Fluid-rock interaction processes during subduction and exhumation of oceanic crust : Constraints from jadeitites in serpentinites, eclogite veins in blueschists and tectonic breccias formed during uplift
The findings presented in this thesis will help to understand the complicity of fluid-rock interaction processes during subduction and exhumation of oceanic crust. The jadeitites studied were formed by precipitation from a fluid derived from serpentinite and by metasomatic replacement of metatrondhjemites. The eclogite veins and veinlets of the Bantimala Complex show that two different processes lead to eclogitisation. During infiltration of an external fluid, which show characteristics of a mixed source (mantle and crustal rocks). Resulting in an eclogite vein, which is highly enriched in LILE, REE and Cr. The other eclogitisation process took place during dehydration of the blueschist host rock and the formation of a drainage system. The element enrichment along this network of eclogite veinlets is moderate. The exhumation process of the (ultra)high-pressure metamorphic rocks of the Banitmala Complex proposed in this thesis, is in contrast to models made by former workers (Wakita et al., 1996; Parkinson et al., 1998; Miyazaki et al., 1996). The deduced exhumation process was driven by repeated intra-slab shearing, hydraulic fracturing and the upward directed motion of a subducted continental fragment.
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