Pumpellyite from the oceanic crust, DSDP/ODP Hole 504B

Online Access: Get full text
doi: 10.1180/002646199548998
Author(s): Ishizuka, H.
Author Affiliation(s): Primary:
Kochi University, Department of Geology, Kochi, Japan
Volume Title: Mineralogical Magazine
Source: Mineralogical Magazine, 63(6), p.891-900. Publisher: Mineralogical Society, London, United Kingdom. ISSN: 0026-461X
Note: In English. 25 refs.; illus., incl. 2 tables, sketch map
Summary: Pumpellyite has been found in doleritic basalt of a sheeted dyke complex drilled from 2072.1 m below sea floor in DSDP/ODP Hole 504B, south of the Costa Rica Rift, eastern Pacific. It occurs as fine-grained crystal aggregates accompanied by albite, chlorite and chalcopyrite, which partially replace a plagioclase phenocryst (An85-88) that is also associated with primary magnetite. Chemical compositions of the pumpellyite vary antithetically in relation to Fe* and Al as well as Fe* and Mg, indicating the dominant substitution of Fe3+ by Al with the minor substitution of Fe2+ by Mg. Such compositional variations overlap with those of prehnite-pumpellyite facies rocks dredged from other oceanic ridges and intra-oceanic arcs, and those of similar facies rocks from ophiolites, but are aluminous compared with those of zeolite facies metabasites in ophiolites. These observations suggest that the breakdown of the plagioclase phenocryst and magnetite in the presence of a Cu- and S-bearing fluid phase led to the formation of pumpellyite + albite + chlorite + chalcopyrite during oceanic ridge hydrothermal alteration.
Year of Publication: 1999
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 01 Mineralogy and Crystallography; Costa Rica Rift; Crust; DSDP Site 504; Deep Sea Drilling Project; East Pacific; Hydrothermal alteration; IPOD; Leg 111; Leg 137; Leg 140; Leg 148; Leg 69; Leg 70; Leg 83; Leg 92; Metasomatism; Ocean Drilling Program; Oceanic crust; Orthosilicates; Pacific Ocean; Pumpellyite; Pumpellyite group; Silicates; Sorosilicates
Coordinates: N000000 N100000 W0800000 W0850000
Record ID: 2000026819
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute.