Origin of clasts and matrix within the Milano and Napoli mud volcanoes, Mediterranean Ridge accretionary complex

Aloisi

2003

Authigenic carbonates and muds from six mud volcanoes in the eastern Mediterranean Sea were recovered during the French/Dutch MEDINAUT cruise utilizing the submersible Nautile in November 1998. The mud volcanoes are active seafloor vents in two areas at the plate boundary between the converging African and Eurasian Plates: the Mediterranean Ridge accretionary prism near Crete (Greece) and the Anaximander Mountains south of Turkey. B contents and 6HB signatures were measured with the aim of identifying the diagenetic processes and source depths of the material in the collision zone. B concentrations of the carbonate precipitates cover a range of 8-45 ppm and vary isotopically from +15.6 to +22.9%0 (corresponding to a parent solution of 34.9-42.2%0 at pH 7). Both the B-enrichment and a 6 laB valve slightly lower than seawater suggest the mud domes originate from a moderately deep fluid source, with local admixture of seawater. B contents and 6HB of the mud show distinct differences between the areas: the Mediterranean Ridge mud domes have lower B contents and higher 8 ~B (average 3.9%0) compared to Anaximander Mountains mud volcanoes (611B average -0.6%0). These B results attest the release of structurallybound B from clay mineral lattices, probably due to stronger deformation near Turkey. These mudstones, which had previously been affected by deep-seated thrusting beneath the Antalya Complex, may have been liquefied and remobilized in their present setting. By contrast, the mud on the Mediterranean Ridge represents offscraped clay-rich strata that was incorporated into the large accretionary wedge.

Section: Discussionmentioning

confidence: 92%

Boron and boron isotopes as tracers for diagenetic reactions and depth of mobilization, using muds and authigenic carbonates from eastern Mediterranean mud volcanoes

Deyhle

Aloisi

2003

“…Low permeability of the crestal MV deposits, either due to high smectite contents (with permeability of those mud breccias 2 orders of magnitude lower than other deep sea clays [Kopf et al, 1998]) or presence of massive gas hydrates [Reed et al, 1990;Bouriak et al, 2000], at times blocks the conduit completely. Such temporary inactivity allows excess pore fluid pressures to build up, which, at lithostatic pressure, results in a usually violent eruption and sudden release, as evidenced by hydrofractured clasts [Robertson and Kopf, 1998b]. This mechanism applies to diatreme-like features more than to diapiric ones, as scaly fabrics often evolve along mud diapirs, causing an increase in permeability due to widened shear zones, increased effective stresses, and failure to create fluid overpressures [Moore and Byrne, 1987].…”

Section: Fluid Discharge and Related Phenomena (Biosphere And Gas Emimentioning

confidence: 99%

“…Only recent deep drilling of the Milano and Napoli domes allowed a fuller understanding of MVism near the backstop to the large accretionary prism [Robertson et al, 1996]. Clast petrography and provenance of components of redeposited sandstones from nine drill holes provided the basis for a reevaluation of the origin of the mud breccia [Robertson and Kopf, 1998b]. Despite the presence of Cretaceous microfossils in the matrix and in some sandstone clasts (both of which are products of reworking), the oldest clast has been related to Miocene (Burdigalian).…”

Section: Origin Of Mudmentioning

confidence: 99%

Significance of Mud Volcanism

2002

Reviews of Geophysics

746

646

Mud volcanism and diapirism have puzzled geoscientists for ∼2 centuries. They have been described onshore and offshore in many places on Earth, and although they occur in various tectonic settings, the majority of the features known to date are located in compressional tectonic scenarios. This paper summarizes the main thrusts in mud volcano research as well as the various regions in which mud volcanism has been described. Mud volcanoes show variable geometry (up to tens of kilometers in diameter and several hundred meters in height) and a great diversity regarding the origin of the fluid and solid phases. Gas (predominantly methane), water, and mud may be mobilized at subbottom depth of only a few meters but, in places, can originate from several kilometers depth (with minor crustal or mantle input). The possible contribution of mud extrusion to global budgets, both from quiescent fluid emission and from the extrusive processes themselves, is important. In regions where mud volcanoes are abundant, such as the collision zones between Africa and Eurasia, fluid flux through mud extrusion exceeds the compaction‐driven pore fluid expulsion of the accretionary wedge. Also, quiescent degassing of mud volcanoes may contribute significantly to volatile budgets and, hence, to greenhouse climate.

“…A model of evolution of the state of consolidation of such sediments following a specific stress path, which eventually leads to the formation of mud volcanoes and sedimentary diatremes following gas expansion in the pore spaces, has been proposed by Brown (1990). In this study, the findings of the ODP drilling campaign (Emeis & Shipboard Scientific Party 1996) together with analyses of facies, clast composition and physical factors such as viscosity, particle size, strength and permeability on the material recovered (Kopf et al 1998) were combined with geophysical data and quantitative approaches from earlier expeditions (Camerlenghi et al 1995). This extensive data compilation was undertaken as a large number of variables is required to calculate the rate of mud efflux and the diameter of the feeder channel of the mud dome from Poiseuille's and Stokes' laws, and to estimate the depth of origin of unconsolidated mud using a quasi-static (rather than a dynamic) approach, which was already published in gas exploration literature (Cherskiy 1961).…”

mentioning

confidence: 97%

“…1) permitted insights into their formation and evolution (Robertson & Shipboard Scientific Party of ODP Leg 160 1996). Different types of mud volcano deposits (for convenience summarized as 'mud breccia' in this paper, as they usually contain a certain amount of clasts) were recovered and provided information concerning the anatomy, age and origin of these enigmatic structures (see Robertson & Kopf 1998). The mechanisms of formation of mud volcanoes are strongly dependent on the consolidation and saturation conditions of fine grained sediments at depth.…”

mentioning

confidence: 99%

Extrusion dynamics of mud volcanoes on the Mediterranean Ridge accretionary complex

Behrmann

2000

Drilling of two submarine mud domes situated in the Olimpi field on the northern flank of the Mediterranean Ridge accretionary complex has documented episodic eruptive activity over the last 1 to > 1.5 Ma. Mud extrusion is related to plate convergence between Africa and Eurasia, having caused backthrust faulting of accreted strata containing overpressured mud at depth. The domes mainly consist of mud breccia with up to 65% of polymictic clasts embedded in a clayey matrix. On the basis of modifications of Poiseuille's and Stokes' laws, mud extrusion rates were calculated for Milano and Napoli mud domes. Mud ascent velocities are estimated to be up to 60-300kma-', and are comparable with those of silicate magmas. Using physical property, structural and flux data of the mud breccias, and compiled data from mud domes on land, the diameter of the feeder channel and the depth of origin for the overpressured muds could be reliably estimated for the first time. Feeder channels are likely to be only a few metres wide. Gas efflux estimates constrain a source depth to c. 1700 4-50 m below sea floor in the Olimpi field, which is considerably shallower than estimations made from the thermal maturity of solid organic carbon in the mud breccias. The efflux data suggest that the overpressured muds were not mobilized at d6collement depth, but at a shallower level within the accretionary prism. A comparison of mud ascent rates (as determined from Poiseuille flow) and the total volumes of mud extruded indicate that only a fraction of the time span constrained from biostratigraphic data (c.