scholarly journals A Framework for Evaluating Variation in (U-Th)/He Datasets

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1111
Author(s):  
Francis J. Sousa ◽  
Kenneth A. Farley
Keyword(s):  
Thermal History ◽  
Synthetic Data ◽  
Diffusion Parameters ◽  
Modeling Software ◽  
History Of ◽  
Single Grain ◽  
Thermal Histories ◽  
The Impact ◽  
And Diffusion ◽  
New Framework

This paper presents a framework for evaluating variation in (U-Th)/He datasets. The framework is objective, repeatable, and based on compatibility of thermal histories derived from individual (U-Th)/He dates. The structure of this new method includes three fundamental steps. First, the allowable thermal history of each individual grain is quantitatively constrained with a model. Second, the thermal histories of all grains from a sample are visualized on the same axes. Third, the compatibility of the allowable thermal histories of each individual grain is evaluated. This allows a user to assess whether variation among single grain dates can plausibly be explained (referred to here as legitimate) or not (illegitimate). Additionally, this methodology allows for accurate representation of the impact that illegitimate variation has on the thermal history constraints of a sample. We demonstrate the application of this new framework using a variety of examples from the literature, as well as with synthetic data. Modeling presented here is executed using the modeling software QTQt (version 5.6.0) and the He diffusion kinetics based on the radiation damage accumulation and annealing model, but the framework is designed to be easily adaptable to any modeling software and diffusion parameters.

scholarly journals Exploiting Thermochronology to Quantify Exhumation Histories and Patterns of Uplift Along the Margins of Tibet

2021 ◽  
Vol 9 ◽  
Author(s):  
Kevin P. Furlong ◽  
Eric Kirby
Keyword(s):  
Thermal History ◽  
Data Sets ◽  
The Tibetan Plateau ◽  
Tectonic History ◽  
Time Histories ◽  
Major Fault ◽  
History Of ◽  
Cooling Behavior ◽  
Exhumation Rates ◽  
The Impact

The utilization of thermal-chronological data to constrain mountain building processes exploits the links among rock uplift, exhumation, and cooling during orogenesis. Conceptually, periods of rapid uplift and associated denudation will lead to cooling of rocks as they approach Earth’s surface. The linkage between uplift and exhumation can be complex, but in practice exhumation is often assumed to directly track uplift. The reconstruction of temperature-time histories via thermochronologic systems provides a proxy method to relate the cooling of rock as it is exhumed toward the surface to orogenesis. For the rapid exhumation rates that can occur in active orogenic systems the thermal history will be complex as a result of heat advection, rates of propagation of thermal perturbations, and other processes that affect the cooling behavior. These effects become amplified as exhumation rates increase, and in regions experiencing exhumation rates greater than ∼0.2–0.3 mm/yr (0.2–0.3 km/Ma) simple assumptions of cooling through a constant geotherm will bias the subsequent interpretation. Here we explore, through a suite of generalized models, the impact of exhumation rate and duration on the resulting thermal history and apparent age results. We then apply lessons from these simple exhumation systems to data sets from the high-relief ranges along the eastern margin of the Tibetan Plateau to determine exhumation histories constrained by those data. The resulting exhumation histories provide constraints on the onset of Cenozoic exhumation, the subsequent pace of exhumation, and on the tectonic history of one of the major fault systems in the central Longmen Shan.

Resolving thermal histories via multi-kinetic apatite fission track data: A case study from Phanerozoic strata within the Peel Plateau NWT, Canada

2021 ◽  
Author(s):  
Jennifer Spalding ◽  
Jeremy Powell ◽  
David Schneider ◽  
Karen Fallas
Keyword(s):  
Low Temperature ◽  
Thermal History ◽  
Fission Track ◽  
Sedimentary Basins ◽  
Source Rocks ◽  
Apatite Fission Track ◽  
Petroleum Systems ◽  
History Of ◽  
Thermal Histories ◽  
Peel Plateau

