Estimates of terrestrial heat flow in offshore eastern Canada

1985 ◽  
Vol 22 (10) ◽  
pp. 1503-1517 ◽  
Author(s):  
Marshall Reiter ◽  
Alan M. Jessop
Keyword(s):  
Heat Flow ◽  
Heat Generation ◽  
Newfoundland And Labrador ◽  
High Heat ◽  
Magmatic Activity ◽  
Shelf Edge ◽  
Eastern Canada ◽  
Heat Flows ◽  
Bottom Hole ◽  
Outer Half

From available bottom-hole temperatures and conductivities estimated from lithologic descriptions, heat-flow estimates are calculated for 72 sites on the Canadian Atlantic Shelf. The resulting data suggest a pattern of low heat flow (~055 mW/m2) within the Paleozoic basins in proximity to land areas and generally intermediate heat flow (~60–80 mW/m2) along the outer half of the continental shelf. Higher heat flows (~90 mW/m2) are estimated along the shelf edge in some areas, e.g., the southwestern Scotian Shelf and the eastern Newfoundland and Labrador shelves. Radioactive heat generation in sediments that thicken seawards probably does not account for the observed increase in heat flow. The possibility that higher heat flows in some areas may arise because of fluid movement from depth is suggested. Various other causes for the high heat flows, e.g., tectonic or magmatic activity, are considered less likely.

scholarly journals Terrestrial Heat Flow in New Zealand

2021 ◽  
Author(s):  
◽  
Om Prakash Pandey
Keyword(s):  
New Zealand ◽  
Heat Flow ◽  
Heat Generation ◽  
Plate Tectonics ◽  
High Heat ◽  
The North ◽  
Rock Types ◽  
Flow Heat ◽  
Geophysical Anomalies ◽  
First Time

<p>In this regional heat flow study of New Zealand temperatures have been measured in available boreholes using a specially constructed thermistor probe, and existing temperature information has been incorporated from various sources including oil prospecting boreholes. Thermal conductivity has been measured in the laboratory on 581 samples. Newly determined values of heat flow are given for 105 locations; values for the South Island are here presented for the first time. Most of the heat flow values have been grouped in eight regions based on the level of heat flow. This classification can be related to the occurrence of certain surface manifestations and geophysical anomalies, and to regional plate tectonics. High heat flow in three regions is consistent with melting conditions being reached at depths between 35km and 45km. These are the Taranaki Region, the West Coast Region and the Great South Basin. The average regional heat flow for these regions varies from 86.4 mW/m2 to 110.7 mW/m2. Much lower heat flow is obtained in the Hikurangi and Marlborough-Canterbury Regions; these may possibly be interconnected. Elsewhere the heat flow is low to normal with isolated highs. The broad distribution of heat flow in the North Island is typical for an active subduction region. Radioactive heat generation has been measured on rock types from various localities, and large variations have been found. The heat flow - heat generation relationship has been studied for 42 sites. A linear relationship is found only in the Taranaki and Hikurangi Regions. Temperature calculations show large differences in the deep-seated temperature distribution beneath New Zealand, and this has also been reflected in the distribution of "reduced heat flow". Temperature and heat flow can be correlated with upper mantle inhomogeneity. The inferred variation of radioactive heat generation with depth has been studied for areas beneath the Western Canterbury Region. A mean heat generation of 1.56 plus-minus .07 muW/m3 has been found in a sequence which has been inferred to occur between 17km and 30km in depth under the region; this is very much higher than the usually adopted values for the lower crust. Normal heat flow observed in the Western Cook Strait Region, and the existence of good seismic wave transmission beneath the same region, can be attributed to crustal and lithospheric thickening. The relevance of present study to petroleum occurrences has been examined and it is found that in areas of proven hydrocarbon potential the heat flow is high.</p>

scholarly journals Terrestrial Heat Flow in New Zealand

2021 ◽  
Author(s):  
◽  
Om Prakash Pandey
Keyword(s):  
New Zealand ◽  
Heat Flow ◽  
Heat Generation ◽  
Plate Tectonics ◽  
High Heat ◽  
The North ◽  
Rock Types ◽  
Flow Heat ◽  
Geophysical Anomalies ◽  
First Time

