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Definition of phyllic alteration

Hydrothermal alteration typically resulting from removal of sodium, calcium, and magnesium from calc-alkalic igneous rocks, with pervasive hydrous replacement of most silicates, (eg. K-feldspar to sericite), usually destroying the original rock texture and it may form a schistose texture. It is a common style of alteration in porphyry base-metal systems [glossary item missing] around a central, higher temperature zone of potassic alteration [glossary item missing].
See Also: propylitization


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