Petrographic and chemical characteristics of abyssal tholeiites at DSDP Leg 63 Holes

DOI

Tholeiitic basalts were obtained from basaltic basement ranging in age from 6 to 17 m.y. on IPOD/DSDP Leg 63. The main rock types encountered at all sites but 473 are basaltic pillow lavas. Although many of these pillow basalts are highly or moderately altered, fresh glass is usually present. At Site 473, we recovered coarse-grained, massive basalts; no clearly defined pillowed forms were observed. Phenocrysts or microphenocrysts present in the Leg 63 basalts are Plagioclase and clinopyroxene at Site 469; olivine, Plagioclase, and spinel at Site 470; and olivine, Plagioclase, and clinopyroxene at Sites 472 and 473. Olivines of the basalts from Holes 470A and 472 (Fo85-88) are generally more magnesian than those of the Hole 473 basalts (Fo77-81). Also, plagioclases of Holes 470A and 472 basalts (An70-85) are generally more calcic than those of Holes 469 and 473 basalts (An66-72). Geochemical study of the Leg 63 basalts indicates that in all cases they are large-ion-lithophile (LIL) element depleted tholeiites like typical abyssal tholeiites. In particular, they are very similar in composition to those described from the eastern Pacific, although the degree of iron enrichment found in the Leg 63 basalts is not as extensive as in basalts from the Galapagos spreading center. Hence, the geochemical evidence of the Leg 63 basalts is compatible with their formation at a spreading center. Compositional variations in Leg 63 basalts from any single drill hole is small. Major and trace element data indicate that the samples from Holes 469 and 473 are more fractionated in chemical composition than are the samples from Holes 470A and 472; this compositional variation may be largely ascribed to differences in the extent of shallow-level fractional crystallization of similar parental magma. The Hole 472 samples, however, show a LIL element character distinct from the other Leg 63 samples.

Supplement to: Shibata, Tsugio; DeLong, Stephen E; Lyman, Peter (1981): Petrographic and chemical characteristics of abyssal tholeiites from Deep Sea Drilling Project Leg 63 off Baja California. In: Yeats, RS; Haq, BU; et al. (eds.), Initial Reports of the Deep Sea Drilling Project (U.S. Govt. Printing Office), 63, 687-699

Identifier
DOI https://doi.org/10.1594/PANGAEA.819290
Related Identifier https://doi.org/10.2973/dsdp.proc.63.125.1981
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.819290
Provenance
Creator Shibata, Tsugio; DeLong, Stephen E; Lyman, Peter
Publisher PANGAEA
Publication Year 1981
Rights Creative Commons Attribution 3.0 Unported; https://creativecommons.org/licenses/by/3.0/
OpenAccess true
Representation
Resource Type Supplementary Publication Series of Datasets; Collection
Format application/zip
Size 8 datasets
Discipline Earth System Research
Spatial Coverage (-120.548W, 20.965S, -107.064E, 32.617N); North Pacific/ESCARPMENT; North Pacific/ABYSSAL FLOOR; North Pacific/PLATEAU; North Pacific/Gulf of California/CONT RISE
Temporal Coverage Begin 1978-10-27T00:00:00Z
Temporal Coverage End 1978-11-22T00:00:00Z