Heat flow in the Lesser Antilles island arc and adjacent back arc Grenada basin

Abstract

[1] Using temperature gradients measured in 10 holes at 6 sites, we generate the first high fidelity heat flow measurements from Integrated Ocean Drilling Program drill holes across the northern and central Lesser Antilles arc and back arc Grenada basin. The implied heat flow, after correcting for bathymetry and sedimentation effects, ranges from about 0.1 W/m 2 on the crest of the arc, midway between the volcanic islands of Montserrat and Guadeloupe, to <0.07 W/m 2 at distances >15 km from the crest in the back arc direction. Combined with previous measurements, we find that the magnitude and spatial pattern of heat flow are similar to those at continental arcs. The heat flow in the Grenada basin to the west of the active arc is 0.06 W/m 2 , a factor of 2 lower than that found in the previous and most recent study. There is no thermal evidence for significant shallow fluid advection at any of these sites. Present-day volcanism is confined to the region with the highest heat flow.

Forearc structure in the Lesser Antilles inferred from depth to the Curie temperature and thermo-mechanical simulations

“…This anomaly is well correlated with a doming of the CPD beneath the active arc. The deepening of the CPD in front of the subduction trench is consistent with the relatively low thermal gradient evidenced by Manga et al [2012], commonly reported in similar contexts [Schubert and Peter, 1974]. Even at our scale, these evidences support CPD variations (or 580°C isotherm depth variations) as a witness of differences in thermal structure at the lithospheric scale.…”

“…At first order correlation can be observed between our CPD results and the measurements from Manga et al [2012]. According to Manga et al [2012], a main high heat flow anomaly corresponds to the active arc and fore-arc domain (~0.08 W/m 2 ). We have to remember that high heat flow values are commonly attributed to volcanic and metamorphic regions (high thermal conductivities).…”

“…Accordingly, we do not consider these values and will focus on the measurements from Manga et al [2012]. At first order correlation can be observed between our CPD results and the measurements from Manga et al [2012].…”

“…This approach will help characterizing the regional thermal structures of the LAA but also better constraining the very complex structure of the fore-arc domain in its northern part where: (1) almost no heat flow data are available [synthesis in Manga et al, 2012], (2) an oligocene-miocene remnant arc is present East of the present-day active volcanic arc, thus in a fore-arc setting [e.g., Bouysse, 1979;Bouysse et al, 1985Bouysse et al, , 1988Bouysse and Westercamp, 1988] and (3) extensional tectonics is active since at least the early Miocene [Münch et al, 2014;De Min et al, 2015]. One of the main goals of this study is therefore to better understand the origin of magnetic anomalies along the LAA subduction zone.…”

Site U1398

“…Using measured thermal conductivity, the implied heat flow is 59 ± 5 mW/m 2 . This estimate does not need a correction for bathymetry, and sedimentation lowers the measured near-surface heat flow by as much as 4% (Manga et al, 2012). Of all the sites, this is the only one where a quadratic fit to the data (rather than a linear fit) produces a quadratic term that is statistically significant; however, modeling of this data indicates that a linear fit is still favored (Manga et al, 2012).…”