The stockwork microbreccia found in the Dabie and Helan Mountains bears no relation to either meteorite impact and cryptoexplosion, or fault displacement. It is con- trolled by tensional or transtensional fracture network in relatively hard felsic crystalline rocks, appearing as breccia with dark cryptocrystalline matrix. The kilometer-scale dis- tribution and complicated relation to fracture system of the stockwork microbreccias, randomly distributed autochtho- nous fragments of host rock, ultracataclasis without notable displacement in the cryptocrystalline matrix, and a probable solid-state amorphization deformation mechanism all suggest that large-scale, high-energy and rapid brittle fracturing event might have occurred in the rocks at relatively deep crustal level in the areas.