<p>Resolving the thermal history of sedimentary basins through geological time is essential when evaluating the maturity of source rocks within petroleum systems. Traditional methods used to estimate maximum burial temperatures in prospective sedimentary basin such as and vitrinite reflectance (%Ro) are unable to constrain the timing and duration of thermal events. In comparison, low-temperature thermochronology methods, such as apatite fission track thermochronology (AFT), can resolve detailed thermal histories within a temperature range corresponding to oil and gas generation. In the Peel Plateau of the Northwest Territories, Canada, Phanerozoic sedimentary strata exhibit oil-stained outcrops, gas seeps, and bitumen occurrences. Presently, the timing of hydrocarbon maturation events are poorly constrained, as a regional unconformity at the base of Cretaceous foreland basin strata indicates that underlying Devonian source rocks may have undergone a burial and unroofing event prior to the Cretaceous. Published organic thermal maturity values from wells within the study area range from 1.59 and 2.46 %Ro for Devonian strata and 0.54 and 1.83 %Ro within Lower Cretaceous strata. Herein, we have resolved the thermal history of the Peel Plateau through multi-kinetic AFT thermochronology. Three samples from Upper Devonian, Lower Cretaceous and Upper Cretaceous strata have pooled AFT ages of 61.0 ± 5.1 Ma, 59.5 ± 5.2 and 101.6 ± 6.7 Ma, respectively, and corresponding U-Pb ages of 497.4 ± 17.5 Ma (MSWD: 7.4), 353.5 ± 13.5 Ma (MSWD: 3.1) and 261.2 ± 8.5 Ma (MSWD: 5.9). All AFT data fail the χ<sup>2</sup> test, suggesting AFT ages do not comprise a single statistically significant population, whereas U-Pb ages reflect the pre-depositional history of the samples and are likely from various provenances. Apatite chemistry is known to control the temperature and rates at which fission tracks undergo thermal annealing. The r<sub>mro</sub> parameter uses grain specific chemistry to predict apatite’s kinetic behaviour and is used to identify kinetic populations within samples. Grain chemistry was measured via electron microprobe analysis to derive r<sub>mro</sub> values and each sample was separated into two kinetic populations that pass the χ<sup>2</sup> test: a less retentive population with ages ranging from 49.3 ± 9.3 Ma to 36.4 ± 4.7 Ma, and a more retentive population with ages ranging from 157.7 ± 19 Ma to 103.3 ± 11.8 Ma, with r<sub>mr0</sub> benchmarks ranging from 0.79 and 0.82. Thermal history models reveal Devonian strata reached maximum burial temperatures (~165°C-185°C) prior to late Paleozoic to Mesozoic unroofing, and reheated to lower temperatures (~75°C-110°C) in the Late Cretaceous to Paleogene. Both Cretaceous samples record maximum burial temperatures (75°C-95°C) also during the Late Cretaceous to Paleogene. These new data indicate that Devonian source rocks matured prior to deposition of Cretaceous strata and that subsequent burial and heating during the Cretaceous to Paleogene was limited to the low-temperature threshold of the oil window. Integrating multi-kinetic AFT data with traditional methods in petroleum geosciences can help unravel complex thermal histories of sedimentary basins. Applying these methods elsewhere can improve the characterisation of petroleum systems.</p>

scholarly journals On the Impact of Build Envelope Sizes on E-PBF Processed Pure Iron

2021 ◽  
Author(s):  
C. J. J. Torrent ◽  
P. Krooß ◽  
T. Niendorf
Keyword(s):  
Mechanical Properties ◽  
Electron Beam ◽  
Additive Manufacturing ◽  
Thermal History ◽  
Powder Bed Fusion ◽  
Parameter Setting ◽  
Powder Bed ◽  
History Of ◽  
Specific Temperature ◽  
The Impact

AbstractIn additive manufacturing, the thermal history of a part determines its final microstructural and mechanical properties. The factors leading to a specific temperature profile are diverse. For the integrity of a parameter setting established, periphery variations must also be considered. In the present study, iron was processed by electron beam powder bed fusion. Parts realized by two process runs featuring different build plate sizes were analyzed. It is shown that the process temperature differs significantly, eventually affecting the properties of the processed parts.

The Impact of Stationary Crossed Electrical and Magnetic Fields on Excess Charge Carriers Generated by Radiation in P-Type Mercury-Cadmium-Telluride Epitaxial Films (Review)

2010 ◽  
Vol 5 (1) ◽  
pp. 66-81
Author(s):  
Vladimir Ya. Kostyuchenko
Keyword(s):  
Magnetic Fields ◽  
Cadmium Telluride ◽  
Mercury Cadmium Telluride ◽  
Epitaxial Films ◽  
Charge Carriers ◽  
Excess Charge ◽  
Diffusion Parameters ◽  
P Type ◽  
The Impact ◽  
And Diffusion

The main characteristics of infrared photodetectors on base of p-type mercury-cadmium-telluride epitaxial films are mainly governed by recombination and diffusion parameters of minor charge carriers. The investigation of excess charge carriers behavior in epitaxial films placed in stationary crossed electrical and magnetic fields is allows determining of this parameters. This paper reviews of such photoelecromagnetic methods for investigation of excess charge carriers’ recombination and diffusion properties as methods of photomagnetic effects and photoconductivity in magnetic fields for Voight and Faradey geometry.

scholarly journals An optimized Ly α forest inversion tool based on a quantitative comparison of existing reconstruction methods

