Other rocks adjacent to the magma may be altered by contact metamorphism or metasomatism as they are affected by the heat and escaping or externally circulating hydrothermal fluids.
32.
In all cases these alteration zones are metasomatism effects in the strictest sense, resulting in addition of potassium, silica, magnesium, and depletion of sodium.
33.
When these fluids come into contact with reactive rocks, usually carbonates such as limestone or dolostone, the fluids react with them, producing alteration ( metasomatism ).
34.
Formation of minerals less common in peridotite, such as dolomite, calcite, ilmenite, rutile, and armalcolite, is also attributed to melt or fluid metasomatism.
35.
This chill zone may represent a chill zone which infers an intrusive origin for the ultramafic, or it may represent a zone of metasomatism and / or contamination.
36.
Metasomatism is currently not well favored as a mechanism for pegmatite formation and it is likely that metamorphism and magmatism are both contributors toward the conditions necessary for pegmatite genesis.
37.
Modal metasomatism may result in formation of amphibole and phlogopite, and the presence of these minerals in peridotite xenoliths has been considered strong evidence of metasomatic processes in the mantle.
38.
Hematitic jasperoid is only found within the Glengarry basin, Western Australia, although it probably represents an end-member state of a variety of alteration and metasomatism styles found elsewhere.
39.
His sampling beyond the shear zone revealed an undeformed, felsic biotite diorite whose primary plagioclase was being replaced from the inside out by K-feldspar due to K-metasomatism.
40.
His extensive studies by thin sections, cathodoluminescence, electron microprobe and scanning-electron images supported an entirely different model in which K-metasomatism of primary plagioclase produced the myrmekite.
