New thermal constraints for the Anatolian lithosphere from Curie depth point and Pn tomography

2021 ◽  
Author(s):  
Ali Deger Ozbakir ◽  
Hayrullah Karabulut
Keyword(s):  
Velocity Structure ◽  
Thermal Structure ◽  
Dynamic Topography ◽  
Transform Method ◽  
Radiogenic Heat ◽  
Spectral Leakage ◽  
Support Mechanism ◽  
Pn Velocity ◽  
Curie Depth ◽  
Dynamic Support

<p><span>Continental deformation can be </span><span>described in two end-member approaches: </span><span><em>block</em></span><span> (or microplate) and </span><span><em>continuum </em></span><span>models</span><span>. The first considers a strong lithosphere with deformation localized in fault zones. For </span><span>t</span><span>he latter, however,</span><span> the lithosphere is weak</span><span> and deforms as a thin viscous sheet. The Anatolia – Aegean domain represents both continuum and plate-like deformation. Furthermore, </span><span>r</span>ecent modeling studies suggest a dynamic support mechanism of the Anatolian plateaus, with dynamic topography estimates ranging from 1 to 3 km for various crustal models and geodynamic scenarios, although the gravity and crustal thickness data support predominant Airy isostasy. The solution to both intricacies relies on the thermal structure of the crust and the lithosphere. Available thermal considerations stem from either the uppermost mantle velocity structure or thermal modeling with assumptions on radiogenic heat production and boundary conditions. Yet, homogeneous and independent constraints on the lithospheric structure are scarce. We aim to contribute to this knowledge gap by providing Curie Point Depths (CPDs), which corresponds to the depth at which rock-forming minerals lose their magnetization at the Curie temperature, ~580 <sup>o</sup>C.<br><br>R<span>esolution of deep magnetic sources requires spectral methods with large windows, which reduce the CPD resolution. Moving & overlapping smaller windows have been used in order to increase the resolution, but these introduce spectral leakage and bias. </span>In previous studies, subjective wavenumber ranges of the magnetic anomaly spectra were used, often combined with wrong scaling factors between map units and the equations. This resulted in generally erroneous CPD estimates. Furthermore, CPD uncertainties have often been unquantified for the study area. <span>We use a wavelet transform method, which overcomes the artifacts due to segmentation of magnetic signal to finite windows, results in higher spatial resolution as well as enabling uncertainty estimation. </span>We used as large an area as possible for constraining the edge effects away from the study area. The resultant CPD map spatially correlates well with low Pn velocity areas, locations of volcanoes, and thermal springs.</p>

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 Effects of upper mantle heterogeneities on lithospheric stress field and dynamic topography

2017 ◽  
Author(s):  
Anthony Osei Tutu ◽  
Bernhard Steinberger ◽  
Stephan V. Sobolev ◽  
Irina Rogozhina ◽  
Anton A. Popov
Keyword(s):  
Heat Flow ◽  
Stress Field ◽  
Upper Mantle ◽  
Western Europe ◽  
Thermal Structure ◽  
Mantle Flow ◽  
Density Structure ◽  
Dynamic Topography ◽  
S Wave ◽  
Lithospheric Stress

Abstract. The orientation and tectonic regime of the observed crustal/lithospheric stress field contribute to our knowledge of different deformation processes occurring within the Earth's crust and lithosphere. In this study, we analyze the influence of the thermal and density structure of the upper mantle on the lithospheric stress field and topography. We use a 3D lithosphere-asthenosphere numerical model with power-law rheology, coupled to a spectral mantle flow code at 300 km depth. Our results are validated against the World Stress Map 2016 and the observation-based residual topography. We derive the upper mantle thermal structure from either a heat flow model combined with a sea floor age model (TM1) or a global S-wave velocity model (TM2). We show that lateral density heterogeneities in the upper 300 km have a limited influence on the modeled horizontal stress field as opposed to the resulting dynamic topography that appears more sensitive to such heterogeneities. There is hardly any difference between the stress orientation patterns predicted with and without consideration of the heterogeneities in the upper mantle density structure across North America, Australia, and North Africa. In contrast, we find that the dynamic topography is to a greater extent controlled by the upper mantle density structure. After correction for the chemical depletion of continents, the TM2 model leads to a much better fit with the observed residual topography giving a correlation of 0.51 in continents, but this correction leads to no significant improvement in the resulting lithosphere stresses. In continental regions with abundant heat flow data such as, for instant, Western Europe, TM1 results in relatively a small angular misfits of 18.30° between the modeled and observation-based stress field compared 19.90° resulting from modeled lithosphere stress with s-wave based model TM2.

