BOWENS REACTION SERIES     I. BOWENS REACTION SERIES (Norman Bowen--1915) The end product, the actual rock formed, is never the same composition as the original melt Mineral stability field--the pressure and temperature range over which a mineral is stable A. Two types of reactions 1. Discontinuous reaction--early formed minerals react discontinuously with the melt to form new minerals with different structures and chemistries 2. Continuous reaction--early formed minerals react continuously with the melt to form new minerals with the same structure, but different chemistries II. BOWENS REACTION SERIES Fe, Mg, Si, O = dunite Fe, Mg, Si, O, Ca, Al = gabbro = dunite Fe, Mg, Si, O, Ca, Al, K, Na = all the above 5 - 10% of the melt would form granite A. Fractional (partial) crystallization--process by which early-formed crystals are physically separated from the melt B. Crystal settling--early formed crystals sink e.g. olivine density ~ 3.27-4.37 C. Crystal floating--early formed crystals float e.g. anorthite density ~ 2.62 - 2.76 III. TYPES OF IGNEOUS ROCK BODIES A. Sills--concordant with layering of country rock, tabular B. Dikes--discordant, tabular C. Lopoliths--spoon shaped, concave up D. Laccolith--spoon shaped, concave down E. Stock--small < 100 Km2 intrusion e.g. Stone Mtn., GA F. Batholith-- > 100 Km2 e.g. Sierra Nevada batholith