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Projects

Austrian Science Fund (FWF) P 27982-N29: Fault- and fluid-systems subsequent to subduction initiation in the outer Izu-Bonin-Mariana fore arc and within supra subduction zone ophiolites
International Ocean Discovery Program Expedition 342, Izubonin Mariana Forearc (start November 1st 2015, end: October 31st 2018)

During International Ocean Discovery Program Expedition 352, a section through the volcanic stratigraphy of the outer fore-arc of the Izu-Bonin-Mariana system was drilled in order to trace the processes of magmatism, tectonics, and crustal accretion associated with subduction initiation. This study in turn has implications for understanding the origin of the many ophiolites that are now believed to form in this setting, and the expedition provides a good opportunity to test this supra-subduction zone ophiolite model. Previous studies have established a stratigraphy in which peridotites, gabbros, and sheeted dikes are overlain by “fore-arc basalt” (FAB) and then in turn by boninites. The expedition provided (1) a high-fidelity record of magmatic evolution during subduction initiation; (2) a test of the hypothesis that FAB tholeiites lie beneath boninites; (3) a record of the chemical gradients within these units and across  their transitions; (4) information on how mantle melting processes evolve during subduction initiation from early decompression melting of fertile asthenosphere to late flux melting of depleted mantle, providing key empirical constraints for realistic subduction initiation geodynamic models; and (5) a test of the hypothesis that fore-arc lithosphere created during subduction initiation is the birthplace of supra-subduction zone ophiolites.

Two important hypotheses to be tested by drilling are (1) that subduction initiation produces a consistent volcanic stratigraphy; and (2) that this sequence was originally stacked vertically before erosion and therefore represents an in situ analog for sections through many supra-subduction zone ophiolites.

 

Austrian Science Fund (FWF) P 26634-N29: Deformation mechanisms within an erosive plate margin: The Cocos-Caribbean plate boundary; Integrated Ocean Drilling Program
Expedition  344, Costa Rica Seismogenesis Project, Program A Stage 2 (CRISP-A2)) (start October 1st 2014, end: September 30st 2017)

The Costa Rica Seismogenesis Project (CRISP) was designed to elucidate the processes that control nucleation and seismic rupture of large earthquakes at erosional subduction zones. CRISP is located at the only known seismogenic zone at an erosional margin within reach of scientific drilling. With a low sediment supply, fast convergence rate, abundant seismicity, subduction erosion, and a change in subducting plate relief along strike, CRISP offers excellent opportunities to better understand earthquake nucleation, rupture propagation, and the mechanisms of deformation along the updip sections of a convergent plate margin.

This project aims to test various hypotheses related to the transition from aseismic to seismic behaviour along erosive plate boundaries, that are mainly related to the activity of fluids within the subduction zone: 1) The architecture of the subduction megathrust evolves down dip and the transition from stable to unstable slip corresponds to the transition from a fluid-rich, broad fault zone to a thinner and drier fault. Geological, physical and structural characteristics of material in the subduction channel influence fault mechanics and the transition from stable to unstable slip. 2) Fluid advection affects the localization of faulting and locking of erosional plate boundaries. Fluid chemistry, P-T conditions and residence time affect the state of eroded material through upper-plate basement alteration, diagenesis and low-grade metamorphism. Variations in material/fluid properties and distribution affect fault propagation.

This study will focus on constraining the boundary conditions of lithology and fluid flow that control the deformation mechanisms in the seismogenic and aseismic zone along the IODP Expedition 344 drilling transect.

Poster: Lower Plate deformation structures along the Costa Rica erosive plate boundary - results from IODP Expedition 344 (CRISP 344)
Poster: Microstructures and fluid inclusion petrography and microthermometry of hydrothermal veins of Site U1414, IODP Expedition 344 (CRISP 2)

Austrian Science Fund (FWF) P17697-N10 („Structural evolution of faults and fault rocks“) (start January 1st 2005, end: December 31st 2008)
Faults are of major interest both in structural geology, tectonics, and in engineering geology and rock mechanics. The interest in faults and fault zones is practical as well as scientific and aestethic because faults and associated structures form the major discontinuities in the Earth's upper crust and are largely responsible for the design and shape of the great mountain belts.

The formation of faults dramatically changes the characteristics of an orogen and of rock mass at all scales. At the scale of the orogen and at outcrop-scale, associated structures (shear and extensional fractures) result in disintegration of the rock mass and enhanced accessibility to several weathering processes; at smaller scales, it results in structural, chemical and mechanical changes (e.g., shear resistence).

The main intention of this project is the the reconstruction of the evolution of fault rocks during continuous deformation within a brittle shear zone, the chemical alterations of both the host and the fault rocks, and the relationship between confining faults and structures in the internal parts of an uplifting massif. For a case study, we have chosen the Lavanttal Fault at the western margin of the Koralm Complex. This area has been selected because of our wide knowledge of this part of the Eastern Alps due to own field studies, and because the Koralm Tunnel with a length of 32.8 km is planned to be built under Koralm Massif between Deutschlandsberg and St. Andrä south of Wolfsberg. Especially a certain number of deep core drillings, partly reaching depths of up to 1200 m, has extended the access to geological and geotechnical samples to a third dimension. The acquisition of this material shall facilitate the elaboration of a model providing a detailed reconstruction of the structural inventory and its influence on rock mass behaviour. The Koralm Massif is bordered by major confining faults along its western margin (the Lavanttal Fault system), and along its eastern margin. Thus, the Koralm Massif exposes a well situated testing area providing the elaboration of the relationships between faulting along the margins of the Koralm Complex, brittle structures in the internal parts and morphological processes, as well as the investigation of the structural evolution of a major fault zone (the Lavanttal Fault) and related fault rocks.

Gouge and cataclasite are a common product of near-surface faulting. One aim of this study is to identify and explore the consequences of the processes that may occur in clay gouge based on preliminary mineralogic, chemical and textural observations made in natural fault exposures.

We plan to discuss gouge that is dominated by clays. Whereas it is generally assumed that gouge is a result of brittle deformation processes, we will focus on the role of clays in extensive mineral reactions and associated microfabric changes. In spite of their common occurrence and likely importance for fault dynamics, our understanding of the important processes in natural clay gouge is limited up to now. However, clay mineralogy plays a more important role in the development of zones than abundance of clay-size particles, while both clay mineralogy and relative proportions of each particle size fraction control the response of particles to shear deformation. Clays participate in extensive mineral reactions and microfabric changes during faulting. The consequences of these changes are manifested in geochemical, geochronologic and microfabric characteristics of clay gouge.

On the basis of microstructural studies we plan to establish the deformation conditions within major cataclastic shear zones with a comprehensive study using structural, geochemical, geochronological and mechanical methods.

Austrian Science Fund (FWF) P9918-GEO („Collisional Orogens“).
Austrian Science Fund (FWF) P-12179 GEO ("X-ray texture analyses of naturally deformed polymineralic rocks")
Erwin-Schrödinger-Research Fellowship Austrian Science Fund (FWF) (J-1986, J-2155 GEO)
("Structural and textural studies of Alpine eclogites as a contribution to understanding the exhumation of high-pressure rocks").

 

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