Thursday, June 15, 2006

Other Injection Structures - the fabulous Wpt 014

In fact there are a lot of injection-type structures at Pasagshak Point, but most of them are not as typical as the ones I posted yesterday. At Wpt 014 there are some which resemble the structures formed by soft sediment deformation. In these first two pictures you can see a vein of black material (2-3cm thick) which cross cuts the cataclastic fabric at a low angle. The top of the vein resembles "flame structures" with the black material (lower viscosity) ductilly intruding upwards into the cataclasite (must have been higher viscosity) similar to a mud layer forming flames into an overlying sand layer. In fact, the "flames" are also sheared (top to the left in this photograph) and some are even disconnected from the source vein.

The subtle vertical cleavage you may see cutting the black material is a steep weak pressure solution cleavage which cross-cuts all subduction related faulting.

Along the same source vein we find this large sill/dike complex. The injection of the black material upward from the source vein deformed the cataclastic fabric of the fault zone. The cataclastic fabric is defined by the alignment of sandstone clasts which are tectonically rounded and have slickenlined surfaces. In some places there are elongated boudins and stringers of sandstone and hyaloclastite also along the fabric. This injection was also shown in our paper of 2005 which you can also download now from the links at the side of this page.

Your comments please!


Blogger Francesca said...

What really impressed us here is the fluidal character of the black material, resembling magmatic textures. I would not expect a gouge acting this way, nor a sort of ultra-fine implosion breccia. this looks to me something fluid, or with ductile behavior, but I might be wrong.
Pretty interesting in also how the "dike-like" intrusion deforms hosting cataclasite.

1:20 AM  

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