Formation and destruction of graphitic material in fault zones: Implications for fault strength and the carbon cycle

Our work will test these research questions in extrusion-related graphitic faults in the Eastern Alps such as the SEMP and Periadriatic faults and graphitic faults along subvertical limestone-to-evaporite contacts of Eastern Alps. The results will potentially permit us to meaningfully: (1) recognize faults with graphitic lubricants during faulting and, therefore, allow assess crustal strength over various temporal and spatial scales, (2) assess how carbon-bearing material is moving through the fault zone hence recording the complex structural history, and (3) how carbon represents a monitor of fluid transport through fault zones. The new data will allow assessment of carbon transfer between depth and surface aims to contribute to the knowledge of the global carbon cycle. The results will also have important implications for fault mechanics, engineering geology, nuclear waste repositories and assessment of seismic hazard. The proposed work will include: (1) characterization of microfabrics (by microscopy, scanning electron microscopy-SEM) and textures (by EBSD, X-ray geometry) of graphitic material-bearing fault rocks; (2) assessment of temperature conditions of graphite-forming processes (by Raman thermometry); (3) assessment of the origin of graphitic material (by carbon stable isotopes δ13C); and (4) assessment of the fluid composition (by fluid microthermometry and stable isotopes). Interaction of graphitic material with polyhalite on evaporite faults and sericite in other faults could potentially allow 40Ar/39Ar dating of graphitic material formation. The project intends to study the formation and destruction of graphitic material in fault rocks of exhumed fault zones. Because of the low strength, the presence of lubricating graphitic material along fault zones has important implications for understanding tectonic movements in various crustal levels. Fault zones are permeable for ascending and descending fluids and represent, therefore, effective pathways of fluids between deep lithospheric levels and Earth´s surface, and this plumbing system is part of the carbon exchange system of the global carbon cycle. The project aims to fill the gaps of knowledge of this system. We propose to use graphitic material in fault zone to address key research questions, which are still enigmatic: (1) What are the important changes of structure, microfabrics and origin of graphitic material-bearing fault rocks at various crustal levels, especially across the brittle-ductile transition zone, and which cover a wide range of temperature conditions? (2) What are the formation and destruction mechanisms of graphitic material along the fault zones, particularly for the upward motion of carbon? (3) How leads the interaction of carbonic fluids with other, hydrous fluids to precipitation of graphitic material? (4) How the formation and destruction of graphitic material weaken a fault? (5) What is the contribution of carbon released from fault zones to the global carbon cycle?