Precambrian thermal régimes

1978 ◽  
Vol 288 (1355) ◽  
pp. 431-440 ◽  
Keyword(s):  
Heat Flow ◽  
High Heat ◽  
Wide Distribution ◽  
Global Scale ◽  
High Heat Flow ◽  
Crustal Rocks ◽  
Thermal Regimes ◽  
Metamorphic Facies ◽  
Lateral Variations ◽  
Present Pattern

Regional studies of Archaean and Proterozoic complexes provide the basis for one approach to the problem of reconstructing the thermal regimes of Precambrian eras. Such studies have a bearing both on the PT conditions under which metamorphism and deformation of continental crustal rocks took place and on the conditions of magma-generation at depth. Although several lines of evidence, including the wide distribution of low-pressure metamorphic facies series, are consistent with the inference that Archaean geothermal gradients tended to be steep, the characters of many complexes formed before 2700 Ma suggest PT ranges not far from those indicated by rocks which suffered deformation and metamorphism in Phanerozoic zones of high heat flow. Tectonic patterns developed on a global scale in early Proterozoic times suggest that lateral variations of heat flow in continental crust did not conform to the present pattern, zones of high heat flow being developed within as well as at the borders of continental rafts. There are, nevertheless, indications that the lithosphere had locally attained thicknesses comparable with those found today in many cratonic regions soon after the end of the Archaean era.

The Mid-Atlantic Ridge Near 45 °N. XVIII. Heat Flow Measurements

1972 ◽  
Vol 9 (6) ◽  
pp. 664-670 ◽  
Author(s):  
R. D. Hyndman ◽  
D. S. Rankin
Keyword(s):  
Heat Flow ◽  
High Heat ◽  
Flow Profile ◽  
High Heat Flow ◽  
Flow Zone ◽  
Flow Measurements ◽  
Crustal Rocks ◽  
Mid Atlantic Ridge ◽  
Sediment Cover ◽  
Lower Crustal

Eighteen heat flow measurements on the Mid-Atlantic Ridge, in the detailed study area between 45 and 46 °N, have a pattern of low values up to 20 km from the median valley, high heat flow 30 to 40 km away, low values again 50 to 100 km away, finally increasing to normal heat flow at great distances. The smoothed heat flow profile is everywhere lower than that predicted by theoretical cooling plate models.It is concluded that convective water flow in the fractured, porous crustal rocks of the ridge is responsible for the low heat flow near the crest. Higher values (at 30 to 40 km from the crest) occur when the sediment cover is sufficient to cut off communication between the crust and seawater. The low heat flow zone at 50 to 100 km from the crest can be explained by heat required to warm the convectively cooled crust when the rocks are sealed and circulation stops, and by the heat absorbed in lower crustal metamorphic reactions.

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.

scholarly journals Possible interrelation between the lead time of precursory seismic electric signals (SES) and geodynamics in Aegean Sea

2011 ◽  
Vol 11 (6) ◽  
pp. 1599-1603 ◽  
Author(s):  
E. Dologlou
Keyword(s):  
Heat Flow ◽  
Flow Rate ◽  
Lead Time ◽  
Aegean Sea ◽  
High Heat ◽  
Heat Flow Rate ◽  
Seismic Signals ◽  
High Heat Flow ◽  
Area North ◽  
Electric Signals

Abstract. The seismicity of the last 15 years in the Aegean Sea revealed that earthquakes (Mw > 5) with epicentres falling within the Sporades basin and the confined area north of Samos island were preceded by electric seismic signals (SES) with a remarkably long lead time. A possible explanation of this behaviour by means of specific tectonics and geodynamics which characterise these two regions, such as a significant small crustal thickness and a high heat flow rate, has been attempted. New data seem to strengthen the above hypothesis.

High heat flow in southern Tibet

Nature ◽  
1984 ◽  
Vol 307 (5946) ◽  
pp. 32-36 ◽  
Author(s):  
Jean Francheteau ◽  
Claude Jaupart ◽  
Shen Xian Jie ◽  
Kang Wen-Hua ◽  
Lee De-Lu ◽  
...  
Keyword(s):  
Heat Flow ◽  
High Heat ◽  
High Heat Flow ◽  
Southern Tibet
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