Mud Volcano Systems: Structure, Evolution and Processes

Abstract

Mud volcano systems erupt sediment and fluid onto the Earth’s surface producing edifices up to 25 km3 in volume however, little is known about how such volumes are transported through the Earth’s crust. This thesis investigates whether transport is through mud-dyke-sill complexes, or is diapiric. Structural field mapping of exhumed mud volcano intrusive domains onshore in Azerbaijan, shows that feeder complexes are 200-800 m wide and roughly circular. These complexes consist of various fracture networks and a megabreccia of country rock blocks tens-of-metres-across that have rotated up to 90° in a matrix of mud. A structural domain model categorises regions within the feeder complex which formed during stoping processes.

Structural mapping is combined with nearest neighbour and 2-point-azimuth statistical analysis of vent distributions described from nine mud volcanoes in Azerbaijan and Lusi mud volcano, East Java. Vent distributions are non-random, showing alignments with: 1) anticline crestal faulting, 2) fractures 3) ring faults, and 4) detachment faults indicating that fracture systems and regional stresses significantly influence feeder complex architecture. Lusi’s vent alignments change orientation from 2006-2010 implying regions 10 km east and west of the main vent are more likely to be impacted by new vents due to the onset of elongate-caldera collapse.

Kilometre-scale, elongate scarps are identified as ‘sector collapses’ on mud volcanoes in Azerbaijan due to morphological similarity to those on igneous volcanoes. Shape parameters distinguish sector collapses and eruptive mud breccia flows allowing identification in field and satellite-based mapping. The updip domains are characterised by vents showing there is linkage to deeper mud volcano fluid flow pathways. A model of a deflating mud chamber triggering ‘thin-skinned’ sector collapse is proposed. This sector collapse model, vent alignment orientation analysis and intrusive domain structural model are ultimately integrated into a comprehensive schematic model of the mud volcano system.