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Book Chapter

Petrology and geochemistry of eastern Pacific spreading centers

By
Rodey Batiza
Rodey Batiza
Hawaii Institute of Geophysics, University of Hawaii, Honolulu, Hawaii 96822
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Published:
January 01, 1989

The petrologic and geochemical characteristics of the East Pacific Rise and other actively spreading ridges provide important direct evidence concerning the composition of the Earth’s upper mantle because mid-ocean ridge basalts are thought to represent partial melts of upper mantle material rising beneath mid-ocean ridges. Since the characteristics of the upper mantle can be used to constrain models for the accretion and differentiation history of the Earth as well as the nature of physical and chemical processes taking place in the mantle, MORB (midocean ridge basalt) and other oceanic basalts play an important role in constraining models of mantle convection, continent formation, and related questions.

This chapter describes the petrologic and geochemical characteristics of lavas from the axes of East Pacific spreading ridges, primarily the East Pacific Rise (EPR) between the Tamayo Fracture Zone and the equator, and the Galapagos spreading center (GSC). The Juan de Fuca Ridge and the Gulf of California are considered in other chapters of this book (Johnson and Holmes, this volume; Lonsdale, this volume).

Figure 1 shows locations of the principal sampling areas along the EPR and the GSC and Figure 2 shows the distribution of dredge hauls in the eastern Pacific. Until very recently, the spreading centers of the eastern Pacific were very poorly sampled compared to the Mid-Atlantic Ridge. The Juan de Fuca and Gorda Ridges are reasonably well sampled (Melson and others, 1976; Delaney and others, 1982; Davis and Clague, 1987; Dixon and Clague, 1986). The Gulf of California is mostly covered with sediment, but basalt has been recovered by drilling (Saunders and others, 1982; Lonsdale, this volume). The data base for the GSC includes analyses from Melson and others (1976), Schilling and others (1976), Fornari and others (1983), Christie and Sinton (1981), White and others (1987), and references therein. For the EPR, detailed studies have been conducted at 23°N near the Tamayo fracture zone (Bender and others, 1984), 21°N (Moore and others, 1977; Juteau and others, 1980; Hawkins and Melchior, 1980), 12° to 13°N (Hekinian and others, 1983; Batiza and Vanko, 1984; Macdougall and Lugmair, 1986), and 8° to 9°N (Batiza and others, 1977; Batiza and Johnson, 1980; Natland and Melson, 1980; Morel and Hekinian, 1980). Many of these papers include analyses of volcanic rocks from the EPR axis, as do Engel and Engel (1964), Engel and others (1965), Bonatti (1967), Kay and others (1970), and Sun and others (1979). Recent expeditions have greatly increased the number of dredge hauls of the EPR axis at 10° to 12°N (Thompson and others, 1985), 5°30′ to 14°30′N (Langmuir and others, 1986) and overlapping spreading centers (OSCs) at 12°54′N, 9°03′N, 5°30′N, and 3°57′N (Natland and others, 1986), but these studies are not yet fully complete.

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DNAG, Geology of North America

The Eastern Pacific Ocean and Hawaii

E. L. Winterer
E. L. Winterer
Scripps Institution of Oceanography La Jolla, California 92093
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Donald M. Hussong
Donald M. Hussong
University of Hawaii Department of Geology and Geophysics Honolulu, Hawaii 96822
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Robert W. Decker
Robert W. Decker
4087 Silver Bar Road Mariposa, California 95338
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Geological Society of America
Volume
N
ISBN electronic:
9780813754659
Publication date:
January 01, 1989

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