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- Title
Hydrothermal Models Constrained by Fine‐Scale Seismic Velocities Confirm Hydrothermal Cooling of 7–63 Ma South Atlantic Crust.
- Authors
Kardell, Dominik A.; Zhao, Zeyu; Ramos, Evan J.; Estep, Justin; Christeson, Gail L.; Reece, Robert S.; Hesse, Marc A.
- Abstract
Although 70% of the Earth's heat loss occurs in the oceans, the nature of hydrothermal heat flow in oceanic crust is controversial. Lithospheric cooling models, heat flow measurements, and seismic experiments provide conflicting accounts on the longevity of hydrothermal systems and their efficiency at removing heat from the crust. Here we present five hydrothermal models along a crustal flowline in the western South Atlantic at ∼31°S to quantify how conductive and advective heat loss change as a function of crustal age and structure. The model sites cover crustal ages of 7–63 Ma and are collocated with planned drill sites of International Ocean Discovery Program Expeditions 390 and 393. We constrained our hydrothermal models with detailed physical property distributions that we estimated from new high‐resolution seismic velocity models. The hydrothermal models yield conductive and advective heat fluxes that closely match lithospheric cooling models and conductive heat flow measurements on the seafloor, supporting a hydrothermal sealing age of ∼65 Ma. Our results also agree with global estimates of fluid volume flux into the oceans and are consistent with a previously published analysis of upper crustal seismic velocities in the study area, indicating ongoing hydrothermal activity at relatively old crustal ages. This study broadly confirms and unifies existing concepts of oceanic heat flow and its modes of transport. Moreover, it provides a regional framework of seismic velocities and modeled hydrothermal fluxes, in which future in‐situ measurements can be integrated. Plain Language Summary: The Earth slowly loses its internal heat in two different ways: passive heat conduction through the crust, and heat removal by fluids that circulate between the crust and the Earth's surface. At mid‐ocean ridges, where magma occasionally reaches the seafloor and fuels the circulation of very hot fluids within the crust, fluid circulation accounts for most of the total heat loss. However, it is poorly understood for how long this circulation remains active as the newly formed crust cools and migrates away from the spreading center. In this study, we take a closer look at five study sites in the western South Atlantic, covering crustal ages of 7–63 million years. We first estimate crustal porosity and permeability, which are important factors controlling fluid flow. We then model heat transport and find that fluid circulation loses its significance as a heat loss mechanism around a crustal age of 60 million years. This result confirms the findings of previous studies that approached the problem using different methods. Fluid circulation is thus an important cooling agent in a large areal portion of the Earth's oceanic crust. Our models can be used as a reference for an upcoming drilling expedition in the study area. Key Points: We constrain hydrothermal models with seismic velocities at 31°S in the western South AtlanticComputed heat and fluid volume fluxes support a 65 Ma hydrothermal sealing ageHigh‐velocity anomalies in intermediate spreading rate crust may indicate frozen magma bodies that formed at or near the spreading center
- Subjects
SEISMOLOGY; OCEANIC crust; HYDROTHERMAL circulation (Oceanography); OCEAN convection; HEAT flow (Oceanography); HEAT transfer
- Publication
Journal of Geophysical Research. Solid Earth, 2021, Vol 126, Issue 6, p1
- ISSN
2169-9313
- Publication type
Article
- DOI
10.1029/2020JB021612