Cyclic activity of mud volcanoes: Evidences from Trinidad (SE Caribbean) E. Deville * , S.-H. Guerlais IFP, 1-4, av. de Bois-Pre ´au, 92 506 Rueil-Malmaison, France article info Article history: Received 13 June 2008 Received in revised form 4 March 2009 Accepted 10 March 2009 Available online 28 March 2009 Keyword: Mud volcano cycle eruption temperature abstract Fluid and solid transfer in mud volcanoes show different cyclic phases of activity, including catastrophic events and periods of relative quiescence characterized by moderate activity. This is notably well-shown by the compilation of historical data onshore Trinidad. It appears that each eruptive mud volcano has its own period of catastrophic activity, and this period is variable from one volcano to another. The frequency of the eruptions seems essentially controlled by local pressure regime within the sedimentary pile. The dynamics of expulsion of the mud volcanoes during the quiescent phases has been studied with the help of temperature measurements within the mud conduits. The mud temperature in these conduits is notably concurrently controlled by the gas flux (endothermic gas depressurizing induces a cooling effect), and by the mud flux (mud is a vector for convective heat transfer). Complex temper- ature distribution was observed in large conduits and pools. Especially in the bigger pools, the temperature distribution characterizes convective cells with an upward displacement of mud above the deep outlet, and ring-shaped rolls associated with the burial of the mud on the flanks of the pools. In tube-like shaped narrow conduits, the temperature is more regular, but we observed different types of profiles, with either downward increasing or decreasing temperatures. Near constant to even negative gradients compared to the general temperature gradient are typical for very dynamic fluid systems. The temperature profiles varied from one place to another, as well as over time. The temperatures measured within the conduits and their base show that the fluid flow is not constant but highly variable through short time-periods. We observed locally a significant daily change of the temperature of the expelled mud which shows also that the mud flux is changing very rapidly due to the migration dynamics of the mud in fracture systems. We also observed very short time-period cyclic variations with a frequency of several minutes. These high frequencies temperature changes could be related to the dynamics of two- phase flows (gas and mud) through the mud volcano conduits. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction The most famous subsurface clay-rich sediment mobilization phenomenon is mud volcanism, which corresponds to surface vents expelling 1) water (of different salinities), 2) solids (thin solid particles in the mud and clasts), 3) liquid hydrocarbons and 4) gas flows. Mud volcanoes are the superficial consequence of the transfer of liquefied sediments and gas from depth towards the surface. They develop in different geologic contexts, mostly in convergent orogens and offshore deltaic systems (see Higgins and Saunders, 1974; Guliyiev and Feizullayev, 1998; Milkov, 2000; Dimitrov, 2002; Kopf, 2002, for inventories and references). They are present in greater numbers in offshore regions than on land and many offshore mud volcanoes remain to be found. They are found notably in accretionary wedges such as the Barbados prism (Biju-Duval et al., 1982; Westbrook and Smith, 1983; Brown, 1990; Figs. 1 and 2), Trinidad (Kugler, 1965; Higgins and Saunders, 1974; Yassir, 1987; Dia et al., 1999; Deville et al., 2003a,b), North Venezuela (Duerto and McClay, 2002; Jacome et al., 2003), the Mediterranean ridge (Kopf and Behrmann, 2000), the south Caspian basin (Hovland et al., 1997; Cooper, 2001; Planke et al., 2003; Yusifov and Rabinowitz, 2004; Stewart and Davies, 2006), the Apennines (Martinelli, 1999), and the Makran accretionary prism (Ellouz-Zimmermann et al., 2007a,b). They are also present in numerous passive margins within deltaic settings, such as the Niger (Damuth, 1994; Cohen and McClay, 1996; Graue, 2000), the Nile (Loncke et al., 2004) and the Mississippi deltas (Sassen et al., 2003). They also develop in active hydrothermal areas, such as the Yellowstone Park (Pitt and Hutchinson, 1982) and the Etna area in Sicily (Etiope et al., 2002). Understanding mud volcanism processes is a matter of concern for a wide range of disciplines in earth sciences (budget of greenhouse gases in the atmosphere, * Corresponding author. E-mail address: eric.deville@ifp.fr (E. Deville). Contents lists available at ScienceDirect Marine and Petroleum Geology journal homepage: www.elsevier.com/locate/marpetgeo 0264-8172/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpetgeo.2009.03.002 Marine and Petroleum Geology 26 (2009) 1681–1691