Bear Mountain Igneous Complex, Klamath Mountains, California: an Ultrabasic to Silicic Cale-Alkaline Suite

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Abstract
The Bear Mountain igneous complex, Klamath Mountains, California, can be divided into distinct lithologic suites (order according to apparent relative age): (1) satellitic masses of clinopyroxene-rich ultramafic and gabbroic rocks with subordinate dunite and hornblende-plagioclase pegmatoid; (2) two-pyroxene-biotite diorite and monzodiorite; (3) heterogeneous hornblende-rich rocks varying from gabbro to diorite; (4) leucocratic rocks, chiefly consisting of biotite tonalite and granodiorite; and (5) late dikes (mafic to felsic). Elongate masses of unit (1) flank a composite pluton consisting of units (2–4), while the late dikes (unit 5) intrude the adjacent country rocks. The rocks of the complex invaded an ophiolite allochthon during the Late Jurassic Nevadan orogeny, and well-defined contact aureoles surround the complex. Lower greenschist facies rocks, chiefly metabasalt, impure siliceous metasedimentary rocks, and serpentinized peridotite, have been dynamothermally metamorphosed to mineral assemblages indicative of hornblende-hornfels facies and locally pyroxene-hornfels facies. The emplacement of the igneous complex was chiefly by forcible shouldering aside, although local tectonic features such as faults in the ophiolite allochthon were instrumental in the emplacement history.

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