Description
Listvenites, formed from oceanic mantle peridotite thrust over carbonate-bearing sediments,
provide an outcrop exposure in the Oman Ophiolite recording peridotite carbonation
processes in the hanging wall of a subduction zone. Core BT1 of the ICDP Oman Drilling
Project (OmDP) is a unique sample of a carbonated and serpentinized peridotite (including
the basal thrust) from an oceanic plate boundary.
We aim to better understand the interplay of reaction-induced volume change, tectonic
forces, and pore pressure during large scale hydration and carbonation processes in BT1
and test hypotheses on driving forces, structural evolution and fluid transport pathways in this
system. A second aim is to obtain fundamental understanding of the process of crystal
growth in veins driven by the force of crystallization. More generally, we hope to contribute a
process-oriented perspective to studies of mass transfer and element “recycling” in
subduction zones, and to understand the effect of mass transfer and mineralogical
transformation on plate-boundary deformation.
We propose a micro- and macrostructural study of deformation and reaction structures in
listvenite and serpentinized peridotite in the Oman ophiolite, in Core BT1 and in the
surrounding field exposures. Using optical and electron microscopy (ViP, CL, BIB-SEM,
EDX, EBSD) integrated with core description and with the state of the art imaging data
collected by OmDP, we will focus on (i) the microstructure of protolith serpentinites and
partially altered peridotites, (ii) the microstructure of listvenite, testing the presence of a
ductile shear zone during carbonation, (iii) the different generations of fault, cataclasite and
fracture and vein structures modifying the listvenite microstructure, analyzing overprinting
relationships and deformation mechanisms, (iv) microstructures in syntaxial and antitaxial
veins to distinguish reaction-induced- from tectonically and pore pressure-induced fracturing,
and finally (v) on micro- and nano-porosity and its connectivity to constrain potential fluid
pathways in the matrix.
