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We discuss the space relationship between upper mantle plumes revealed earlier from analysis of long-wavelength isostatic gravity anomalies and the subducting Pacific slab. According to global seismic tomography, the oceanic slab in its segments corresponding to the Japan and Izu-Bonin island arcs flattens out at the bottom of the mantle transition zone, extends horizontally far beneath Eurasia, and then resumes sinking into the lower mantle. The upper mantle plumes are located beyond the western endpoint of the slab sector that advances the farthest beneath the continent.
A considerable part in the plume material may belong to fertilized (enriched with incompatible elements) peridotite. A layer of fertilized peridotite forms at depths between 200 and 600 km under the effect the melts produced by partial melting of the slab oceanic crust cause on the overlying depleted mantle. The peridotite layer integrates into the slab and heats up by friction along the slab top during the horizontal motion of the latter in the transition zone where the mantle material is of relatively high strength. Portions of hot fertilized peridotite detach from the slab as it sinks into the lower mantle, rise by buoyancy through the upper part of the transition zone, and become entrained into an elongate asthenospheric convection cell which arises beneath the continent behind the subduction zone. The ascending convection flow splits into separate streams which are the upper mantle plumes.

A new version of garnet thermobarometer is proposed. It ensures better correlations of TP-estimates with results of pyroxene-pyrope thermobarometry than the previous version proposed by Ryan et al. The dependence of KD of the internal exchange reaction, KD = MgO · TiO₂/ ((CaO+ MgO)² · FeO · Al₂O₃), on temperature estimated with the Brey and Kohler orthopyroxene thermometer ( R = 0.783) is as follows: T (

Nickel-pyrope geothermometer, based on proton microprobe determination of Ni contents in pyropes, has been reproduced by applying electron probe microanalysis (EPMA). The measurements were made on a JEOL JXA-8100 microprobe. The detection limit of 6ppm was reached, which is nearly a record value for EPMA. Precision standard deviation is 3ppm. The accuracy of determination, estimated as the difference between the data obtained by the PIXE and EPMA methods, is 9 ppm, which corresponds to a temperature standard deviation of about 50

The stress-strain state of undeformed but gravity-strained lithosphere is simulated in a 2D numerical model in the elastic-brittle-plastic approximation using combined seismic and density cross sections to depths of 80 km. The cross sections follow DSS profiles across the Baikal rift (Ust'-Uda-Khilok) and along the northeastern flank of the rift system (Ust'-Kut-Nizhneangarsk-Chara). Gravity instability is produced by a zone of anomalous mantle and the 10-12 km deep Baikal basin which have low elastic moduli and density.
We estimated the depth-dependent variations in shear strength and internal friction coefficient required for strain in the upper crust to fit the crustal density and velocity distributions and the observed Cenozoic shallow geological and tectonic structures. The greatest stress-strain contrasts are attributed to zones of most prominent density contrasts and show up in the horizontal stress component to 0.15 GPa. Relative strain in the crust and at the Moho reaches 10-15%. Gravity instability may have contributed significantly to lithospheric deformation and rift evolution.

The method of contracting mapping of the function space is suggested as a tool of spatial approximation of electromagnetic fields. This transformation is physically justified being associated with the dynamics of space field variation. Formulated are the basic requirements for scale transformation of the solution space. Three basic types of contracting mapping are applied to some linear-symmetry VES problems. A special algorithm is suggested for smoothness control of signals and automated filling of the space with additional reference points in intervals of strongly varying field components. The new approach allows high-performance modeling in problems that require high-density recovery of functions.

The rifting in the Baikal region predetermined the existence of three types of hydrogeologic structures: rift depressions - hydrogeologic basins; rift

