Gold-brannerite nuggets in placers of the Ozernoe ore cluster (Buryatia)

Abstract Large gold-brannerite aggregates (nuggets up to 50 g in weight) were found in placers of the Ozernoe ore cluster, western Transbaikalia. Brannerite occurs as large crystals and crystal aggregates and has the near-stoichiometric composition UTi 2 O 6 . It lacks REE, contains little, if any, Th, and has admixtures of FeO (2.0–3.7 wt.%), CaO (up to 2.7 wt.%), and SiO 2 (up to 2.14 wt.%). It also bears fine ( 3 ), dolomite, siderite, and muscovite. High contents of Te and Bi were detected in Fe, Ti, and U hydroxides. A specific relationship between gold and rutile has been revealed both in large aggregates and in gold microinclusions (