Differentiated Mafic–Ultramafic Intrusions of the Kruglogorsky Type in the Noril’sk Area: Petrology and Ore Potential

Intrusions of the Kruglogorsky type are an integral part of magmatic formations in the Noril’sk area. The marginal portions of these intrusions are composed of microdolerite, dolerite, and contact gabbrodolerite. The central parts of the intrusions consist of leucogabbro and of olivine-free, olivine...

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Bibliographic Details
Published in:Petrology 2018-05, Vol.26 (3), p.280-313
Main Authors: Sluzhenikin, S. F., Malitch, K. N., Grigor’eva, A. V.
Format: Article
Language:English
Subjects:
Area
Augite
Bearing
Chemical composition
Composition
Copper
Earth and Environmental Science
Earth Sciences
Gabbro
Geochemistry
Intrusion
Isotope composition
Isotopes
Lithology
Magma
Mineralization
Mineralogy
Minerals
Nickel
Olivine
Ores
Petrology
Rock
Rocks
Strontium 87
Strontium isotopes
Vertical sections
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Summary:Intrusions of the Kruglogorsky type are an integral part of magmatic formations in the Noril’sk area. The marginal portions of these intrusions are composed of microdolerite, dolerite, and contact gabbrodolerite. The central parts of the intrusions consist of leucogabbro and of olivine-free, olivine-bearing, and olivine gabbro-dolerite. Leucogabbro is a characteristic rock of this type of intrusions and sometimes composes up to half of the thicknesses of the rock units. The rocks with plagioporphyritic textures are widespread. Olivine-free, olivine-bearing, and olivine gabbro-dolerite occur as horizons with indistinct boundaries, which are unevenly distributed over the vertical sections of the lithological units. The olivine is the most magnesian ( Fo 89-64 ) and richest in Ni (up to 0.23 wt % NiO) in the olivine gabbro-dolerite. The clinopyroxene is represented by augite ( Fs 12-29 ). The rock-forming minerals are typically zoned. The Sr isotopic composition of the rocks (calculated for an age of 250 Ma) varies within a considerable range ( 87 Sr/ 86 Sr = 0.705972–0.708006), due to metasomatic alterations. The variations in the Nd and Sr isotopic composition of the Kruglogorsky intrusion are close to those in rocks of the Noril’sk-type ore-bearing intrusions. The olivine-bearing and taxitic gabbro-dolerite host Pt–Cu–Ni ore mineralization, which are of economic value for disseminated ores of the Talnakh area.
ISSN:0869-5911
1556-2085
DOI:10.1134/S0869591118030050