Myrmekite in the Rubidoux Mountain leucogranite - a replacement pluton

The Rubidoux Mountain leucogranite is one of many granitic plutons that occur in the eastern part of the Southern California batholith in the Peninsular Range province (Larsen, 1948; Banks, 1963). Scattered outcrops of this leucogranite in and around Riverside, California (USA), suggest that this pluton covers an area of at least 32 square kilometers (Fig. 1). Myrmekite in leucogranite on Mount Rubidoux (northwest of Riverside) has been studied in detail by electron-microprobe, scanning electron microscopy, and cathodoluminescence methods (Hopson and Ramseyer, 1990ab). These investigators reached conclusions that the myrmekite was formed by multi-replacement processes. In my studies I examined thin sections of the leucogranite in all of its scattered locations as well as thin sections of the Bonsall tonalite west of Mount Rubidoux, south and east of Quarry Hill, and on the east side of the pluton, north of Arlington Avenue.