TY - JOUR
T1 - The Cocos and Carnegie aseismic ridges
T2 - A trace element record of long-term plume-spreading center interaction
AU - Harpp, Karen S.
AU - Wanless, Virginia D.
AU - Otto, Robert H.
AU - Hoernle, Kaj
AU - Werner, Reinhard
PY - 2005/1
Y1 - 2005/1
N2 - The aseismic Cocos and Carnegie Ridges, two prominent bathymetric features in the eastern Pacific, record ∼20 Myr of interaction between the Galápagos hotspot and the adjacent Galápagos Spreading Center. Trace element data determined by inductively coupled plasma-mass spectrometry in >90 dredged seamount lavas are used to estimate melt generation conditions and mantle source compositions along the ridges. Lavas from seamount provinces on the Cocos Ridge are alkalic and more enriched in incompatible trace elements than any in the Galápagos archipelago today. The seamount lavas are effectively modeled as small degree melts of a Galápagos plume source. Their eruption immediately follows the failure of arizone at each seamount province's location. Thus the anomalously young alkalic lavas of the Cocos Ridge, including Cocos Island, are probably caused by post-abandonment volcanism following either a ridge jump or rift failure, and not the direct activity of the Galápagos plume. The seamounts have plume-like signatures because they tap underlying mantle previously infused with Galápagos plume material. Whereas plume heterogeneities appear to be long-lived, tectonic rearrangements of the ridge plate boundary may be the dominant factor in controlling regional eruptive behavior and compositional variations.
AB - The aseismic Cocos and Carnegie Ridges, two prominent bathymetric features in the eastern Pacific, record ∼20 Myr of interaction between the Galápagos hotspot and the adjacent Galápagos Spreading Center. Trace element data determined by inductively coupled plasma-mass spectrometry in >90 dredged seamount lavas are used to estimate melt generation conditions and mantle source compositions along the ridges. Lavas from seamount provinces on the Cocos Ridge are alkalic and more enriched in incompatible trace elements than any in the Galápagos archipelago today. The seamount lavas are effectively modeled as small degree melts of a Galápagos plume source. Their eruption immediately follows the failure of arizone at each seamount province's location. Thus the anomalously young alkalic lavas of the Cocos Ridge, including Cocos Island, are probably caused by post-abandonment volcanism following either a ridge jump or rift failure, and not the direct activity of the Galápagos plume. The seamounts have plume-like signatures because they tap underlying mantle previously infused with Galápagos plume material. Whereas plume heterogeneities appear to be long-lived, tectonic rearrangements of the ridge plate boundary may be the dominant factor in controlling regional eruptive behavior and compositional variations.
KW - Abandoned rift
KW - Galápagos
KW - Mantle plume
KW - Mid-ocean ridge
KW - Partial melting of the mantle
UR - http://www.scopus.com/inward/record.url?scp=12444318612&partnerID=8YFLogxK
U2 - 10.1093/petrology/egh064
DO - 10.1093/petrology/egh064
M3 - Article
AN - SCOPUS:12444318612
SN - 0022-3530
VL - 46
SP - 109
EP - 133
JO - Journal of Petrology
JF - Journal of Petrology
IS - 1
ER -