ALBERT

Description: Since 1963, the International Heat Flow Commission has been fostering the compilation of the Global Heat Flow Database to provide reliable heat-flow data. Over time, techniques and methodologies evolved, calling for a reorganization of the database structure and for a reassessment of stored heat-flow data. Here, we provide the results of a collaborative, community-driven approach to set-up a new, quality-approved global heat-flow database. We present background information on how heat-flow is determined and how this important thermal parameter could be systematically evaluated. The latter requires appropriate documentation of metadata to allow the application of a consistent evaluation scheme. The knowledge of basic data (name and coordinates of the site, depth range of temperature measurements, etc.), details on temperature and thermal-conductivity data and possible perturbing effects need to be given. The proposed heat-flow quality evaluation scheme can discriminate between different quality aspects affecting heat flow: numerical uncertainties, methodological uncertainties, and environmental effects. The resulting quality codes allow the evaluation of every stored heat-flow data entry. If mandatory basic data are missing, the entry is marked accordingly. In cases where more than one heat-flow determination is presented for one specific site, and all of them are considered for the site, the poorest evaluation score is inherited to the site level. The required data and the proposed scheme are presented in this paper. Due to the requirements of the newly developed evaluation scheme, the database structure as presented in 2021 has been updated and is available in the appendix of this paper. The new quality scheme will allow a comprehensible evaluation of the stored heat-flow data for the first time.

Description: Heat flow is estimated at eight sites drilled during the International Ocean Discovery Program Expedition 385 into the Guaymas Basin, Gulf of California. The expedition sought to understand the thermal regime of the basin and heat transfer between off-axis sills intruding the organic-rich sediments of the Guaymas Basin, and the basin floor. The distinct sedimentation rates, active tectonics, and magmatism makes the basin interesting for scientific discoveries. Results show sedimentation corrected heat flow values range 119-221 mW/m2 in the basin and 257-1003 mW/m2 at the site of a young sill intrusion, denominated Ringvent. Thermal analysis shows that heat in the Guaymas Basin is being dissipated by conduction for plate ages 〉0.2 Ma, whereas younger plate ages are in a state of transient cooling by both conduction and advection. Drilling sites show that Ringvent is an active sill being cooled down slowly by circulating fluids with discharge velocities 10–200 mm/yr. Possible recharge sites are located ~1 km away from the sill's border. Modeling of the heat output at Ringvent indicates a sill thickness of ~240 m. A simple order-of-magnitude model predicts that relatively small amounts of magma are needed to account for the elevated heat flow in non-volcanic, sediment-filled rifts like the central and northern Gulf of California in which heating of the upper crust is achieved via advection by sill emplacement and hydrothermal circulation. Multiple timescales of cooling control the crustal, chemical and biological evolution of the Guaymas Basin. Here we recognize at least four timescales: the time interval between intrusions (~103 yr), the thermal relaxation time of sills (~104 yr), the characteristic cooling time of the sediments (~105 yr), and the cooling of the entire crust at geologic timescales.

Description: Since 1963, the International Heat Flow Commission (IHFC) has been fostering and maintaining the compilation of the Global Heat Flow Database (GHDB). Over time, techniques and methodologies in heat-flow density determination evolved and called for frequent updates of the database. The increasing number of data and their diverse underlying methods also require an adequate and consistent evaluation scheme to assess the quality of the respective heat-flow density determination. Here, we provide the intermediate results of a collaborative, community-driven approach started in 2021 to set-up a new, authenticated GHDB. We document the new basic structure to report heat-flow data to the IHFC and present a newly developed consistent evaluation scheme. The quality scheme, for the first time, combines three independent quality criteria in one combined score, comprising the quantified uncertainty, the methodological quality, and the status of overruling effects. It allows a quick comparison of heat-flow data and reveals missing data or insufficient documentation at one glance. With the new quality scheme, users are enabled toselectappropriatereliable heat-flow values for their specific purpose. The process to screen and update incomplete, wrong or empty database entries is ongoing and will last for a couple of years. The most recent intermediate update – the data release 2023 – contains data generated between 1939 and 2022. The data release contains 73,033 heat-flow data from 1,414 publications. 55% of the reported heat-flow values are from the continental domain (n ~40,082), while the remaining 45% are located in the oceanic domain (n ~32,951).

Description: 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/m〈sup〉2〈/sup〉 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/m〈sup〉2〈/sup〉 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〈sup〉-14〈/sup〉 m〈sup〉2〈/sup〉 and 10〈sup〉-6〈/sup〉 m/s, respectively, and ~10〈sup〉-16〈/sup〉 m〈sup〉2〈/sup〉 and 10〈sup〉-8〈/sup〉 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.

