (e.g., column shape, branching style). The taxonomic significance of characters may vary in different taxa. A binomial (but not biological) form nomenclature is applied, using “groups” (analogous to genera) and “forms” (analogous to species). The biostratigraphic potential of Precambrian stromatolites, theoretically possible from what is now understood of the controls of Recent stromatolite morphology, can only be tested empirically by determining the time ranges of defined taxa. This relies heavily on other means of dating and correlation. Initial results of stromatolite biostratigraphy in Australia proved encouraging and appeared to confirm the applicability of the biostratigraphic scheme worked by Russian geologists. However, none of the stromatolite assemblages described from Australia is identical to any from the U.S.S.R.: none contains all of the elements described from the Russian assemblages, and most of the common elements are comparable only at group level. New data suggest that the time ranges of several groups are longer than previously accepted, and caution is therefore urged in using group level identifications alone as a basis of correlation. Identity of forms is a better criterion for correlation, but most forms have a limited geographic distribution. Further systematic description and identification of stromatolites from rock sequences of all ages on all continents are needed to establish the actual time ranges of taxa and assemblages of taxa, and hence their biostratigraphic applicability. Stromatolite assemblages presently known from various Proterozoic basins of Australia are discussed. Pre-Riphean assemblages include groups previously known only from the Riphean, as well as groups not found in the younger rocks. Partial equivalents of each of the subdivisions of the Riphean occur in a number of basins, but their stromatolite assemblages are not yet well known. Late Riphean equivalents have the best documented assemblages and the groups present are generally consistent with their time ranges determined in the U.S.S.R. However, the Burra Group (Adelaidean) of South Australia lacks typical Late Riphean stromatolites and was originally correlated with the Middle Riphean. New radiometric and stromatolite data suggest that deposition of the whole Adelaidean sequence commenced during the Late Riphean.

The Precambrian Banded Iron-Formations of the Soviet Union

The Precambrian iron-formations in the European part of the Soviet Union occur mainly along a trend which can be followed between the Azov Sea coastal region in the south and Kola Peninsula in the north. The deposits of Krivoy Rog and Kremenchug, within the Ukrainian Shield, and those of the Kursk magnetic anomalies (Voronezh plate) form a gigantic metallogenic province. Precambrian banded ores also occur in the Urals and the Asiatic part of the Soviet Union in the cores of Caledonian and Hercynian orogenic belts.Lithologically the iron-formations consist of intercalated, rather continuous bands of silica and iron oxides, or in rare cases, of iron carbonates (carbonate facies). Separate bands range in thickness from a fraction of a millimeter to several centimeters. The bands in turn are composed of microbands. The average iron content of the iron-formations is about 35 percent. The iron-formations are part of a marine geosynclinal sequence and typically are represented by magnetite and hematite facies, the latter being considered by most Russian geologists as the product of sedimentation in relatively deep water far offshore. They are part of the transgressive series. Most of the iron-formations of the Russian platform are thought to be correlative, but the detailed stratigraphy, such as the number of banded ore members, differs from one locality to another. The iron-formation in Krivoy Rog consists of seven members having a total thickness of 1,300 m, whereas that of Kursk consists of five members having a thickness of 500 m.The iron-formations of the Russian platform are underlain by a formation consisting mainly of arkose, phyllite, schist, and quartzite, whereas they are overlain by a succession consisting mainly of carbonaceous shale or schist and dolomite.Reconstruction of the ancient environments in which the iron-formations were formed suggests deposition under both miogeosynclinal and eugeosynclinal conditions. The iron was concentrated in the middle formation of the sequence, corresponding to a sedimentary metallogenic epoch, which probably can be correlated throughout the gigantic metallogenic province of the Russian platform. The major iron-formations in the province are between 2,000 m.y. and 2,600 m.y. old. Some of the smaller iron-formations in other areas are apparently either older or younger than the main ones.Five hypotheses have been proposed to explain the origin of the Precambrian iron-formations and the banding. Among these, hypotheses for a sedimentary origin and a volcanic-sedimentary origin appear to be most realistic and best substantiated.

