scholarly journals Regions of anomalous geothermal fields in the State of Tocantins, Central Brazil

2019 ◽  
Vol 2 (1) ◽  
pp. 30-36
Author(s):  
Patricia Lopes Descovi ◽  
Fábio Pinto Vieira
Keyword(s):  
Heat Flow ◽  
Gas Flow ◽  
High Heat ◽  
The State ◽  
Near Surface ◽  
Geothermal Gradients ◽  
Central Brazil ◽  
Geothermal Fields ◽  
Source Mechanisms ◽  
Carbonic Gas

We report recent progress in determination of geothermal gradients and heat flow in the State of Tocantins, Central Brazil. This region lying between the Amazonas and Sao Francisco cratons has been affected by metamorphic folding events (Brasilia and Araguaia) during Proterozoic times. This area is also characterized by moderate micro-seismic seismic activity. Results of recent investigations have revealed the presence of several areas where geothermal gradients and heat flow have values higher than normal, which is considered atypical of stable tectonic settings. In southern parts of the State of Tocantins heat flow values are higher than 80 mW/m2. Extrapolations based on near surface heat flow data point to crustal temperatures in excess of 200°C at depths less than 5 km. However, there are no evidences of magmatic intrusions at shallow intra-crustal depths. In the absence of other geologic source mechanisms and tectonic events the process responsible for high heat flow has been postulated to be enhanced heat transport by carbonic gas flow in the upper crust. This possible alternative is supported by observations of carbonic gas flow at sites of thermal springs within the study area and also in geothermal areas in the neighboring state of Goiás. Model simulations of deep crustal geotherms indicate that temperatures may approach levels of partial fusion at the crust mantle boundary.

scholarly journals Estimation of Curie-point depths, geothermal gradients and near-surface heat flow from spectral analysis of aeromagnetic data in the Loum – Minta area (Centre-East Cameroon)

2018 ◽  
Vol 27 (4) ◽  
pp. 1291-1299
Author(s):  
Jean Aimé Mono ◽  
Théophile Ndougsa-Mbarga ◽  
Yara Tarek ◽  
Jean Daniel Ngoh ◽  
Olivier Ulrich Igor Owono Amougou
Keyword(s):  
Spectral Analysis ◽  
Heat Flow ◽  
Curie Point ◽  
Surface Heat ◽  
Aeromagnetic Data ◽  
Near Surface ◽  
Geothermal Gradients ◽  
Surface Heat Flow

scholarly journals Gas Hydrate Estimate in an Area of Deformation and High Heat Flow at the Chile Triple Junction

2018 ◽  
Author(s):  
Lucía Villar-Muñoz ◽  
Iván Vargas-Cordero ◽  
Joaquim P. Bento ◽  
Umberta Tinivella ◽  
Francisco Fernandoy ◽  
...  
Keyword(s):  
Heat Flow ◽  
Marine Sediments ◽  
Gas Hydrate ◽  
Triple Junction ◽  
High Heat ◽  
Spreading Ridge ◽  
High Heat Flow ◽  
Geothermal Gradients ◽  
Free Gas ◽  
Chile Triple Junction

Large amounts of gas hydrate are present in marine sediments offshore Taitao Peninsula, near the Chile Triple Junction. Here, marine sediments on the forearc contain carbon that is converted to methane in a zone of very high heat flow and intense rock deformation above the downgoing oceanic spreading ridge separating the Nazca and Antarctic plates. This regime enables vigorous fluid migration. Here we present an analysis of the spatial distribution, concentration, estimate of gas phases (gas hydrate and free gas) and geothermal gradients in the accretionary prism and forearc sediments offshore Taitao (45.5° - 47° S). Velocity analysis of Seismic Profile RC2901-751 indicates gas hydrate concentration values <10% of the total rock volume, and extremely high geothermal gradients (<190 °Ckm-1). Gas hydrates are located in shallow sediments (90-280 meters below the seafloor). The large amount of hydrate and free gas estimated (7.21x1011 m3 and 4.1x1010 m3, respectively), the high seismicity, the mechanically unstable nature of the sediments, and the anomalous geothermal conditions, set the stage for potential massive releases of methane to the ocean mainly through hydrate dissociation and/or migration directly to the seabed through faults. We conclude that the Chile Triple Junction is an important methane seepage area and should be the focus of novel geological and ecological research.

scholarly journals Gas Hydrate Estimate in an Area of Deformation and High Heat Flow at the Chile Triple Junction

Geosciences ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 28 ◽  
Author(s):  
Lucía Villar-Muñoz ◽  
Iván Vargas-Cordero ◽  
Joaquim Bento ◽  
Umberta Tinivella ◽  
Francisco Fernandoy ◽  
...  
Keyword(s):  
Heat Flow ◽  
Marine Sediments ◽  
Gas Hydrate ◽  
Triple Junction ◽  
High Heat ◽  
Spreading Ridge ◽  
High Heat Flow ◽  
Geothermal Gradients ◽  
Free Gas ◽  
Chile Triple Junction

