TY - JOUR

T1 - Charnockites of the Central Part of the Anabar Shield: Distribution, Petrogeochemical Composition, Age, and Formation Conditions

AU - Nozhkin, A. D.

AU - Turkina, O. M.

AU - Sal’nikova, E. B.

AU - Likhanov, I. I.

AU - Savko, K. A.

N1 - Funding Information: The studies were made in the framework of the government-financed task of the Institute of Geology and Mineralogy of the Siberian Branch of the Russian Academy of Sciences and was financially supported by the Russian Science Foundation (project no. 21-77-20018). Publisher Copyright: © 2022, Pleiades Publishing, Ltd.

PY - 2022/8

Y1 - 2022/8

N2 - The geological position, U-Pb monazite age, and composition of charnockites from the central part of the Anabar shield are presented. The charnockites are localized in a block of the Paleoproterozoic metasedimentary granulite-facies rocks, which include aluminous schists, sapphirine-bearing schists, and hypersthene plagiogneisses typical of the Archean Daldyn granulite complex. Moderate-K charnockites form small pockets and lenses in the hypersthene plagiogneisses, inherit their gneissic appearance, and are related with them by gradual transitions. High-K charnockites compose large vein bodies with cutting contacts. The charnockites differ in the structural position, but have similar age (1982 Ma) and are separated in time from metasedimentary rocks, whose age is estimated at 2.4–2.5 Ga. Hypersthene plagiogneisses correspond to igneous rocks of predominantly intermediate composition, while charnockites are granodiorites and granites. Compared to the plagiogneisses, charnockites are enriched in Th, light REE, Zr, Nb, Rb, and Ba. Hypersthene plagiogneisses and charnockites are characterized by a highly fractionated REE distribution pattern with an increase in (La/Yb)n and Eu minimum in charnockites. According to geochemical data and close Nd isotopic composition, high-K charnockites could have been generated during the high-temperature melting of hypersthene plagiogneisses. Charnockites (~2.0 Ga) are almost coeval to the Paleoproterozoic granulite metamorphism and emplacement of granite intrusion in collision zones. All these processes are caused by the accretion of Early Precambrian terranes into the structure of the Siberian craton. Charnockitization was superimposed on the hypersthene plagiogneisses, which have been already deformed in folds and migmatized, and on the metasedimentary sequence. This process completes the formation of the granulite complex of the Anabar Shield.

AB - The geological position, U-Pb monazite age, and composition of charnockites from the central part of the Anabar shield are presented. The charnockites are localized in a block of the Paleoproterozoic metasedimentary granulite-facies rocks, which include aluminous schists, sapphirine-bearing schists, and hypersthene plagiogneisses typical of the Archean Daldyn granulite complex. Moderate-K charnockites form small pockets and lenses in the hypersthene plagiogneisses, inherit their gneissic appearance, and are related with them by gradual transitions. High-K charnockites compose large vein bodies with cutting contacts. The charnockites differ in the structural position, but have similar age (1982 Ma) and are separated in time from metasedimentary rocks, whose age is estimated at 2.4–2.5 Ga. Hypersthene plagiogneisses correspond to igneous rocks of predominantly intermediate composition, while charnockites are granodiorites and granites. Compared to the plagiogneisses, charnockites are enriched in Th, light REE, Zr, Nb, Rb, and Ba. Hypersthene plagiogneisses and charnockites are characterized by a highly fractionated REE distribution pattern with an increase in (La/Yb)n and Eu minimum in charnockites. According to geochemical data and close Nd isotopic composition, high-K charnockites could have been generated during the high-temperature melting of hypersthene plagiogneisses. Charnockites (~2.0 Ga) are almost coeval to the Paleoproterozoic granulite metamorphism and emplacement of granite intrusion in collision zones. All these processes are caused by the accretion of Early Precambrian terranes into the structure of the Siberian craton. Charnockitization was superimposed on the hypersthene plagiogneisses, which have been already deformed in folds and migmatized, and on the metasedimentary sequence. This process completes the formation of the granulite complex of the Anabar Shield.

KW - Anabar shield

KW - charnockites

KW - Paleoproterozoic

KW - petrogeochemistry

KW - structural position

UR - http://www.scopus.com/inward/record.url?scp=85135251615&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/e48f6d06-fc66-3a6e-b782-04bd8c8114c0/

U2 - 10.1134/S0016702922080055

DO - 10.1134/S0016702922080055

M3 - Article

AN - SCOPUS:85135251615

VL - 60

SP - 711

EP - 723

JO - Geochemistry International

JF - Geochemistry International

SN - 0016-7029

IS - 8

M1 - 1

ER -