Vol 64 Iss. 2

The idea of the leading role of the scattered form of existence of chemical elements in the Earth's crust has now become generally accepted, against the background of which increased concentrations of elements are observed, under certain conditions referred to as ore occurrences or mineral deposits. The formation of increased concentrations, naturally, is possible only given an expenditure of energy, whose source may be processes of both endogenous and exogenous nature.

Within South Gissar, small intrusions and extrusive formations, represented by monchiquites, picritic porphyrites, camptonites, analcime basaltoids, monzonites and their transitional varieties, are widely developed. They occur among the Upper Paleozoic granitoids of the Gissar batholith and the volcanogenic sequence of Lower Permian age.

Long-term prospecting and exploration work in the Kola-Karelia region has established the association of mica-bearing pegmatites with aluminous gneisses, theoretically substantiated by G. I. Buntin, D. S. Korzhinsky, and V. D. Nikitin.

The numerous aspects of the extremely complex problem of the zonality of postmagmatic ore deposits have been considered for several decades by many Soviet and foreign researchers — V. Emmons, S. S. Smirnov, Yu. A. Bilibin, N. A. Khrushchov, P. M. Tatarinov, V. I. Smirnov, V. V. Shcherbina, Ya. Kutina, etc.

The Nezhdaninskoye gold deposit is located in the northern part of the South Verkhoyansk synclinorium and is situated in the crestal part of the southern periclinal closure of the box-shaped Dyba anticline. The host rocks are represented by a monotonous sequence of sandy siltstones and shales of Lower Permian age.

All the most practically interesting deposits and ore occurrences within the South Slope of the Gissar Range are hydrothermal in nature and are localized within zones of discontinuous faults. In this connection, geochemical sampling of the material composing the zones of tectonic faults acquires extremely important significance, since it is obvious that the basic patterns of introduction or removal of elements in discontinuous faults can be used as geochemical criteria in the age subdivision of faults or in assessing their ore potential.

In searching for deep-seated ore bodies using primary halos, two main parameters are usually used: zonality and the gradient of element contents in primary halos along the rise, across, and along the strike of ore zones. For studying zonality, the assessment of the stages of ore deposition is of great importance. Only by assessing the stages of ore deposition is it possible to study zonality and use it both for searching for blind ore bodies and for assessing the level of the erosion cut and the prospects of deep horizons of ore bodies not exposed by erosion.

In addition to copper-nickel mineralization, pyrite-pyrrhotite mineralization is widespread in the Monchegorsk region, and prospecting geologists often have to resolve the question of the relationship between pyrite-pyrrhotite mineralization and copper-nickel mineralization. Until recently, most of the identified pyrite-pyrrhotite ore bodies had been traced by mining and drilling operations in the hope of a possible transition of pyrite-pyrrhotite mineralization into copper-nickel mineralization, but no case of such a transition has been established.

An experimentally substantiated hypothesis on the existence of film halos was first put forward by N. F. Mayorov. To quantitatively describe the concentration distribution in film halos, a system of differential equations was proposed. ...

Lithochemical surveying under the conditions of the Kola Peninsula and Karelia is now beginning to be widely used in combination with geophysical methods at the stage of detailed prospecting. Verification by drilling confirms the high efficiency of the method, which makes it possible to reject numerous geophysical anomalies caused by virtually nickel-free pyrrhotite ores and non-ore objects.

When searching for sulfide ores, sulfur is usually not determined in lithochemical samples. Meanwhile, with clark values in the lithosphere of 0.047%, its content in sulfide ores reaches tens of percent. Thus, in samples of sulfide copper-nickel ores of the Allarechensky and Monchegorsk districts of the Kola Peninsula, up to 27–33% of sulfur was found, and in samples of pyrrhotite ores of the Allarechensky district, 20–26%.

Based on the theoretical analysis of the distribution of element concentrations in residual dispersion halos of vein-shaped ore bodies, R. I. Dubov proposed using specially calculated nomograms of theoretical curves constructed on a semi-logarithmic scale for interpreting the halos. Interpretation using nomograms, as is known, consists in superimposing the experimentally obtained curve, constructed at the same scale, on one of the theoretically calculated curves. A disadvantage of the nomogram method of interpretation is the need for interpolation between neighboring curves on the nomogram. The similar character of curves with different parameters can lead to ambiguity of the solution.

Partial escape of radon into the borehole, subjected to prolonged flushing during drilling, leads to a decrease in the intensity of radiation along the borehole axis and an underestimation of linear uranium reserves from gamma logging data.

Uranium content in rocks by gamma-spectrometric and radiochemical methods is determined on the assumption of radioactive equilibrium between uranium and radium. Studies of the state of radioactive equilibrium in rocks are contradictory. Some researchers point to significant disturbances of radioactive equilibrium, while others point to the presence of equilibrium within the accuracy of the methods used to determine uranium and radium.

