Geochemistry of the Pitcairn seamounts, I: source character and temporal trends.

Woodhead, J.D. and Devey, Colin W. (1993) Geochemistry of the Pitcairn seamounts, I: source character and temporal trends. Earth and Planetary Science Letters, 116 (1-4). pp. 81-99. DOI 10.1016/0012-821X(93)90046-C.

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Seabeam mapping in the central Pacific Ocean, southeast of Pitcairn Island, has revealed a number of large volcanic edifices, some of which appear to be currently active. Here we document the first isotope and trace element data obtained for dredge samples from these volcanoes which are believed to represent the present-day surface expression of the Pitcairn mantle plume.
Striking linear trends in multi-isotope plots suggest the operation of a simple two-component mixing process in the genesis of these lavas with end-members of extreme EM-I and isotopically more depleted type. Isotope-trace element covariations allow limits to be placed upon the composition of the Pitcairn plume source, which is then compared with other EM-type oceanic islands. Current hypotheses for the generation of EM components are then evaluated in the light of these data.
Temporal trends, similar to those seen on Pitcairn Island, are present within the seamount data, although samples equivalent to the post-shield formations on Pitcairn Island are not observed. These evolutionary trends suggest a high level origin for the depleted component rather than entrainment of asthenospheric material into a rising diapir.
Three of the Pitcairn seamounts are much older, in the region of 20–25 Ma, and were probably formed in a near-ridge environment.

Document Type: Article
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/0012-821X(93)90046-C
ISSN: 0012-821X
Date Deposited: 18 Feb 2008 17:27
Last Modified: 14 Nov 2016 13:16

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