Svyatonosites, which are intermediate moderately alkaline to alkaline andradite rocks, were found for the first time on the Svyatoi Nos Peninsula at the beginning of the 20th century. One of the discussible questions is related to their age, which has not precisely been determined by isotopic methods. The results of U/Pb dating of accessory zircon from svyatonosites and leucosyenite showed the Late Paleozoic age for the Markov (310‒297 Ma) and Eskola (317‒312 Ma) plutons of the Svyatoi Nos Peninsula, which is synchronous with the formation of granitoids of the Barguzin complex (330‒290 Ma). Zircon from leucosyenite of the Markov pluton has a typical magmatic structure, which is in agreement with a Th/U ratio of >0.3. Anhedral zircon grains from svaytonosites together with the Th/U ratio of <0.1 indicates the recrystallization processes at the origination stage of the Markov and Eskola plutons. The slightly older 40Ar/39Ar age of amphibole from svyatonosites of the Markov pluton (360‒336 Ma) is related to the presence of excessive 40Ar, which can be sourced from the Early Paleozoic metamorphic rocks.

Hydrochemical analysis of the high-salinity lakes in the Ishim Plain (>250–300 g/L) located at the border with the Northern Kazakhstan uranium ore province is performed. The studies have shown that the main factor of concentration and redistribution of uranium in the lake basins of the Ishim Plain are the processes of intense salt deflation causing sanding of lakes and uranium depletion in the near-surface layer of the bottom deposits. The correlation between the hydroxide forms of uranium binding in the bottom lacustrine deposits of the Ishim Plain and the coffinite composition of the Semizbai deposit makes it possible to consider this province to be promising for the discovery of hydromineral uranium deposits.

In the Dornogobi Aimag region of Southern Mongolia, the main source of groundwater contamination by U, As, and Se is hydrogenic-or sandstone-type uranium deposits. These environmentally hazardous deposits, located in close proximity to populated settlements, pose a serious threat to drinking water quality and human health. Fifty samples were analyzed and levels of uranium were found to be elevated in deep and shallow waters (200 and 34.7 mu g/L, respectively), with nearly 25% exceeding the World Health Organization (WHO) guideline level for drinking water quality (30 mu g/L). Local rocks and soils appear to be the natural source of uranium. In particular, water from deep hydrologic wells near the largest deposits (Dulaan Uul and Zoovch Ovoo) exceeds the WHO guideline levels for U, As, Se, Sb, Cd, and Fe. At the same time, shallow groundwater (Argalant area) contains 50.5 mu g/L of As, 34.7 mu g/L of U, and 35.9 mu g/L of Cd. Although multiple metal and metalloid contamination of groundwater is an issue of global concern, our understanding of the physical- chemical conditions of its accumulation is limited. This study provides a plausible explanation of the geochemical situation at the uranium Dornogobi province based on thermodynamic calculations.

Монгол, Оросын ШУА-иудын хоорондын 2009-2012 онуудын шинжлэх ухааны суурь судалгааны хамmарсан төслийн хүрээнд Монгол орны эрдэсжилт ихтэй, шорвог нууруудын микроэлементийн агуулгыг анх удаа судалж, зарим эрдэст нууруудын усанд уран (238U -1 мг/л) ба бусад дагалдах ховор элементүүдийн (Br, Li, B, Sr, Rb) агуулга өндөр байгааг илрүүлсэн юм. Үүнээс гадна Баруун Монголын эрдэсжилт ихтэй томоохон нууруудын усанд урантай геохимийн эвшил үүсгэдэг литий, хүнцэл зэрэг хорт элементүүдийн агуулга зөвшөөрөгдөх хэмжээнөөс илүү их байгааг илрүүлэв.. Эрдэсжилттэй нууруудын усны уран ба хорт элементийн микроэлементийн хуримтлал нь тухайн газар нутгийн хүрээлэн байгаа орчны уулын чулуулгын найрлагатай холбоотой үүсдэг. Иймд байгаль дээрхи гадаргын усны хорт элементүүдийн (U,As,Se, Mo, V, Li) экогеохимийн асуудалд анхаарал хандуулах хэрэгтэй болж байна.

