Iblean diatremes 3: volcanic processes on a Miocene carbonate platform (Iblean Mountains,SE-Sicily): a comparison of deep vs. shallow marine eruptive processes |
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Authors: | Ines Suiting H-U Schmincke |
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Institution: | 1.Leibniz-Institut für Meereswissenschaften an der Universit?t Kiel (IFM-GEOMAR),Kiel,Germany |
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Abstract: | Evolution and magma fragmentation processes of two contrasting, well-exposed diatreme complexes interbedded with Late Miocene
calcareous marine sediments in distinct sedimentary environments of a carbonate platform (Iblean Plateau, Sicily) are compared
with each other. The nephelinitic Cozzo Molino diatreme (CMD) to the east developed in shallow water (0–80 m water depth);
the alkali basaltic Valle Guffari seamount (VGS) to the west grew on a deeper water carbonate ramp (150–200 m water depth).
We focus on the dominant boundary conditions inferred to have governed depth of magma fragmentation and subaqueous emplacement
mechanisms: water depth, physical nature of host rocks, magma composition, and inferred differences in initial volatile concentrations.
There are gross similarities in the composition of the two moderately evolved magmas. The low-viscosity magmas in both diatremes
were laden with xenoliths originating from mantle to lower crustal sites. Although similar, the eastern shallow water CMD
was likely more volatile-rich, with magma fragmented prior to reaching the surface and the surrounding tephra cone was partly
emergent. The eruptions of the entirely submarine VGS diatreme complex in the deeper water environment were dominated by interaction
of soft sediment and alkali basaltic magma or a pre-fragmented volatile-particle mixture. Eruption columns were, thus, strongly
damped and the submarine complex never pierced the water surface. |
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