scholarly journals Martian surface heat production and crustal heat flow from Mars Odyssey Gamma-Ray spectrometry

2011 ◽  
Vol 38 (14) ◽  
pp. n/a-n/a ◽  
Author(s):  
B. C. Hahn ◽  
S. M. McLennan ◽  
E. C. Klein
Keyword(s):  
Heat Flow ◽  
Heat Production ◽  
Gamma Ray ◽  
Surface Heat ◽  
Gamma Ray Spectrometry ◽  
Martian Surface ◽  
Mars Odyssey

Heat production and thermal conductivity of rocks from the Pikwitonei–Sachigo continental cross section, central Manitoba: implications for the thermal structure of Archean crust

1987 ◽  
Vol 24 (8) ◽  
pp. 1583-1594 ◽  
Author(s):  
David M. Fountain ◽  
Matthew H. Salisbury ◽  
Kevin P. Furlong
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Cross Section ◽  
Heat Production ◽  
Thermal Structure ◽  
Granulite Facies ◽  
Surface Heat ◽  
Gamma Ray Spectrometry ◽  
Surface Heat Flow ◽  
Greenstone Belts

The Pikwitonei and Sachigo subprovinces of central Manitoba provide a cross-sectional view of the Superior Province crust. In cross section, the upper to mid-level crust is composed of synformal greenstone belts surrounded by tonalitic gneisses, both of which are intruded by granitoid plutons. This crustal structure persists downward into the granulite facies, where keels of the greenstone belts can be found. To constrain thermal models of the crust, we measured heat production and thermal conductivity in 60 rocks from this terrain using standard gamma-ray spectrometry and divided bar techniques. Large vertical and lateral heterogeneities in heat production in the upper crust are evident; heat production is high in granites and metasedimentary rocks, intermediate in tonalite gneisses, and low in the portions of greenstone belts dominated by mafic meta-igneous rocks. In the deeper granulite facies rocks, heat production decreases by a factor of two in the tonalitic gneisses and remains low in the high-grade mafic rocks. When applied to the Pikwitonei–Sachigo crust cross section, the laboratory data here do not support step function or exponential models of the variation of heat production with depth. However, estimates of surface heat flow and surface heat production for various sites in the crustal model yield the well-known linear relationship between surface heat production and surface heat flow observed for heat-flow provinces for both one- and two-dimensional models. This demonstrates that determinations of heat production with depth based on inversion of the linear heat-production–heat-flow relationship are nonunique.

Deep Drill 1972. Heat Flow and Heat Production in Bermuda

1974 ◽  
Vol 11 (6) ◽  
pp. 809-818 ◽  
Author(s):  
R. D. Hyndman ◽  
G. K. Muecke ◽  
F. Aumento
Keyword(s):  
Heat Flux ◽  
Heat Flow ◽  
Heat Production ◽  
Land Surface ◽  
Gamma Ray ◽  
Gamma Ray Spectrometry ◽  
Geothermal Heat ◽  
Sea Floor ◽  
Average Value ◽  
The Mean

The geothermal heat flux determined in a borehole on Bermuda is 1.36 μcal/cm2 s (57 mW/m2). The value is corrected for the topographic effect of the Bermuda sea-mount and the difference between sea floor and land surface temperatures. Radioactive heat production in the borehole core determined by gamma-ray spectrometry has an average value of 1.45 × 10−13 cal/cm3 s (6.11 × 10−7 W/m3). Of the altered tholeiite flows and intrusive lamprophyric sheets which make up the section to 800 m, the sheets have 10 times the heat production of the flows. If the heat production attributable to the Bermuda seamount is subtracted from the measured heat flux a value of 1.26 μcal/cm2 s (53 mW/m2) is obtained which is in good agreement with the mean of surrounding sea floor measurements and with the mean for Cretaceous ocean floor. The low heat flow and the small amount of subsidence substantiates the radioactive dating data which indicates the present seamount structure was produced about 33 m.y. ago by intrusion and uplift of a much older structure.