1 Introduction Increasing demand for uranium raw materials for the nuclear industry has stimulated interest in non-traditional sources,including hydromineral ones[Qin,2009].Those are saline lakes located in the uranium ore districts.Accumulation of uranium in such lakes results from the leaching of uranium from the rocks by surface and ground

Comparative analysis of lithium deposits and ore manifestations of spodumene pegmatites of Siberia was carried out for the purpose of their development and substantiation of the investment attractivity for nuclear, electrochemical industry and defense technologies. The characteristics of the geological structure of ore fields of spodumene pegmatites are presented, along with the mineralogical and geochemical characterization of lithium-bearing complexes contained therein. The richest in lithium spodumene ore species are those from the deposits of the Eastern Sayan, Tuva and Eastern Transbaikalia. Comparable concentrations of lithium oxide are present in the ore from the Tashelga deposit in the Shoria Highlands. The ore from the Alakha stockwork situated in the south of the Altai Highlands has the lowest lithium oxide content; however, due to the uniformity of its distribution and substantial scale of mineralization, largescale resources are concentrated there. After ore concentrating, the concentrate consists mainly of spodumene. Iron should be mentioned as one of the most abundant admixtures. The level of concentrate enrichment with lithium oxide is determined by its concentration in spodumene. In this respect, among the studied deposits the most promising ones appear to be the pegmatites of the Eastern Sayan (Goltsovoye deposit). We emphasize that there is a necessity to perform additional geological prospecting, chemical engineering and inspection examinations for the purpose of allocating the sites with the richest lithium ore species within the Zavitino deposit (Transbaikalia), as well as at the Goltsovoye, Belorechensk and Urik deposits (Eastern Sayan), Tastyg deposit (Tuva) and promising ore manifestations Tashelga (Mountain Shoria) and Alakha (Altai Highlands). It is concluded that the spodumene pegamitites of Siberia are able to become the necessary and sufficient mineral raw material basis for the development of lithium industry in Siberia.

Оловоносные гранит-лейкограниты Пиа Оак, расположенные в провинции Као Банг Северного Вьетнама, слагают штокообразное интрузивное тело гипабиссальной фации глубинности. Вмещающие породы представлены карбонатными толщами раннедевонского и “черными” сланцами раннетриасового возраста. Геохронологический возраст гранит-лейкогранитов Пиа Оак отвечает позднему мелу: Т = 83.5 ± 6.2 млн. лет, 87Rb/86Sr метод; Т = 89.7 ± 1.0 млн. лет, 39Ar/40Ar метод. Массив имеет простое гомодромное строение: двуслюдяные и мусковитовые гранит-лейкограниты редкометалльные аплиты, пегматиты оловоносные грейзены и гидротермальные жилы. Петрографические и микроструктурные исследования показывают, что на позднемагматической стадии произошло резкое изменение условий кристаллизации гранит-лейкогранитной магмы, вызвавшее инконгруэнтное замещение протолитионита мусковитом. По данным изучения расплавных и сосуществующих флюидных включений солидусная кристаллизация проходила во флюидонасыщенных условиях при 635–600°С. По вещественному составу гранит-лейкограниты массива Пиа Оак отвечают редкометалльно-плюмазитовому геохимическому типу (по Л.В. Таусону), а по содержаниям редких элементов достигают уровня литий-фтористой фации. Состав аплитов и пегматитов показывает, что дифференциация не сопровождалась существенным накоплением литофильных и летучих компонентов в остаточном расплаве, а высокая редкометалльность была присуща гранит-лейкогранитной магме изначально. Наиболее вероятным источником расплава являлись структурно-вещественные комплексы протерозойского возраста и перекрывающие их “черные” сланцы нижнего триаса.

