East pacific ridge (2°S–19°S) versus nazca intraplate volcanism: Rare-earth evidence |
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Authors: | J-G Schilling E Bonatti |
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Institution: | Graduate School of Oceanography, University of Rhode Island Kingston, R.I. U.S.A.;Lamont-Doherty Geological Observatory of Columbia University, Palisades, N.Y. U.S.A. |
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Abstract: | Basalts from seamounts within the Nazca Plate representing intraplate volcanism, and the East Pacific Ridge between 19°S and 2°N have similar light rare earth depleted abundance patterns. Both intraplate and ridge basalts appear to have been derived from the low-velocity layer apparently depleted in large lithophile elements (DLVL). Nepheline-normative basalts and ferrobasalts occasionally occurring on the East Pacific Rise are shown to have also been derived from the same DLVL source. Furthermore, the rare-earth pattern similarity of nepheline-normative and tholeiitic basalts from the East Pacific Rise is best explained by distinct, pressure induced, conditions of partial melting of the DLVL source; whereas total rare-earth pattern enrichment and relative europium depletion of the ferrobasalts are consistent with shallow depth fractional crystallization during ascent. |
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