The Cobb-Eickelberg seamount chain: Hotspot volcanism with mid-ocean ridge basalt affinity
- Oregon State Univ., Corvallis (United States)
Cobb hotspot, currently located beneath Axial seamount on the Juan de Fuca ridge, has the temporal but not the isotopic characteristics usually attributed to a mantle plume. The earlier volcanic products of the hotspot, form eight volcanoes in the Cobb-Eickelberg seamount (CES) chain, show a westward age progression away from the hotspot and a westward increase in the age difference between the seamounts and the crust on which they formed. These results are consistent with movement of the Pacific plate over a fixed Cobb hotspot and eventual encroachment by the westwardly migrating Juan de Fuca ridge. CES lavas are slightly enriched in alkalies and incompatible elements relative to those of the Juan de Fuca ridge but they have Sr, Nd, and Pb isotopic compositions virtually identical to those found along the ridge. Therefore, Cobb hotspot is a stationary, upper mantle melting anomaly whose volcanic products show strong mid-ocean ridge basalt (MORB) affinity. These observations can be explained by low degrees of partial melting of entrained heterogeneous upper mantle MORB source material within a thermally driven lower mantle diapir or by an intrinsic MORB-like composition of the deeper mantle source region from which northeast Pacific plumes rise.
- OSTI ID:
- 5085718
- Journal Information:
- Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 95:B8; ISSN 0148-0227; ISSN JGREA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
150200* -- Geology & Hydrology of Geothermal Systems
58 GEOSCIENCES
580000 -- Geosciences
AGE ESTIMATION
ALKALINE EARTH ISOTOPES
BASALT
CHEMISTRY
EARTH MANTLE
GEOCHEMISTRY
HOT SPOTS
IGNEOUS ROCKS
ISOTOPES
LAVA
LEAD ISOTOPES
NEODYMIUM ISOTOPES
PACIFIC OCEAN
ROCKS
SEAS
STRONTIUM ISOTOPES
SURFACE WATERS
TECTONICS
VOLCANIC ROCKS
VOLCANISM
VOLCANOES