2020 ◽  
Vol 497 (4) ◽  
pp. 4937-4955
Author(s):  
Hendrik Müller ◽  
Christoph Behrens ◽  
David J E Marsh
Keyword(s):  
Newton Method ◽  
Thermal History ◽  
Statistical Approach ◽  
Synthetic Data ◽  
Inversion Methods ◽  
Systematic Uncertainties ◽  
Reconstruction Methods ◽  
History Of ◽  
Numerical Complexity ◽  
Accurate Reconstruction

ABSTRACT We present a same-level comparison of the most prominent inversion methods for the reconstruction of the matter density field in the quasi-linear regime from the Ly α forest flux. Moreover, we present a pathway for refining the reconstruction in the framework of numerical optimization. We apply this approach to construct a novel hybrid method. The methods which are used so far for matter reconstructions are the Richardson–Lucy algorithm, an iterative Gauss–Newton method and a statistical approach assuming a one-to-one correspondence between matter and flux. We study these methods for high spectral resolutions such that thermal broadening becomes relevant. The inversion methods are compared on synthetic data (generated with the lognormal approach) with respect to their performance, accuracy, their stability against noise, and their robustness against systematic uncertainties. We conclude that the iterative Gauss–Newton method offers the most accurate reconstruction, in particular at small S/N, but has also the largest numerical complexity and requires the strongest assumptions. The other two algorithms are faster, comparably precise at small noise-levels, and, in the case of the statistical approach, more robust against inaccurate assumptions on the thermal history of the intergalactic medium (IGM). We use these results to refine the statistical approach using regularization. Our new approach has low numerical complexity and makes few assumptions about the history of the IGM, and is shown to be the most accurate reconstruction at small S/N, even if the thermal history of the IGM is not known. Our code will be made publicly available.

scholarly journals The Global Politics of Anti-Racism: A View from the Canal Zone

2020 ◽  
Vol 125 (2) ◽  
pp. 460-486
Author(s):  
Rebecca Herman
Keyword(s):  
World War Ii ◽  
Global Politics ◽  
Color Line ◽  
Canal Zone ◽  
Racial Hierarchy ◽  
History Of ◽  
Global North ◽  
The One ◽  
The Impact ◽  
New Framework

Abstract During World War II, when Axis theories of racial supremacy became purported antonyms to Allied values, leaders of “non-white” countries gained a new framework for challenging a global order grounded in racialized notions of fitness for self-government. But the story is more complex than a sole focus on the international sphere allows, as those leaders who adopted anti-racist rhetoric to challenge their disadvantaged position in international politics were sometimes architects of racial hierarchy at home. This article examines how anti-racist struggles within Panama and the Canal Zone mapped onto the anti-imperialist project of a racist Panamanian state. Scholars of race and international relations have highlighted the challenges that anti-imperialist struggles posed to racialized criteria for international legitimacy, on the one hand, and the impact of geopolitical conflict on domestic struggles for racial equality, on the other. The view from the Canal Zone reveals the interplay between those two phenomena. Foregrounding Latin America in a history of the global politics of anti-racism precludes escape into binary visions of a world divided between colonizers and colonized, a racist Global North and an anti-racist Global South, or a tidy color line that splits humanity in two.

scholarly journals Thermal history of the East European Platform margin in Poland based on apatite and zircon low-temperature thermochronology

Solid Earth ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 1899-1930
Author(s):  
Dariusz Botor ◽  
Stanisław Mazur ◽  
Aneta A. Anczkiewicz ◽  
István Dunkl ◽  
Jan Golonka
Keyword(s):  
Low Temperature ◽  
Thermal History ◽  
East European Platform ◽  
Thermal Modelling ◽  
Thermal Maturity ◽  
Near Surface ◽  
East European ◽  
Basement Rocks ◽  
History Of ◽  
The Impact