scholarly journals K and Cl concentrations on the Martian surface determined by the Mars Odyssey Gamma Ray Spectrometer: Implications for bulk halogen abundances in Mars

2010 ◽  
Vol 37 (12) ◽  
pp. n/a-n/a ◽  
Author(s):  
G. Jeffrey Taylor ◽  
William V. Boynton ◽  
Scott M. McLennan ◽  
Linda M. V. Martel
Keyword(s):  
Gamma Ray ◽  
Martian Surface ◽  
Gamma Ray Spectrometer ◽  
Mars Odyssey

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.

scholarly journals Crustal heat production and estimate of terrestrial heat flow in central East Antarctica, with implications for thermal input to the East Antarctic ice sheet

2018 ◽  
Vol 12 (2) ◽  
pp. 491-504 ◽  
Author(s):  
John W. Goodge
Keyword(s):  
Heat Flow ◽  
Heat Production ◽  
Ice Sheet ◽  
Surface Heat ◽  
East Antarctica ◽  
Antarctic Ice Sheet ◽  
Surface Heat Flow ◽  
Terrestrial Heat Flow ◽  
Production Values ◽  
East Antarctic Ice Sheet

Abstract. Terrestrial heat flow is a critical first-order factor governing the thermal condition and, therefore, mechanical stability of Antarctic ice sheets, yet heat flow across Antarctica is poorly known. Previous estimates of terrestrial heat flow in East Antarctica come from inversion of seismic and magnetic geophysical data, by modeling temperature profiles in ice boreholes, and by calculation from heat production values reported for exposed bedrock. Although accurate estimates of surface heat flow are important as an input parameter for ice-sheet growth and stability models, there are no direct measurements of terrestrial heat flow in East Antarctica coupled to either subglacial sediment or bedrock. As has been done with bedrock exposed along coastal margins and in rare inland outcrops, valuable estimates of heat flow in central East Antarctica can be extrapolated from heat production determined by the geochemical composition of glacial rock clasts eroded from the continental interior. In this study, U, Th, and K concentrations in a suite of Proterozoic (1.2–2.0 Ga) granitoids sourced within the Byrd and Nimrod glacial drainages of central East Antarctica indicate average upper crustal heat production (Ho) of about 2.6  ±  1.9 µW m−3. Assuming typical mantle and lower crustal heat flux for stable continental shields, and a length scale for the distribution of heat production in the upper crust, the heat production values determined for individual samples yield estimates of surface heat flow (qo) ranging from 33 to 84 mW m−2 and an average of 48.0  ±  13.6 mW m−2. Estimates of heat production obtained for this suite of glacially sourced granitoids therefore indicate that the interior of the East Antarctic ice sheet is underlain in part by Proterozoic continental lithosphere with an average surface heat flow, providing constraints on both geodynamic history and ice-sheet stability. The ages and geothermal characteristics of the granites indicate that crust in central East Antarctica resembles that in the Proterozoic Arunta and Tennant Creek inliers of Australia but is dissimilar to other areas like the Central Australian Heat Flow Province that are characterized by anomalously high heat flow. Age variation within the sample suite indicates that central East Antarctic lithosphere is heterogeneous, yet the average heat production and heat flow of four age subgroups cluster around the group mean, indicating minor variation in the thermal contribution to the overlying ice sheet from upper crustal heat production. Despite these minor differences, ice-sheet models may favor a geologically realistic input of crustal heat flow represented by the distribution of ages and geothermal characteristics found in these glacial clasts.

