Physical and Chemical Conditions of Basaltic Magmatism at the Franz Josef Land Archipelago

Abstract

Data on the mineralogy and melt inclusions in rocks of basaltic complexes of different age at the Franz Josef Land Archipelago (FJL) provide an insight into systematic changes in the composition of the plagioclase, clinopyroxene, and melt inclusions with time. The composition of the inclusions indicate that the Early Jurassic melts were dominated by plateau basaltic ones, whose concentrations of major components, trace elements, and REE were similar to those in typical tholeiites of the Siberian Platform. The Early Cretaceous melts were enriched and subalkaline. Data on the melt inclusions were used to calculate parameters of the magma-generating processes. The results demonstrate how the melts evolved from the Early Cretaceous to Early Jurassic and point to the three peaks of magmatic activity at 192.2 ± 2.8, 157.4 ± 3.5, and 131.5 ± 0.8 Ma, with the magmas derived at the following depths and temperatures: 120 km, 1430–1580°С → 60–110 km, 1390–1580°С → 50–140 km, 1350–1690°С by means of mantle melting, with the development of FJL magma sources.