Possible physicochemical facies of wehrlitization of ultramafic rocks in the mantle wedge under volcanoes of the Kuril–Kamchatka frontal zone

A quantitative model describing the dynamics of the process of metasomatic wehrlitization of ultramafics is put forward. It is elaborated for the process taking place in permeable fault zones over a time span of 50 kyr with fluid source depths in the range of 150–50 km at initial temperatures of 1000–1200°C. The possibility of existence of two physical–chemical facies of this process has been demonstrated: one occurs at the level of garnet and the other is at the level of spinel depth facies. Their realization is related to the dependence of the activity of Mg–Ca–Si metasomatism against variation in the composition of low–molecular hydrocarbons in a fluid under conditions of changing T and P in a system.     

On the dynamics of the rhythmic crystallization of magmatic bodies during the directional solidification of cotectic melts

A problem on the directional crystallization of melt was solved taking into account heat and mass exchange between the two-phase zone and the cooling volume of a magmatic body. Conditions were determined for the development of rhythmic crystallization by the example of the solidification of the pseudobinary Di-An system.     

Modeling the dynamics of sublimation of fractured rocks in the lithospheric mantle wedge beneath volcanoes of the Avacha group (Kamchatka)

A quantitative analysis of sublimation of intensely fractured rocks in the mantle wedge was performed using a model of planar fracture channel. The use of dimensionless variables allowed us to analyze the influence of the Nusselt and Sherwood criteria on temperature and variation of the rates of dissolution of minerals and films on fracture walls and estimate both linear and mass sublimation rates. The results of this study predict relatively high rates of major element dissolution and remobilization by flows of magmatic and metamorphic gases over wide temperature range. Physical modeling of this process using natural mantle rock samples confirms the plausibility of the proposed model at least for the case of metamorphic-driven remobilization of elements from gas-liquid inclusions in metasomatized ultramafic rocks. This model provides a satisfactory explanation for the observed local heterophase alterations within ultramafic rocks that have experienced multistage deformation beneath volcanoes of the Kamchatka volcanic front.     

Metasomatic zoning of subcratonic lithosphere in Siberia: physicochemical modeling

Nonisothermal equilibrium physicochemical dynamics has been numerically modeled to estimate the effect of reduced asthenosphere fluids on continental lithosphere profiles beneath the Siberian Platform (SP). When the over-asthenosphere continental mantle is metasomatically changed by reduced magmatic fluids, the following sequence of zones forms: (1) zone where initial rocks are intensively sublimated and depleted by most petrogenic components; the restite in this case becomes carbonated, salinated and graphitized; (2) zone of Si and Fe enrichment and carbon deposition in initial rocks depleted in Na, K, P, Mn; (3) zone of diamond-bearing lherzolites enriched with Na; (4) zone of hydrated rocks enriched with K; (5) zone of hydrated rocks not enriched with petrogenic components. Zone 1 can be responsible for the formation of kimberlite melts, zones 3 and 4 can be substrates of alkaline magma melting, and zone 5 can be the source of mafic tholeiitic magma.     

Time patterns of magmatic ore systems in circum-Pacific volcanoplutonic belts

Integrate statistical processing of more than 1000 isotope dates tracing the history of circum-Pacific magmatic ore systems and related mineral deposits in volcanoplutonic belts allows the following inferences: (1) magmatic ore systems (MOS) of volcanic arcs generate monoand polycyclic volcanoplutonic deposits (VPD) with notably different formation times (longevities); (2) the MOS chronology bears periodicity of events in the post-Paleozoic history of the Pacific continental margin; (3) the time series of magmatic ore systems from different circum-Pacific segments show quasi-periodic patterns but the respective metallogenic epochs within the same time intervals have different phases and amplitudes, especially over the past 30 Myr; (4) each mineral type of VPD has its own periodicity; (5) the periodicity in formation times of mono- and polycyclic VPD differs from that in the times of their origin.