In southern Israel and on the Sinai Peninsula, ultrapotassic quartz porphyries (UPQP) with 6.5-10 wt.% K₂O and 0.1-2.5 wt.% Na₂O were found in a bimodal dike suite that formed at the final stage of the Pan-African orogeny. The suite is made up mainly of quartz porphyry (4-5.5 wt.% K₂O); mafic rocks amount to ~5%. The UPQP form rare dikes or patches in quartz porphyry dikes. These are typical igneous rocks with microgranophyric and spherulitic matrices. There is no mineralogical evidence for the gain of K at the postmagmatic stage. Evidence for low-temperature adularization found in some ultrapotassic rhyolites from other world areas has not been revealed either. Alkali-feldspar phenocrysts in the UPQP and quartz porphyries have high contents of orthoclase (≥ 85-90%). Study of melt inclusions in quartz phenocrysts in both the UPQP and ordinary quartz porphyries showed that the phenocrysts crystallized from magmas of quartz porphyry composition that contained 2-3 wt.% H₂O, up to ~1% F, and 0.1-0.15% Cl. Scanning electron microscope studies showed that many alkali quartz porphyry dikes have a heterogeneous matrix. Rounded and oval segregations (0.3-15 mm across) with microgranophyric and spherulitic textures amount to ~50%. They are enriched in K₂O and are compositionally similar to typical UPQP. In the microcrystalline aggregates hosting these segregations Na dominates over K.
To account for the UPQP generation, a model is proposed for the disequilibrium crystallization of silicic magma during its flow along fractures in cooled country rocks. The magma was of alkali rhyolite composition and contained 5-7% phenocrysts. At the early stages of the matrix crystallization, spherulitic and microgranophyric segregations formed. They were enriched in K, which is typical of a haplogranite system at the beginning of crystallization. Since the system remained closed for major components, the portion of Na in the residual melt increased. The disequilibrium crystallization conditions inhibited a chemical interaction between early and late phases. During the

High-potassium rocks have been found among ultrabasites of the Il'chir ophiolite nappe. Stock- and sill-like bodies are composed of greenish-gray to dark-gray holocrystalline (sometimes, porphyritic) rocks. Three rock varieties are recognized: albitized monzonitoids (wt.%): SiO₂ - 53.2-53.8; Al₂O₃ - 14.6-14.9; MgO - 3.3-8.3; Na₂O - 5.0-5.9; and K₂O - 0.05-0.1; syenites (orthoclasites) (wt.%): SiO₂ - 63.0-66.1; Al₂O₃ - 17.2-18.6; Na₂O - 0.2-3.1; and K₂O - 8.2-16.7; granosyenites (wt.%): SiO₂ - 71.5-77.3; Al₂O₃ - 11.5-13.5; Na₂O - 0.1-1.72, and K₂O - 9.2-10.7. The K-richest varieties are composed of allotriomorphic grains of perthites, K-antiperthites, and, sometimes, plagioclase. Biotite, amphibole, and chlorite occur in small amounts (1-5 vol.%). The rocks are strongly altered to blastocataclasites with a feldspathic groundmass. Along with intense shearing and pseudoporphyritic texture (porphyroclasts), a distinctive feature of K-feldspar and plagioclase preserved as porphyroclasts in relics is their carbonization. Neogenic K-feldspar, albite, and dark-colored minerals lack cloud-like carbon pigmentation. Potassium-rich rocks have high contents of Ba and Rb and show a distinct Eu minimum on their REE patterns. According to Rb-Sr dating, these rocks have an age of 419 ± 30 Ma (⁸⁷Sr/⁸⁶Sr = 0.7061 ± 0.0021), which is, most likely, close to the age of the last metamorphism. Indirect data evidence that primary island-arc rocks might have formed in island-arc setting, possibly, in the foreland of island arcs.

Based on Ovchinnikov's genetic-type formula, geologo-genetic models have been constructed for Mesozoic gold deposits localized in chamber-dome and chamber-depression structures in the Transbaikalian area of the Mongolo-Okhotsk fold belt. This formula includes 12 factors that characterize ore formation processes, their depth of occurrence and geodynamic settings, the sources of ore matter and ore-forming solution, energy of ore formation processes, composition of ore-forming solution, environment and mechanism of ore deposition, zoning, interaction of ores with host rocks, and thermodynamic setting of ore deposition.

Mathematical properties of the inverse dynamic seismic problem for determining the elasticity parameters of a homogeneous layered anisotropic medium are investigated for the case of orthorhombic symmetry. Analysis of the mathematical properties of the inverse problem allows predicting which parameters can be estimated to a satisfactory accuracy. The suggested inversion algorithm is tested in numerical experiments for determining elastic parameters of a thinly stratified medium including several anisotropic layers.