Migration of Reservoir Fluids

Abstract The application of reservoir and production engineering experience to problems of migration and accumulation of oil and gas, is presented. The principle of differential entrapment is reviewed and updated, and geological evidence for selective trapping of oil and gas is illustrated. This theory, first published in 1953, explains why many good traps are dry while adjacent structures are prolific oil fields. It explains why some traps are gas fields and contain no oil, and why gas is trapped downdip in some areas while synclinal oil occurs in others. The law of gravity explains the gravity distribution of gas, oil and water in a reservoir. However, differential entrapment explains why some oil reservoirs are stratified, and why some oil accumulations are light-gravity condensates while others are medium or heavy crudes. Under superimposed hydrodynamic conditions, oil and gas accumulations are modified in accordance with the hydrodynamic gradient, causing tilted interfaces, spilling and remigration. When folding and faulting are super-imposed on a basin with oil and gas accumulations, the oil and gas usually remigrate into the new structures in accordance with the principle of differential entrapment, and these new accumulations conform to the existing hydrology. How undersaturated oils are formed, why crudes have different GOR'S, and the origin and significance of saturation pressures and how these are used for determining the time of accumulation are discussed. Introduction Migration is fully discussed in the geological literature and is reviewed and updated here for the benefit of the petroleum engineer. Petroleum engineers are well aware that each oil and gas field has special characteristics all its own. This paper discusses the reasons for these differences and how they came about. The oil and gas in an accumulation concentrated from somewhere and have left little trace of their source. Few petroleum geologists have an engineering background and yet this is becoming more and more essential for a successful exploration effort. The geologist and geophysicist are learning to work together and they realize the need for teamwork in applying their specialties. A similar and much greater effort of cooperation is needed between the reservoir engineer and the exploration geologist to find the remaining undiscovered oil and gas reserves. The engineer should carry his share of the burden and help the exploration geologist find more oil. This mutual understanding and cooperative effort is even more necessary since many engineers are now in management positions charged with making important exploration decisions. The general application of the structural theory, together with migration, now is accepted by virtually all petroleum geologists. The so-called anomalous occurrences of oil and gas in interconnected traps long baffled the petroleum industry throughout the world. Why are some apparently good structures gas fields rather than oil fields, while others are dry? This is explained by the principle of differential entrapment. This simple principle explains why gas fields may occur in a downdip position and produce little or no oil, while structures farther undip produce oil with little or no gas and others still farther updip are dry. In reality, this carries the structural theory to its logical conclusion. Following publication of a paper in 1954, two earlier attempts to explain these apparently anomalous occurrences were found, in spite of the fact that 4 man-years had been spent searching the literature without discovering the slightest hint. The work of a Russian geologist came the closest, but it veered off. In 1916 Loyal W. Trumbell, state geologist for Wyoming, set forth ideas almost identical with those developed nearly 35 years later, and yet Trumbell's idea lay dormant except in the minds of a few of his associates and received little attention. Trumbell was certainly on the right track. In 1932 Strong developed an explanation for anomalous occurrences in the Middle East. This was based entirely on the effect of solution gas in the oil. He visualized saturated oil migrating updip without any free gas. With decreasing depth (and pressure), solution gas would be released from the oil. By this line of reasoning, every trap would contain a gas cap at the time of migration. These would be larger and larger basinward since the farther downdip the trap occurred, the more oil would have passed a specific trap. Strong then explained the absence of gas caps in the updip traps by the selective leakage of gas from shallower structures. Pratt wrote that he had been made aware of Strong's idea many years earlier by George M. Lees; and A. I. Levorsen (personal communication) also intimated that he had ". . . bought leases based on the idea many years ago". The effect of solution gas in the oil is believed to be a secondary complication that obscures the underlying principle of differential entrapment. JPT P. 353ˆ

