Influence of the Galpagos hotspot on the East Pacific Rise during Miocene superfast spreading
J. Geldmacher et al., GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstrasse 1-3, 24148 Kiel, Germany. Posted online 28 Nov. 2012; http://dx.doi.org/10.1130/G33533.1.
This study investigates the geochemical composition of lava rocks that formed between 7 and 23 million years ago at the equatorial East Pacific Rise, one of the major seafloor spreading centers where oceanic crust is produced by submarine volcanism. Spreading center magmas generally originate at relatively shallow depths. It is found that lavas formed between 11 and ca. 22 m.y. show the influence of a geochemically enriched magma source, which is commonly ascribed to the deep Earth's mantle. This material is believed to rise to the surface at local melting anomalies, the so-called hotspots. Although the Galpagos hotspot (forming the famous volcanic Galpagos Islands) is located near the investigated segment of the East Pacific Rise, no evidence for any influence of the hotspot on the current spreader center and its lava compositions can be seen. However, the observed geochemical influence of hotspot material in the 11-22 m.y. lavas correlates with an interval of extreme ("superfast") seafloor spreading (up to 200 mm/y in contrast to today's 130 mm/y). It is suggested that increased spreading and magma production could have facilitated shallow flow of Galpagos hotspot material to the East Pacific Rise were it has contaminated the local upper mantle spreading center source region.
Earliest chitinozoans discovered
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