—On the territory of the Egor’evsk district, 3500 results of probe microanalyses of surface gold particles taken from 17 placers, weathering crusts, and orebodies were processed and summarized. High-fineness and mercury-containing gold is predominantly found within mother lodes and placers, and medium- and low-fineness gold is distributed in subordinate and dramatically subordinate quantities, especially in the placers. A unique feature of the gold composition, rarely occurring in other districts, is the constant and commonly simultaneous presence of mercury and copper impurities. Analysis of Ag, Hg, and Cu content variations has enabled us to identify five main grades of gold. The mother lodes of the predominant gold grades are metasomatites with beresite and listwaenite compositions, which are developed primarily after lower Cambrian volcanoterrigenous-carbonate rocks and ore-bearing mafic dikes. Mercury-containing gold is characteristic of beresites, but copper-bearing gold is typical of listwaenites. The relationship between corresponding grades of surface and ore gold is confirmed by the presence of microinclusions in the gold grains. Nonconformity between the content of gold from mother loads, weathering crusts, and placers is explained by the losses of Hg and Ag impurities by endogenous gold under subsurface hypergene conditions. Identification of mineral-geochemical properties of surface gold is of exceptional practical importance in ore-grade gold mineralization prediction.
The platinum-group minerals (PGM) in placer deposits provide important information on the types of their primary source rocks and ores and formation and alteration conditions. Different characteristics of minerals can be determined by a set of conventional and modern in situ analytical techniques (scanning electron microscopy (SEM) and electron probe microanalysis (EPMA)). A study of PGM from placers of southern Siberia (Kuznetsk Alatau, Gornaya Shoria, and Salair Ridge) shows that the morphology and composition of PGM grains, the texture, morphology, and composition of silicate, oxide, and intermetallic microinclusions, and the type of mineral alteration can serve as efficient indicators of the primary sources of PGM. The widespread rock associations in the Kuznetsk Alatau, Gornaya Shoria, and Salair Ridge, the compositions of PGM and microinclusions in them, and the dominant mineral assemblages testify to several possible primary sources of PGE mineralization: (1) Uralian–Alaskan-type intrusions; (2) ophiolite associations, including those formed in a subduction zone; (3) ultramafic alkaline massifs; and, probably, (4) rocks of the picrite–basalt association. The preservation of poorly rounded and unrounded PGM grains in many of the studied placers of the Altai–Sayan Folded Area (ASFA) suggests a short transport from their primary source.
Summary:The main methods of estimating the mean volume of ciliates are given:-cell-shape comparison to a simple geometrical figure, -direct determination, -models method.The last is more precise and its simplified variant allows us to computerize the procedure of calciilation the mean cell volume (mass).Correct estiniatibn of biomass, production and destruction of organic matter by hydrobionts are an extremely important problem in Hydrobiology. It depends on the precision of the determination of the individual's mean mass. Therefore, the consideration of the authors concentrates on the problem.Without colorimetry (SOHOLANDER et al.), all methods are based on the calculation of a mean cell volume and its density. The density of Protozoa is estimated a t 1.02 ... Frequently used are nomograms that give its volume from the data on a shape, cut form and size of the body (CHISLENKO). These methods are best applied to geometrical regular cells. The results are similar with the data of the direct determination (TROIT-SKY and SOROKIN). However, some ciliates are nonideal in shape and the use of the above mentioned methods may produce mistakes (KLEKOWSKI and TUMANTSEVA).2. Direct determination of the cell volume. The cell volume is measured by squeezing the cell between two glass surfaces spaced at a known distance and tracing the surface contour. The known distance is prepared by platinum filaments of a known diameter.
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