scholarly journals Entropy-information perspective to radiogenic heat distribution in continental crust

2013 ◽  
Vol 20 (3) ◽  
pp. 423-428
Author(s):  
R. N. Singh ◽  
A. Manglik
Keyword(s):  
Heat Flow ◽  
Continental Crust ◽  
Heat Generation ◽  
Depth Distribution ◽  
Thermal Structure ◽  
Generation Model ◽  
Heat Sources ◽  
Radiogenic Heat ◽  
Entropy Principle ◽  
Mantle Heat Flow

Abstract. Depth distribution of radiogenic heat sources in continental crust is an important parameter that controls its thermal structure as well as the mantle heat flow at the base of continental lithosphere. Various models for the depth distribution of radiogenic heat sources have been proposed. Starting from constant and exponential models based on linear heat flow–heat generation relationship the present-day layered models integrate crustal structure and laboratory measurements of radiogenic heat sources in various exposed rocks representing crustal composition. In the present work, an extended entropy theory formalism is used for estimation of radiogenic heat sources distribution in continental crust based on principle of maximum entropy (POME). The extended entropy principle yields a constant heat generation model if only a constraint given by total radiogenic heat in the crust is used and an exponential form of radiogenic heat sources distribution if an additional constraint in the form of a second moment is used in the minimization of entropy.

scholarly journals Effects of upper mantle heterogeneities on the lithospheric stress field and dynamic topography

Solid Earth ◽  
2018 ◽  
Vol 9 (3) ◽  
pp. 649-668 ◽  
Author(s):  
Anthony Osei Tutu ◽  
Bernhard Steinberger ◽  
Stephan V. Sobolev ◽  
Irina Rogozhina ◽  
Anton A. Popov
Keyword(s):  
Heat Flow ◽  
Stress Field ◽  
Upper Mantle ◽  
Thermal Structure ◽  
Mantle Flow ◽  
Density Structure ◽  
Dynamic Topography ◽  
S Wave ◽  
Mantle Heterogeneities ◽  
Lithospheric Stress

Abstract. The orientation and tectonic regime of the observed crustal/lithospheric stress field contribute to our knowledge of different deformation processes occurring within the Earth's crust and lithosphere. In this study, we analyze the influence of the thermal and density structure of the upper mantle on the lithospheric stress field and topography. We use a 3-D lithosphere–asthenosphere numerical model with power-law rheology, coupled to a spectral mantle flow code at 300 km depth. Our results are validated against the World Stress Map 2016 (WSM2016) and the observation-based residual topography. We derive the upper mantle thermal structure from either a heat flow model combined with a seafloor age model (TM1) or a global S-wave velocity model (TM2). We show that lateral density heterogeneities in the upper 300 km have a limited influence on the modeled horizontal stress field as opposed to the resulting dynamic topography that appears more sensitive to such heterogeneities. The modeled stress field directions, using only the mantle heterogeneities below 300 km, are not perturbed much when the effects of lithosphere and crust above 300 km are added. In contrast, modeled stress magnitudes and dynamic topography are to a greater extent controlled by the upper mantle density structure. After correction for the chemical depletion of continents, the TM2 model leads to a much better fit with the observed residual topography giving a good correlation of 0.51 in continents, but this correction leads to no significant improvement of the fit between the WSM2016 and the resulting lithosphere stresses. In continental regions with abundant heat flow data, TM1 results in relatively small angular misfits. For example, in western Europe the misfit between the modeled and observation-based stress is 18.3°. Our findings emphasize that the relative contributions coming from shallow and deep mantle dynamic forces are quite different for the lithospheric stress field and dynamic topography.

