HR: 1340h
AN: V13B-1346    [Abstracts]
TI: CANDIDATE MUD VOLCANOES IN THE NORTHERN PLAINS OF MARS
AU: * Kite, E S
EM: kite@berkeley.edu
AF: Cambridge University, Department of Earth Sciences Downing Street, Cambridge, CB3 2EQ, United Kingdom
AU: * Kite, E S
EM: kite@berkeley.edu
AF: University of California, Berkeley, Earth and Planetary Science 307 McCone Hall, Berkeley, CA 94720, United States
AU: Hovius, N
EM: nhovius@esc.cam.ac.uk
AF: Cambridge University, Department of Earth Sciences Downing Street, Cambridge, CB3 2EQ, United Kingdom
AU: Hillier, J K
EM: jkh34@cam.ac.uk
AF: Cambridge University, Department of Earth Sciences Downing Street, Cambridge, CB3 2EQ, United Kingdom
AU: Besserer, J
EM: jonathan.besserer@etu.univ-nantes.fr
AF: Université de Nantes, 2, rue de la Houssinière BP 92208, Nantes Cedex 3, 44322, France
AB: Domes in the the `Borealis back-basin' (centre 76N 160W) on Mars resemble products of mud volcanism (MV) on Earth. Description of domes: Our mapping shows ~30 Early Amazonian domes in the back-basin (~50 x 40 km, height ~300 m). Many have marginal and central peaks (~7 x 5 km, height ~400 m), and moats ~2.5 km wide. Domes are rough at km-scale; some have central depressions; some have annular ridges. Mean rise/run is (0.93±0.22)%. Dome orientations, and alignments of multiple domes, run parallel to the continuation of grabens associated with Alba Patera diking [1]. Distributary channels are found in association with one dome. Aspect-frequency plots for the domes region show significant deviations from randomness. (Detrended) slopes facing S or N are more common than other aspects; local maxima are (S±5°) and (N±5°). N-facing slopes are more abundant than S-facing slopes, so mean S- facing slope must be steeper. A control region at the same latitude shows no comparable anomaly. Interpretation: Many worlds show igneous volcanism, but only Earth has confirmed MV. So, when assessing an extraterrestrial construct, one should assign a high prior probability to igneous volcanism. However, (1) Dome morphologies can be matched with MV in the Caspian Basin and Cadiz Gulf [2], though Martian domes have diameters ~5 times greater. (2) Moat morphometry excludes flexural origin and suggests a collapse origin. Collapse moats are often associated with MV on Earth. (3) Aspect anomalies suggest that near-surface dome material was subject to insolation-driven processing, requiring dome near-surface material to have been partially volatile [3]. (4) Volcanic constructs are rare closer to Alba Patera, inferred to have triggered dome construction. So there must be a major increase in the fusibility of materials in our basin. In the absence of Martian granites, volatile-rich deposits satisfy this requirement. (5) Mars' thick sediment piles permit MV. Crater fill studies suggest that the Scandia and Borealis back- basins contain the greatest thickness of cover in the Northern Plains, making these preferred MV locations [4]. We infer that domes may well result from MV. Outstanding puzzles: We currently lack a compelling mechanism for expulsion in the extensional tectonic setting required for dyking. One possibility is direct triggering of MV through intersection of dyke fluids with a volatile-rich sediment column. OMEGA spectra of domes show no significant differences between dome and non-dome terrain. Band depth methods and linear unmixing models [5] yield compositions uniformly dominated by ferric oxides and pyroxenes. This may be due to recent mantling, or MV may tap a source layer of similar composition to adjacent plains. Implications: Post-Hesperian cover in our study area is too thin for MV; older sediments are probably the source. These may record catastrophic flooding or oceans. Our results have implications for the ease of future drill-rig access to these ancient deposits. There is also a tempting geographic link with young evaporates [6]. [1] K.L.Tanaka (2006), 4th Mars Polar Sci., Abs. #8024. [2]L.Somoza et al. (2003), Mar. Geol. 195, doi:10.1016/S0025-3227(02)00686-2. [3] M.A.Kreslavsky and J.W.Head (2003),GRL 30, doi:10.1029/2003GL017795. [4] D.Buczkowski(2007),JGR-E, doi:10.1029/2006JE002836. [5] J.- P.Combe(2005),PhD thesis, U. Nantes. [6] K.E.Fishbaugh et al.(2007),JGR-E 112, doi:10.1029/2006JE00286.
UR: http://www.climatefutures.com/MVsEMSEC.pdf
DE: 1824 Geomorphology: general (1625)
DE: 5462 Polar regions
DE: 5480 Volcanism (6063, 8148, 8450)
DE: 6225 Mars
DE: 8426 Mud volcanism
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting