Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Lyons, J. Articles by Vervoort, J. Search for Related Content GeoRef GeoRef Citation

Crustal growth by magmatic overplating in the Galápagos

¹ Michigan Technological University, Geological and Mining Engineering and Sciences, 1400 Townsend Drive, Houghton, Michigan 49931, USA
² University of Idaho, Department of Geological Sciences, Moscow, Idaho 83844, USA
³ Colgate University, Geology Department, Hamilton, New York 13346, USA
⁴ University of Idaho, Department of Geological Sciences, Moscow, Idaho 83844, USA
⁵ Washington State University, Department of Geology, Pullman, Washington 99164, USA

The isotopic compositions of xenoliths hosted in lavas from Floreana Island indicate that they formed from magmas unlike those at present-day Floreana. Instead, the xenoliths are geochemically more similar to magmas now erupting from Sierra Negra and Cerro Azul volcanoes, at the leading edge of the Galápagos hotspot. This is the first evidence for compositional evolution at a Galápagos volcano and indicates increasing contributions from an iso topically enriched source with time as the volcano is carried away from the focus of the hot-spot. Clinopyroxenes in many of the xenoliths exhibit positive anomalies of Sr and Eu, which are attributed to the breakdown of plagioclase. The growth of clinopyroxene at the expense of plagio clase results from compression as the crust cools. Compression is caused by growth mostly from above, as shallow intrusions and lavas load the middle and upper oceanic crust.

Key Words: xenoliths • underplating • Galápagos Islands • compression • trace elements • igneous petrology