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Geology 110 Syllabus

BOWENS REACTION SERIES

 

Igneous Rock Volcanoes

 

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