scholarly journals Density, temperature, and composition of the North American lithosphere-New insights from a joint analysis of seismic, gravity, and mineral physics data: 2. Thermal and compositional model of the upper mantle

2014 ◽  
Vol 15 (12) ◽  
pp. 4808-4830 ◽  
Author(s):  
Magdala Tesauro ◽  
Mikhail K. Kaban ◽  
Walter D. Mooney ◽  
Sierd A. P. L. Cloetingh
Keyword(s):  
North American ◽  
Upper Mantle ◽  
Joint Analysis ◽  
Mineral Physics ◽  
Compositional Model ◽  
The North

Electromagnetic images of the Trans-Hudson orogen: the North American Central Plains anomaly revealed

2005 ◽  
Vol 42 (4) ◽  
pp. 457-478 ◽  
Author(s):  
Alan G Jones ◽  
Juanjo Ledo ◽  
Ian J Ferguson
Keyword(s):  
Electrical Properties ◽  
North American ◽  
Upper Mantle ◽  
Lithospheric Mantle ◽  
Three Dimensional ◽  
Conductivity Anomaly ◽  
Central Plains ◽  
Slave Craton ◽  
The North ◽  
Kimberlite Field

Magnetotelluric studies of the Trans-Hudson orogen over the last two decades, prompted by the discovery of a significant conductivity anomaly beneath the North American Central Plains (NACP), from over 300 sites yield an extensive database for interrogation and enable three-dimensional information to be obtained about the geometry of the orogen from southern North Dakota to northern Saskatchewan. The NACP anomaly is remarkable in its continuity along strike, testimony to along-strike similarity of orogenic processes. Where bedrock is exposed, the anomaly can be associated with sulphides that were metamorphosed during subduction and compression and penetratively emplaced deep within the crust of the internides of the orogen to the boundary of the Hearne margin. A new result from this compilation is the discovery of an anomaly within the upper mantle beginning at depths of ~80–100 km. This lithospheric mantle conductor has electrical properties similar to those for the central Slave craton mantle conductor, which lies directly beneath the major diamond-producing Lac de Gras kimberlite field. While the Saskatchewan mantle conductor does not directly underlie the Fort à la Corne kimberlite, which is associated with the Sask craton, the spatial correspondence is close.

A Consistent Thermo-Compositional Model of the South American Cratonic Lithosphere from Integrated Inversion of Gravity and Seismic Data

2020 ◽  
Author(s):  
Nils-Peter Finger ◽  
Mikhail Kaban ◽  
Magdala Tesauro ◽  
Carina Haeger ◽  
Walter Mooney ◽  
...  
Keyword(s):  
South America ◽  
Upper Mantle ◽  
Seismic Data ◽  
Seismic Velocities ◽  
Double Positive ◽  
Mineral Physics ◽  
Compositional Model ◽  
Positive Ions ◽  
Gravity Signal ◽  
Crustal Density

<p>We present an integrated model of the cratonic lithosphere of South America. Gravity and seismic data were jointly analyzed using mineral physics constraints to assess state and evolution of the cratonic roots in South America in terms of temperature, density and composition. At the cratons, our model enables separation of two counteracting effects: the increased density due to cooling with age and decreased density due to depletion of iron. The depletion of iron can be described by the Mg# which gives the partition of Mg<sup>2+</sup> among the double positive ions. A new crustal model (including depth to the Moho) based on existing seismic data was used to correct the gravity field for crustal effects and to uncover the gravity signal of the mantle. In addition, residual topography was calculated as a measure of the part of topography not balanced by the crustal density variations and depth to the Moho. Temperatures within the lithospheric mantle were estimated based on seismic velocities and mineral physics equations, initially assuming a juvenile mantle composition (Mg# of 89). The residual fields were corrected for the respective effects. In the following inversion of residual gravity and topography, we have determined additional density variations which can be interpreted as compositional ones. Furthermore, these results were employed to recompute the upper mantle temperatures taking into account possible compositional changes in the cratonic roots. In this iterative procedure, a consistent thermo-compositional model of the upper mantle has been obtained. Negative compositional density variations imply depletion of iron, leading to higher Mg#s. The highest depletion occurs in the Amazonas and São Francisco Cratons reaching values in the cratons’ centers of up to 90 (Mg#). At the same time, their centers show very low temperatures, down to 600° C in the depth of 100 km. They stay below 1300° C even at a depth of 200 km, indicating deep lithospheric roots. Higher temperatures are found in the Andean forelands and along the Trans-Brasiliano-Lineament (TBL), dividing the Amazonas and São Francisco Cratons. Compositional density variations yield smaller to no amounts of depletion in the Amazonas Craton below a depth of 100 km. The São Francisco Craton still shows depletion in 200 km depth (Mg# up to 89.5). Slightly negative compositional density variations southwest of the São Francisco Craton also exist at depths up to 200 km, indicating the Paranapanema cratonic fragment.</p>

