The intrusive breccias consist of angular to rounded fragments of the pre-Cretaceous rock formations in a matrix of quartz-rich rock flour. They form smooth-walled dikes, sills, pipes, and irregular masses cutting the pre-Cretaceous formations. They followed intrusion of porphyries and the silica-pyrite stage of hydrothermal mineralization. Low-grade copper mineralization accompanied the breccia intrusion, and this was followed by deposition of massive sulfides of copper, lead, and zinc. Breccias and all stages of hydrothermal solutions followed the same tectonic channelways. The breccias are regarded as hydrothermal in origin, and the fluid phase the source of the low-grade copper mineralization.

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