The volcanic history of central Elysium Planitia: Implications for martian magmatism

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2009.06.032 Byline: J. Vaucher (a), D. Baratoux (a), N. Mangold (b), P. Pinet (a), K. Kurita (c), M. Gregoire (a) Keywords: Mars; Volcanism Abstract: Central Elysium Planitia (CEP) is located south of Elysium Mons. Back to the era of the Viking orbiters, clues accumulated in favor of recent volcanism in relation with ground water release and the formation of long sub-parallel fissures. Four aqueous flood channel systems emanate from linear fissures. Recent eruptions of low viscosity lavas originate from these fissures and from low shield volcanoes. The objective of this paper is to constrain the volcanic history of this region, and to determine the chronological relationships with fluvial/erosional processes. New observations (e.g., new shield volcanoes and one new fluvial event) are summarized on a context map. Thirty-five surfaces have been dated from the count of about 15,000 impact craters. Ages have been cross-checked with relative stratigraphy when possible. A probabilistic approach has been introduced to compare similar ages and define periods of volcanic activity. Our results confirm that some volcanic features are extremely recent ([approximately equal to]2My). Active periods are found at 2.5-3My, 4.3My, 13.5-16.2My, 19My, 21-32My, 58My, 71My, 85-95My, 134My, 173My and 234My, not excluding the possibility that some of the gaps would be filled with additional crater counts. The volcanic activity thus extended for at least the last 250My. The lava volumes have been estimated from the topographic modeling of the floor of depressions filled up by volcanic products, including the volumes of several large crater cavities buried under lavas (>20% of the total volume). Our new estimation of the total lava volume is 1.5[+ or -]0.2x10.sup.5 km.sup.3. This value corresponds to an average thickness of one hundred meters of lavas for the young volcanic plain. As a consequence, the total eruption rate at CEP, defined as the total volume of lava divided by the time of emplacement 1.4x10.sup.-2-1.8x10.sup.-2 m.sup.3/s is lower than values typically estimated for terrestrial hot spots or large igneous provinces, suggesting longer inactive periods. The concept of mantle plumes responsible for terrestrial flood volcanism may not be applicable to the case of CEP and the mechanism proposed in offers a plausible alternative to explain our observations. Author Affiliation: (a) Laboratoire Dynamique Terrestre et Planetaire, UMR 5562, Observatoire Midi-Pyrenees, Universite de Toulouse and CNRS, Toulouse, France (b) Universite de Nantes, UFR des Sciences et des Techniques, Laboratoire de Planetologie et Geodynamique, 2 rue de la Houssiniere, B.P. 92208, 44322 Nantes Cedex 3, France (c) Earthquake Research Institute, Zip. 113-0032, 1-1-1, Yayoi, Bunkyo-ku, Tokyo, Japan Article History: Received 12 June 2007; Revised 17 May 2009; Accepted 1 June 2009