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The mafic high-pressure rocks of the Tianshan (NW China) display an interconnected network of eclogite-facies veins derived by prograde blueschist dehydration. They provide insight into fluid–rock interaction and element load during long-distance fluid flow occurring due to the major fluid release of subducting oceanic crust. This case study focuses on an eclogite-facies transport vein, its blueschist...
The tectonic style and viability of modern plate tectonics in the early Earth is still debated. Field observations and theoretical arguments both in favor and against the uniformitarian view of plate tectonics back until the Archean continue to accumulate. Here, we present the first numerical modeling results that address for a hotter Earth the viability of subduction, one of the main requirements...
Eclogites and eclogites-facies rocks in mountain belts provide evidence that material in subduction zones material can return from depths of more than 100 km to the surface in the early stages of orogenic processes. Their relationship with lower metamorphic grade rock of i.e. blueschist and greenschist facies can provide information on the late stages of orogenic processes, but are often matter of...
Pressure variation due to deformation is an intrinsic property of fracture and flow in all materials, including rocks under geological conditions. Strong gradients occur at rheological boundaries (due to inclusions, layers, channels, shear zones, boudin necks, etc) and these gradients are instrumental in driving local pore fluid and/or melt flow during deformation. The pressure distribution in deforming...
Dispersed blocks of various types of metamorphic rocks in serpentinite mélanges of the northern Dominican Republic (Hispaniola) provide fossil evidence for the dynamics of the subduction zone channel in the intra-oceanic Caribbean subduction zone system between 120 and 55 Ma. Comprehensive petrological and geochronological data on three exemplary samples of eclogite and blueschist are presented that...
A number of models of continental collision already exist, but the role of foregoing oceanic plate subduction or variable coupling between plates still remains to be explored. In addition, heat generation by radioactive decay may be quite variable. For example, our geochemical data from low-to-high grade metamorphic rocks of the Lesser and Higher Himalayan sequences reveal measured heat production...
Two-dimensional numerical modeling of early continental collision associated with subduction of the lithospheric mantle shows that the formation and exhumation of coesite- and diamond-bearing rocks metamorphosed at 700 to 900 °C in the presence of dense supercritical silicate fluids and melts may be explained by a transient “hot channel effect”. Anomalously high temperature is caused by intense viscous...
Numerical and laboratory experiments beside natural observations suggest that hydration and partial melting along the subducting slab can trigger Rayleigh–Taylor instabilities that evolve into partially molten diapiric structures (“cold plumes”) that rise through the hot asthenospheric wedge. Mixed cold plumes composed of tectonic melanges derived from subduction channels can transport the fertile...
There was much debate recently on the mechanisms of continental convergence and related pressure–temperature (P–T) conditions, both in modeling and petrologic community. Depending on the mechanisms of convergence (subduction, collision, folding or RT instability) one can argue about the possibility of large-scale deviations of pressure and temperature in the accretion prism and below it, from “reference”...
We employ high-resolution 2D thermomechanical modelling with complex elasto-visco-plastic rheology to analyse stresses in subducting and overriding plates. The model contains a dynamic subduction channel, defined as a few km thick zone of specific (weak) visco-plastic rheology between the slab and the overriding plate. Our high-resolution model corresponds to the zoom-in of the large-scale thermomechanical...
Mineral inclusions in garnets are usually considered to be relict testimony of earlier metamorphic history, and thus play a key role in deciphering the pressure–temperature evolution of rocks. An experimental study on eclogitic garnets with different mineral inclusions (including hydrous phases and carbonates) from several subduction-related complexes reveals considerable modification of garnet interiors...
Many Precambrian granulite facies terrains experienced two regional high-grade events, with the first one having occurred in the Neoarchaean and the subsequent overprints in the Palaeoproterozoic. Since structural and geochronological studies often are unable to discriminate between these two tectono-metamorphic events (D/M), we used the configuration of a composite P–T path as a signature of two...
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