East Spanish Peak is the younger of the two Spanish Peaks stocks and was intruded 23.36 +/- 0.18 million years ago. The stock consists of a granite porphyry core surrounded by granodiorite porphyry. It is likely that the granite porphyry represents the upper portion of the magma chamber, the top of which eroded to expose at the summit the less-evolved larger portion of the magma chamber consisting of granodiorite porphyry.