Lecture 6 Feb 1 2008 Intrusive igneous rocks

Lecture 6 Feb 1 2008 Intrusive igneous rocks - As the main...

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As the main magma body cools, water originally present in low concentrations becomes concentrated in the molten rock because it does not get incorporated into most minerals that crystallize. This late-stage watery magma is also rich in silica and in other weird elements that do not fit into ordinary aluminosilicate minerals. Often, this water-rich magma moves off into fractures above or around the magma chamber and when it finally crystallizes it forms a pegmatite .
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Beryl crystals in pegmatite. Amelia albite (Na-plagioclase), Amelia County, Virginia.
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Beryl (Be) Tourmaline (B) Spodumene (Li) Topaz (F) Unusually small rare elements go into late- stage crystallization products.
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Unusually large rare elements go into late-stage crystallization products. Uraninite (U) Scheelite (W)
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Who thinks up these mineral names anyway?? Names are given on the basis of - some physical or chemical property of the mineral - albite is white (from Latin) - rhodonite is pink (from Greek) - chromite has chromium in it
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Lecture 6 Feb 1 2008 Intrusive igneous rocks - As the main...

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