Сибирский федеральный университет

Тип публикации: статья из журнала

Год издания: 2020

Идентификатор DOI: 10.5382/econgeo.4745

Аннотация: The Norilsk 1 intrusion (Russia), renowned for its abundance of sulfide ores, contains an upper contact zone, which hosts sulfide-poor and Cr spinel and platinum group element (PGE)-rich discontinuous reefs with significant economic potential. Located within strongly inhomogeneous contact rocks of various compositions, the origin of these reefs is complex and debated. Enrichment in PGEs in these rocks is distributed heterogeneously, occasionally occurring in extremely dense disseminations of Cr spinel, which are unusual for other rocks of the Norilsk 1 intrusion. The compositions of Cr spinel vary significantly between individual samples, even within the same samples across clusters of several Cr spinel grains and single grains. Chromium spinel grains are broadly characterized by low Mg# (3-50 mol %), moderate to extremely high TiO2 content (1-18 wt %), diverse Fe2+/Fe3+ ratios, and elevated V and Zn. Multiphase silicate inclusions hosted by Cr spinel are dominated by orthopyroxene, alkali-feldspar, clinopyroxene, Na phlogopite, high-Al amphibole, chlorite, and albite, along with minor felsic glass, sulfide, apatite, baddeleyite, titanite, calcite, halite, and cordierite. Heating experiments (1,250 degrees C) on the silicate inclusions failed to produce homogeneous glasses but showed evidence of partial melting and reactions with precursor minerals that crystallized new phases. The experimentally obtained glasses are characterized by compositions that strongly differ from any known igneous rock in the Norilsk region, and the assemblage of phases in these inclusions is not supportive of the entrapment of a homogeneous silicate melt. Trace element patterns of the glasses of the experimentally heated inclusions are compositionally distinct from the Norilsk trap basalts, and instead are closer to the sedimentary rocks of the Norilsk region. We suggest that an in situ interaction between the mafic melt and the sedimentary rocks was responsible for Cr spinel mineralization and the formation of the host rocks. The subsequent subsolidus modification of the initial rocks expanded the Cr spinel compositional range and formed muscovite-albite-chlorite assemblages, which replaced the original silicate minerals.

Журнал: ECONOMIC GEOLOGY

Выпуск журнала: Vol. 115, Is. 6

Номера страниц: 1321-1342

ISSN журнала: 03610128

Место издания: LITTLETON

Издатель: SOC ECONOMIC GEOLOGISTS, INC

• Chayka Ivan F. (Russian Acad Sci, Siberian Branch, VS Sobolev Inst Geol & Mineral, Novosibirsk 630090, Russia; Russian Acad Sci, Inst Expt Mineral, Chernogolovka, Russia)
• Kamenetsky Vadim S. (Russian Acad Sci, Inst Expt Mineral, Chernogolovka, Russia; Univ Tasmania, Sch Nat Sci, Hobart, Tas 7001, Australia)
• Zhitova Liudmila M. (Russian Acad Sci, Siberian Branch, VS Sobolev Inst Geol & Mineral, Novosibirsk 630090, Russia; Novosibirsk State Univ, Novosibirsk 630090, Russia)
• Izokh Andrey E. (Russian Acad Sci, Siberian Branch, VS Sobolev Inst Geol & Mineral, Novosibirsk 630090, Russia; Novosibirsk State Univ, Novosibirsk 630090, Russia)
• Tolstykh Nadezhda D. (Russian Acad Sci, Siberian Branch, VS Sobolev Inst Geol & Mineral, Novosibirsk 630090, Russia; Novosibirsk State Univ, Novosibirsk 630090, Russia)
• Abersteiner Adam (Univ Tasmania, Sch Nat Sci, Hobart, Tas 7001, Australia; Russian Acad Sci, Far Eastern Branch, Inst Volcanol & Seismol, Petropavlovsk Kamchatski 683006, Russia)
• Lobastov Boris M. (Siberian Fed Univ, Krasnoyarsk 660041, Russia)
• Yakich Tamara Yu (Tomsk Polytech Univ, Tomsk 634050, Russia)

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