Data obtained in the investigation of the microcomponential (Li, U etc.) and macrocomponential (Na, Ca, K, Mg, Cl, SO4, CO3, HCO3) composition of water in salt lakes of Western Mongolia are generalized. It is revealed that the majority of salt lakes in this region are characterized by an increased concentration of a number of micro components (lithium, uranium etc.). It is demonstrated that lithium is concentrated in chloride lakes, whereas uranium does in sodium ones. Calculations of equilibria in lake water with the basic minerals of water-enclosing rocks are presented.

The Piaoak tin-bearing granite-leucogranites located in the Caobang Province of Northern Vietnam compose a stock-like hypabyssal body. Host rocks are represented by Early Devonian carbonate sequences and Early Triassic “black” shales. The geochronological age of the Piaoak granite-leucogranites corresponds to the Late Cretaceous: T = 83.5 ± 6.2 Ma, 87 Rb/ 86 Sr method; T = 89.7 ± 1.0 Ma, 39 Ar/ 40 Ar method. The massif has a simple basic to acid order: two-mica and muscovite granite-leucogranite → raremetal aplites, pegmatites → tin-bearing greisens and hydrothermal veins. The petrographic and microstructural studies revealed a sharp change in crystallization conditions of the granite-leucogranite magma at the late magmatic stage and formation of muscovite via incongruent melting of protolithionite. The study of melt and coexisting fluid inclusions showed that solidus crystallization occurred under fluid-saturated conditions at 635–600°C. In composition, the granite-leucogranites of the Piaoak Massif correspond to the raremetal-plumasite geochemical type (according to L.V. Tauson), and reach Li-F facies in terms of their rare-element composition. The composition of aplites and pegmatites demonstrates that granite-leucogranite magma did not accumulate lithophile and volatile components in the residual melt during differentiation, but was initially enriched in rare-metals. It is most probable that the melt was generated from Proterozoic lithotectonic complexes and overlaying Lower Triassic “black” shales.

Analysis of major- and trace-element compositions of water in hypersaline soda closed basin lakes of Northwestern Mongolia and Chuya basin (Gorny Altai) shows high enrichment in 238U (up to 1 mg/l). Proceeding from new data, uranium accumulation in water has been attributed to (i) location of the lakes and their watersheds in potential provinces of U-bearing rocks and (ii) uranium complexing with carbonate in presence of carbonate (bicarbonate) anions. Among the explored hypersaline soda lakes of the area, the greatest uranium resources are stored in Lake Hyargas Nuur (about 6000 ton).

The Kalguty ore-magmatic system comprises two intrusive complexes: the Kalguty granite-leucogranite complex and Eastern Kalguty complex of dikes and small intrusions. U-Pb dating of individual zircon grains from granites of the main intrusive phase demonstrated that the crystallization age of small grains of magmatic habits and outer rims of large grains is almost concordant and is 216 ± 3 Ma. Ar-Ar isotope study shows that the K-Ar system of biotites from granites of the main phase within the Kalguty ore field was disturbed (radiogenic Ar was partially lost) and gave an age of 202 ± 1 Ma. The Ar-Ar dating of muscovites from intraore and postore dikes of the Eastern Kalguty complex devoid of signatures of postmagmatic recrystallization and superimposed greisenization gave similar ages of 205–201 Ma. This date is considered as the emplacement age of the Eastern Kalguty dikes and associated complex W-Mo-Bi-Be ore mineralization. Sm-Nd and Pb-Pb isotopic study of granites, ongonites, and elvans of the Kalguty ore-magmatic system and host rocks shows that these systems were closed. For example, recalculation of Nd isotopic ratios for corresponding ages of crystallization of magmatic systems (216 and 205 Ma) shows that ɛNd(T) values decrease from −1.9 to −3.5 ... −5.08 with transition from granite-leucogranite to subvolcanic granite porphyry, ongonite, and elvan dikes with corresponding increase of model ages of protoliths from 1.0 to 1.25 Ga. Lead isotopic ratios for leaching residues of whole-rock samples of all rock varieties (206Pb/204Pb = 18.305–18.831; 207Pb/204Pb = 15.527–15.571) are plotted well below the line of average crustal lead evolution according to the Stacey-Kramers model.