Localized heat flow and Tertiary mineralization in southern New Mexico

Geophysics ◽  
1983 ◽  
Vol 48 (9) ◽  
pp. 1212-1218
Author(s):  
Gary W. Zielinski ◽  
Gail Moritz DeCoursey
Keyword(s):  
New Mexico ◽  
Heat Flow ◽  
Heat Source ◽  
Heat Production ◽  
Convective Instability ◽  
Local Scale ◽  
Surface Heat ◽  
The Body ◽  
Hydrothermal Mineralization ◽  
Granitic Intrusion

Eight shallow (<100 m deep) relative heat flow determinations from southern New Mexico reveal a systematic 3 HFU [Formula: see text] increase occurring within a distance of 2 km. The maximum surface heat flow appears roughly to overlie a Tertiary granitic body at a depth of about 600 m within an area of known hydrothermal mineralization. The presence of the anomaly, believed to be of subsurface origin, implies an active heat source centered at a depth of 1140 m, perhaps associated with hydrothermal circulation. Higher radioactive heat production in granites may contribute to convective instability and explain the apparent lateral coincidence between the anomaly and the body. This situation appears, on a local scale, analogous to coinciding zones of high present‐day heat flow and mineralization in England and Wales (Brown et al, 1980). In both cases, mineralization is associated with granitic intrusion that has occurred at a previous time which is much greater than the thermal time constant for cooling bodies. Shallow heat flow determinations may be useful in locating other similar areas and investigating possible associations of mineralization and thermal history.

scholarly journals Crustal heat production and estimate of terrestrial heat flow in central East Antarctica, with implications for thermal input to the East Antarctic ice sheet

2017 ◽  
Author(s):  
John W. Goodge
Keyword(s):  
Heat Flow ◽  
Heat Production ◽  
Ice Sheet ◽  
Surface Heat ◽  
East Antarctica ◽  
Antarctic Ice Sheet ◽  
Surface Heat Flow ◽  
Terrestrial Heat Flow ◽  
Production Values ◽  
East Antarctic Ice Sheet

Abstract. Terrestrial heat flow is a critical first-order factor governing the thermal condition and, therefore, mechanical stability of Antarctic ice sheets, yet heat flow across Antarctica is poorly known. Previous estimates of terrestrial heat flow come from inversion of seismic and magnetic geophysical data, by modeling temperature profiles in ice boreholes, and by calculation from heat production values reported for exposed bedrock. Although accurate estimates of surface heat flow are important as an input parameter for ice-sheet growth and stability models, there are no direct measurements of terrestrial heat flow in East Antarctica coupled to either subglacial sediment or bedrock. Bedrock outcrop is limited to coastal margins and rare inland exposures, yet valuable estimates of heat flow in central East Antarctica can be extrapolated from heat production determined by the geochemical composition of glacial rock clasts eroded from the continental interior. In this study, U, Th and K concentrations in a suite of Proterozoic (1.2–2.0 Ga) granitoids sourced within the Byrd and Nimrod glacial drainages of central East Antarctica indicate average upper crustal heat production (Ho) of about 2.6 ± 1.9 μW m-3. Assuming typical mantle and lower crustal heat flux for stable continental shields, and a length scale for the distribution of heat production in the upper crust, the heat production values determined for individual samples yield estimates of surface heat flow (qo) ranging from 33–84 mW m-2 and an average of 48.0 ± 13.6 mW m-2. Estimates of heat production obtained for this suite of glacially-sourced granitoids therefore indicate that the interior of the East Antarctic ice sheet is underlain in part by Proterozoic continental lithosphere with average surface heat flow, providing constraints on both geodynamic history and ice-sheet stability. The ages and geothermal characteristics of the granites indicate that crust in central East Antarctica resembles that in the Proterozoic Arunta and Tenant Creek inliers of Australia, but is dissimilar to other areas characterized by anomalously high heat flow in the Central Australian Heat Flow Province. Age variation within the sample suite indicates that central East Antarctic lithosphere is heterogeneous, yet the average heat production and heat flow of four age subgroups cluster around the group mean, indicating minor variation in thermal contribution to the overlying ice sheet from upper crustal heat production. Despite their minor differences, ice-sheet models may favor a geologically realistic model of crustal heat flow represented by such a distribution of ages and geothermal characteristics.