Metasomatic sulfur deposits of Kamchatka and Kuril Islands

More than 30 sulfur deposits of various sizes are now known in Kamchatka and the Kuril Islands. They are associated with volcanic rocks and the series extends into the Japanese Islands along the volcanic arc. Some ten years ago the Russian geologists concluded that the larger volcanic sulfur deposits are of metasomatic origin. A few years later Japanese geologists decided that some of their large sulfur deposits are probably also metasornatic. These deposits occur in the older (Miocene-Pliocene) arc of volcanoes. In the younger outer arc, sulfur occurs as crater-lacustrine deposits that are smaller near surface accumulations. The metasomatic deposits occur characteristically in agglomerates capped by impervious tuffs. This is taken as evidence for their origin, as is the fact that the sulfur cuts across agglomerate layering and the larger ones are thicker than any of the individual agglomerate layers. Also, the sulfur grades downward into S-pyrite accumulations, then Hg-As, Sb, Au-Ag, Pb-Zn, and Cu-Mo, in that order, which is characteristic of hydrothermal metasomatic deposits. Sulfur oxidizes rapidly at the surface, so that best deposits are those that have remained sealed. Some are as much as 200–300 m below the surface, so geophysical methods (mostly electrical and magnetic) are used to localize the large deposits before drilling. Porous zones in the agglomerate, silicified with quartz and opal, are good indicators of the proximity of sulfur. -- E. Ingerson.

Contemporary Nonmarine Sedimentation in Soviet Central Asia

In Soviet central Asia sediments are being deposited in a wide variety of nonmarine environments. This is an area containing large inland seas similar to those that must have been present in the U.S. several times in the geologic past. Many ancient rock units were formed in epicontinental seas under similar conditions. The Caspian Sea is a huge lake of brackish water on whose margins are deltas of rivers, some draining tectonically active and others tectonically stable areas. Sands, muds, carbonates, and evaporites are being deposited in the sea, and their areal patterns can be related both to bathymetry and oceanography. East of the Caspian is a desert, partially covered by recent windblown sand. Rivers from high mountains on the south flow onto the desert, depositing broad areas of fine-grained, fluvial sand and silt. The Aral Sea is a smaller inland lake with two important deltas and a variety of bottom sediments. These recent sediments have been studied by Russian geologists and oceanographers for more than 30 years. Their work is described in several monographs and many technical articles, and he present paper is a review of their work.

The boundary between Cambrian and Precambrian

Generally, the Olenellus -bearing beds and associated fauna have been regarded by Russian geologists as occurring in the upper one-third of a continuous sedimentary sequence which was unfossiliferous below and which rested on crystalline basement. Presumably early fossil groups began producing carbonate skeletal material at different times and migrated so as to arrive in various areas earlier or later than elsewhere. Hence, paleontological identification of the Lower Cambrian boundary requires knowledge, now lacking, of vertical distribution of the skeleton-producing organisms, of the conditions of their emergence, and of related sedimentary facies. Previously used physical criteria for the recognition of the Cambrian-Precambrian boundary are unsatisfactory. It is suggested that this boundary be determined by absolute dating. The author reviews recent findings on geologic age, absolute age, and faunal content of many formations in the Siberian Platform and adjacent regions that bear on this problem. — C. ...

Some recent Russian studies of ignimbritic rocks

Abstract Summarised translations of recent papers by the Russian geologists Vlodavetz, Petrov, Maleyev, Piip, Aprelkov, and Bykovskaya and Rottman are presented and discussed. Current classifications of volcanic rocks in the U.S.S.R. include a group of rocks, called “tufolavas”, not generally recognised elsewhere. They are reported to be like ash-flow tuffs or ignimbrites, but are characterised by lens-like inclusions and have a “fluidal” or lava-like matrix. Their distinction from welded tuffs deposited at high temperature is not clear in the literature. In the U.S.S.R. ignimbrites and tufolavas have been studied in detail in the Quaternary volcanics of Armenia and Kamchatka. Other, older deposits have been found in volcanic provinces in eastern Siberia, in the Urals, and in the high mountain ranges south of Kazakhstan. Chemically, they range mainly between rhyolite and dacite. Most writers ascribe their origin to some degree of magmatic differentiation. Phenocryst modes differ in the different volcanic ...

