Feldspar thermometry in pegmatites: truth and consequences

Temperatures of crystallization for all or portions of three thin granitic pegmatite dikes in southern California are derived from feldspar solvus thermometry, with supporting data from the K/Cs ratio of K-feldspar, the extent of Al/Si order in K-feldspar, and the texture of granophyre found along the margins of dikes. Although K-feldspars become perthitic and increasingly ordered toward the centers of dikes, their ratio of K/Cs falls from...