Analysis of Heat Flow Data–Vertical Variations of Heat Flow and Heat Producing Elements in Sediments

1975 ◽  
Vol 12 (6) ◽  
pp. 996-1005 ◽  
Author(s):  
V. M. Hamza ◽  
A. E. Beck
Keyword(s):  
Heat Flow ◽  
Heat Production ◽  
Gamma Ray ◽  
Detailed Examination ◽  
Uranium Content ◽  
Thermal Resistivity ◽  
Geochemical Reactions ◽  
Vertical Variations ◽  
Heat Flow Variations

Gamma ray spectrometric techniques have been used for the determination of uranium, thorium and potassium contents from cores selected at 3 to 4 m intervals from a 600 m deep borehole in sedimentary formations and the results compared with a similarly detailed examination of heat flow, and some physical properties, from the same borehole.The results indicate a broad positive correlation between thermal resistivity and some of the radio-element parameters and between heat flow and heat production. The heat production variations down the borehole are not quantitatively sufficient to explain the observed heat flow variations. The uranium series appears to be in radioactive equilibrium even in those sections where the uranium content is low, the porosity relatively high and the heat flow low; it is therefore concluded that the depletion of uranium is due to an ancient rather than a recent leaching process and that it is unlikely that the heat flow variations along the borehole are due to existing or recent underground waterflows. Long term geochemical reactions are now thought to be the most likely explanation of the heat flow variations.

Temperature structure of the Andean subduction zone as derived from the 3D geometry of crustal and upper mantle discontinuities

2020 ◽  
Author(s):  
Andres Tassara ◽  
Joaquín Julve ◽  
Iñigo Echeverría ◽  
Ingo Stotz
Keyword(s):  
Heat Flow ◽  
Heat Production ◽  
Thermal Structure ◽  
Surface Heat ◽  
Thermal Parameters ◽  
Continental Lithosphere ◽  
Flow Measurements ◽  
Study Region ◽  
Surface Heat Flow ◽  
Input Model

&lt;p&gt;The distribution of temperature inside active continental margins plays a fundamental role on regulating first order geodynamic processes as the isostatic balance, rheologic behavior of crust and mantle, magmagenesis, volcanism and seismogenesis. In spite of these major implications, well-constrained 3D thermal models are known for few regions of the world (Europe, Western USA, China) where large geophysical databases have been integrated into compositional and structural models of crust and lithospheric mantle from which a thermal model is derived. Here we present a three-dimensional representation of the distribution of temperature underneath the Andean active margin of South America (10&amp;#176;-45&amp;#176;S) that is based on a geophysically-constrained model for the geometry of the subducted slab, continental lithosphere-asthenosphere boundary (LAB), Moho discontinuity and an intracrustal discontinuity (ICD). This input model was constructed by forward modelling the satellite gravity anomaly under the constraint of most of the seismic information published for this region. We use analytical expressions of 1D conductive continental geotherms with adequate boundary conditions that consider the compositional stratification of crust and mantle included in the input model, and the advective thermal effect of slab subduction. The 1D geotherms are assembled into a 3D volume defining the thermal structure of the study region. We test the influence of several thermal parameters and structural configurations of the Andean lithosphere by comparing the resulting surface heat flow distribution of these different models against a database containing heat flow measurements that we compile from the literature. Our results show that the thermal structure and derived surface heat flow is dominantly controlled by the geometry of the thermal boundary layer at the base of the lithosphere, i.e. the slab upper surface below the forearc and LAB inland. Variations on the modeled configuration of the continental lithosphere (i.e. the way on which the geometry of the continental Moho and ICD are considered into the definition of a space-variable thermal conductivity or the length scale for radiogenic heat production) have an effect on surface heat flow that is lower than the average uncertainty of the measurements and therefore can be considered as second-order. The simplicity of our analytical approach allows us to compute hundreds of different models in order to test the sensitivity of results to changes on thermal parameters (conductivity, heat production, mantle potential temperature, etc), which provides a tool for discussing their possible range of values in the context of a subduction margin. We will also show how variations of these models impact on the Moho temperature and therefore in the expected mechanical behavior of crust and mantle in this geotectonic context&lt;/p&gt;

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