期刊
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
卷 124, 期 8, 页码 7725-7755出版社
AMER GEOPHYSICAL UNION
DOI: 10.1029/2018JB016461
关键词
earthquakes; lower crust; fluids; metamorphism
资金
- European Union's Horizon 2020 Research and Innovation Programme under the ERC Advanced Grant [669972]
- Natural Science and Engineering Research Council (NSERC) of Canada Postgraduate Scholarship Doctoral (PGS-D) [489392]
- Feodor Lynen Fellowship from the Alexander von Humboldt Foundation
- Norwegian Research Council [272217]
- UK Natural Environment Research Council [NE/P001548/1]
- NERC [NE/P001548/1] Funding Source: UKRI
Rock rheology and density have first-order effects on the lithosphere's response to plate tectonic forces at plate boundaries. Changes in these rock properties are controlled by metamorphic transformation processes that are critically dependent on the presence of fluids. At the onset of a continental collision, the lower crust is in most cases dry and strong. However, if exposed to internally produced or externally supplied fluids, the thickened crust will react and be converted into a mechanically weaker lithology by fluid-driven metamorphic reactions. Fluid introduction is often associated with deep crustal earthquakes. Microstructural evidence, suggest that in strong highly stressed rocks, seismic slip may be initiated by brittle deformation and that wall-rock damage caused by dynamic ruptures plays a very important role in allowing fluids to enter into contact with dry and highly reactive lower crustal rocks. The resulting metamorphism produces weaker rocks which subsequently deform by viscous creep. Volumes of weak rocks contained in a highly stressed environment of strong rocks may experience significant excursions toward higher pressure without any associated burial. Slow and highly localized creep processes in a velocity strengthening regime may produce mylonitic shear zones along faults initially characterized by earthquake-generated frictional melting and wall rock damage. However, stress pulses from earthquakes in the shallower brittle regime may kick start new episodes of seismic slip at velocity weakening conditions. These processes indicate that the evolution of the lower crust during continental collisions is controlled by the transient interplay between brittle deformation, fluid-rock interactions, and creep flow.
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