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The Salinian block is an elongate block of granitic basement that has presumably been displaced by large lateral movements on the San Andreas fault system. Its point of origin was most likely some place farther south within the Cordilleran batholithic belt, but its present position, immersed in the Franciscan "subduction" assemblage, is a challenge to all reconstruction models for the western margin of North America. The granitic rocks generally have abundant quartz and range from quartz diorite to quartz monzonite1. In chemical character, they straddle the boundary between calcic and calc-alkalic with a Peacock index of about 61. The most common framework metamorphic rocks are strongly deformed, thinly layered gneiss, granofels, and impure quartzite, with lesser amounts of schist and marble, which suggest a dominantly thin-bedded silty, sandy protolith. The absence of thick pure quartzite and marble units suggests that they are not correlative with the Cordilleran miogeoclinal deposits — traditionally considered to be their parent terrane. The virtual absence of metallic mineralization is also anomalous relative to other granitic terranes of the region.

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