Friday, February 28, 2020

Bowen's Reaction Series


In addition to the "3 Utilizations" of the Bowen Reaction Series listed and described in the videos of the three previous days, understanding the Bowen Reaction Series helps you understand why - in igneous rocks - certain minerals "associate" with others, while other minerals don't usually "associate" with each other.

For instance, because of the higher temperatures associated with Ultramafic and Mafic rocks, Quartz and Muscovite are not usually found with those rock types, as they are still molten while the ultramafic/mafic minerals are crystallizing and "squeezing out" the remaining liquids.  [Or if the mafics were erupted in a setting with a paucity of "free quartz", e.g., the Mid-Atlantic Ridge or the Hawaiian Hot Spot" or where the crust is thin, allowing the mafic magmas to "quickly" reach the surface, e.g., a Continental Rift Zone.]

Likewise, it is not "normal" for there to be Olivine in a Granite (or similar Felsic rock).  The Geology Department chair at my undergraduate college had a sizeable chunk of Olivine Granite that he had collected from the Big Bend region of Texas.  Most likely, the semi-molten granite had "plucked" the olivine granites from an adjacent peridotite, preserving them as "micro-xenoliths" or xenocrysts.

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