Lithiophorite and coronadite-varieties of vernadite and todorokite-make up finely dispersed colloform mixtures along with minor grains and nanoparticles of aluminosilicates and ore minerals in meta somatic rocks of the Dukat ore field, which were formed in local areas of fluid and hydrothermal solution dis charge at the upper level of the ore forming system. Fe vernadite associates with feroxyhyte, magnetite, apa tite, K feldspar, native silver, and acanthite in greisenized granitoids and with epidote, cerianite, plattnerite, and Fe chlorite in quartz-garnet-chlorite propylites. Todorokite with high Pb, Tl, and Sn contents associ ates with epidote, albite, bitumen, and native silver in quartz-epidote-chlorite propylites. Al vernadite, coronadite, and lithiophorite associate with opal, kaolinite, Fe chlorite, zincite, uraninite, native silver, and acanthite in argillisites. These data allowed us to estimate the conditions of manganese accumulation in the epithermal ore forming system and deposition conditions of Mn rich, finely dispersed mineral mixtures in mineralized zones hosted in metasomatic rocks of the ore field.

The previously published and newly obtained geological and geochronological (Rb-Sr and Ar-Ar) data show that the igneous rocks and products of hydrothermal alteration in the Dukat ore field pertain to two ore-forming magmatic-hydrothermal systems (OMHSs). The igneous rocks of the Early Cretaceous rift-related OMHS are represented by potassium rhyolites of the Askol'd Formation with Rb-Sr ages of 124 ± 3 and 119.3 ± 3.4 Ma and intercalating amygdaloidal basalts. The products of the hydrothermal activity of this OMHS are the metasomatic anatase-chlorite assemblage of the root zone, which replaces potassium rhyolites, and shallowseated quartz-adularia and quartz-carbonate-feldspar veinlets retained in rhyolite fragments in Late Cretaceous conglomerate and breccia. The Late Cretaceous OMHS was related to the origination of the OkhotskChukotka volcanic belt and consists of calc-alkaline basaltic andesites of the Tavvatum Formation and moderately silicic K-Na rhyolites of the Nayakhan Formation with a Rb-Sr age of 84 ± 4 Ma. The Late Cretaceous postmagmatic hydrothermal activity in the Dukat ore field resulted in the formation of preore metasomatic rocks and orebodies of the unique Dukat Au-Ag deposit. The first stage of the Late Cretaceous hydrothermal activity gave birth to preore propylites with a Rb-Sr isochron age of adularia samples estimated at 85 ± 1 Ma and quartz-chlorite-sulfide and Ag-bearing quartz-chlorite-adularia orebodies with Rb-Sr isochron ages of adularia estimated at 84 ± 1 and 86.1 ± 4 Ma. The second stage was marked by the formation of garnet-bearing propylites and quartz-rhodonite orebodies with a Rb-Sr age of 73 ± 3 Ma. Further hydrothermal activity occurred after a break related to structural rearrangement of the ore field and was expressed in the replacement of propylites by products of argillin alteration and Ag-bearing Mn hydroxides. Paleogene basaltic dikes and related subeconomic mineralization concluded magmatic and hydrothermal processes in the Dukat ore field.

Data on the morphology and crystal structure of micro-and nanoparticles of zincite and native zinc that occur among the newly formed minerals of metasomatic rocks in the Dukat ore field are presented. The origin of minute particles in the discharge areas of hydrothermal fluids is caused by the specific dynamics of the heterogeneous mineral-forming environment, resulting in the formation of ultralocal zinc concentrations. In propylite and greisen, the minute particles, which are products of the earliest stages of ore deposition, arise at the front of growing Fe-chlorite and apophyllite crystals. Aggregation of zincite nanoparticles with formation of metalliferous inclusions and fibrous native zinc proceeds in the greisen zones during aggradation recrystallization of a finely dispersed mineral system under the effect of additional portions of reduced fluids. In the zone of argillic alteration, dendritic zincite crystals result from crystallization of gels formed during coagulation of colloid solutions.

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