TY - JOUR

T1 - Tectonic and Geodynamic Settings of Formation of the Mesozoic Cumulative Dunite–Wehrlite–Olivine Clinopyroxenite—Gabbro Massif in Eastern Chukotka

AU - Ledneva, G. V.

AU - Bazylev, B. A.

AU - Layer, P.

AU - Kuzmin, D. V.

AU - Kononkova, N. N.

N1 - Funding Information: The research was supported by the Russian Science Foundation (grant no. 20-17-00197), by the budget state research projects (nos. 0135-2019-0078 and 0137-2019-0012) and by the state research projects for the Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences. Publisher Copyright: © 2020, Pleiades Publishing, Inc. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.

PY - 2020/7/1

Y1 - 2020/7/1

N2 - The dunite–wehrlite–clinopyroxenite–gabbro massif in Eastern Chukotka, a key object for geodynamic reconstructions of the Vel’may terrane, which represents one of the segments of the southern border of the Chukotka folded system (Chukotka microcontinent, or Arctic Alaska–Chukotka microplate), is investigated. Mineralogical and petrological–geochemical studies of rocks of this massif are carried out. A comparative analysis of the primary mineralogy and formation conditions of cumulative rocks of dunite–wehrlite–pyroxenite–gabbro assemblages from modern island-arc systems, mantle transition zones, and crustal sections of ophiolites and ancient island arcs shows that the rocks studied are cumulates crystallized from a tholeiitic melt in an intraoceanic island arc at a moderately high pressure. The 40Ar/39Ar age of magnesian hornblende from gabbro indicates the massif was formed no later than in the Early–Middle Jurassic. The petrological and geochemical modeling suggests that the analyzed olivine clinopyroxenites and gabbros are probable plutonic comagmates of the Late Triassic island-arc basalts and dolerites of the Vel’may terrane. The arc segment represented by these rocks of the Vel’may terrane was probably part of the system of island arcs which had been reconstructed in this region for the age interval of 163 to 230 Ma. In addition, there is a tendency for the rejuvenation of the Middle Triassic–Late Jurassic island-arc magmatism in the direction from west to east, namely, from the South Anyui terrane of Western Chukotka through the Vel’may terrane of Eastern Chukotka to the Angayucham terrain of Alaska.

AB - The dunite–wehrlite–clinopyroxenite–gabbro massif in Eastern Chukotka, a key object for geodynamic reconstructions of the Vel’may terrane, which represents one of the segments of the southern border of the Chukotka folded system (Chukotka microcontinent, or Arctic Alaska–Chukotka microplate), is investigated. Mineralogical and petrological–geochemical studies of rocks of this massif are carried out. A comparative analysis of the primary mineralogy and formation conditions of cumulative rocks of dunite–wehrlite–pyroxenite–gabbro assemblages from modern island-arc systems, mantle transition zones, and crustal sections of ophiolites and ancient island arcs shows that the rocks studied are cumulates crystallized from a tholeiitic melt in an intraoceanic island arc at a moderately high pressure. The 40Ar/39Ar age of magnesian hornblende from gabbro indicates the massif was formed no later than in the Early–Middle Jurassic. The petrological and geochemical modeling suggests that the analyzed olivine clinopyroxenites and gabbros are probable plutonic comagmates of the Late Triassic island-arc basalts and dolerites of the Vel’may terrane. The arc segment represented by these rocks of the Vel’may terrane was probably part of the system of island arcs which had been reconstructed in this region for the age interval of 163 to 230 Ma. In addition, there is a tendency for the rejuvenation of the Middle Triassic–Late Jurassic island-arc magmatism in the direction from west to east, namely, from the South Anyui terrane of Western Chukotka through the Vel’may terrane of Eastern Chukotka to the Angayucham terrain of Alaska.

KW - Chukotka

KW - cumulative gabbro

KW - cumulative ultramafites

KW - Island arc

KW - subduction geodynamic settings

KW - Vel’may terrane

KW - SPREADING RIDGE

KW - Vel'may terrane

KW - HIGH-PRESSURE ULTRAMAFICS

KW - PEKULNEY COMPLEX

KW - GODZILLA MEGAMULLION

KW - ISLANDS OPHIOLITE

KW - LOWER CRUSTAL ROCKS

KW - TITANIAN PARGASITE

KW - ARM MOUNTAIN MASSIF

KW - OCEANIC CORE COMPLEX

KW - CHROMIAN SPINEL

UR - http://www.scopus.com/inward/record.url?scp=85091316724&partnerID=8YFLogxK

U2 - 10.1134/S0016852120040068

DO - 10.1134/S0016852120040068

M3 - Article

AN - SCOPUS:85091316724

VL - 54

SP - 455

EP - 476

JO - Geotectonics

JF - Geotectonics

SN - 0016-8521

IS - 4

ER -