Zeolite to prehnite-pumpellyite facies metamorphism in the Toa Baja drill hole, Puerto Rico
- Stanford Univ., CA (United States)
Secondary mineral assemblages in Eocene volcanic and volcaniclastic rocks of the Toa Baja drill hole progressively change as a function of depth. Four metamorphic zones are delineated with increasing depth: Ca-clinoptilolite{yields}heulandite{yields}laumontite{yields}prehnite-pumpellyite zone. The deepest belongs to the prehnite-pumpellyite facies, whereas the three zones at shallower depths (< 2,350 m) belong to the zeolite facies. Ca-clinoptilolite and heulandite exhibit continuous solid solution with varying Si/Al (2.9-5.2) and Ca/(Ca + Na + K) ratios (0.45-0.89). Pumpellyites are characterized by extensive variation in the Fe/(Fe + Al + Mg) ratio (0.29-0.74) and extreme Fe-enrichment in the laumontite zone. Temperatures estimated from mineral assemblages and facies transitions suggest that the North Coast Basin, Puerto Rico, has been subject to a metamorphic field gradient of {approximately}50 to 70C/km.
- OSTI ID:
- 5597807
- Journal Information:
- Geophysical Research Letters (American Geophysical Union); (United States), Vol. 18:3; ISSN 0094-8276
- Country of Publication:
- United States
- Language:
- English
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