Multiple expressions of plume‐ridge interaction in the Galápagos: Volcanic lineaments and ridge jumps

Abstract

[1] Anomalous volcanism and tectonics between near-ridge mantle plumes and mid-ocean ridges provide important insights into the mechanics of plume-lithosphere interaction. We present new observations and analysis of multibeam, side scan sonar, sub-bottom chirp, and total magnetic field data collected during the R/V Melville FLAMINGO cruise (MV1007; May-June, 2010) to the Northern Galápagos Volcanic Province (NGVP), the region between the Galápagos Archipelago and the Galápagos Spreading Center (GSC) on the Nazca Plate, and to the region east of the Galápagos Transform Fault (GTF) on the Cocos Plate. The NGVP exhibits pervasive off-axis volcanism related to the nearby Galápagos hot spot, which has dominated the tectonic evolution of the region. Observations indicate that $94% of the excess volcanism in our Copyright 2012 by the American Geophysical Union 1 of 31 survey area occurs on the Nazca Plate in three volcanic lineaments. Identified faults in the NGVP are consistent with normal ridge spreading except for those within a $60 km wide swath of transform-oblique faults centered on the GTF. These transform-oblique faults are sub-parallel to the elongation direction of larger lineament volcanoes, suggesting that lineament formation is influenced by the lithospheric stress field.We evaluate current models for lineament formation using existing and new observations as well as numerical models of mantle upwelling and melting. The data support a model where the lithospheric stress field controls the location of volcanism along the lineaments while several processes likely supply melt to these eruptions. Synthetic magnetic models and an inversion for crustal magnetization are used to determine the tectonic history of the study area. Results are consistent with creation of the GTF by two southward ridge jumps, part of a series of jumps that have maintained a plume-ridge separation distance of 145 km to 215 km since $5 Ma.

Patterns in Galápagos Magmatism Arising from the Upper Mantle Dynamics of Plume‐Ridge Interaction

“…The lithosphere also thins more rapidly to the N-NE, and this allows for more rapid upslope flow and melting along its base. The localized area of high magma production predicted by Model 1 implies that magma need not migrate laterally very far to feed the active Galápagos Islands as well as the numerous volcanoes and volcanic lineaments between the main islands and the GSC [e.g., Harpp and Geist, 2002;Sinton et al, 2003;Mittelstaedt et al, 2012]. The total volume flux of magma that is assumed to erupt off of the GSC and presumably as off-axis volcanism is 4.5-5.3 × 10 5 km 3 / Myr, for ξ = 0.5-1.0, respectively.…”

“…ability in mantle temperatures, compositions, melting conditions, and magmatic fluxes associated with plumeridge interaction [e.g., Harpp and White, 2001;Detrick et al, 2002;Harpp and Geist, 2002;Hooft et al, 2003;Schilling et al, 2003;Christie et al, 2005;Villagomez et al, 2007;Mittelstaedt et al, 2012]. However, what this variability indicates about the rheology of the upper mantle and the dynamical processes by which heat and mass transfer from the hotspot center toward and along the ridge axis are not well-understood.…”

A 1.5 Ma record of plume-ridge interaction at the Western Galápagos Spreading Center (91°40′–92°00′W)

“…All samples are situated within 8 km of the center profile line, except DR69 and DR72, which are located 17 and 23 km east of the profile line respectively. The profile was collected north of the spreading center to avoid overprinting by younger volcanism as is evident from the numerous volcanic edifices between the Galápagos Platform and the WGSC, largely clustered along the lineaments described above (Harpp and Geist, 2002;Sinton et al 2003;Mittelstaedt et al, 2012). A further advantage of the sampled profile is that there is no evidence for ridge jumps or overlapping spreading centers along the 50 km profile.…”

“…1; e.g., Handschumacher, 1976;Hey and Vogt, 1977;Wilson and Hey, 1995;Canales et al, 1997;Werner et al, 1999Werner et al, , 2003. Over the last 5 Ma, the GSC, located north of the Galápagos hotspot, has been progressively drifting northwards but has been repeatedly captured by the hotspot, as reflected by numerous ridge-jumps (Wilson and Hey, 1995;Mittelstaedt et al, 2012;Gibson et al, 2015).…”

“…At the Western GSC (WGSC), possible surface expressions of plume transport towards the GSC are several arcuate chains of volcanic seamounts and islands (up to ~1.8 Ma old) in the western inside corner of the 91°W transform of which the most widely known is the Wolf-Darwin Lineament (Morgan, 1978;White et al, 1993;Sinton et al, 1996;Harpp and Geist, 2002;Mittelstaedt et al, 2012). These arcuate volcanic chains radiate from Pinta Island northwestwards until they intersect the WGSC at 91°00'W, 91°16'W, 91°47'W and 92°10'W (Sinton et al, 2003).…”