TY - JOUR

T1 - PETROLOGY OF THE LAMPROITE AND GRANITE–SYENITE SERIES OF THE BILIBIN (Lomam) MASSIF (Aldan–Stanovoy Shield)

AU - Chayka, I. F.

AU - Izokh, A. E.

AU - Sotnikova, I. A.

AU - Alymova, N. V.

AU - Kolotilina, T. B.

AU - Karimov, A. A.

AU - Shcherbakov, V. D.

AU - Lobastov, B. M.

N1 - The authors thank Nikolai Vasil\u2019evich Vladykin for the provided collection and dedicate this work to his blessed memory. We thank M. Milaushkin for the scientific discussion and V.A. Danilovskaya, M.V. Khlestov, E.N. Nigmatullina, V.F. Posokhov, N.G. Soloshenko, V.V. Shabykova, and T.I. Kirnozova for the analytical work performed. Also, thanks go to reviewers A.G. Doroshkevich and T.V. Donskaya for detailed and valuable comments, from which the work significantly benefited. The study was carried out with the support of the Russian Science Foundation, project No. 23-27-00224.

PY - 2025/4/1

Y1 - 2025/4/1

N2 - The Bilibin massif is a Mesozoic intrusion located in the southeastern part of the Aldan high-potassium igneous province of the Aldan–Stanovoy Shield of the Siberian Platform. This massif consists of the alkaline–mafic–ultramafic and granite–syenite phases, which form a concentric structure with the rocks becoming more silica-rich from periphery to center. Earlier studies proposed that these phases formed either from different parental magmas or from a common lamproitic magma via magmatic differentiation. In this study, we examined a representative set of rock samples from the Bilibin massif: phlogopite clinopyroxenites, melashonkinites, shonkinites, alkali syenites, quartz syenites, and granites. Mineralogical–petrographic, geochemical, and isotope–geochemical data imply that the series of differentiation of lamproitic magma comprises rocks from clinopyroxenites to shonkinites and possibly alkali syenites, which form the first phase. The quartz syenites and granites, which form the second phase, belong to a separate magmatic series. According to geochemical data and the Nd, Sr, and O isotope composition of the quartz syenites and granites, the magmas which formed the syenites and granites were derived from the lower crust rather than from the lithospheric mantle and originated owing to either crustal melting during mantle-derived magmatism or collisional tectonics at the southern margin of the Siberian Platform in the Mesozoic Era. Rocks of the lamproite series allow us to consider it as an example of complete differentiation of a mantle lamproitic melt, with the following stages of cotectic crystallization: olivine + chromite, olivine + clinopyroxene + chromite, olivine + clinopyroxene + phlogopite, clinopyroxene + phlogopite + leucite, and clinopyroxene + phlogopite + K-feldspar. Spot analyses of trace elements in clinopyroxene, phlogopite, leucite, and apatite allow estimation of the melt–mineral partition coefficients in such a system.

AB - The Bilibin massif is a Mesozoic intrusion located in the southeastern part of the Aldan high-potassium igneous province of the Aldan–Stanovoy Shield of the Siberian Platform. This massif consists of the alkaline–mafic–ultramafic and granite–syenite phases, which form a concentric structure with the rocks becoming more silica-rich from periphery to center. Earlier studies proposed that these phases formed either from different parental magmas or from a common lamproitic magma via magmatic differentiation. In this study, we examined a representative set of rock samples from the Bilibin massif: phlogopite clinopyroxenites, melashonkinites, shonkinites, alkali syenites, quartz syenites, and granites. Mineralogical–petrographic, geochemical, and isotope–geochemical data imply that the series of differentiation of lamproitic magma comprises rocks from clinopyroxenites to shonkinites and possibly alkali syenites, which form the first phase. The quartz syenites and granites, which form the second phase, belong to a separate magmatic series. According to geochemical data and the Nd, Sr, and O isotope composition of the quartz syenites and granites, the magmas which formed the syenites and granites were derived from the lower crust rather than from the lithospheric mantle and originated owing to either crustal melting during mantle-derived magmatism or collisional tectonics at the southern margin of the Siberian Platform in the Mesozoic Era. Rocks of the lamproite series allow us to consider it as an example of complete differentiation of a mantle lamproitic melt, with the following stages of cotectic crystallization: olivine + chromite, olivine + clinopyroxene + chromite, olivine + clinopyroxene + phlogopite, clinopyroxene + phlogopite + leucite, and clinopyroxene + phlogopite + K-feldspar. Spot analyses of trace elements in clinopyroxene, phlogopite, leucite, and apatite allow estimation of the melt–mineral partition coefficients in such a system.

KW - Aldan–Stanovoy Shield

KW - Bilibin massif

KW - Lamproites

KW - differentiation

KW - geochemistry

KW - isotope geochemistry

UR - https://www.mendeley.com/catalogue/4bb3532c-da8f-36d8-9066-ec8612eee483/

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-105001981661&origin=inward&txGid=e9389d311cfb6c19e9d4d867e682d6fc

U2 - 10.2113/RGG20244784

DO - 10.2113/RGG20244784

M3 - Article

VL - 66

SP - 424

EP - 449

JO - Russian Geology and Geophysics

JF - Russian Geology and Geophysics

SN - 1068-7971

IS - 4

ER -