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- Title
Transport of Heat by Hydrothermal Circulation in a Young Rift Setting: Observations From the Auka and JaichMaa Ja'ag' Vent Field in the Pescadero Basin, Southern Gulf of California.
- Authors
Negrete‐Aranda, Raquel; Neumann, Florian; Contreras, Juan; Harris, Robert N.; Spelz, Ronald M.; Zierenberg, Robert; Caress, David W.
- Abstract
Heat flow measurements collected throughout the Auka and JaichMaa Ja'ag' hydrothermal vent fields in the central graben of the Southern Pescadero Basin, southern Gulf of California, indicate upflow of hydrothermal fluids associated with rifting dissipate heat in excess of 10 W/m2 around faults that have a few kilometers in length. Paradoxically, longer faults do not show signs of venting. Heat flow anomalies slowly decay to background values of ∼2 W/m2 at distances of ∼1 km from these faults following an inverse square‐root distance law. We develop a near‐fault model of heat transport in steady state for the Auka vent field based on the fundamental Green's function solution of the heat equation. The model includes the effects of circulation in fracture networks, and the lateral seepage of geothermal brines to surrounding hemipelagic sediments. We use an optimal fitting method to estimate the reservoir depth, permeability, and circulation rate. Independently derived constraints for the model, indicate the heat source is at a depth of ∼5.7 km; from the model, permeability and flow rates in the fracture system are ∼10−14 m2 and 10−6 m/s, respectively, and ∼10−16 m2 and 10−8 m/s in the basin aquitards, respectively. Model results point to the importance of fault scaling laws in controlling sediment‐hosted vent fields and slow circulation throughout low permeability sediments in controlling the brine's chemistry. Although the fault model seems appropriate and straightforward for the Pescadero vents, it does seem to be the exception to the other known sediment‐hosted vent fields in the Pacific. Plain Language Summary: The Earth cools down primarily by the release of heat transported from the planetary interior by magmas and hydrothermal fluids to the surface. A global system of underwater mountain ranges, ridge flanks, dissipate most of that heat while simultaneously forming new oceanic lithosphere. Porous pathways formed by fault networks and porous layers ultimately guide the process in the brittle upper crust. The Auka and JaichMaa Ja'ag' hydrothermal vent fields in the central graben of the Pescadero Basin, southern Gulf of California, are exemplary cases to study this process. We develop a model for heat transport that is, rather simple and straightforward that explains quite well the dissipation of heat observed across the Auka hydrothermal vent field and the chemistry of its waters. In our case, the motion of fluids by hydrothermal flow through porous layers causes a steady transference of heat across fault walls into its surroundings, forming a heat flow anomaly that decays as the square root of distance. Key Points: The Pescadero Basin is an incipient oceanic rift basin with vigorous hydrothermal activity along graben‐bounding faultsAspects of the thermal regime of rifting of this basin are explored using an analytical model that incorporates conjugate heat transferHydrothermal circulation modeling shows an enormous exchange of heat takes place through fault walls to the surrounding sediments
- Subjects
HEAT flow (Oceanography); HYDROTHERMAL circulation (Oceanography); GREEN'S functions; GEOTHERMAL brines; OCEAN convection
- Publication
Journal of Geophysical Research. Solid Earth, 2021, Vol 126, Issue 8, p1
- ISSN
2169-9313
- Publication type
Article
- DOI
10.1029/2021JB022300