What is Bowen's Reaction Series? #Bowen's reaction series is | Geology of the world and the Environment
What is Bowen's Reaction Series?
#Bowen's reaction series is the work of the #petrologist Norman L. Bowen, who summarized, based on experiments and observations of natural rocks, the sequence of #crystallization of common silicate minerals from typical basaltic #magma undergoing fractional crystallization (i.e. crystallization wherein early-formed crystals are removed from the magma by crystal settling, leaving behind a liquid of slightly different composition). Bowen's reaction series is able to explain why certain types of #minerals tend to be found together while others are almost never associated with one another.
Bowen determined that specific minerals form at specific temperatures as a #magma cools. At the higher temperatures associated with mafic and #intermediate magmas, the general progression can be separated into two branches. The continuous branch describes the evolution of the #plagioclase #feldspars as they evolve from being #calcium-rich to more #sodium-rich. The discontinuous branch describes the formation of the #mafic minerals #olivine, #pyroxene, #amphibole, and #biotite mica.
The weird thing that Bowen found concerned the discontinuous branch. At a certain temperature a magma might produce olivine, but if that same magma was allowed to cool further, the olivine would "react" with the residual magma, and change to the next mineral on the series (in this case pyroxene). Continue cooling and the pyroxene would convert to amphibole, and then to #biotite. Mighty strange #stuff, but if you consider that most #silicate minerals are made from slightly different proportions of the same 8 elements, all we're really doing here is adjusting the internal crystalline lattice to achieve stability at different temperatures. Really no big deal.
At lower temperatures, the branches merge and we obtain the minerals common to the #felsic rocks - #orthoclase feldspar, #muscovite #mica, and #quartz (the banana slug of the mineral world).
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