Large amounts of gas hydrate are present in marine sediments offshore Taitao Peninsula, near the Chile Triple Junction. Here, marine sediments on the forearc contain carbon that is converted to methane in a regime of very high heat flow and intense rock deformation above the downgoing oceanic spreading ridge separating the Nazca and Antarctic plates. This regime enables vigorous fluid migration. Here, we present an analysis of the spatial distribution, concentration, estimate of gas-phases (gas hydrate and free gas) and geothermal gradients in the accretionary prism, and forearc sediments offshore Taitao (45.5°–47° S). Velocity analysis of Seismic Profile RC2901-751 indicates gas hydrate concentration values <10% of the total rock volume and extremely high geothermal gradients (<190 °C·km−1). Gas hydrates are located in shallow sediments (90–280 m below the seafloor). The large amount of hydrate and free gas estimated (7.21 × 1011 m3 and 4.1 × 1010 m3; respectively), the high seismicity, the mechanically unstable nature of the sediments, and the anomalous conditions of the geothermal gradient set the stage for potentially massive releases of methane to the ocean, mainly through hydrate dissociation and/or migration directly to the seabed through faults. We conclude that the Chile Triple Junction is an important methane seepage area and should be the focus of novel geological, oceanographic, and ecological research.

High heat flow at the SW passive margin of the Gulf of California

Terra Nova ◽  
2021 ◽  
Author(s):  
Rosa Maria Prol‐Ledesma ◽  
Juan Luis Carrillo De La Cruz ◽  
Marco‐Antonio Torres‐Vera ◽  
Alejandro Estradas‐Romero
Keyword(s):  
Heat Flow ◽  
Gulf Of California ◽  
High Heat ◽  
Passive Margin ◽  
High Heat Flow

A heat-flow reconnaissance of southeastern Alaska

1985 ◽  
Vol 22 (3) ◽  
pp. 416-421 ◽  
Author(s):  
J. H. Sass ◽  
L. A. Lawver ◽  
R. J. Munroe
Keyword(s):  
Heat Flow ◽  
Plate Boundary ◽  
Thermal Spring ◽  
High Heat ◽  
Transform Fault ◽  
High Heat Flow ◽  
Queen Charlotte Islands ◽  
Late Tertiary ◽  
The Mean ◽  
Strain Heating

Heat flow was measured at nine sites in crystalline and sedimentary rocks of southeastern Alaska. Seven of the sites, located between 115 and 155 km landward of the Queen Charlotte – Fairweather transform fault, have an average heat flow of 59 ± 6 mW m−2. This value is significantly higher than the mean of 42 mW m−2 in the coastal provinces between Cape Mendocino and the Queen Charlotte Islands, to the south, and is lower than the mean of 72 ± 2 mW m−2 for 81 values within 100 km of the San Andreas transform fault, even farther south. This intermediate value suggests the absence of significant heat sinks associated with Cenozoic subduction and of heat sources related to either late Cenozoic tectono-magmatic events or significant shear-strain heating. At Warm Springs Bay, 75 km from the plate boundary, an anomalously high heat flow of 150 mW m−2 can most plausibly be ascribed to the thermal spring activity from which its name is derived. At Quartz Hill, 240 km landward of the plate boundary, a value of 115 mW m−2 might indicate a transition to a province of high heat flow resulting from late Tertiary and Quaternary extension and volcanism.

scholarly journals High heat flow in the trans-Hudson Orogen, Central Canadian Shield

1996 ◽  
Vol 23 (21) ◽  
pp. 3027-3030 ◽  
Author(s):  
L. Guillou-Frottier ◽  
C. Jaupart ◽  
J. C. Mareschal ◽  
C. Gariépy ◽  
G. Bienfait ◽  
...  
Keyword(s):  
Heat Flow ◽  
High Heat ◽  
Canadian Shield ◽  
High Heat Flow

scholarly journals Gold in Irish Coal: Palaeo-Concentration from Metalliferous Groundwaters

Minerals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 635
Author(s):  
Liam A. Bullock ◽  
John Parnell ◽  
Joseph G.T. Armstrong ◽  
Magali Perez ◽  
Sam Spinks
Keyword(s):  
Heat Flow ◽  
Low Temperature ◽  
Precious Metals ◽  
High Heat ◽  
Selenium Content ◽  
Foreland Basins ◽  
High Heat Flow ◽  
South Wales ◽  
First Time ◽  
Very High

Gold grains, up to 40 μm in size and containing variable percentages of admixed platinum, have been identified in coals from the Leinster Coalfield, Castlecomer, SE Ireland, for the first time. Gold mineralisation occurs in sideritic nodules in coals and in association with pyrite and anomalous selenium content. Mineralisation here may have reflected very high heat flow in foreland basins north of the emerging Variscan orogenic front, responsible for gold occurrence in the South Wales Coalfield. At Castlecomer, gold (–platinum) is attributed to precipitation with replacive pyrite and selenium from groundwaters at redox interfaces, such as siderite nodules. Pyrite in the cores of the nodules indicates fluid ingress. The underlying Caledonian basement bedrock is mineralised by gold, and thus likely provided a source for gold. The combination of the gold occurrences in coal in Castlecomer and in South Wales, proximal to the Variscan orogenic front, suggests that these coals along the front could comprise an exploration target for low-temperature concentrations of precious metals.

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