Why
Does Chrysotile Only Form from the Metamorphism of Peridotite ? |
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The
chemical building blocks of serpentine are:
3MgO
. 2SiO2 · 2H2O. |
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The
ingredients for serpentine are 3 magnesium atoms for every 2 silicon
atoms. For
Serpentine... Mg : Si = 3 : 2 |
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However,
in the Earth's CRUST
silicon is far more abundant than magnesium.
For
the Crust... Mg : Si = 1 : 19 |
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Rocks are composed of
minerals, and the minerals are composed of the atoms that were present
when the rock formed. Thus serpentines can only grow in rocks that have abundant magnesium,
along with silica and a source of water.
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Although
magnesium is scarce in the crust, it is an element that is abundant in the
MANTLE
, which is
composed of the water-free rock called peridotite. Magnesium-rich
silicate rocks are rare in the Earth's crust.
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Chrysotile and other
serpentine minerals only grow in abundance in peridotites because they are
the only silicate rocks with enough magnesium.
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The only problem is
how do you get these dry peridotites up and out of the mantle and add the
water...
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