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The Engteri is a new hidden Au-Ag deposit in the Russian segment of the Pacific ore belt. The discovery of this deposit merits special attention, because it involves repeated attempts to reappraise a lowprospective ore occurrence, which were crowned with success as a result of fulfillment of large-scale drilling project. The average Au grade is 18.6 gpt. The deposit is classified as the gold geochemical type of Au-Ag deposits. The major ore mineral is pyrite, which amounts to no less than 95% of the total ore minerals. The native phases comprise electrum and to a lesser extent native gold of low fineness (730). The homogenization temperature of fluid inclusions is 125–255°C with a distinct maximum at 145–150°C. Despite blind localization of some orebodies, the Engteri deposits bears evidence for a deep erosion level: (1) small vertical range of economic mineralization (50–100 m); (2) predominant occurrence of massive sugarlike quartz with a low sulfide content; (3) prevalence of massive and brecciated textures above rhythmically banded textures; and (4) lack of low-temperature propylites. The southern part of the ore field distinguished by occurrence of rhythmically banded, framework-tabular, and brecciated texture has the best prospect for revealing new orebodies. The Engteri deposit allowed us to outline the following prospecting guides and methods of prospecting for hidden Au-Ag deposits: (1) these deposits are regularly arranged in ore clusters between heavy concentrate anomalies of cinnabar and gold-silver or silver-base-metal occurrences (method of missed link); (2) findings of fragments of ore mineral assemblages with sporadically high Au and Ag contents in barren calcite-quartz veins (method of indicators); (3) linear zones of ankeritization in the fields of low- and mediumtemperature propylites (mapping of metasomatic rocks); and (4) pyrite-quartz veinlets with rhythmically banded pockets (mineralogical mapping of halos of stringer-disseminated mineralization).

Abstract: The problem of high-resolution image reconstruction from noisy frames that are received by a photodetector array and shifted with respect to each other is considered. A wavelet technique is proposed for solution of this problem. The technique uses a 2D wavelet decomposition as a parametric model of the brightness function of an image in the plane of the photodetector array. A recurrent-iteration algorithm is developed for combined estimation of variable frame shifts and of the coefficients of the wavelet docomposition corresponding to the doubly improved resolution. It is shown that, under various conditions, the algorithm provides for estimation of shifts with an error no greater than 0.06 of the array pitch and for estimation of an observed-object’s brightness function with a resolution twice as high as the input-frame resolution.

The authors consider the processes of silicate and glass formation in iron-containing glass batches based on technical materials (oxides and carbonates) and using magma rock (metadiabase). The specific features of these processes depending on the chemical composition of glass are identified. It is established that the crystalline phases arising in silicate formation persist in the glass melt in the form of structural groups. The possibility of decreasing the temperature of glaze-frit synthesis in the case of using metadiabase is considered.

The synthesis of tinted pigment-free low-melting glazes based on Belarus metadiabase is investigated. The time/temperature parameters for formation of high-quality glaze coatings are identified. The processes of structure and texture formation in the coatings are studied in relation to the chemical composition of the glass and the character of crystal-phase formation, and their main properties are evaluated.

Abstract: Phase transformations proceeding in base rocks (metadiabases, metagabbro) upon heat treatment are considered. It is found that metadiabases can be used as fluxes in ceramic mixtures intended for high-temperature firing and in raw and fritted glazes as well.

Julietta is a rich epithermal gold-silver deposit of the low-sulfidation, adularia-sericite type, located in the Cretaceous Okhotsk-Chukchi volcanic-plutonic belt 250 km northeast of Magadan. The deposit was discovered in 1989 by a regional soil geochemical survey in an area previously considered barren on the basis of a regional stream-sediment survey. The deposit has not been completely explored, but presently is in the feasibility stage; proven reserves are 26 metric tons of Au (grades averaging 23 g/t) and the Au/Ag ratio is about 1:10.The deposit occurs on the periphery of a large volcanic-tectonic depression. Host andesite, andesite-basalt lava, corresponding subvolcanic bodies, and tuff are cut by Early Cretaceous quartz diorite stocks. Six vein zones occur in tensional and compression fissures. Ore shoots and smaller bonanzas comprising most of the gold reserves are located in flexures of the ore-host fissures. Ore mineralization was preceded by intense voluminous propylitization and linear sericitization (sericite + quartz + pyrite + ankerite). Orebodies occur within the low-temperature propylite (pyrite + calcite + quartz + chlorite + hydromica). Colloform-crustiform banded textures are commonly observed in the ore. Most of the ore minerals occur within thin, cyclically repeated, fine-grained bands of a hydromica-carbonate-adularia-quartz aggregate. Ore-bearing, fine-grained bands probably formed by periodic fracturing of the veins, whereas barren bands were deposited in relatively quiet conditions. “Micro-stalactites” and other gravitational textures demonstrate that minerals grew in open spaces. Ore-host structures gradually opened during mineralization.Gangue minerals are primarily quartz, various carbonates (calcite, dolomite, Fe-dolomite [Mg:Fe>2:1], parankerite [Mg: Fe = 2:1], ankerite [Mg: Fe = 1:1], and mesitite [Mg: Fe = 1:1]), and minor hydromica and adularia. Major ore minerals include pyrite, sphalerite, chalcopyrite, galena, tetrahedrite, silver sulfosalts, native gold, and custelite (Au: Ag = 9: 1). Ore mineralization occurred in two stages-an early, post-volcanic stage and a late, post-granitoid stage. The early stage contains most of the precious metals and includes two substages-(1) gold-polymetallic (200 to 260° C) and (2) gold-silver-sulfosalt (90 to 200° C). The late stage also includes two substages-(1) carbonate-rhodonite-quartz (260 to 380° C) and (2) postore quartz-carbonate. Fluid-inclusion homogenization temperatures demonstrate complex temperature zoning. Fluid composition was mainly aqueous, with Cl-, HCO3-, Na+, K+, Ca2+, and a salinity less than 4 to 9%. The isotopic age of the deposit is 136 ± 3 Ma by the Rb-Sr method on adularia. The 87Sr/86Sr ratio is about 0.7075 ± 0.0005, indicating a mixed crust-mantle source of the vein matter. Chloride complexes transported gold and silver. The gas composition of the fluid suggests a near-surface, “closed” paleohydrothermal system. A major ore-forming factor could have been high seismic activity related to intrusion of the subvolcanic bodies. Breccias and multiphase veinlets may be related to relatively large-magnitude earthquakes, whereas cyclically banded ores may reflect local pH variations caused by smaller earthquakes.