TY - JOUR

T1 - Heterogeneous Subcontinental Lithospheric Mantle below the South Margin of the Siberian Craton: Evidence from Composition of Paleoproterozoic Mafic Associations

AU - Turkina, O. M.

AU - Izokh, A. E.

N1 - The authors thank D.P. Gladkochub, Corresponding Member of the Russian Academy of Sciences, and Ph.D. A.S. Mekhonoshin for providing the samples and part of the analytical data for rocks of the Malyi Zadoi massif. We are grateful to the staff of the Analytical Center for Multi-Ele-mental and Isotope Research, Siberian Branch of the Russian Academy of Sciences (Novosibirsk), Ph.D. I.V. Niko-laeva, Ph.D. S.V. Palesskii, and N.G. Karmanova, who performed analytical work. The authors are grateful to D.P. Gladkochub, Corresponding Member of the Russian Academy of Sciences, and Prof. A.A. Vorontsov for constructive reviews, which contributed to the improvement of the paper. The study of the Paleoproterozoic mafic associations of the Irkut block was done with financial support of the Russian Foundation for Basic Research (project No. 20-05-00265). A summary of the data on Paleoproterozoic magmatism was done on state assignment of V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences (No. 122041400044-2). Публикация для корректировки.

PY - 2023/10

Y1 - 2023/10

N2 - Paleoproterozoic mafic associations of the Irkut block from the Sharyzhalgai uplift are gabbro-dolerite dikes and small gabbronorite and monzodiorite massifs, which formed at 1.87–1.84 Ga and were coeval with granitoids and basite intrusions of the South Siberian magmatic belt (SSB). All the Paleoproterozoic mafic associations of the Irkut block are characterized by the presence of biotite and alkali feldspar, enrichment in K2O, LILE, Th, and light REE, highly fractionated multielement spectra with sharp Nb and Ti depletion, and extremely low eNd(T) from –5.1 to –10.1. In these compositional features, they are similar to mafic complexes in the central and eastern parts of the SSB (the Baikal uplift and the western Aldan shield). Their geochemical and isotopic characteristics did not result from crustal contamination but point to derivation from the subcontinental lithospheric mantle (SCLM) enriched by reaction with felsic subduction-related and OIB-like mafic melts formed at a low degree of melting. The geochemically contrasting Paleoproterozoic gabbronorites in the Onot block of the Sharyzhalgai uplift are marked by depletion in K2O, Ba, LILE, Th, and light REE, weak depletion in Nb, and higher eNd(T) from –0.3 to –1.4. The gabbronorites indicate not only an increase in the contribution of a depleted source to their genesis but also the heterogeneity of the subcontinental lithospheric mantle below the south margin of the Siberian Craton. The formation of enriched SCLM domains throughout the South Siberian belt was mainly the result of Archean subduction-related metasomatic processes. The wide distribution of Paleoproterozoic mafic complexes with subduction geochemical signatures and negative eNd(T) on most early Precambrian cratons is due to global change in the composition and an increase in the heterogeneity of the subcontinental lithospheric mantle toward the end of the Archean.

AB - Paleoproterozoic mafic associations of the Irkut block from the Sharyzhalgai uplift are gabbro-dolerite dikes and small gabbronorite and monzodiorite massifs, which formed at 1.87–1.84 Ga and were coeval with granitoids and basite intrusions of the South Siberian magmatic belt (SSB). All the Paleoproterozoic mafic associations of the Irkut block are characterized by the presence of biotite and alkali feldspar, enrichment in K2O, LILE, Th, and light REE, highly fractionated multielement spectra with sharp Nb and Ti depletion, and extremely low eNd(T) from –5.1 to –10.1. In these compositional features, they are similar to mafic complexes in the central and eastern parts of the SSB (the Baikal uplift and the western Aldan shield). Their geochemical and isotopic characteristics did not result from crustal contamination but point to derivation from the subcontinental lithospheric mantle (SCLM) enriched by reaction with felsic subduction-related and OIB-like mafic melts formed at a low degree of melting. The geochemically contrasting Paleoproterozoic gabbronorites in the Onot block of the Sharyzhalgai uplift are marked by depletion in K2O, Ba, LILE, Th, and light REE, weak depletion in Nb, and higher eNd(T) from –0.3 to –1.4. The gabbronorites indicate not only an increase in the contribution of a depleted source to their genesis but also the heterogeneity of the subcontinental lithospheric mantle below the south margin of the Siberian Craton. The formation of enriched SCLM domains throughout the South Siberian belt was mainly the result of Archean subduction-related metasomatic processes. The wide distribution of Paleoproterozoic mafic complexes with subduction geochemical signatures and negative eNd(T) on most early Precambrian cratons is due to global change in the composition and an increase in the heterogeneity of the subcontinental lithospheric mantle toward the end of the Archean.

KW - Paleoproterozoic

KW - basite

KW - isotopic composition

KW - subcontinental lithospheric mantle

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-85174023747&origin=inward&txGid=f4c3497cfe68a336927ecbc455bfcc40

UR - https://www.mendeley.com/catalogue/585c170c-9fcd-3a66-b98b-3b5ffab9dc9c/

U2 - 10.2113/RGG20234575

DO - 10.2113/RGG20234575

M3 - Article

VL - 64

SP - 1141

EP - 1160

JO - Russian Geology and Geophysics

JF - Russian Geology and Geophysics

SN - 1068-7971

IS - 10

ER -