Extreme variability of Tibetan thermal lithosphere

Mapping Intimacies ◽

10.5194/egusphere-egu21-14135 ◽

2021 ◽

Author(s):

Bing Xia ◽

Irina Artemieva ◽

Hans Thybo

Keyword(s):

Heat Flow ◽

High Surface ◽

Surface Heat ◽

Moho Depth ◽

Yangtze Craton ◽

Surface Heat Flow ◽

The North ◽

Indian Lithosphere ◽

Extreme Variability ◽

Seismic Models

<p>We present a thermal model for the lithosphere in Tibet and adjacent regions based on the new thermal isostasy method and our compilation of the Moho depth based on published seismic models. The predicted surface heat flow is in agreement with the few available, reliable borehole measurements. Cratonic-type cold and thick lithosphere (200-240 km) with a surface heat flow of 40-50 mW/m<sup>2</sup> typifies the Tarim craton, the north-western Yangtze craton, and most of the Lhasa Block that is possibly refrigerated by underthrusting Indian lithosphere. The thick lithosphere of the Lhasa block extends further north in its western and eastern segments than in its central section. We identify a North Tibet anomaly with a thin (<80 km) lithosphere and high surface heat flow (>80-100 mW/m<sup>2</sup>), possibly associated with the removal of lithospheric mantle and asthenospheric upwelling. Other parts of Tibet have an intermediate lithosphere thickness of 120-160 km and a surface heat flow of 45-60 mW/m<sup>2</sup>, with a patchy style in eastern Tibet. In the Qaidam deep sedimentary basin the lithosphere is about 100-120 km thick. The heterogeneous thermal lithosphere beneath Tibet suggests an interplay of several mechanisms as the driver of the observed uplift.</p>

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Variations of surface heat flow and lithospheric thermal structure beneath the North American craton

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2004.04.002 ◽

2004 ◽

Vol 223 (1-2) ◽

pp. 65-77 ◽

Cited By ~ 120

Author(s):

J MARESCHAL

Keyword(s):

Heat Flow ◽

North American ◽

Thermal Structure ◽

Surface Heat ◽

Surface Heat Flow ◽

The North ◽

North American Craton ◽

Lithospheric Thermal Structure

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The Tibet lithosphere is not all hot

10.5194/egusphere-egu2020-2181 ◽

2020 ◽

Author(s):

Bing Xia ◽

Irina Artemieva ◽

Hans Thybo

Keyword(s):

Heat Flow ◽

Large Scale ◽

North China ◽

Receiver Function ◽

Thermal Structure ◽

Surface Heat ◽

Moho Depth ◽

Good Match ◽

Isostatic Compensation ◽

Surface Heat Flow

<p>We calculated the thermal lithosphere structure of Tibet and adjacent regions based on the new thermal isostasy method. Moho depth is constrained by the published receiver function results. The calculated surface heat flow in the surrounded Tarim, North China, and Yangtze cratons have a good match with the real measurements of surface heat flow. We recognize the northern Tibet anomaly where has a relatively thin lithosphere with a thermal thickness of <80 km and surface heat flow of >80 - 100 mW/m 2 may cause by the removal of lithospheric mantle and upwelling of asthenosphere. In Lhasa Block, the cold and thick lithosphere (>200 km) with a surface heat flow of 40 - 50 mW/m 2. In the east Tibet, the heterogeneous thermal lithosphere does not follow the widely spread large scale strike-slip faults and suggested that the faults do not cut down to the lithosphere. The surrounding cratons have different thermal lithosphere features. The Tarim and Yangtze cratons show typical cold and thick lithosphere with a lithosphere of >200km and surface heat flow of <50 mW/m2. The western North China Craton has an intermated lithosphere with a thickness of 120-200km and surface heat flow of 45-60 mW/m2. Our result suggested that high and flat Tibet has different isostatic compensation in different blocks. The heterogeneous lithosphere thermal structure of the Tibet suggested that the uplife force drive are difference in Tibet.</p><div> <div>&#160;</div> </div>

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Constraining the geotherm beneath the British Isles from Bayesian inversion of Curie depth: integrated modelling of magnetic, geothermal, and seismic data