Abstract. The Phanerozoic tectonothermal evolution of the SW slope of the East European Platform (EEP) in Poland is reconstructed by means of thermal maturity, low-temperature thermochronometry, and thermal modelling. We provide a set of new thermochronometric data and integrate stratigraphic and thermal maturity information to constrain the burial and thermal history of sediments. Apatite fission track (AFT) analysis and zircon (U-Th)/He (ZHe) thermochronology have been carried out on samples of sandstones, bentonites, diabase, and crystalline basement rocks collected from 17 boreholes located in central and NE Poland. They penetrated sedimentary cover of the EEP subdivided from the north to south into the Baltic, Podlasie, and Lublin basins. The average ZHe ages from Proterozoic basement rocks as well as Ordovician to Silurian bentonites and Cambrian to lower Carboniferous sandstones range from 848 ± 81 to 255 ± 22 Ma with a single early Permian age of 288 Ma, corresponding to cooling after a thermal event. The remaining ZHe ages represent partial reset or source ages. The AFT ages of samples are dispersed in the range of 235.8 ± 17.3 Ma (Middle Triassic) to 42.1 ± 11.1 Ma (Paleogene) providing a record of Mesozoic and Cenozoic cooling. The highest frequency of the AFT ages is in the Jurassic and Early Cretaceous prior to Alpine basin inversion. Thermal maturity results are consistent with the SW-ward increase of the Paleozoic and Mesozoic sediments thickness. An important break in a thermal maturity profile exists across the base Permian–Mesozoic unconformity. Thermal modelling showed that significant heating of Ediacaran to Carboniferous sedimentary successions occurred before the Permian with maximum paleotemperatures in the earliest and latest Carboniferous for Baltic–Podlasie and Lublin basins, respectively. The results obtained suggest an important role of early Carboniferous uplift and exhumation at the SW margin of the EEP. The SW slope of the latter was afterward overridden in the Lublin Basin by the Variscan orogenic wedge. Its tectonic loading interrupted Carboniferous uplift and caused resumption of sedimentation in the late Viséan. Consequently, a thermal history of the Lublin Basin is different from that in the Podlasie and Baltic basins but similar to other sections of the Variscan foreland, characterized by maximum burial at the end of Carboniferous. The Mesozoic thermal history was characterized by gradual cooling from peak temperatures at the transition from Triassic to Jurassic due to decreasing heat flow. Burial caused maximum paleotemperatures in the SW part of the study area, where the EEP was covered by an extensive sedimentary pile. However, further NE, due to low temperatures caused by shallow burial, the impact of fluids can be detected by vitrinite reflectance, illite/smectite, and thermochronological data. Our new results emphasize the importance of using multiple low-temperature thermochronometers and thermal modelling in connection with thermal maturity analysis to elucidate the near-surface evolution of platform margins.

scholarly journals The development impact of genetic use restriction technologies: a forecast based on the hybrid crop experience

2003 ◽  
Vol 8 (1) ◽  
pp. 149-165 ◽  
Author(s):  
Timo Goeschl ◽  
Timothy Swanson
Keyword(s):  
Developing Countries ◽  
Genetic Material ◽  
Wide Spread ◽  
Gene Manipulation ◽  
Diffusion Parameters ◽  
Hybrid Seeds ◽  
Potential Impact ◽  
The Impact ◽  
And Diffusion ◽  
Do So

Advances in biotechnology have made available gene-manipulation techniques that enable the protection of genetic material from unauthorized use and the prevention of self-supply of commercial seeds by farmers—in order to allow enhanced appropriation of the values of innovation in agricultural R&D. These techniques have become known as Genetic Use Restriction Technologies (GURTs).This paper forecasts the potential impact of wide-spread adoption of GURTs by the providers of HYV seeds on the yield development in developing countries. To do so, it assesses (1) the effects of enhanced appropriation through GURTs on the technological expansion at the yield frontier and (2) the effects of technological protection of value-adding traits through GURTS on the diffusion of yield gains from the frontier to developing countries. These assessments are based on a particular hypothesis, which is that GURTs will replicate across most staple crops the experiences that were made with a previous use restriction technology (hybridization) in only a few crops. The estimation of impacts is carried out as a simulation and is based on expansion and diffusion parameters estimated for hybrid seeds over a 38-year period. It shows that the impact of GURTs on developing countries' yields will vary considerably. Specifically, those countries that currently have the lowest yields would be most adversely affected in their future yield development by the wide-spread use of GURTs.

scholarly journals Water in omphacite fingerprints the thermal history of eclogites

Geology ◽  
2021 ◽  
Author(s):  
Peilin Jiang ◽  
Hanyong Liu ◽  
Henrik Skogby ◽  
Ren-Xu Chen ◽  
Xiaozhi Yang
Keyword(s):  
Thermal History ◽  
Ultrahigh Pressure ◽  
Temperature Sensitive ◽  
Absorption Bands ◽  
Oh Groups ◽  
Different Temperatures ◽  
History Of ◽  
First Time ◽  
New Framework ◽  
Temperature Water

Omphacite is a diagnostic mineral of high- and ultrahigh-pressure rocks, and its association with garnet is characteristic of eclogites from subduction-related massifs and volcano-entrained xenoliths. Omphacite can accommodate significant amounts of water as structurally bound hydroxyl (OH) groups, and is able to convey water into Earth’s interior. We show, for the first time, experimental evidence that the infrared absorption patterns of water in omphacite are temperature sensitive. This provides a new framework for discriminating water in natural omphacite equilibrated at different temperatures. We also demonstrate that in low-temperature omphacite, the integral absorbance ratio between the infrared OH absorption bands at 3620 cm–1 and 3450 cm–1 is linearly related to temperature. Water in omphacite of massif eclogites records the temperature of OH equilibrium, allowing reconstruction of the fluid-involved thermal history and tectonics of rock evolution.

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