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Low-temperature emplacement of phreatomagmatic pyroclastic flow deposits at the monogenetic Mt Gambier volcanic complex, South Australia, and their relevance for understanding some deposits in diatremes
journal contribution
posted on 2023-05-19, 03:02 authored by Van Otterloo, J, Raymond CasRaymond CasThe occurrence of pyroclastic flow deposits is not restricted to polygenetic and/or felsic volcanic systems, but can also occur at mafic monogenetic volcanic centres. At the c. 5 ka Mt Gambier Volcanic Complex, Australia, two small-volume pyroclastic flow deposits resulted from phreatomagmatic eruptive phases of the Blue Lake East and the Valley Lake maar craters. The facies descriptions of the two massive, poorly sorted lapilli tuff and tuff breccia deposits are given. Low-grade carbonized wood fragments in the deposits mark low emplacement temperatures (180–270°C) for these deposits with only c. 12–23% of the total thermal energy of the original magma preserved at the time of deposition. The Blue Lake East vent erupted by forming a short-lived vertical eruption column, which could not be sustained and collapsed. The Valley Lake pyroclastic flow deposit has a highly asymmetric dispersal to the west, indicating that this deposit was formed during an eruptive phase with a large westward-directed lateral component. Such massive, poorly sorted deposits outside the maar crater indicate that some similar deposits in diatremes may have originated from surface eruptions and not just from subsurface debris jets.
History
Publication title
Journal of the Geological SocietyVolume
173Issue
4Pagination
701-710ISSN
0016-7649Department/School
School of Natural SciencesPublisher
Geological Soc Publ HousePlace of publication
Unit 7, Brassmill Enterprise Centre, Brassmill Lane, Bath, England, Avon, Ba1 3JnRights statement
© 2016 The Author(s).Repository Status
- Restricted