Solid Earth ◽

10.5194/se-10-839-2019 ◽

2019 ◽

Vol 10 (3) ◽

pp. 839-850 ◽

Cited By ~ 6

Author(s):

Ben Mather ◽

Javier Fullea

Keyword(s):

Heat Flow ◽

Flow Field ◽

Mantle Plume ◽

Heat Production ◽

Surface Heat ◽

Integrated Modelling ◽

Moho Depth ◽

British Isles ◽

Surface Heat Flow ◽

Curie Depth

Abstract. Curie depth offers a valuable constraint on the thermal structure of the lithosphere, based on its interpretation as the depth to 580 ∘C, but current methods underestimate the range of uncertainty. We formulate the estimation of Curie depth within a Bayesian framework to quantify its uncertainty across the British Isles. Uncertainty increases exponentially with Curie depth but this can be moderated by increasing the size of the spatial window taken from the magnetic anomaly. The choice of window size needed to resolve the magnetic thickness is often ambiguous but, based on our chosen spectral method, we determine that significant gains in precision can be obtained with window sizes 15–30 times larger than the deepest magnetic source. Our Curie depth map of the British Isles includes a combination of window sizes: smaller windows are used where the magnetic base is shallow to resolve small-scale features, and larger window sizes are used where the magnetic base is deep in order to improve precision. On average, the Curie depth increases from Laurentian crust (22.2±5.3 km) to Avalonian crust (31.2±9.2 km). The temperature distribution in the crust, and associated uncertainty, was simulated from the ensemble of Curie depth realizations assigned to a lower thermal boundary condition of a crustal model (sedimentary thickness, Moho depth, heat production, thermal conductivity), constructed from various geophysical and geochemical datasets. The uncertainty in the simulated heat flow field substantially increases from ±10 mW m−2 for shallow Curie depths at ∼15 km to ±80 mW m−2 for Curie depths >40 km. Surface heat flow observations are concordant with the simulated heat flow field except in regions that contain igneous bodies. Heat flow data within large batholiths in the British Isles exceed the simulated heat flow by ∼25 mW m−2 as a result of their high rates of heat production (4–6 µW m−3). Conversely, heat refraction around thermally resistive mafic volcanics and thick sedimentary layers induce a negative heat flow misfit of a similar magnitude. A northward thinning of the lithosphere is supported by shallower Curie depths on the northern side of the Iapetus Suture, which separates Laurentian and Avalonian terranes. Cenozoic volcanism in Northern Britain and Ireland has previously been attributed to a lateral branch of the proto-Icelandic mantle plume. Our results show that high surface heat flow (>90 mW m−2) and shallow Curie depth (∼15 km) occur within the same region, which supports the hypothesis that lithospheric thinning occurred due to the influence of a mantle plume. The fact that the uncertainty is only ±3–8 km in this region demonstrates that Curie depths are more reliable in hotter regions of the crust where the magnetic base is shallow.

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Constraining the geotherm beneath the British Isles from Bayesian inversion of Curie depth: Integrated modelling of magnetic, geothermal and seismic data

10.5194/se-2019-9 ◽

2019 ◽

Cited By ~ 1

Author(s):

Ben Mather ◽

Javier Fullea

Keyword(s):

