Heat flow and thermal structure of the lithosphere across the Baltic Shield and northern Tornquist Zone

Balling, Niels

doi:10.1016/0040-1951(94)00215-u

Cited by 111 publications

(73 citation statements)

References 59 publications

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“…The surface z = 0 correction is 19 mW m -2 and it decreases with depth due to diffusive process. It is comparable to corrections proposed by Balling (1995) in northern Tornquist zone, 15-20 mW m -2 , though ours is on the high side in accordance with newest findings on the amplitude of the surface changes as discussed above.…”

Section: Heat Flow In the Niedźwiedź Massifsupporting

confidence: 93%

Lithosphere thermal structure at the eastern margin of the Bohemian Massif: a case petrological and geophysical study of the Niedźwiedź amphibolite massif (SW Poland)

Puziewicz

Czechowski

Krysiński

et al. 2011

Int J Earth Sci (Geol Rundsch)

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The crustal section beneath amphibolite Niedźwiedź Massif (Fore-Sudetic Block in NE Bohemian Massif), modelled on the basis of geological and seismic data, is dominated by gneisses with subordinate granites (upper and middle crust) and melagabbros (lower crust). The geotherm was calculated based on the chemical analyses of the heat-producing elements in the rocks forming the crust and the measurements of their density and heat conductivity. The results were verified by heat flow calculations based on temperature measurements from 1,600 m deep well in the Niedźwiedź Massif and by temperaturedepth estimates in mantle xenoliths coming from the nearby ca. 4.5 My basanite plug in Lutynia. The paleoclimate-corrected heat flow in the Niedźwiedź Massif is 69.5 mW m -2 , and the mantle heat flow is 28 mW m -2 . The mantle beneath the Massif was located marginally relative to the areas of intense Cenozoic thermal rejuvenation connected with alkaline volcanism. This results in geotherm which is representative for lithosphere parts located at the margins of zones of continental alkaline volcanism and at its waning stages. The lithosphereasthenosphere boundary (LAB) beneath Niedźwiedź is located between 90 and 100 km depth and supposedly the rheological change at LAB is not related to the appearance of melt.

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Section: Heat Flow In the Niedźwiedź Massifsupporting

confidence: 93%

Lithosphere thermal structure at the eastern margin of the Bohemian Massif: a case petrological and geophysical study of the Niedźwiedź amphibolite massif (SW Poland)

Puziewicz

Czechowski

Krysiński

et al. 2011

Int J Earth Sci (Geol Rundsch)

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“…3) are consistent with the estimates previously obtained for particular areas of the Fennoscandian Shield [Balling, 1995;Pasquale et al, 1991]. These values make it possible to differentiate the recent thermal activity of the mantle.…”

Section: Thermal Model Of the Earth's Crust And Upper Mantlesupporting

confidence: 90%

Geologic transect across the Grenville orogen of Ontario and New York

et al. 2000

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Abstract:The complex geophysical 3D model of the Earth's crust and the upper mantle is created for the Archaean Karelian Craton and the Late Palaeoproterozoic accretionary Svecofennian Orogen of the southeastern Fennoscandian Shield with the use of methods of complex inversion of geophysical data based on stochastic description of interrelations of physical properties of the medium (density, P-wave velocity, and heat generation). To develop the model, we use results of deep seismic studies, gravity and surficial heat flow data on the studied region. Numerical solutions of 3D problems are obtained in the spherical setting with an allowance for the Earth's surface topography. The geophysical model is correlated with the regional geological data on the surface and results of seismic CMP studies along 4B, FIRE-1 and FIRE-3-3A profiles. Based on results of complex geophysical simulation and geological interpretation of the 3D model, the following conclusions are drawn. (1) The nearly horizontal density layering of the continental crust is superimposed on the previously formed geological structure; rock differentiation by density is decreasing with depth; the density layering is controlled by the recent and near-recent state of the crust, but can be disturbed by the latest deformations. (2) Temperature variations at the Moho are partially determined by local variations of heat generation in the mantle, which, in turn, are related to local features of its origin and transformation. (3) The concept of the lower continental crust being a reflectivity zone and the concept of the lower continental crust being a layer of high density and velocity are not equivalent: the lower crust is the deepest, high-density element of near-horizontal layering, whereas the seismic image of the reflectivity zone is primarily related to transformation of the crust as a result of magmatic under-and intraplating under conditions of extension and mantle-plume activity. (4) At certain combinations of crustal thickness and temperature at the level of Moho discontinuity, the crust in a platform region can be transformed into eclogites. In this case, the crust-mantle boundary is determined by quantitative proportions of the rocks that underwent eclogitization or escaped this process and by corresponding density and velocity values. (5) High compaction of rocks in the crust under lithostatic loading cannot be explained by «simple» concepts of metamorphism and/or rock compaction, which are based on laboratory studies of rock samples and mathematical simulations; this is an evidence of the existence of additional, quite strong mechanisms providing for reversible changes of the rocks.Key words: geophysical simulation, complex inversion, thermal model, density model, CMP seismic profiling, crustalmantle boundary, velocity-density Moho discontinuity, Karelian Craton, Svecofennian Orogen.Recommended by E.V. Sklyarov Аннотация: Трехмерная комплексная геофизическая модель земной коры и верхней части мантии архейско-го Карельского кратона и позднепалеопро...

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“…Assuming a surface temperature of about 208C at the time of inversion then we derive average thermal gradients in the basin of about 28-388C/km. Using our unpublished conductivity measurements cited above, these data yield heat flows of c. 75 -100 mWm 22 during the late stages of basin evolution, comparable with the range of modern thermal gradients and somewhat higher than in the Tornquist zone in western Europe (Balling 1995).…”

Section: Styles Of Inversion In Naturesupporting

confidence: 53%

Lower crustal rheological expression in inverted basins

Sandiford

Hansen

McLaren

2006

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Although lithospheric modelling has provided extraordinary insights into the processes that shape the continental crust, considerable uncertainty surrounds the basic rheology that governs behaviour at geological timescales. In part, this is because it has proved difficult to identify the geological observations that might discriminate, or unify, models of lithospheric rheology. In particular, the relative strength of lower crust and upper mantle remains a contentious aspect of continental lithospheric rheology. We show that various models for lower crustal rheology may produce distinct patterns of inversion in extensional sedimentary basins, consistent with some of the observed natural variability of inversion styles. Inversion of basin interiors, as is common in European Mesozoic basins, is favoured by a lithospheric rheology more sensitive to lateral thermal structure than to changes in the depth of the Moho, consistent with there being little strength contrast between the lower crust and upper mantle in these settings. In contrast, inversion of basin margins, particularly involving basinward verging structures, is consistent with a rheological sensitivity to the depth of Moho as would apply for a lower crust much weaker than the upper mantle. We use an example from central Australia to demonstrate this later response, together with thermochronologic data that suggests that a relatively weak lower crust in this setting may reflect abnormally high geothermal gradients.

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Heat flow and thermal structure of the lithosphere across the Baltic Shield and northern Tornquist Zone

Cited by 111 publications

References 59 publications

Lithosphere thermal structure at the eastern margin of the Bohemian Massif: a case petrological and geophysical study of the Niedźwiedź amphibolite massif (SW Poland)

Lithosphere thermal structure at the eastern margin of the Bohemian Massif: a case petrological and geophysical study of the Niedźwiedź amphibolite massif (SW Poland)

Geologic transect across the Grenville orogen of Ontario and New York

Lower crustal rheological expression in inverted basins

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