TY - JOUR

T1 - The evolution of the ore-forming system in the low sulfide horizon of the Noril'sk 1 intrusion, Russia

AU - Tolstykh, Nadezhda D.

AU - Zhitova, Liudmila M.

AU - Shapovalova, Maria O.

AU - Chayka, Ivan F.

N1 - Publisher Copyright: © Mineralogical Society of Great Britain and Ireland 2019

PY - 2019/10

Y1 - 2019/10

N2 - We present here new data on the low-sulfide mineralisation in the upper endocontact of the Noril'sk 1 intrusion. Twenty four mineral species of platinum-group elements and their solid solutions, as well as numerous unnamed phases, including an Sb analogue of vincentite, As and Sn analogues of mertieite-I and a Sn analogue of mertieite-II have been found. It is shown that the features of the mineral association: (1) the atypical trend of TiO2 and Fe2+ in chromian spinel; (2) the composition of the Pt-Fe alloys with a Fe/Fe + Pt range of 0.26-0.37 (logfO2 ≈ - (9-10); and (3) crystallisation of high-temperature sperrylite from silicate melt (at >800°C and logfS2 < -10.5), which is possible under fO2 of FMQ to FMQ-2 in mafic magma, are due to the reducing conditions of their formation and evolution. Droplet-like inclusions of silicate-oxide minerals in сhromian spinels and sulfides in platinum-group minerals are interpreted to be trapped droplets of co-existing sulfide melt. The captured sulfide melt has evolved in the direction of increasing the fugacity of sulfur: troilite + pentlandite (Fe>Ni) - in sperrylite (paragenesis I) to monoclinic pyrrhotite + pentlandite (Ni≈Fe) + chalcopyrite - in Pt-Fe alloys (paragenesis II). Paragenesis from the sulfide aggregates in the silicate matrix are more fractionated: pyrrhotite + pyrrhotite (Ni>Fe) + chalcopyrite (III) and pyrite + pentlandite (Ni>>Fe) + millerite (IV). Pd arsenides and antimonides crystallised later than sperrylite and isoferroplatinum, as a result of the evolution of a sulfide melt with an increased activity of the element ligands (Te, Sn, Sb and As).

AB - We present here new data on the low-sulfide mineralisation in the upper endocontact of the Noril'sk 1 intrusion. Twenty four mineral species of platinum-group elements and their solid solutions, as well as numerous unnamed phases, including an Sb analogue of vincentite, As and Sn analogues of mertieite-I and a Sn analogue of mertieite-II have been found. It is shown that the features of the mineral association: (1) the atypical trend of TiO2 and Fe2+ in chromian spinel; (2) the composition of the Pt-Fe alloys with a Fe/Fe + Pt range of 0.26-0.37 (logfO2 ≈ - (9-10); and (3) crystallisation of high-temperature sperrylite from silicate melt (at >800°C and logfS2 < -10.5), which is possible under fO2 of FMQ to FMQ-2 in mafic magma, are due to the reducing conditions of their formation and evolution. Droplet-like inclusions of silicate-oxide minerals in сhromian spinels and sulfides in platinum-group minerals are interpreted to be trapped droplets of co-existing sulfide melt. The captured sulfide melt has evolved in the direction of increasing the fugacity of sulfur: troilite + pentlandite (Fe>Ni) - in sperrylite (paragenesis I) to monoclinic pyrrhotite + pentlandite (Ni≈Fe) + chalcopyrite - in Pt-Fe alloys (paragenesis II). Paragenesis from the sulfide aggregates in the silicate matrix are more fractionated: pyrrhotite + pyrrhotite (Ni>Fe) + chalcopyrite (III) and pyrite + pentlandite (Ni>>Fe) + millerite (IV). Pd arsenides and antimonides crystallised later than sperrylite and isoferroplatinum, as a result of the evolution of a sulfide melt with an increased activity of the element ligands (Te, Sn, Sb and As).

KW - Noril'sk 1 intrusion

KW - low-sulfide horizon

KW - platinum-group minerals (PGM)

KW - unnamed PGE phases

KW - chromian spinets

KW - sulfide inclusion in PGM

KW - reducing conditions

KW - ELECTRON-PROBE MICROANALYSIS

KW - PLATINUM-GROUP MINERALS

KW - SIBERIAN TRAPS

KW - CHROME-SPINELS

KW - COPPER-NICKEL

KW - CU

KW - PENTLANDITE

KW - PROVINCE

KW - COMPLEX

KW - BASALT

KW - chromian spinels

UR - http://www.scopus.com/inward/record.url?scp=85127646911&partnerID=8YFLogxK

U2 - 10.1180/mgm.2019.47

DO - 10.1180/mgm.2019.47

M3 - Article

VL - 83

SP - 673

EP - 694

JO - Mineralogical Magazine

JF - Mineralogical Magazine

SN - 0026-461X

IS - 5

ER -