Abstract

The mesothermal gold-quartz veins at Grass Valley, California, contain many inclusions of country rock in quartz, some of which are broken and the segments separated. When the quartz is removed from the inclusions they can be reassembled into larger, original units of country rock. Adjacent walls of the veins have not shared in the movements that dislocated the inclusions and no evidence of faulting is found in the massive quartz matrix, which exhibits features of original texture. Dislocation of the fragments is attributed to thrust from an injected, vein-forming solution, which forcibly entered rock fractures and spread apart their walls.

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