FORWARD MODELLING OF LONG-WAVELENGTH MAGNETIC ANOMALIES FROM THE UPPER MANTLE
Long-wavelength magnetic anomalies (LWMA) are broad scale magnetic fields that are usually observed at satellite altitudes. The origin of these fields have been assumed to be solely from the crust, disregarding possible contributions from the upper mantle. Using data from magnetic mantle xenoliths,...
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ftsilluniv:oai:opensiuc.lib.siu.edu:theses-3204 2023-05-15T16:59:06+02:00 FORWARD MODELLING OF LONG-WAVELENGTH MAGNETIC ANOMALIES FROM THE UPPER MANTLE Idoko, Chijioke Modestus 2017-08-01T07:00:00Z application/pdf https://opensiuc.lib.siu.edu/theses/2190 https://opensiuc.lib.siu.edu/cgi/viewcontent.cgi?article=3204&context=theses unknown OpenSIUC https://opensiuc.lib.siu.edu/theses/2190 https://opensiuc.lib.siu.edu/cgi/viewcontent.cgi?article=3204&context=theses Theses Anomalies Craton Forward-Modelling Geomagnetism Hotspots Long-Wavelength text 2017 ftsilluniv 2021-09-30T20:28:20Z Long-wavelength magnetic anomalies (LWMA) are broad scale magnetic fields that are usually observed at satellite altitudes. The origin of these fields have been assumed to be solely from the crust, disregarding possible contributions from the upper mantle. Using data from magnetic mantle xenoliths, the possible mantle contribution to LWMA was investigated for different regions including Siberian craton, Kamchatka subduction zone fore-arc, Hawaii hotspot, and French Massif Central plume. To do this, a MATLAB-based forward-modeling of magnetic anomalies from tectonic regions with different upper mantle geotherms and magnetized mantle geometries was developed. This model incorporated the increase in Curie temperature of magnetite with pressure, the current geotherms of the specific regions, and the statistical distributions of magnetic data from xenoliths in the specific regions. A Monte-Carlo method of random selection of values and repeated calculations was utilized in constraining the range of potential mantle contributions to satellite-observable LWMA. The Siberian craton shows the highest possible contribution to satellite magnetic anomalies with amplitudes ranging from 2 nT to 9 nT, with a wavelength equivalent to the long-axis of the craton. The Hawaii hotspot region displays a significant contribution of its upper mantle to satellite measured magnetic anomalies with an amplitude of the order of 2 nT, while the Massif Central plume regions shows an insignificant contribution of its upper mantle to satellite magnetic anomalies with potential total magnetic anomaly amplitude of 0.07 nT. Finally, the mantle portion of Kamchatka subduction zone shows a sizeable contribution to magnetic anomalies measurable at satellite altitude with an amplitude up to 1.3 nT. These results when compared with lithospheric total field intensity model derived from SWARM satellite data, show that the upper mantle can contribute significantly to LWMA depending on (a) the average remanent magnetization in xenoliths from such regions, (b) the thickness of magnetized mantle, and (c) the size of the region under consideration. Text Kamchatka Southern Illinois University Carbondale: OpenSUIC |
institution |
Open Polar |
collection |
Southern Illinois University Carbondale: OpenSUIC |
op_collection_id |
ftsilluniv |
language |
unknown |
topic |
Anomalies Craton Forward-Modelling Geomagnetism Hotspots Long-Wavelength |
spellingShingle |
Anomalies Craton Forward-Modelling Geomagnetism Hotspots Long-Wavelength Idoko, Chijioke Modestus FORWARD MODELLING OF LONG-WAVELENGTH MAGNETIC ANOMALIES FROM THE UPPER MANTLE |
topic_facet |
Anomalies Craton Forward-Modelling Geomagnetism Hotspots Long-Wavelength |
description |
Long-wavelength magnetic anomalies (LWMA) are broad scale magnetic fields that are usually observed at satellite altitudes. The origin of these fields have been assumed to be solely from the crust, disregarding possible contributions from the upper mantle. Using data from magnetic mantle xenoliths, the possible mantle contribution to LWMA was investigated for different regions including Siberian craton, Kamchatka subduction zone fore-arc, Hawaii hotspot, and French Massif Central plume. To do this, a MATLAB-based forward-modeling of magnetic anomalies from tectonic regions with different upper mantle geotherms and magnetized mantle geometries was developed. This model incorporated the increase in Curie temperature of magnetite with pressure, the current geotherms of the specific regions, and the statistical distributions of magnetic data from xenoliths in the specific regions. A Monte-Carlo method of random selection of values and repeated calculations was utilized in constraining the range of potential mantle contributions to satellite-observable LWMA. The Siberian craton shows the highest possible contribution to satellite magnetic anomalies with amplitudes ranging from 2 nT to 9 nT, with a wavelength equivalent to the long-axis of the craton. The Hawaii hotspot region displays a significant contribution of its upper mantle to satellite measured magnetic anomalies with an amplitude of the order of 2 nT, while the Massif Central plume regions shows an insignificant contribution of its upper mantle to satellite magnetic anomalies with potential total magnetic anomaly amplitude of 0.07 nT. Finally, the mantle portion of Kamchatka subduction zone shows a sizeable contribution to magnetic anomalies measurable at satellite altitude with an amplitude up to 1.3 nT. These results when compared with lithospheric total field intensity model derived from SWARM satellite data, show that the upper mantle can contribute significantly to LWMA depending on (a) the average remanent magnetization in xenoliths from such regions, (b) the thickness of magnetized mantle, and (c) the size of the region under consideration. |
format |
Text |
author |
Idoko, Chijioke Modestus |
author_facet |
Idoko, Chijioke Modestus |
author_sort |
Idoko, Chijioke Modestus |
title |
FORWARD MODELLING OF LONG-WAVELENGTH MAGNETIC ANOMALIES FROM THE UPPER MANTLE |
title_short |
FORWARD MODELLING OF LONG-WAVELENGTH MAGNETIC ANOMALIES FROM THE UPPER MANTLE |
title_full |
FORWARD MODELLING OF LONG-WAVELENGTH MAGNETIC ANOMALIES FROM THE UPPER MANTLE |
title_fullStr |
FORWARD MODELLING OF LONG-WAVELENGTH MAGNETIC ANOMALIES FROM THE UPPER MANTLE |
title_full_unstemmed |
FORWARD MODELLING OF LONG-WAVELENGTH MAGNETIC ANOMALIES FROM THE UPPER MANTLE |
title_sort |
forward modelling of long-wavelength magnetic anomalies from the upper mantle |
publisher |
OpenSIUC |
publishDate |
2017 |
url |
https://opensiuc.lib.siu.edu/theses/2190 https://opensiuc.lib.siu.edu/cgi/viewcontent.cgi?article=3204&context=theses |
genre |
Kamchatka |
genre_facet |
Kamchatka |
op_source |
Theses |
op_relation |
https://opensiuc.lib.siu.edu/theses/2190 https://opensiuc.lib.siu.edu/cgi/viewcontent.cgi?article=3204&context=theses |
_version_ |
1766051290852360192 |