<p>In this regional heat flow study of New Zealand temperatures have been measured in available boreholes using a specially constructed thermistor probe, and existing temperature information has been incorporated from various sources including oil prospecting boreholes. Thermal conductivity has been measured in the laboratory on 581 samples. Newly determined values of heat flow are given for 105 locations; values for the South Island are here presented for the first time. Most of the heat flow values have been grouped in eight regions based on the level of heat flow. This classification can be related to the occurrence of certain surface manifestations and geophysical anomalies, and to regional plate tectonics. High heat flow in three regions is consistent with melting conditions being reached at depths between 35km and 45km. These are the Taranaki Region, the West Coast Region and the Great South Basin. The average regional heat flow for these regions varies from 86.4 mW/m2 to 110.7 mW/m2. Much lower heat flow is obtained in the Hikurangi and Marlborough-Canterbury Regions; these may possibly be interconnected. Elsewhere the heat flow is low to normal with isolated highs. The broad distribution of heat flow in the North Island is typical for an active subduction region. Radioactive heat generation has been measured on rock types from various localities, and large variations have been found. The heat flow - heat generation relationship has been studied for 42 sites. A linear relationship is found only in the Taranaki and Hikurangi Regions. Temperature calculations show large differences in the deep-seated temperature distribution beneath New Zealand, and this has also been reflected in the distribution of "reduced heat flow". Temperature and heat flow can be correlated with upper mantle inhomogeneity. The inferred variation of radioactive heat generation with depth has been studied for areas beneath the Western Canterbury Region. A mean heat generation of 1.56 plus-minus .07 muW/m3 has been found in a sequence which has been inferred to occur between 17km and 30km in depth under the region; this is very much higher than the usually adopted values for the lower crust. Normal heat flow observed in the Western Cook Strait Region, and the existence of good seismic wave transmission beneath the same region, can be attributed to crustal and lithospheric thickening. The relevance of present study to petroleum occurrences has been examined and it is found that in areas of proven hydrocarbon potential the heat flow is high.</p>

Review: The thermal regime along the southern Canadian Cordillera Lithoprobe corridor

1995 ◽  
Vol 32 (10) ◽  
pp. 1611-1617 ◽  
Author(s):  
R. D. Hyndman ◽  
T. J. Lewis
Keyword(s):  
Heat Flow ◽  
Heat Generation ◽  
Thermal Regime ◽  
Volcanic Belt ◽  
Normal Fault ◽  
High Heat ◽  
General Level ◽  
Canadian Cordillera ◽  
Seismic Structure ◽  
Brittle Ductile Transition

This summary article describes the surface heat flow and heat generation data available for the Southern Canadian Cordillera Lithoprobe Transect, and the inferred crustal temperatures. At the western end of the transect, the continental margin has the characteristic heat flow pattern of a subduction zone; there are high heat flows over the young oceanic crust of the deep-sea Cascadia Basin (~120 mW·m−2), decreasing values landward on the continental slope and shelf (90–50 mW·m−2), and very low heat flow and low crustal temperatures in the forearc region of Vancouver Island and the adjacent mainland (30–40 mW·m−2). Very high and irregular heat flow occurs in the Garibaldi Volcanic Belt at the northern end of the Cascade volcanic arc. To the east, across the Intermontane and Omineca belts to the Rocky Mountain Trench, the heat flow and inferred crustal temperatures are high. The highest values are in the east in the Omineca Belt, where the radioactive heat generation is especially great. The crustal thermal regime has important implications for the interpretation of the deep seismic structure: (1) The brittle–ductile transition (~450 °C), which occurs in the mid-crust for most of the transect, is expected to represent a general level of thrust and normal fault detachment. The deeper crust may be mechanically decoupled from that above. (2) Crustal thickness may be related to temperature. If the lithosphere temperature is high and its density decreased by thermal expansion, there can be isostatic equilibrium with a thin crust and high topography. (3) The thermal regime appears to control the depth to the widespread crustal reflectivity and high electrical conductivity in the deep crust.

Heat flux measurements in southwestern British Columbia: the thermal consequences of plate tectonics

1985 ◽  
Vol 22 (9) ◽  
pp. 1262-1273 ◽  
Author(s):  
T. J. Lewis ◽  
A. M. Jessop ◽  
A. S. Judge
Keyword(s):  
Heat Flux ◽  
British Columbia ◽  
Heat Flow ◽  
Heat Generation ◽  
High Heat ◽  
Heat Fluxes ◽  
Eastern Coast ◽  
Plutonic Complex ◽  
Coast Plutonic Complex ◽  
Reduced Heat Flow

