This article provides an example of the application of the method of depicting the chemical compositions of rocks using vectors to the study of the phenomena of magma differentiation and magmatic evolution. As such an example, I took the only one of its kind, the most well-studied case, namely the famous volcano Vesuvius in the history of mankind. In the depths of igneous bodies - plutons - processes occur under conditions significantly different from those in which we directly observe magma reaching the earth's surface in the form of lava. Compared to other volcanoes, Vesuvius, thanks to its study, has the advantage that here we even have some data on the progress of the process over time. Regardless of this or that hypothesis, the presence of a shift in the line of differentiation of lavas with each new cycle of volcanic activity can be considered established for the chemistry of rocks. This displacement turns the line of differentiation into a strip of points or vectors. This arrangement of elements, depicting the chemical compositions of rocks in the form of a strip, is a characteristic feature of almost all such diagrams. The general arrangement of these geometric elements, the position of some of the axial lines of their stripes provide a clear general characteristic of the chemistry of the volcanic and plutonic formations presented in the diagram. But this is only the first step towards studying their chemistry with the help of a diagram.
One can get a thin section drawing in different ways. It goes without saying that only someone who knows how to draw well and who also knows enough petrography can draw a picture observed under a microscope without using any auxiliary equipment. These two qualities are not so common are combined in one person, and besides, this work is so tedious and requires such attention that in practice it is hardly worth using, therefore it is necessary to use some auxiliary devices. There are three main ways: drawing using a drawing device; drawing by projecting an image onto a table; drawing from a photograph. The method of obtaining a thin section pattern outlined in this note is by no means new. It was not only applied, but also described. The purpose of our work was to test its applicability in the conditions with which most of our petrographers now have to deal. One can hope that the use of these simple techniques will lead to an improvement in the quality of petrographic drawings in our publications. It goes without saying that the same techniques can be used to obtain line drawings and other objects, for example, polished opaque sections and even individual outcrops/shapes, etc.
By "petrochemistry" we should understand the totality of our information about the chemical composition of rocks, consisting of “many” (in the mathematical sense) chemical analyzes of rocks, and the conclusions that can be drawn from this information. Developing those methods of calculation of chemical analysis that were used by Michel-Levy and Ozanne, the author of this article has shown in other works that the main features of the chemical composition of igneous rock, data in its analysis, can be especially conveniently reflected in the form of such series of ratios, the sum sets of which uniquely reflects the set of chemical analyzes and is equivalent to it (see article). The diagram clearly shows the desired correlation between the lengths and directions of the strokes, depending, obviously, on their position on the diagram. This shows an important correlation between the characteristics of the salic and femic components of an igneous rock.
We studied random samples of thin sections of melted rocks, which were given to us by A.V. Vvedenskii. We did not pursue the goals of a systematic study of this random, although quite extensive (about 200 thin sections) material, and in this note we limited ourselves to only some data, characterizing the more common types of these "artificial rocks". The vast majority of the studied thin sections represent glasses that have just begun to crystallize with the formation of spherulites or various kinds of skeletal formations. Only in a few thin sections could one find individualized minerals in such a form that they were amenable to optical examination. Therefore, the main task of the study was the study of structures, and much less work was the study of minerals.
This article proposes an attempt to deduce the main principles underlying the use of converging light, based on the basics of the theodolite method. This particular path is the most appropriate if you follow the requirement to go from simpler to more complex. As will be seen from what follows, the logical development in this the direction of the main provisions of the theodolite method leads to almost the same ideas from which Becke proceeded when explaining the phenomena detected by a crystal in converging light. In addition to some theoretical interest that the presentation of these techniques may have, based on the ideas underlying the theodolite method, it seemed to me useful for the purpose of comparatively assessing the limits of application of each of these two different methods of research (see article).
In summer 1909 I undertook several petrographic excursions in the vicinity of the Miass plant, mainly to become familiar with the alkaline rocks developed in this area. The collected material was subjected to microscopic examination, which provided some data that, perhaps, will be useful for determininh the petrographic composition and structure of this area.
Regarding the petrography in the vicinity of the gold deposits of the Tsarevo-Alexandrovskaya distance of the Miass Dacha, which became famous especially due to the discovery of the largest of the Russian gold nuggets (2 paragraph 7 f. 92 z.), the information available in the literature is very scarce; for the most part it is only brief instructions. A geological map of this area, quite schematic, is given in the article. by mining Engineer Kulibin. The rocks are highlighted on it, but without their description. The author mainly lists the gold-bearing veins known at that time and dwells on some nuggets.
I found this mineral in its entirety in slightly rounded pebbles up to half a fist in size, consisting of barite with a small inclusion of leaded sheen, in the bed of the Narataya River, two miles southwest of the Narataevsky iron mine. The barite of these pebbles forms a medium-grained to coarse-grained aggregate, which is indivisible, often located, being elongated in one direction, so that a somewhat layered composition is formed.
All available samples contain inclusions of ore minerals in greater or lesser quantities: pyrite, zinc blende and partly lead luster. This clearly indicates that they were taken in the immediate vicinity of the ore sequence. The spatial location of these samples is clear from the attached diagram. As is known, the Zyryanovskoe deposit is a rather irregularly branched jelly-like mass.
This method, proposed by Bekke in 1893, has become widespread. As is known, it is based on observing the movement of a light strip that appears when using strong lenses at the boundary of neighboring mineral grains, if you move the microscope tube, focusing it either on the upper (upper setting) or on the lower surface of the section (lower setting).
The study on the Mountain Magnitnaya, carried out by me last summer on behalf of the Board of the Joint Stock Company of the Beloretskii Iron Works, is the beginning of work, which practical goal is to determine the iron ore reserves of this deposit. In addition, these studies were supposed to clarify the features in the structure of the deposit, with which must be taken into account when drawing up a rational development plan. The work consisted of drawing up as detailed a geological map as possible; in determining, in accordance with the data obtained as geological research progresses, the location and type of exploration work necessary to determine reserves, and in the organization of these works.
Two provisions are considered: 1. Property of crystals with an angle of optical axes 2V=90°C. 2. Determination of the optical sign of a biaxial crystal on a universal stage, when no optical axis is visible. It is possible to determine the position of the obtuse and acute bisector of the angle of the optical axes, and therefore the optical sign of the crystal.
The studied samples are graphite-hosting rocks from various graphite deposits: the Mariinsky mine at the Botogolsky Golets (Aliberovskoye deposit), the Barrowdelsky mine in Cumberland and two Ural deposits - one near the Sysertsky plant; the location of the other deposit is unknown - probably from the Ilmen Mountains.
