Experimental Constraints on Parameters Controlling the Difference in the Eruptive Dynamics of Phonolitic Magmas: the Case of Tenerife (Canary Islands)

摘要: We have performed phase equilibrium experiments to determine the pre-eruptive conditions of explosive eruption Montana Blanca (2020 BP) that occurred from a satellite vent located in east flank Teide volcano (Tenerife Island). Crystallization were using phonolitic obsidian fall out deposit contains 5 wt% anorthoclase, diopside and magnetite with minor amounts biotite ilmenite, set glassy matrix microlites Ca-rich alkali feldspars. Temperature was varied between 850oC 800oC, pressure 200MPa 50 MPa. The oxygen fugacity (fO2) NNO+0.2 (0.2 log units above Ni-NiO solid buffer) NNO-2, whilst dissolved water contents 7 1.5 wt%. Comparison natural experimental proportions compositions indicates main body phonolite magma stored at 850±15oC, 50±20MPa, 2.5±0.5wt% H2O an fO2 around NNO-0.5 prior eruption, equivalent depths 1 2 km below surface. Some clinopyroxene hosting H2O-rich melt inclusions possibly originates intermittent supply somewhat deeper levels (100 MPa). Ca Fe-rich composition feldspar phenocrysts rims attests intrusion mafic reservoir just as borne by banded pumices appearing later products eruptive sequence. comparison other magmas Tenerife elsewhere (e.g., Vesuvius, Laacher See) shows differences dynamic can be correlated storage depths, along variation volatile contents.