Measured heat fluxes from previously published data and 34 additional boreholes outline the terrestrial heat flow field in southern British Columbia. Combined with heat generation representative of the crust at 10 sites in the Intermontane and Omineca belts, the data define a heat flow province with a reduced heat flow of 63 mW m−2 and a depth scale of 10 km. Such a linear relationship is not found or expected in the Insular Belt and the western half of the Coast Plutonic Complex where low heat fluxes are interpreted to be the result of recent subduction. The apparent boundary between low and high heat flux is a transition over a distance of 20 km, located in Jervis Inlet 20–40 km seaward of the Pleistocene Garibaldi Volcanic Belt.The warm, thin crust of the Intermontane and Omenica Crystalline belts is similar to that of areas of the Basin and Range Province where the youngest volcanics are more than 17 Ma in age. Processes 50 Ma ago that completely heated the crust and upper mantle could theoretically produce such high heat fluxes by conductive cooling of the lithosphere. But it is more likely that the asthenosphere flows towards the subduction zone, bringing heat to the base of the lithosphere. Since the reduced heat flow is high but constant, large differences in upper crustal temperatures within this heat flow province at present are caused by large variations in both crustal heat generation and near-surface thermal conductivity. The sharp transition in heat flux near the coast is the result of the combined effects of convective heating of the eastern Coast Plutonic Complex, pronounced differential uplift and erosion across a boundary within the Coast Plutonic Complex, and the subducting oceanic plate.

Heat flow measurements under some lakes in the Superior Province of the Canadian Shield

1979 ◽  
Vol 16 (10) ◽  
pp. 1951-1964 ◽  
Author(s):  
R. G. Allis ◽  
G. D. Garland
Keyword(s):  
Heat Flow ◽  
High Heat ◽  
Flow Measurements ◽  
Average Heat ◽  
Heat Flows ◽  
Climatic Variations ◽  
Northwestern Ontario ◽  
Flow Heat ◽  
Lateral Heat ◽  
Made In

Six heat flow values have been obtained from measurements made in the sediments of thermally-stable lakes in four major structural belts of northwestern Ontario. Each heat flow is the average of measurements from 3–6 neighbouring lakes. Corrections for the thermal history, lateral heat flow, sedimentation, and refraction effects have been applied. High heat flows which were measured in the Quetico gneiss superbelt (77 mW/m2) and on the Indian Lake intrusion in the Wabigoon superbelt (64 mW/m2) are related to above-average heat productivities at these locations, but the extent in depth of the sources is shown to be very different in the two cases. The consistency of the lake results with borehole measurements, on a heat flow – heat productivity plot, strongly suggests that the former are not perturbed by recent climatic variations.

The flow of heat through the floor of the Atlantic Ocean

1954 ◽  
Vol 222 (1150) ◽  
pp. 408-429 ◽  
Keyword(s):  
Heat Flow ◽  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
High Heat ◽  
Unexpected Result ◽  
Heat Flows ◽  
The North ◽  
The Mean ◽  
The Individual

The measurement of the temperature gradient and thermal conductivity in the sediments beneath the floor of the North Atlantic Ocean is described. Measurements were made at five stations. The mean heat flow and conductivity were found to be 0·98 × 10 -6 cal/cm 2 s and 25 × 10 -4 cal/cm °Cs. The heat flows at the individual stations range from 0·58 to 1·42 × 10 -6 cal/cm 2 s. The high heat flow is an unexpected result, and it is difficult to find a source for so much heat.

Geothermal measurements in five small lakes of northwest Ontario

1976 ◽  
Vol 13 (7) ◽  
pp. 987-992 ◽  
Author(s):  
R. G. Allis ◽  
G. D. Garland
Keyword(s):  
Heat Flow ◽  
High Heat ◽  
Canadian Shield ◽  
Small Lakes ◽  
Bottom Water Temperature ◽  
Heat Flows ◽  
Small Correction ◽  
Flow Through ◽  
Gradient Measurements ◽  
Lateral Temperature

The heat flow through the floors of five small lakes of known thermal history on the Canadian Shield was measured with a modified Bullard probe. A small correction for seasonal bottom water temperature variations was applied to temperature gradient measurements, and the heat flows are corrected for glaciation, lateral temperature gradients, sedimentation rates, and lateral thermal conductivity changes. Four lakes have an average heat flow of 49 ± 4 mW/m2 (1.2 ± 0.1 μcal/cm2 s). A high heat flow in the fifth lake is thought due to unusual refraction effects. The heat generation–heat flux combination yields a point that falls near accepted lines for the Canadian Shield.

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.

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