Differential uplift of three Pliocene sea level indicator sites in southern Argentina driven by upwelling asthenosphere through the Patagonian slab window 

2021 ◽  
Author(s):  
Andrew Hollyday ◽  
Jacqueline Austermann ◽  
Andrew Lloyd ◽  
Mark Hoggard ◽  
Fred Richards ◽  
...  
Keyword(s):  
Sea Level ◽  
Thermal Structure ◽  
Passive Margin ◽  
Earth Model ◽  
Temperature Structure ◽  
Dynamic Topography ◽  
Level Indicator ◽  
Isostatic Adjustment ◽  
Global Mean ◽  
Slab Window

<div> <p>Bivalve and gastropod shell beds deposited during the Early Pliocene (4.69-5.23 Ma) occur in uplifted outcrops (36 – 180 m above sea level) along the east coast of Patagonian Argentina. These rock units provide a record of sea level during a geologic period when atmospheric CO2 and temperatures were higher than today. As such, reconstructing the elevation of global mean sea level (GMSL) during this time allows us to better understand how sensitive ice sheets are to increased past and future warming. However, reconstructing GMSL from local sea level indicators is hindered by effects such as mantle dynamic topography and glacial isostatic adjustment (GIA) that cause local sea level to deviate from the global mean. Here we use geodynamic modeling to better understand this complex dynamic setting and quantify the amount of uplift along this coastline.</p> </div><div> <p>Despite being located on a relatively stable passive margin, significant variations in the elevation of the paleo shoreline indicators imply that the underlying convecting mantle is deforming the coastline. In particular, the subduction of the Chile Rise beginning ~18 Ma beneath Patagonia has generated a slab window underneath this region through which hot asthenosphere ascends. However, the former slab is still present deeper in the mantle, which causes a complex interplay between the downwelling slab and the upwelling asthenosphere. To quantify the effects of dynamic topography change since the Pliocene, we run 3D mantle convection simulations using the code ASPECT. We initialize our global model with a composite temperature structure derived from recent tomographic studies and a calibrated parameterization of upper mantle anelasticity. Independent estimates of pressure and temperature from thermobarometric calculations of proximal Pali-Aike xenoliths agree with the thermal structure of the tomography-based Earth model. We back-advect temperature perturbations and extract the resulting change in dynamic topography. Pairing GIA models and a suite of convection simulations in which we vary the viscosity and buoyancy structure with the observed differential paleo shoreline elevations allows us to forward model the most likely scenario for uplift along this coast.</p> </div>

The thermal structure of the central Nova Scotia Slope (eastern Canada): seafloor heat flow and thermal maturation models

2017 ◽  
Vol 54 (2) ◽  
pp. 146-162 ◽  
Author(s):  
Eric Negulic ◽  
Keith E. Louden
Keyword(s):  
Heat Flow ◽  
Thermal Structure ◽  
Conductive Heat ◽  
Borehole Data ◽  
Eastern Canada ◽  
Flow Measurements ◽  
Seismic Reflection Data ◽  
Radiogenic Heat ◽  
Reflection Data ◽  
Hydrocarbon Maturation

The thermal history and maturation potential of the central Scotian Slope is constrained using a combination of 47 recently acquired seafloor heat flow measurements, two-dimensional (2D) seismic reflection data, available well data, simple lithospheric rift models, and thermal and petroleum systems modelling. Consistent heat flow values of 41–46 mW·m−2 were measured seaward of the salt diapiric province and across the slope away from the influence of salt structures. Significant but highly variable increases in heat flow were measured for stations overlying salt diapiric structures, reaching values upwards of 72 mW·m−2. Simple models of conductive heat transfer with static salt geometries constrained from reflection profiles indicate that two of the four models fit the data, whereas two indicate much higher values suggestive of additional, convective effects. Dynamic 2D thermal models were developed to incorporate the effects of lithospheric rifting, crustal stretching, and radiogenic heat production in the sediment and basement. These models help constrain the hydrocarbon maturation potential of the central Scotian Slope, where deep borehole data are lacking. Our results suggest that a potential Late Jurassic source rock interval rests primarily within the late oil window and that salt structures act primarily to reduce maturation in the adjacent deep sediment layers.

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