Geothermal measurements in Newfoundland

1980 ◽  
Vol 17 (10) ◽  
pp. 1370-1376 ◽  
Author(s):  
J. A. Wright ◽  
A. M. Jessop ◽  
A. S. Judge ◽  
T. J. Lewis
Keyword(s):  
Heat Flow ◽  
Heat Production ◽  
Eastern United States ◽  
Maritime Provinces ◽  
Heat Flows ◽  
Iapetus Ocean ◽  
Data Yield ◽  
Orogenic Belts ◽  
Oceanic Rocks ◽  
Reduced Heat Flow

We report heat flow values for ten holes at five sites in Newfoundland. The average observed heat flow is 43 ± 4 mW m−2. Corrected for Pleistocene surface temperature variations, the average becomes 50 ± 4 mW m−2, with a range from 38–82 mW m−2. The Dunnage zone (a vestige of the Iapetus Ocean) exhibits a heat flow lower than normal for Paleozoic orogenic belts. The highest heat flow is associated with the Carboniferous St. Lawrence granite intrusion. Heat production measurements were made at three of the sites. Those in the Dunnage zone are low (< 0.8 μW m−3), as expected for former oceanic rocks, while that for the St. Lawrence granite is high (4.9 μW m−3). A plot of heat flow versus heat production for these data and the data of Hyndman et al. for the Maritime Provinces demonstrates that Newfoundland belongs to the same heat flow province as the Maritimes and the eastern United States. The reduced heat flow for the Canadian Atlantic Provinces data is 32 ± 3 mW m−2, uncorrected, and 40 ± 3 mW m−2 when corrected for Pleistocene temperature effects. Computed geotherms for heat flows and heat productions corresponding to the upper and lower observed limits of the data yield temperatures at 30 km depth of about 575 and 475 °C respectively.

Heat flow in the Maritime Provinces of Canada

1979 ◽  
Vol 16 (6) ◽  
pp. 1154-1165 ◽  
Author(s):  
R. D. Hyndman ◽  
A. M. Jessop ◽  
A. S. Judge ◽  
D. S. Rankin
Keyword(s):  
Nova Scotia ◽  
Heat Flow ◽  
New Brunswick ◽  
Heat Production ◽  
Prince Edward Island ◽  
High Heat ◽  
Eastern United States ◽  
Maritime Provinces ◽  
Heat Flows ◽  
Maritime Canada

Heat-flow values have been obtained at six new sites in Nova Scotia and New Brunswick. These values and six previously reported for Maritime Canada range from 45 to 79 mW m−2 (1.07 to 1.89 μcal cm−2 s−1) after correction for Pleistocene glaciation. The mean 62 ± 3 mW m−2 (1.48 ± 0.06 μcal cm−2 s−1) after a glacial correction and 54 ± 3 mW m−2 (1.29 ± 0.06 μcal cm−2 s−1) without the correction are in general agreement with the average for Paleozoic orogenic belts. High heat flows in New Brunswick are probably associated with acidic or felsic volcanics with high radioactive heat production. Low heat-flow values are associated with the deep Carboniferous sedimentary basin of Prince Edward Island and northwestern Nova Scotia. Probably the region was uplifted and the surface crystalline rocks with high radioactive heat production were eroded prior to Carboniferous time. During subsequent slow subsidence, low heat production sediments were deposited in the resulting basin. High heat flows in Nova Scotia are associated with the Devonian granites and the older Meguma sediments and metasediments, which have high radioactive heat production. The heat-flow data from Nova Scotia, together with estimates of the radioactive heat production of basement rocks, are consistent with the heat-flow–heat-production relations for the eastern United States, the Canadian Shield, and for other stable areas. The temperature at the base of the crust at 35 km depth is estimated to average about 750 °C.

New heat flow density and radiogenic heat production data in the Canadian Shield and the Quebec Appalachians

1989 ◽  
Vol 26 (4) ◽  
pp. 845-852 ◽  
Author(s):  
J. C. Mareschal ◽  
C. Pinet ◽  
C. Gariépy ◽  
C. Jaupart ◽  
G. Bienfait ◽  
...  
Keyword(s):  
Heat Flow ◽  
Heat Production ◽  
Flow Density ◽  
Superior Province ◽  
Heat Flow Density ◽  
Grenville Province ◽  
Radiogenic Heat ◽  
Radiogenic Heat Production ◽  
Sedimentary Sequences ◽  
Reduced Heat Flow

New heat flow density (HFD) measurements were performed at 10 sites in Quebec. For five of the sites located in the Superior Province, the heat flow density varies between 24 and 35 mW/m2 (26 and 37 mW/m2 after adjustment for Pleistocene climatic variations). In the Grenville Province, the values obtained range between 25 and 28 mW/m2 (29 and 31 mW/m2 after adjustment). For two nearby sites in the Gaspé region (Appalachians), the heat flow density is 47 mW/m2 (48 mW/m2 after adjustment). Radiogenic heat production was also measured. At the sites located in the meta-volcano-sedimentary sequences of the Superior Province, the heat production is low (0.1–0.6 μW/m3) and it does not always correlate with the surface heat flow. In the Grenville Province, the HFD is close to (slightly higher than) the reduced heat flow of the Superior. The higher HFD in the Appalachians is partly explained by the higher crustal heat production, and partly by higher deep heat flow.

