ASSOCIATIONS AND DEPOSITION CONDITIONS OF MOLYBDENUM MINERALS IN EXHALATION PRODUCTS OF THE KUDRYAVYI VOLCANO, ITURUP, KURIL ISLANDS

A series of molybdenum minerals was detected in products of high-tempe rature fumarole activity of the Kudryavyi volcano (Iturup, Kuril islan ds). These are powellite, molybdenite, disulfides of rhenium and molyb denum, molybdenum oxides, tugarinivite, molybdite, ilsemannite, as wel l as water-soluble molybdenum-containing phases. Closely spatially con nected with molybdenum minerals are wurzite, greenockite, pyrite, tung stenite, cosalite, andradite, wollastonite, babingtonite, cristobalite , magnetite, sulfates, chlorides, fluorides, etc. Mineral diagnostics is based on data of X-ray diffraction and X-ray spectral analysis and electron microscopy. A common location of oxides with various valences of molybdenum, as well as its sulfide and molybdate forms, shows a sh arp change of mineral-formation conditions (high gradients of temperat ure, pressure, reduction-oxidation potentials, and fugacity of sulfur and oxygen). For molybdenum minerals, the sequence of crystallization was suggested as powellite-ilsemannite-soluble Mo-phase. The ore miner alization of the Kudryavyi volcano is associated with activation of ba salt magmatism and involves crustal material into this process.