Multi-Stage Magmatic-Hydrothermal Sulfide-PGE Mineralization of the Khudolaz Complex (South Urals)

Geology of Ore Deposits - For the first time, from the standpoint of magmatism and subsequent hydrothermal–metasomatic alteration, sulfide and platinum-metal mineral assemblages of rocks of...     

Variations in parameters of aerosol optical thickness in Dushanbe

The results of studies of aerosol optical thickness (AOT) in Dushanbe conducted from July 2010 to March 2011 within the AERONET program are discussed. The statistical characteristics of AOT have been shown to significantly vary during dust intrusions. The seasonal variations in the dustiness of the atmosphere have been analyzed.     

Water-vapor content in the atmosphere of arid zone

The variation in water-vapor content W in the atmosphere of the arid zone is studied. The seasonal oscillations in W for the arid zone are characterized by changes in the moisture content from 2.3 to 3.6 times during the transition from winter to summer. The summer-fall period is characterized by a well-expressed midday minimum of moisture content. In winter the moisture content monotonically decreases during the day. In spring the water-vapor content has a wide maximum in midday. The water-vapor content in the atmosphere during dust haze increases up to two times.     

Interaction between protokimberlite melts and mantle lithosphere: Evidence from mantle xenoliths from the Dalnyaya kimberlite pipe,Yakutia (Russia)

The Dalnyaya kimberlite pipe(Yakutia,Russia) contains mantle peridotite xenoliths(mostly Iherzolites and harzburgites) that show both sheared porphyroclastic(deformed) and coarse granular textures,together with ilmenite and clinopyroxene megacrysts.Deformed peridotites contain high-temperature Fe-rich clinopyroxenes,sometimes associated with picroilmenites,which are products of interaction of the lithospheric mantle with protokimberlite related melts.The orthopyroxene-derived geotherm for the lithospheric mantle beneath Dalnyaya is stepped similar to that beneath the Udachnaya pipe.Coarse granular xenoliths fall on a geotherm of 35 mWm-2 whereas deformed varieties yield a 45 mWm-2)geotherm in the 2-7.5 GPa pressure interval.The chemistry of the constituent minerals including garnet,olivine and clinopyroxene shows trends of increasing Fe~#(=Fe/(Fe+Mg))with decreasing pressure.This may suggest that the interaction with fractionating protokimberlite melts occurred at different levels.Two major mantle lithologies are distinguished by the trace element patterns of their constituent minerals,determined by LA-ICP-MS.Orthopyroxenes,some clinopyroxenes and rare garnets are depleted in Ba,Sr,HFSE and MREE and represent relic lithospheric mantle.Re-fertilized garnet and clinopyroxene are more enriched.The distribution of trace elements between garnet and clinopyroxene shows that the garnets dissolved primary orthopyroxene and clinopyroxene.Later high temperature clinopyroxenes related to the protokimberlite melts partially dissolved these garnets.Olivines show decreases in Ni and increases in Al,Ca and Ti from Mg-rich varieties to the more Fe-rich,deformed and refertilized ones.Minerals showing higher Fe~#(0.11-0.15) are found within intergrowths of low-Cr ilmenite-clinopyroxene-garnet related to the crystallization of protokimberlite melts in feeder channels.In P-f(O_2) diagrams,garnets and Cr-rich clinopyroxenes indicate reduced conditions at the base of the lithosphere at-5 log units below a FMQ buffer.However,Cr-poor clinopyroxenes,together with ilmenite and some Fe-Ca-rich garnets,demonstrate a more oxidized trend in the lower part of lithosphere at-2 to 0 log units relative to FMQ.Clinopyroxenes from xenoliths in most cases show conditions transitional between those determined for garnets and megacrystalline Cr-poor suite.The relatively low diamond grade of Dalnyaya kimberlites is explained by a high degree of interaction with the oxidized protokimberlite melts,which is greater at the base of the lithosphere.     

First Finds of Platinum and Palladium Minerals in Sulfide Ores of the Khudolaz Intrusive Complex (Southern Urals)

Forms of occurrence of platinum (sperrilite, moncheite) and palladium (Sb-michenerite, Pd–Bi phase) minerals in intrusive rocks of the Khudolaz differentiated complex have been studied. Platinum minerals were identified in disseminated Cu–Ni sulfide ores from ultramafic olivine–hornblende rocks of the Khudolaz complex, whereas palladium minerals were found in ores from olivine–hornblende gabbroids. The structural arrangement of grains as inclusions in sulfides of the primary magmatic association testifies that they were formed as a result of segregation of platinum group elements, which partitioned into the composition of sulfides during low-temperature mineral formation process at the late-magmatic stage.     

Conditions for the formation of the chemical composition of the water of the Firuza MGU carbonated spring (Northern Pamirs)

We considered the geological conditions and chemical composition of the water of the Firuza MGU carbonated spring, which was discovered in 2015 in Northern Pamir. This paper reports on the detailed composition of the miсrocomponents of the water as determined by an Inductively Coupled Plasma Mass Spectrometry analysis (ICP-MS). A comparative review of the water composition and content of similar microcomponents in waters of carbonated springs in Kamchatka and the Russian Far East is given. On the basis of the B: Cl and K: Li: Rb: Cs ratios, which are close to the same ratios for chloride sodium hot springs in areas of active volcanism, it is concluded that the water of the spring has a deep origin. The temperature of the formation of water calculated by a Na–K geothermometer method is 147.3°C, suggesting the formation of the spring at a depth of approximately 5 km.