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[Display omitted] • Strong Fe oxide (hematite), Cu, and REE mineralization (together with minor Au and locally U) suggests IOCG-type signatures. • Mineralization bears many signatures of the "classic" IOCG (-REE, U) deposits typical of Precambrian terranes but occurs in a Phanerozoic (Paleozoic) setting. • Mineralization is associated with transitional shoshonitic to A-type subvolcanic potassic granite intrusions emplaced in a post-collisional setting. • Mineralization occurs mainly in phyllic to carbonate-phyllic alteration assemblages. • A shallow level of mineralization possibly corresponds to an upper (to the uppermost) part of a vertically extended magmatic-hydrothermal system. The Ulandryk and related prospects in the Altaid orogenic belt (near the Russian-Mongolian border) comprise intense iron oxide (hematite), Cu, REE, and locally U mineralization and are estimated to contain in excess of 240 Mt iron oxide ores and 3.7 Mt copper. These prospects bear many signatures of the "classic" IOCG (-REE, U) deposits typical of Precambrian terranes but, in contrast, are situated in a Phanerozoic (Paleozoic) setting. They are related to the Early Devonian subvolcanic potassic granite stocks with transitional shoshonitic to A-type granite signatures suggesting a post-orogenic (post-collisional) setting, with some anorogenic (intracontinental to within-plate) affinity. The stocks have been intruded into a coeval local volcanic structure (a volcanic dome complicated by the central caldera) composed of Devonian trachyandesite, trachydacite, quartz latite, rhyolite, rhyolite-dacite, and dominant trachyrhyolite lavas, tuffs and subovolcanic porphyry intrusions. The granitic stocks are accompanied by magmatic and multi-staged hydrothermal breccias, zones of sodic (albite-quartz), potassic (quartz-K-feldspar), propylitic (quartz-albite-chlorite-amphibole) and dominant phyllic to carbonate-phyllic (quartz-sericite to quartz-sericite-carbonate) to possibly argillic (quartz-kaolinite) alteration, with intense development of hematite. Fluorite is also ubiquitous and locally abundant. The mineralization occurs in several wide (typically 60–100 m, up to 200 m) and extended (1.4–6 km) linear to arc-like paralleling steeply dipping zones of breccias surrounding the granite stocks, with the host rock and quartz fragments cemented by fine-grained quartz-hematite and coarser hematite (specularite) material. Copper-gold, REE, and locally U mineralization overprints hematite-rich zones. Wider quartz-sulfide stockworks with Cu-Au mineralization zones containing minor to trace hematite are also present. Quartz is generally abundant forming quartz-hematite veins, stockworks, and breccias (locally with crustiform texture), and zones of quartzite-like pervasive silicification (typically with sericite and clay minerals). Fluid inclusions in quartz contain daughter halite crystals and homogenize by halite dissolution after vapor bubble disappearance indicating a homogenous, high-salinity (35–45 wt%), Na-Ca-K-chloride, aqueous mineralizing fluid. The relatively low homogenization temperatures (∼200–260 °C) and generally subvolcanic-level pressure (∼0.2–0.5 kbar) conditions suggest a shallow level of mineralization possibly corresponding to an upper (to the uppermost) part of a vertically extended magmatic-hydrothermal system. [ABSTRACT FROM AUTHOR]

Because of low net production in arctic and subarctic surface water, dissolved organic matter (DOM) discharged from terrestrial settings plays an important role for carbon and nitrogen dynamics in arctic aquatic systems. Sorption, typically controlling the export of DOM from soil, may be influenced by the permafrost regime. To confirm the potential sorptive control on the release of DOM from permafrost soils in central northern Siberia, we examined the sorption of DOM by mineral soils of Gelisols and Inceptisols with varying depth of the active layer. Water-soluble organic matter in the O horizons of the Gelisols was less (338 and 407 mg C kg−1) and comprised more dissolved organic carbon (DOC) in the hydrophobic fraction (HoDOC) (63% and 70%) than in the O horizons of the Inceptisols (686 and 706 mg C kg−1, 45% and 48% HoDOC). All A and B horizons from Gelisols sorbed DOC strongly, with a preference for HoDOC. Almost all horizons of the Inceptisols showed a weaker sorption of DOC than those of the Gelisols. The C horizons of the Inceptisols, having a weak overall DOC sorption, sorbed C in the hydrophilic fraction (HiDOC) stronger than HoDOC. The reason for the poor overall sorption and also the preferential sorption of HiDOC is likely the high pH (pH>7.0) of the C horizons and the smaller concentrations of iron oxides. For all soils, the sorption of HoDOC related positively to oxalate- and dithionite–citrate-extractable iron. The A horizons released large amounts of DOC with 46–80% of HiDOC. The released DOC was significantly ( r=0.78, P<0.05) correlated with the contents of soil organic carbon. From these results, we assume that large concentrations of DOM comprising large shares of HiDOC can pass mineral soils where the active layer is thin (i.e. in Gelisols), and enter streams. Soils with deep active layer (i.e. Inceptisols), may release little DOM because of more frequent infiltration of DOM into their thick mineral horizons despite their smaller contents of reactive, poorly crystalline minerals. The results obtained for the Inceptisols are in agreement with the situation observed for streams connecting to Yenisei at lower latitudes than 65°50′ with continuous to discontinuous permafrost. The smaller sorption of DOM by the Gelisols is in agreement with the larger DOM concentrations in more northern catchments. However, the Gelisols preferentially retained the HoDOC which dominates the DOC in streams towards north. This discrepancy can be explained by additional seepage water from the organic horizons that is discharged into streams without intensive contact with the mineral soil. [ABSTRACT FROM AUTHOR]