Fluorian garnets from the host rocks of the Skaergaard intrusion: implications for metamorphic fluid composition
Zoned, silica-deficient, calcic garnets containing up to 5 mol% F substitution for O formed during contact metamorphism of basalts by the Skaergaard intrusion in East Greenland. Fluorian calcic garnets occur as a retrograde alteration of prograde wollastonite and clinopyroxene that fills vesicles and vugs in lavas 30-70 m from the intrusion. The F content of garnet is extremely sensitive to minor changes in fluid composition. The calculations show that a decrease in pH or an increase in log aF- of 0.3 at constant pressure and temperature will decrease the F concentration in garnet from 5 to 0 mol%. The results of this study show that fluorian hydrous grandites provide a mineralogical record of the activities of F species in coexisting metamorphic and hydrothermal fluids. -from Authors
Citation Information
Publication Year | 1990 |
---|---|
Title | Fluorian garnets from the host rocks of the Skaergaard intrusion: implications for metamorphic fluid composition |
Authors | C. E. Manning, D.K. Bird |
Publication Type | Article |
Publication Subtype | Journal Article |
Series Title | American Mineralogist |
Index ID | 70015926 |
Record Source | USGS Publications Warehouse |