Radon and thoron are constituents of the Earth's atmosphere. The distribution of radon concentrations has been studied quite fully. There is much less information on thoron concentrations in the atmosphere. Significant daily and seasonal changes of radon concentrations in the surface layer of the atmosphere have been detected. The concentration of radon and thoron in atmospheric air is determined by their exhalation from rocks and soil, as well as by turbulent mixing in the atmosphere.

In recent years, interest has increased in studying the chemical composition of metamorphic and ultrametamorphic rocks of ancient shields as possible analogs of the material of deep zones of the Earth's crust. The distribution of radioactive elements in these rocks attracts special attention of researchers in connection with the problems of the thermal regime of the Earth's crust, the evolution of the material composition of rocks during their geological development, and the determination of the primary nature of metamorphic sequences.

The most promising method of sampling of uranium-thorium ores, which allows separate determination of uranium and thorium, is the gamma-spectral method in the modification of measurements of the differential effect of radiation. The principle of such sampling was considered earlier. ...

The development of gamma-spectral methods for in situ sampling of complex uranium-thorium ores and the associated increase in the amount of information obtained requires the development of accelerated methods of interpretation of measurement results. The proposed counting and solving device to increase approximately twice the productivity of gamma-spectral measurements processing in comparison with the usual nomographic method, is characterized by universality, high reliability and long service life.

Continuous recording of equivalent contents of radioactive elements instead of registration of count rates in differential channels during gamma-spectral measurements makes it possible to quickly obtain information on the distribution of elements in the studied object and simplify the processing and interpretation of results. This method is used in search gamma-spectral surveys while moving. In our work, continuous recording of uranium (by radium) and thorium contents was used in gamma-spectral logging on the target of two-component uranium-thorium ores.

The largest deposits of Iceland spar are confined to lava sheets of basic composition (the first type of deposits), to small dolerite intrusions (the second type of deposits), and to zones of tectonic fracturing in tuffaceous rocks (the third type of deposits). To date, the known deposits have been studied fairly well and the main geological regularities of their spatial distribution have been identified.

The electronic circuit for stabilizing the energy scale is a device that tracks the photopeak of a gamma reference. The basis of the circuit is two adjacent differential channels with the same window width, tuned, respectively, to the left and right branches of the photopeak of the reference source. At the output of both differential channels a comparison circuit and an actuating device are placed. ...

The concept of the effective atomic number Zef of rocks and ores follows from the concept of equivalence of γ-quantum properties of media of different material composition and is of fundamental importance for the development of γ-γ methods of nuclear geophysics.

The effective application of gamma-gamma density logging in the subdivision of a geologic section is largely determined by the correct choice of the distance between the source and detector of radioactive radiation (probe length), the integration constant and the rate of movement of the logging tool.

The distribution of gamma quanta over the directions of motion is one of the main characteristics of gamma fields. Data on the angular distribution of gamma radiation are used in the design of probe devices, in the selection of optimal geometric conditions and methodological methods of measurements in nuclear geophysical methods of studying rocks.

The different spectral composition of gamma radiation of uranium and thorium ores determines the specifics of accounting for the attenuation of radiation in casing pipes and drilling fluid when interpreting gamma-spectral logs.

When estimating confidence limits for the average metal concentration in ore, data on the moments of distribution and the number of samples are taken into account. It is also important to have an idea of the degree of independence of differences between determinations, since the usual proposition that the variance of the mean is n times smaller than the variance of a single determination is valid only for determinations with independent variations (n being the number of individual determinations).

The influence of host rocks on the regularities of the location of quartz veins within crystal-bearing fields, the genesis of the veins and the formation of crystal nests is quite widely covered in the Russian literature. In many crystal-bearing fields, the confinement of quartz veins to sequences of a certain composition, which are considered productive with respect to crystal content, has been noted. All researchers to one degree or another note the influence of rocks on the mineral paragenesis of crystal nests, and some consider the host rocks as a source of silica in the formation of not only crystal nests, but also the quartz veins themselves.

One of the most promising criteria of nickel potential of basic-ultrabasic massifs is naturally considered to be the content in non-ore rocks of nickel, the main component of copper-nickel ores. The main difficulty in applying this criterion is the non-uniformity of the background nickel content, which in the series of basic-ultrabasic rocks increases from the most acidic representatives of the series to the most basic ones. This phenomenon was first taken into account by D. V. Polferov.

The task of discriminant analysis consists in assigning an object characterized by a set of l features to one of (in our case, two) l-dimensional populations (A or B). Samples from these populations will be called class A or B, respectively.