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Date submitted2023-08-14
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Date accepted2023-10-25
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Date published2023-10-27
Magmatic system of the Klyuchevskoy volcano according to seismic data and their geomechanical interpretation
3D analysis of the magma transport and accumulation mechanism in the structure and basement of the Klyuchevskoy volcano preceding 11 eruptions in 2003-2021 has been performed. Using the Frac-Digger method and seismological data from the Kamchatka Branch Federal Research Center United Geophysical Survey Russia Academy of Sciences it has been shown that magma transport from the deep crustal magma chamber (−30 km) is carried out in the vertical fracturing (dykes) mode to the peripheral shallow magma chamber (+1 km). The feeding dykes orientation corresponds to geomechanical conditions of radial or N-NNE extension. This is followed by inclined dykes and sills of various orientations from the peripheral magmatic chamber. Magma accumulation in the peripheral magmatic chamber in the form of sills (in the horizontal fracturing mode at elevations of +0,3 to +2,3 km) contributes to the efficiency of magma degassing and heat exchange with meteoric waters, and to the formation of a high-pressure vapour-gas reservoir with subsequent venting of the volcano channel and its eruption. Three-dimensional analysis of the distribution of flank eruptions of the Klyuchevskoy volcano in 1932-2021 (16 cinder cones) shows their association with two main low-inclined structural surfaces. Changes in the drainage level of the magmatic system are reflected in the volumes and geochemical history of the 1932-2021 flank eruption products.
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Date submitted2021-04-04
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Date accepted2022-04-26
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Date published2022-07-26
Vendian age of igneous rocks of the Chamberlain valley area (Northern part of the Wedel Jarlsberg Land, Svalbard Archipelago)
The geological structure, structural relations with the underlying complexes, mineral composition, age and origin of sedimentary-volcanogenic and intrusive formations of the Chamberlain valley area (northern part of the Wedel Jarlsberg Land, Svalbard Archipelago) are considered. As a result of the studies, two stages of the Late Precambrian endogenous activity in this area have been identified. For the first time the Vendian ages (593-559 Ma) of intrusive (dolerites) and effusive (basalts, andesites, tuffs) rocks were determined by U-Pb-method (SHRIMP-II) for Svalbard Archipelago. At the same time, the Grenville ages for large bodies of gabbro-diorites, metadolerites bodies (1152-967 Ma), and metagranites (936 Ma) were determined for the first time for this area, which correlates well with the ages of magmatic formations obtained earlier in the southern part of Wedel Jarlsberg Land. A detailed petrographic and petrochemical characterization of all the described objects were compiled and the paleotectonic conditions of their formation were reconstructed. Based on these data, the Chemberlendalen series, which is dated to the Late Vendian, and the Rechurchbreen series, which the authors attribute to the Middle Riphean and correlate with the lower part of the Nordbucht series are distinguished. The data obtained indicate a two-stage Precambrian magmatism in this area of the Svalbard archipelago and, most importantly, provide evidence for the first time ever of endogenous activity on Svalbard in the Vendian time. This fact makes it possible to reconsider in the future the history of the formation of folded basement of the Svalbard archipelago and the nature of the geodynamic conditions in which it was formed.