An integrated thermo-compositional model of the African cratonic lithosphere from gravity and seismic data

2021 ◽  
Author(s):  
Nils-Peter Finger ◽  
Mikhail K. Kaban ◽  
Magdala Tesauro ◽  
Walter D. Mooney ◽  
Maik Thomas
Keyword(s):  
Seismic Data ◽  
Thermal Effects ◽  
Joint Analysis ◽  
S Wave ◽  
Mineral Physics ◽  
Compositional Model ◽  
Consistent Model ◽  
Self Consistent ◽  
Wave Tomography ◽  
Compositional Variations

<p>The presented model describes the lithospheric state of the cratonic regions of Africa in terms of temperature, density and composition based on joint analysis of gravity and seismic data. In addition, a new model of depth to the Moho was calculated from available seismic data. It was then used in combination with data on topography, sediments, and deep mantle anomalies to obtain residual mantle gravity and residual topography. These residual fields were corrected for thermal effects based on S-wave tomography and mineral physics constraints, assuming a juvenile mantle. Afterwards, the thermally corrected fields are jointly inverted to uncover potential compositional density variations. Following the isopycnic hypothesis, negative variations in cratonic areas are interpreted to be caused by iron depletion. Adapting the initially juvenile mantle composition allows to iteratively improve the thermal and compositional variations, culminating in a self-consistent model of the African lithosphere. Deep depleted lithospheric roots exist under the Westafrican, northern to central Congo, and Zimbabwe Cratons. The temperatures in these areas range from below 800 °C at 100 km depth to 1200 °C at 200 km depth. Higher temperatures and absence of depletion at depths below 100 km in wide areas of the eastern to southern Congo and the Kaapvaal Cratons indicate a thinner and strongly reworked lithosphere.</p>

scholarly journals A Large Scale Joint Analysis of Flowering Time Reveals Independent Temperate Adaptations in Maize

2016 ◽  
Author(s):  
Kelly Swarts ◽  
Eva Bauer ◽  
Jeffrey C. Glaubitz ◽  
Tiffany Ho ◽  
Lynn Johnson ◽  
...  
Keyword(s):  
Machine Learning ◽  
North American ◽  
Large Scale ◽  
Predictive Ability ◽  
Joint Analysis ◽  
Whole Genome ◽  
Learning Approaches ◽  
Ontology Term ◽  
Days To Flowering ◽  
The North

AbstractModulating days to flowering is a key mechanism in plants for adapting to new environments, and variation in days to flowering drives population structure by limiting mating. To elucidate the genetic architecture of flowering across maize, a quantitative trait, we mapped flowering in five global populations, a diversity panel (Ames) and four half-sib mapping designs, Chinese (CNNAM), US (USNAM), and European Dent (EUNAM-Dent) and Flint (EUNAM-Flint). Using whole-genome projected SNPs, we tested for joint association using GWAS, resampling GWAS and two regional approaches; Regional Heritability Mapping (RHM) (1, 2) and a novel method, Boosted Regional Heritability Mapping (BRHM). Direct overlap in significant regions detected between populations and flowering candidate genes was limited, but whole-genome cross-population predictive abilities were ≤0.78. Poor predictive ability correlated with increased population differentiation (r = 0.41), unless the parents were broadly sampled from across the North American temperate-tropical germplasm gradient; uncorrected GWAS results from populations with broadly sampled parents were well predicted by temperate-tropical FSTs in machine learning. Machine learning between GWAS results also suggested shared architecture between the American panels and, more distantly, the European panels, but not the Chinese panel. Machine learning approaches can reconcile non-linear relationships, but the combined predictive ability of all of the populations did not significantly enhance prediction of physiological candidates. While the North American-European temperate adaption is well studied, this study suggest independent temperate adaptation evolved in the Chinese panel, most likely in China after 1500, a finding supported by differential gene ontology term enrichment between populations.

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