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Ultra-fine mineral aggregates in K-metasomatic rocks of the Hougou area, northwestern Hebei Province, China contain peculiar and distinct intergranular and intragranular geometries, compositions, and textures. These features indicate solidification of expanded and enclosed relict fluids within tensile microfractures. Two basic morphologic types of textures are present: saw-toothed and wheel-shaped, and several composite patterns also are present, such as X-shaped, grid, and network. The appearance of these features indicate explosion from an instantaneous force. These microscopic explosive microfractures are directly related to the enclosed relict fluids. Theoretical estimates show that volume expansion induced by mineral replacements during K-metasomatism may have caused the K-metasomatic fluids to be confined and strongly compressed in order to build up powerful forces that produced the ultra-fine mineral aggregates and explosive microfractures. The thick-walled texture of K-metasomatic rocks confined fractures that propagated only in the replaced rocks with the lowest strength. Both pumping pressures and the propagation of the K-metasomatism were self-governed and controlled by introduced chemical elements, specially K+. |
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