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Shapes of Venusian “pancake” domes imply episodic emplacement and silicic composition
Author(s) -
Fink Jonathan H.,
Bridges Nathan T.,
Grimm Robert E.
Publication year - 1993
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/92gl03010
Subject(s) - venus , dome (geology) , geology , silicic , volcano , lava dome , petrology , geochemistry , astrobiology , magma , geomorphology , physics
The main evidence available for constraining the composition of the large circular “pancake” domes on Venus is their gross morphology. Laboratory simulations using polyethylene glycol show that the height to diameter (aspect) ratios of domes of a given total volume depend critically on whether their extrusion was continuous or episodic, with more episodes leading to greater cooling and taller domes. Thus without observations of their emplacement, the compositions of venusian domes cannot be uniquely constrained by their morphology. However, by considering a population of 51 venusian domes to represent a sampling of many stages during the growth of domes with comparable histories, and by plotting aspect ratio versus total volume, we find that the shapes of the domes are most consistent with episodic emplacement. On Earth this mode of dome growth is found almost exclusively in lavas of dacite to rhyolite composition, strengthening earlier inferences about the presence of evolved magmas on Venus.