The First Find of Oxyborates in Rocks of the Norilsk-1 Intrusion (Northwestern Siberian Platform)

Abstract

In the taxitic gabbro-dolerites of the upper contact zone of the Norilsk-1 intrusion, five boron minerals were found: kotoite Mg₃(BO₃)₂, suanite Mg₂B₂O₅, warwickite (Mg,Ti,Fe,Cr,Al)₂O(BO₃), ludwigite (Mg)₂Fe³⁺O₂(BO₃), and azoproite (Mg,Fe²⁺)₂(Fe³⁺,Ti,Mg)O₂(BO₃). This is the first find of oxyborates in the rocks of the Norilsk ore-bearing intrusions and in the Norilsk province as a whole. Oxyborates occur as inclusions in olivine in the recrystallization zones of taxitic gabbro-dolerites. This indicates that they formed at the late-magmatic or postmagmatic stage as result of the interaction between rocks and boron-bearing fluids associated with an ore-bearing intrusion. Microinclusions of boron minerals could be the cause of elevated concentrations of boron in the rocks. This is a characteristic feature of Norilsk PGE–Cu–Ni-bearing intrusions that can be used as a prospecting criterion.