Multiple intrusion stages and mantle sources of the Paleozoic Kuznetsk Alatau alkaline province, Southern Siberia: geochemistry and Permian U–Pb, Sm–Nd ages in the Goryachegorsk ijolite-foyaite intrusion

Abstract

ABSTRACT In this work, we present new U–Pb, Sm–Nd geochronology, major and trace‐element and isotopic composition (Nd, Sr, Pb, O) for the Goryachegorsk alkaline-mafic igneous rocks from the Kuznetsk Alatau (Siberia, Russian Federation). The age obtained using U-Pb in zircon, ~ 265 Ma, is considered to represent the crystallization age of Goryachegorsk intrusion in Late Permian times. LILE and HFSE composition, and isotope signatures indicate the heterogeneity of magmatic sources and the mixing of IAB- and OIB- like magmas. We interpret that this intrusion is characterized by the superposition of PREMA + EM 2 mantle plume magmas and other magmas derived from the melting of accretion-collision complexes from the Paleo Asian ocean margin. Mixing of mantle sources and continental crust resulted in variations of Nd-isotope composition (εNd (t) ~ 1.7–6.8) and lead isotope composition (206Pb/204Pb in 19.29, 207Pb/204Pb in 15.58, 208Pb/204Pb in 37.74), as well as an increase of 87Sr/86Sr (t) ~ 0.7049–0.7068 and δ18О 8.5–9.6 ‰, SMOW in igneous rocks. Additional geochronological data on the Kuznetsk Alatau alkaline mafic province suggest its origin at different times during the Paleozoic: at the Cambrian-Ordovician boundary (~ 510–480 Ma); Early-Middle Devonian (~ 410–385 Ma); and Late Permian (~ 266–262 Ma). Geochemical similarity between the regional alkaline magmatism emplaced at different ages provides insights into periodic mantle plume – lithosphere interaction over a time span of ca. 250 Ma.