A lithologic- tectonic framework for the metallogenic provinces of California.

The lithologic-tectonic framwork of California developed principally during Mesozoic time when various terranes of oceanic crust and island-arc crust were accreted to older sialic crust, resulting in westward growth of the continent. Emplacement of great batholithic masses of granitoid rocks cutting all these crustal types also took place during the Mesozoic period. The discrete tectonostratigraphic terranes that resulted from these events and subsequent Tertiary and Quaternary volcanic events are characterized by specific types of metallic mineral deposits or, in some terranes, by the virtual absence of deposits. Epigenetic mineralization occurred at several different times during the Mesozoic, and again during Miocene and Pliocene time. Syngenetic deposits are represented mainly by massive sulfides, chert-associated manganeses, and chromite. The massive sulfide deposits, with one exception, are restricted to island-arc terranes, and nearly all are in silicic volcanic rocks. They occur in volcanic sequences of at least five different ages ranging from Early Devonian to Late Jurassic or Early Cretaceous. -Authors