Heat flow and surface radioactivity in the Quirke Lake Syncline near Elliot Lake, Ontario, Canada

1968 ◽  
Vol 5 (6) ◽  
pp. 1417-1428 ◽  
Author(s):  
J. H. Sass ◽  
P. G. Killeen ◽  
E. D. Mustonen
Keyword(s):  
Heat Flow ◽  
Heat Production ◽  
Gamma Ray ◽  
Average Rate ◽  
Structural Effects ◽  
Gamma Ray Spectrometer ◽  
A Value ◽  
The Mean ◽  
Data Yield ◽  
Ore Zones

Heat flow was measured in seven diamond-drilled holes, ranging in depth from 300 to 900 m, in the Quirke Lake Syncline (82° 30′ W, 46° 30′ N, mean elevation 370 m), Values for individual holes vary from 1.20 to 1.40 with a mean of 1.32 ± 0.02 μcal/cm2s, and no systematic variation was detected within the 50 km2 area studied. Radiometric measurements with a portable, three-channel, gamma-ray spectrometer show a downward concentration (stratigraphically) of Th, U, and K within the lower part of the syncline, with mean concentrations of 12.7 ppm, 3.3 ppm, and 1.9%, respectively. These data yield an average rate of heat production of 4.5 heat generation units (1 hgu = 10−13 cal/cm3s). Taking account of the ore zones, the mean heat production from the syncline is about 6 hgu. Corrections for structural effects and heat production from the ore result in a value of 1.2 for the regional heat flow. This is within the range of other shield values, although somewhat higher than the average for the Canadian Shield. The high value is readily explained if the observed mean surface radioactivity persists to a depth of 7 to 10 km.

Heat flow, heat production and thermo-tectonic setting in mainland UK

1987 ◽  
Vol 144 (1) ◽  
pp. 35-42 ◽  
Author(s):  
M. K. LEE ◽  
G. C. BROWN ◽  
P. C. WEBB ◽  
J. WHEILDON ◽  
K. E. ROLLIN
Keyword(s):  
Heat Flow ◽  
Heat Production ◽  
Tectonic Setting ◽  
Flow Heat

Rheological Models for Continental Seismicity and Maximum Seismogenic Depth

1988 ◽  
Vol 59 (4) ◽  
pp. 316-316
Author(s):  
R. H. Sibson
Keyword(s):  
Heat Flow ◽  
Strain Rate ◽  
Plate Boundaries ◽  
Strain Rates ◽  
Depth Range ◽  
Eastern United States ◽  
Focal Volume ◽  
Rheological Models ◽  
As Stress ◽  
Maximum Earthquake

Abstract In fault systems at plate boundaries, maximum seismogenic depth is likely defined by the transition with depth from unstable frictional slip to localized, high strain rate (γ̇≈1011/s) quasi-plastic shearing in trans-crustal, tabular fault zones; the transition being significantly affected by variations in regional heat flow. However, such deep driven rheological models are probably inappropriate for areas of intraplate seismicity such as the eastern United States where, despite the low cratonic heat flow, the larger earthquakes (mb≈5) seem to nucleate in the 5–10 km depth range. Similar shallow nucleation depths have also been noted for large intraplate events in the cratonic crust of Australia. A more appropriate model for such intraplate activity is to view the upper levels of cratonic crust as a remotely-loaded, flawed stress-guide, where time-dependent failure may occur through processes such as stress corrosion. A rheological criterion accounting for the depths of these cratonic events is that seismogenic failure can only occur when the loading strain rate is greater than the potential rate of flow relaxation within the focal volume, suggesting an important size effect. Loading strain rates estimated from likely earthquake recurrence intervals in such areas are extremely low (<10−16/s ). At such low strain rates, the upper crust is effectively decoupled, even though no geologically obvious strain signature will develop in the middle or lower crust over lengthy time periods. Available strain energy, and perhaps maximum earthquake size, may then be quite sensitively linked to maximum seismogenic depth. A range of intermediate mixed behavior must exist between these end-member models.

scholarly journals Adjoint inversion of the thermal structure of Southeastern Australia

2019 ◽  
Vol 219 (3) ◽  
pp. 1648-1659 ◽  
Author(s):  
B Mather ◽  
L Moresi ◽  
P Rayner
Keyword(s):  
Thermal Properties ◽  
Heat Flow ◽  
Heat Production ◽  
Thermal Structure ◽  
Surface Heat ◽  
Flow Data ◽  
Data Set ◽  
Surface Heat Flow ◽  
Southeastern Australia ◽  
Curie Depth

SUMMARY The variation of temperature in the crust is difficult to quantify due to the sparsity of surface heat flow observations and lack of measurements on the thermal properties of rocks at depth. We examine the degree to which the thermal structure of the crust can be constrained from the Curie depth and surface heat flow data in Southeastern Australia. We cast the inverse problem of heat conduction within a Bayesian framework and derive its adjoint so that we can efficiently find the optimal model that best reproduces the data and prior information on the thermal properties of the crust. Efficiency gains obtained from the adjoint method facilitate a detailed exploration of thermal structure in SE Australia, where we predict high temperatures within Precambrian rocks of 650 °C due to relatively high rates of heat production (0.9–1.4 μW m−3). In contrast, temperatures within dominantly Phanerozoic crust reach only 520 °C at the Moho due to the low rates of heat production in Cambrian mafic volcanics. A combination of the Curie depth and heat flow data is required to constrain the uncertainty of lower crustal temperatures to ±73 °C. We also show that parts of the crust are unconstrained if either data set is omitted from the inversion.

Sign in / Sign up

Export Citation Format

Share Document