Heat Flow ◽

Flow Field ◽

Mantle Plume ◽

Heat Production ◽

Surface Heat ◽

Integrated Modelling ◽

Moho Depth ◽

British Isles ◽

Surface Heat Flow ◽

Curie Depth

Abstract. Curie depth offers a valuable constraint on the thermal structure of the lithosphere, based on its interpretation as the depth to 580 °C, but current methods underestimate the range of uncertainty. We formulate the estimation of Curie depth within a Bayesian framework to quantify its uncertainty across the British Isles. Uncertainty increases exponentially with Curie depth but this can be moderated by increasing the size of the spatial window taken from the magnetic anomaly. The choice of window size needed to resolve the magnetic thickness is often ambiguous, but based on our chosen spectral method, we determine that significant gains in precision can be obtained with windows sizes 15–30 times larger than the deepest magnetic source. Our Curie depth map of the British Isles includes a combination of window sizes: smaller windows are used where the magnetic base is shallow to resolve small-scale features, and larger window sizes are used where the magnetic base is deep in order to improve precision. On average, the Curie depth increases from Laurentian crust (22.2 ± 5.3 km) to Avalonian crust (31.2 ± 9.2 km). The temperature distribution in the crust, and associated uncertainty, was simulated from the ensemble of Curie depth realisations assigned to a lower thermal boundary condition of a crustal model (sedimentary thickness, Moho depth, heat production, thermal conductivity), constructed from various geophysical and geochemical data sets. The uncertainty of the simulated heat flow field substantially increases from ± 10 mW m−2 for shallow Curie depths ~ 15 km to ± 80 mW m−2 for Curie depths > 40 km. Surface heat flow observations are concordant with the simulated heat flow field except in regions that contain igneous bodies. Heat flow data within large batholiths in the British Isles exceed the simulated heat flow by ∼ 25 mW m−2 as a result of their high rates of heat production (4–6 μW m−3). Conversely, heat refraction around thermally resistive mafic volcanics and thick sedimentary layers induce a negative heat flow misfit of a similar magnitude. A northward thinning of the lithosphere is supported by shallower Curie depths on the northern side of the Iapetus Suture, which separates Laurentian and Avalonian terranes. Cenozoic volcanism in Northern Britain and Ireland has previously been attributed to a lateral branch of the proto-Icelandic mantle plume. Our results show that high surface heat flow (> 90 mW m−2) and shallow Curie depth (∼ 15 km) occur within the same region, which supports the hypothesis that lithospheric thinning occurred due to the influence of a mantle plume. That the uncertainty is only ± 3–8 km in this region, demonstrates that Curie depths are more reliable in hotter regions of the crust where the magnetic base is shallow.

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Variations of surface heat flow and lithospheric thermal structure beneath the North American craton

Earth and Planetary Science Letters ◽

10.1016/s0012-821x(04)00238-9 ◽

2004 ◽

Author(s):

J MARESCHAL

Keyword(s):

Heat Flow ◽

North American ◽

Thermal Structure ◽

Surface Heat ◽

Surface Heat Flow ◽

The North ◽

North American Craton ◽

Lithospheric Thermal Structure

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Thermal regime of the lithosphere in the Canadian ShieldThis article is one of a series of papers published in this Special Issue on the theme Lithoprobe — parameters, processes, and the evolution of a continent.

Canadian Journal of Earth Sciences ◽

10.1139/e09-059 ◽

2010 ◽

Vol 47 (4) ◽

pp. 389-408 ◽

Cited By ~ 17

Author(s):

Claire Perry ◽

Carmen Rosieanu ◽

Jean-Claude Mareschal ◽

Claude Jaupart

Keyword(s):

Heat Flow ◽

Heat Generation ◽

Seismic Refraction ◽

Surface Heat ◽

Canadian Shield ◽

P Wave ◽

Seismic Velocities ◽

Flow Measurements ◽

Surface Heat Flow ◽

Mantle Heat Flow

Geothermal studies were conducted within the framework of Lithoprobe to systematically document variations of heat flow and surface heat production in the major geological provinces of the Canadian Shield. One of the main conclusions is that in the Shield the variations in surface heat flow are dominated by the crustal heat generation. Horizontal variations in mantle heat flow are too small to be resolved by heat flow measurements. Different methods constrain the mantle heat flow to be in the range of 12–18 mW·m–2. Most of the heat flow anomalies (high and low) are due to variations in crustal composition and structure. The vertical distribution of radioelements is characterized by a differentiation index (DI) that measures the ratio of the surface to the average crustal heat generation in a province. Determination of mantle temperatures requires the knowledge of both the surface heat flow and DI. Mantle temperatures increase with an increase in surface heat flow but decrease with an increase in DI. Stabilization of the crust is achieved by crustal differentiation that results in decreasing temperatures in the lower crust. Present mantle temperatures inferred from xenolith studies and variations in mantle seismic P-wave velocity (Pn) from seismic refraction surveys are consistent with geotherms calculated from heat flow. These results emphasize that deep lithospheric temperatures do not always increase with an increase in the surface heat flow. The dense data coverage that has been achieved in the Canadian Shield allows some discrimination between temperature and composition effects on seismic velocities in the lithospheric mantle.

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