Crustal thickness constraints on the geodynamic evolution of the Galapagos Volcanic Province

We developed a simple quantitative framework based on crustal thickness estimations along the Carnegie, Cocos and Malpelo ridges, to place first-order constraints on the tectonic evolution of the Galapagos Volcanic Province and on the along-axis intensity of the Galapagos melt anomaly during the last 20 m.y. Our results suggest that the Cocos^ Nazca spreading centre has migrated northwards at 262 4 km/m.y. with respect to the Galapagos hotspot (GHS) during this period of time. At V20 m.y., the GHS was approximately ridge-centered, and thus the along-axis intensity of the melt anomaly at this time was the maximum. At V11.5 m.y. the hotspot was located 1062 27 km north of the spreading center, and the along-axis intensity of the melt anomaly was 0.542 0.04 of that estimated at 20 Ma. At present day it is located at V190 km south of the spreading center and the along-axis intensity is only 0.192 0.03 of that estimated at 20 Ma. These results are used to reconstruct the relative position between the GHS and the Cocos^ Nazca Spreading Center. The spreading center passed over the GHS for the last time at 7.4 2 1.3 Ma. The Panama fracture zone was initiated at 8.9 2 1.6 Ma, leading to the separation between the Cocos and Malpelo ridges. The present configuration of the Galapagos Volcanic Province and the plate velocities are consistent with symmetric spreading with a mean full spreading rate of V60 km/m.y. along the CNSC during the last 20 m.y. A melt flux for excess crustal production of 9.4 2 5.1 m3/s is obtained for the Galapagos melt anomaly at 20 Ma, implying that the maximum potential intensity of the Galapagos plume is similar to that of the Icelandic plume and twice smaller than the Hawaiian one. ? 2003 Elsevier B.V. All rights reserved.