Description: The intrusion of igneous sills into organic-rich sediments accompanies the emplacement of igneous provinces, continental rifting, and sedimented seafloor spreading. Heat from intruding sills in these settings alters sedimentary organic carbon, releasing methane and other gasses. Recent studies hypothesize that carbon released by this mechanism impacts global climate, particularly during large igneous province emplacements. However, the direct impacts of sill intrusion, including carbon release, remain insufficiently quantified. Here, we present results from International Ocean Discovery Program (IODP) Expedition 385 comparing drill-core and wireline measurements from correlative sedimentary strata at adjacent sites cored in Guaymas Basin, Gulf of California, one altered by a recently intruded sill and one unaffected. We estimate 3.30 Mt of carbon were released due to this sill intrusion, representing an order of magnitude less carbon than inferences from outcrops and modeling would predict. This attenuated carbon release can be attributed to shallow intrusion and the high heat capacity of young, high-porosity sediments. Shallow intrusion also impacts sub-seafloor carbon cycling by disrupting advective fluxes, and it compacts underlying sediments, increasing potential carbon release in response to subsequent intrusions.

Description: The Powell Basin is a small oceanic basin bounded by continental blocks that fragmented during drifting of South America from Antarctica. The basin is limited to the east by the South Orkney Microcontinent, to the north by the South Scotia Ridge, and to the west by the Antarctic Peninsula. The timing of its opening is poorly constrained due to low amplitude magnetic anomalies which hampers their identification and cause large uncertainties in proposed ages that range from the Late Eocene to Early Miocene. The Powell basin has been extensively studied using a variety of geophysical methods including seismic, gravity and magnetic surveys intended to unveil the tectonic domains. The magnetic anomalies and the thermal regime of the basin are of particular interest, as some of these studies have suggested that the absence of clear seafloor magnetic anomalies is the result of impermeable layers that prevent the venting of hot fluids into the water column. Using new magnetic and heat flow data together with geophysical data from international databases, we analyze the thermal structure of the Powell Basin its lithosphere and the upper mantle dynamics and discuss the probable causes of the abnormally small amplitudes of magnetic anomalies.

Description: Heat flow is reported at eight sites drilled into the Guaymas Basin, Gulf of California, during the International Ocean Discovery Program Expedition 385. This expedition seeks to understand the thermal regime of the basin and heat transfer between off-axis sills intruding the organic-rich sediments of the Guaymas Basin, and the basin floor. The relatively high sedimentation rates combined with active tectonism and voluminous shallow off-axis magmatism characterizes this basin. Our results bridge a data deficiency allowing basin-wide interpretations shading light on this young rift basin. Results show sedimentation corrected heat flow values range between 119 and 221 mW/m〈sup〉2〈/sup〉 in the basin and between 257 and 1003 mW/m〈sup〉2〈/sup〉 at the site of a young sill intrusion, termed Ringvent. Thermal analysis shows that heat in the Guaymas Basin is being dissipated by conduction for plate ages 〉0.2 Ma, whereas younger plate ages are also dissipating heat by advection. Drilling data show that an active ring of hydrothermal vent root to a shallow sill fueling low-temperature hydrothermal fluids with discharge velocities of 10–200 mm/yr. Possible recharge sites are located ~1 km away from the sill's border. Modeling of the heat output and assuming supplied by a cooling sill, we estimate a sill thickness at Ringvent of ~240 m. A simple order-of-magnitude model predicts that relatively small amounts of magma are needed to account for the elevated heat flow in non-volcanic, sediment-filled rifts like the central and northern Gulf of California where heating of the upper crust is achieved via advection by sill emplacement and hydrothermal circulation. Multiple timescales of cooling control the crustal, chemical and biological evolution of the Guaymas Basin. Here we recognize at least four timescales: the time interval between intrusions (~10〈sup〉3〈/sup〉 yr), the thermal relaxation time of sills (~10〈sup〉4〈/sup〉 yr), the characteristic warming time of the sediments (~10〈sup〉5〈/sup〉 yr), and the cooling of the entire crust at geologic timescales.

Description: For the integration of this dataset, several research articles were collected from the catalog of The Global Heat Flow Data Assessment Project. Specially, this data publication encloses all heat-flow data of onshore India. The resulting updated database contains 617 determinations of heat-flow from 36 publications. The data are presented according to the standards defined by the World Heat Flow Database Project and the International Heat Flow Commission (Fuchs et al., 2023)

Description: The data publication contains all heat-flow data of offshore in the Guaymas basin. The data release contains data generated between 1959 and 2019 and constitutes a substantial update and extension compared to the last compilation provided by Becker & Fisher (1991). The data set comprises new heat-flow determinations published after 1991 as well as data from before 1991, which were not included in the Becker & Fisher (1991). The resulting updated database contains 487 determinations of heat-flow at 464 locations from 17 publications. 95% of the reported heat-flow values are determined from marine probe sensing technique and 5% in boreholes.

Description: The data publication contains the compilation of global heat-flow data by the International Heat Flow Commission (IHFC; www.ihfc-iugg.org) of the International Association of Seismology and Physics of the Earth's Interior (IASPEI). The presented data update 2023 contains data generated between 1939 and 2022 and constitutes the first intermediate update benefiting from the global collaborative assessment and quality control of the Global Heat Flow Database running since May 2021 (http://assessment.ihfc-iugg.org).