Composition and geodynamic setting of granitoid magmatism in the Alyarmaut Uplift, western Chukchi Peninsula

Abstract

This paper reports the compositions of granitoids from the Alyarmaut Uplift in the western Chukchi Peninsula, which is interpreted as a granite-metamorphic dome. A postcollisional origin was inferred for the granitoids. Their petrographic composition, petrochemical characteristics, and the compositions of their biotite allowed us to assign them to high-K I-type granites. The trace-element composition of the granitoids is comparable with that of granite types associating with both collisional and suprasubduction settings, which may reflect magma source heterogeneity generated by previous collisional processes predating dome and granite formation. The significant scatter of ɛNd(T) and 87Sr/86Sr values in the granitoids is also indicative of the heterogeneous composition of the crustal source or variable degree of magma contamination with ancient crustal material. In addition to the dominant process of the submersion of the rim of the Chukchi microcontinent beneath the active margin of the North Asian craton, the tectonic scenario of the formation of the dome structure of the Alyarmaut Uplift should involve either slab detachment or delamination of the lithospheric mantle, which causes the invasion of asthenospheric material into the base of the crust and promotes heat transfer necessary for the derivation of granitoid magmas.