Title: Strontium and neodymium isotope geochemistry of igneous rocks from the North East Pacific and Gulf of California
Abstract: Thirty-three measurements of the 87Sr/86Sr ratios on dredged and drilled whole-rock samples of basalts, diabases and glasses from the NE Pacific and Gulf of California vary from 0.7024 to 0.7057. The 143Nd/144Nd ratios measured on twelve selected whole-rock samples range from ~ 0.5129 to ~ 0.5133. The 87Sr/86Sr ratios measured on thirty acid-leached samples are also widely distributed (range 0.7023–0.7058) but most of the values fall below 0.7030. The 87Sr/86Sr ratios generally decrease on leaching, i.e. Δ87/86Sr (an alteration parameter, defined later in the text) shows generally positive values. Weight loss on leaching as well as Sr content of the leached samples are also measured and show that in the altered samples, most of the Sr resides in the acid-leachable fraction. The concentration of Sr in the leached samples is positively correlated with that in the whole-rock samples. The study of the core-margin-glass or fresh glass- palagonitized glass splits shows that both the Sr content and the 87Sr/86Sr ratio may suffer significant changes upon low-temperature seawater alteration. A plot of the whole-rock 143Nd/144Nd ratio vs. the leached sample 87Sr/86Sr ratio shows that most of the samples analyzed plot within or close to the MORB field. The results from an altered diabase and a considerably less altered glass from D.S.D.P. Site 469 in the NE Pacific and from an altered margin and less altered glass splits of a basalt sample dredged from the mouth of the Gulf of California show that the 143Nd/144Nd ratio may also suffer a very slight but significant decrease upon seawater alteration.
Publication Year: 1983
Publication Date: 1983-01-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 14
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