TY - JOUR

T1 - New Evidence of the Polycyclic Genesis of Platinum Placer-Forming Formations of the Kondyor Alkaline-Ultramafic Massif

T2 - Results of 190Pt–4He Dating

AU - Mochalov, A. G.

AU - Yakubovich, O. V.

AU - Stuart, F. M.

AU - Bortnikov, N. S.

N1 - Publisher Copyright: © 2021, Pleiades Publishing, Ltd.

PY - 2021/6/3

Y1 - 2021/6/3

N2 - Abstract: This article presents the 190Pt–4He dating results of native platinum group minerals from a unique platinum-metals placer deposit in the basin of the Kondyor and Uorgalan rivers and dunite fragments from the Kondyor alkaline-ultramafic massif. The results of 190Pt–4He dating of 75 samples determine the age of the minerals and also date the ore-forming processes. It confirms the previously developed model of polycyclic genesis of placer-forming formations of platinum group minerals (PGMs) and, thus, sheds light on the duration of the formation of the Kondyor alkaline-ultramafic massif. The following 190Pt–4He age stages are distinguished: (a) 143 ± 7 Ma, the formation time of the massif itself and early formation stages of PGMs of magmatogenic platinum (Pt) and the magmatogenic–fluid–metasomatic Pt and Os–Pt (Pt > Os) types, as well as PGMs of fluid-metamorphogenic iridium–platinum (Pt > Ir) type; (b) 128 ± 6 Ma, the early formation stages of the magmatogenic–fluid–metasomatic Pd–Pt (Pt > Pd) type and the late stages of the Pt, Pt > Os, and Pt > Ir types; (c) 115 ± 6 Ma, the late formation stages of the Pt > Pd type. The good agreement of these dates with the geological and mineralogical data allows us to conclude that the formation of placer-forming PGMs and their formations in the Kondyor alkaline-ultramafic massif was a polycyclic process for about 30 Ma.

AB - Abstract: This article presents the 190Pt–4He dating results of native platinum group minerals from a unique platinum-metals placer deposit in the basin of the Kondyor and Uorgalan rivers and dunite fragments from the Kondyor alkaline-ultramafic massif. The results of 190Pt–4He dating of 75 samples determine the age of the minerals and also date the ore-forming processes. It confirms the previously developed model of polycyclic genesis of placer-forming formations of platinum group minerals (PGMs) and, thus, sheds light on the duration of the formation of the Kondyor alkaline-ultramafic massif. The following 190Pt–4He age stages are distinguished: (a) 143 ± 7 Ma, the formation time of the massif itself and early formation stages of PGMs of magmatogenic platinum (Pt) and the magmatogenic–fluid–metasomatic Pt and Os–Pt (Pt > Os) types, as well as PGMs of fluid-metamorphogenic iridium–platinum (Pt > Ir) type; (b) 128 ± 6 Ma, the early formation stages of the magmatogenic–fluid–metasomatic Pd–Pt (Pt > Pd) type and the late stages of the Pt, Pt > Os, and Pt > Ir types; (c) 115 ± 6 Ma, the late formation stages of the Pt > Pd type. The good agreement of these dates with the geological and mineralogical data allows us to conclude that the formation of placer-forming PGMs and their formations in the Kondyor alkaline-ultramafic massif was a polycyclic process for about 30 Ma.

KW - Aldan Shield

KW - alkaline rocks

KW - genesis

KW - Kondyor massif

KW - mineralogical–geochemical types

KW - platinum group minerals

KW - Pt–He dating

KW - ultramafic rocks

UR - http://www.scopus.com/inward/record.url?scp=85107206137&partnerID=8YFLogxK

U2 - 10.1134/S1028334X2105010X

DO - 10.1134/S1028334X2105010X

M3 - Article

AN - SCOPUS:85107206137

VL - 498

SP - 372

EP - 378

JO - Doklady Earth Sciences

JF - Doklady Earth Sciences

SN - 1028-334X

IS - 1

ER -