Alpine Tonalite Outcrop

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This rock with abundant dark inclusions is typical of one of the two tonalitic end members found in the western zone of the PRB. It is hornblende- and biotite bearing with lesser amounts of clinopyroxene and/or orthopyroxene. This outcrop yielded a concordant zircon U-Pb age of 108 Ma. (from Walawender and Girty, 1991)

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