Bowens Reaction series
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. Olivine is the first mineral to be formed
and quartz is the last.
-Granite is visibly granular, igneous rock generally ranging in color
from pink to light or dark grey, and consisting mostly of quartz
and feldspars, accompanied by one or more dark minerals.
-Gabbro is dark grey to black in color, medium to coarse grained. It is mostly made up of amphibole,
pyroxene, biotite mica, plagioclase and olivine. It is a dense, mafic intrusive rock. It generally occurs as
batholiths and laccoliths and is often found along mid-ocean ridges or in ancient mountains composed
of compressed and uplifted oceanic crust. Gabbro is the plutonic equivalent of basalt.
-Rhyolite is a felsic extrusive rock. Due to the high silica content, rhyolite lava is very viscous. It flows
slowly, and tends to pile up and form lava domes. If rhyolite magma is gas rich it can erupt explosively,
forming a frothy solidified magma called pumice (a very lightweight, light-colored, vesicular form of
rhyolite) along with ash deposits. In certain situations extremely porous rhyolite lava flows may develop.
The extreme porosity of such flows allows degassing and subsequent collapse of the flow,
forming obsidian (dark colored volcanic glass). Rhyolite is the volcanic equivalent of granite.
-Pumice is a light-colored, extremely porous igneous rock that forms during explosive volcanic eruptions.
It is a used aggregate in lightweight concrete, as landscaping aggregate, and as an abrasive in a variety of
industrial and consumer products. Many specimens have a high enough porosity that they can float on
water until they slowly become waterlogged
-Obsidian is an igneous rock that forms when molten rock material cools so rapidly that atoms are
unable to arrange themselves into a crystalline structure. It is an amorphous material known as a
mineraloid. The result is a volcanic glass with a smooth uniform texture that breaks with a conchoidal
fracture. Extrusive rock.
-Diorite is an intrusive rock intermediate in composition between gabbro and granite. It is produced in
volcanic arcs, and in mountain building where it can occur in large volumes as batholiths in the roots of
mountains (e.g. Scotland, Norway). Because it is commonly speckled black and white, it is often referred
to as "salt and pepper" rock. Diorite is the plutonic equivalent of andesite.
-Andesite is an extrusive rock intermediate in composition between rhyolite and basalt. Andesite lava is
of moderate viscosity and forms thick lava flows and domes. The word andesite is derived from the
Andes Mountains in South America, where andesite is common. Andesite is the volcanic equivalent
of diorite.