Preparing genetic classification of ore-bearing areas

This is a critical review of theories concerning the relation of tectonics to magmatism and affiliated ore deposits, suggestions concerning the principles of genetic classification of ore deposits, and terminology pertinent to classification. Shatalov presents a spectrum of views expressed predominantly by Russian geologists during the last twenty years. Genetic classification is thought to bring together dialectically all information on the genesis of ore deposits. Besides theoretical aspects, classification is expected to emphasize also an immediate purpose as a guide in prospecting for new mineral deposits.—E. A. Alexandrov.

Development of geological research in U.S.S.R Academy of Sciences and U.S.S.R. Ministry of Geology and Mineral Reserves

On October 12, 1962, a joint session of the Presidium of the U.S.S.R. Academy of Sciences and the Collegium of the U.S.S.R. Ministry of Geology and Mineral Reserves adopted a resolution “On the present state of the geological sciences in the U.S.S.R. Academy of Sciences and the U. S. S. R. Ministry of Geology and Mineral Reserves and their prospects for the future.” Important contributions of Russian geologists are acknowledged, but attention is drawn to many shortcomings. Future goals of geological study and work are given in detail. Twenty-one lines of research to be concentrated on are given, covering all phases of geology, geophysics, and geochemistry. In discussing the failings of the geological profession in Russia, it is of interest to note the following comment: “Geological research in other countries is still insufficiently studied and applied, and we are not making adequate use of geologic information from abroad.” The list of the Russian geologists' shortcomings sounds vaguely familiar. —J. R. Hayes

THE STUDY OF FACIES: BASIC PRINCIPLES

The concept of facies is attributed to the Swiss geologist, Gressly. It is definable in terms of a uniform portion of a land surface or sea floor, with definite implications of geography. Different facies in the Black Sea and Caucasus are cited. Gross uniformity of lithology and biocoenose are implied within facies. The work of numerous Russian and American geologists in facies studies is reviewed. A classification of facies is proposed in which the concept of servia and nimia is introduced. --M. Russell

Teodorovich's Method for Determining Permeability from Pore-Space Characteristics of Carbonate Rocks: GEOLOGICAL NOTES

Outlines the method developed by the Russian geologist G. I. Teodorovich for calculating permeabilities of carbonate reservoir rocks from thin-section analysis of pore-space configuration, and reviews results of its application, noting an average discrepancy of about 10 percent between calculated and measured permeability values.

Relationship Between Ca/Mg Ratio and Geologic Age

The analyses of numerous limestone samples showed that there is a general increase in the average Ca/Mg ratio in going up the geologic column with superimposed periodic fluctuations. A general decline in abundance of dolomites in going up the geologic column was previously shown by R. A. Daly (1910). The writer, however, failed to establish a simple relationship between the Ca/Mg ratio and the age of carbonate rocks. The cyclic occurrence of dolomitic and calcitic limestones, observed by the writer, suggests that the formation of dolomites was occurring in cycles with a gradual accumulation of magnesium in sea water until favorable conditions were established for the formation of dolomites. Inasmuch as high CO2 pressure of the atmosphere during pre-Cambrian and Paleozoic time is advanced by Russian geologists as a possible explanation for the abundance of dolomites, an attempt was made to precipitate dolomite directly out of sea water at high CO2 pressure. This attempt was successful and indicated that some pre-Cambrian and Paleozoic dolomites may have been formed by direct chemical precipitation out of sea water.