Geology topics

E. Hegner

Publications and source records attributed to E. Hegner.

2 recordsLinked to original sources

USGS2012

Pb, Sr, and Nd isotopes in seamount basalts from the Juan de Fuca Ridge and Kodiak-Bowie seamount chain, northeast Pacific

Pb, Sr, and Nd isotopic ratios and their parent/daughter element concentrations for 28 basalts from 10 hotspot and nonhotspot seamounts are reported. Nd and Sr isotopic compositions ( 143 Nd/ 144 Nd = 0.51325–0.51304; 87 Sr/ 86 Sr = 0.70237–0.70275) plot in the envelope for Juan de Fuca-Gorda ridge basalts with tholeiitic basalts showing more depleted sources and a better negative correlation than transitional to alkalic basalts. Pb isotopic ratios in tholeiitic and alkalic basalts overlap ( 206 Pb/ 204 Pb = 18.29–19.44) and display a trend toward more radiogenic Pb in alkalic basalts. The isotopic data for hotspot and nonhotspot basalts are indistinguishable and correlate broadly with rock composition, implying that they are controlled by partial melting. The isotopic variation in the seamount basalts is about 60% (Nd-Sr) to 100% (Pb) of that in East Pacific Rise basalts and is interpreted as a lower limit for the magnitude of mantle heterogeneity in the northeast Pacific. The data indicate absence of a chemically distinct plume component in the linear seamount chains and strongly suggest an origin from mid-ocean ridge basalt-like east Pacific mantle.

Journal of Geophysical Research Solid Earth↗

USGS1986

Nd-Sr-Pb isotope constraints on the sources of west Maui volcano, Hawaii

The origin of the Emperor-Hawaiian volcanic chain is attributed to the northwesterly movement of the Pacific plate over a stationary mantle plume (hotspot)1. There has been considerable controversy as to the nature and number of sources of Hawaiian hotspot volcanism. Thus far, most geochemical models have been based on rock suites that are not representative of fully developed volcanoes. Nd and Sr isotope ratios and trace element concentrations of volcanics from Haleakala (Maui), where all three volcanic stages are developed, have been interpreted as reflecting a mixing process of two isotopically distinct sources2,3. In an attempt to test our earlier multiple-source model4, we have analysed Pb, Sr and Nd isotope ratios in volcanics from West Maui, the only other volcano with a complete volcanic record. Our results, presented here, indicate at least three isotopically distinct sources, one of which is heterogeneous with respect to Pb. Furthermore, the inferred depleted source for post-erosional volcanics has a Pb and Sr isotope composition intermediate between those of depleted and enriched mid-ocean ridge basalts (MORB, N-type and P-type), suggesting that this source is also heterogeneous. ?? 1986 Nature Publishing Group.

Hawaii↗