Mafic Vs. Felsic - AS Geology

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  • Created by: Rock
  • Created on: 18-05-12 10:39

Mafic Vs. Felsic

Mafic

Mafic is a term that describes a silicate rock or mineral that is rich in magnesium and iron and has a lower silica content (45 – 52%). They are usually dark in colour and a relative density of greater than 3.  Common rock-forming mafic minerals include olivine, augite, hornblende, and biotite. Common mafic rocks include basalt, dolerite and gabbro.

 

 

Basalt (http://geology.com/rocks/pictures/basalt-380.jpg)

                 ^Basalt

 

Mafic/basic/pahoehoe magma has a low viscosity as it has a lower silica level. This means that eruptions are less explosive and the lava escaping has a smooth or ropy surface. The lava can also travel a long way because it is more fluid and has a high temperature (in excess of 950°C).

(http://www.geokem.com/images/pix/mauna-loa-lava-flow.JPG)

^ Mafic lava flow

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