ORCID Profile
0000-0002-3482-2518
Current Organisations
University of Western Australia
,
George Institute for Global Health
,
Complete MT Solutions Inc.
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Geophysics | Geodynamics | Seismology and Seismic Exploration | Mineralogy and Crystallography | Physical Chemistry of Materials | Geology | Transport Properties and Non-Equilibrium Processes | Geophysical Fluid Dynamics | Electrical and Electromagnetic Methods in Geophysics | Geophysics not elsewhere classified
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Earth Sciences | Mineral Exploration not elsewhere classified | Expanding Knowledge in Engineering |
Related Links
Publications
Distortion decomposition of the magnetotelluric impedance tensors from a one-dimensional anisotropic Earth
Publisher: Oxford University Press (OUP)
Date: 24-02-2012
Joint inversion of receiver functions, surface wave dispersion, and magnetotelluric data
Publisher: American Geophysical Union (AGU)
Date: 30-04-2010
DOI: 10.1029/2009JB006369
Structure of the Lithosphere Beneath the Barotse Basin, Western Zambia, From Magnetotelluric Data
Publisher: American Geophysical Union (AGU)
Date: 02-2019
DOI: 10.1029/2018TC005246
On the electrical crust--mantle structure in Fennoscandia: no Moho, and the asthenosphere revealed?
Publisher: Oxford University Press (OUP)
Date: 02-1982
Lithospheric structure of the Yukon, northern Canadian Cordillera, obtained from magnetotelluric data
Publisher: American Geophysical Union (AGU)
Date: 04-2004
DOI: 10.1029/2003JB002516
The electrical structure of the Slave craton
Publisher: Elsevier BV
Date: 12-2003
Precise temperature estimation in the Tibetan crust from seismic detection of the α-β quartz transition
Publisher: Geological Society of America
Date: 2004
DOI: 10.1130/G20367.1
The nature of the southern West African craton lithosphere inferred from its electrical resistivity
Publisher: Elsevier BV
Date: 06-2021
Imaging the continental upper mantle using electromagnetic methods
Publisher: Elsevier BV
Date: 09-1999
North American Central Plains conductivity anomaly within the Trans-Hudson orogen in northern Saskatchewan, Canada
Publisher: Geological Society of America
Date: 1993
Crustal rheology of the Himalaya and Southern Tibet inferred from magnetotelluric data
Publisher: Springer Science and Business Media LLC
Date: 11-2005
DOI: 10.1038/NATURE04154
Abstract: The Cenozoic collision between the Indian and Asian continents formed the Tibetan plateau, beginning about 70 million years ago. Since this time, at least 1,400 km of convergence has been accommodated by a combination of underthrusting of Indian and Asian lithosphere, crustal shortening, horizontal extrusion and lithospheric delamination. Rocks exposed in the Himalaya show evidence of crustal melting and are thought to have been exhumed by rapid erosion and climatically forced crustal flow. Magnetotelluric data can be used to image subsurface electrical resistivity, a parameter sensitive to the presence of interconnected fluids in the host rock matrix, even at low volume fractions. Here we present magnetotelluric data from the Tibetan-Himalayan orogen from 77 degrees E to 92 degrees E, which show that low resistivity, interpreted as a partially molten layer, is present along at least 1,000 km of the southern margin of the Tibetan plateau. The inferred low viscosity of this layer is consistent with the development of climatically forced crustal flow in Southern Tibet.
Structure of the crust in the vicinity of the Banggong‐Nujiang suture in central Tibet from INDEPTH magnetotelluric data
Publisher: American Geophysical Union (AGU)
Date: 10-2005
DOI: 10.1029/2003JB002405
Spectral analyses of the KTB sonic and density logs using robust nonparametric methods
Publisher: American Geophysical Union (AGU)
Date: 10-08-1997
DOI: 10.1029/96JB03668
Orthogonality in CSAMT and MT measurements
Publisher: Society of Exploration Geophysicists
Date: 07-1993
DOI: 10.1190/1.1443483
Abstract: The electric and magnetic fields from a single plane‐wave source on a one dimensional (1-D) earth, or a plane‐wave source polarized parallel or perpendicular to strike on a two-dimensional (2-D) earth, are orthogonal. On a layered earth and in the far‐field of a controlled source, the electric and magnetic fields are also orthogonal. Therefore, orthogonality of E and H data is a necessary condition to justify the application of 1-D or 2-D modeling algorithms having a plane wave source. A strict criterion to prove orthogonality, and thus provide a rationale for the choice of interpretation methods, can be defined directly in terms of field data. However, field data acquired in the intermediate and near‐field of any electromagnetic (EM) source are generally not orthogonal, even on a plane‐layered earth. Representing these nonorthogonal data in an orthogonal coordinate system can be misleading, particularly for the minor axis components of the polarization ellipses. Nonorthogonality also arises because of 3-D scattering, with one common ex le being the electric field response of near surface structure. An ex le of field data illustrates the nonorthogonality in CSAMT measurements caused by the response of surficial geology. In these EM data, the angle between E and H is a sensitive indicator of geological contacts and faults. Quantitative analysis of these data can be performed with the assumptions of a “bulk” 1-D earth (i.e., orthogonal E and H in the far‐field) and purely galvanic scattering of the EM fields.
Lithosphere development in the Slave craton: a linked crustal and mantle perspective
Publisher: Elsevier BV
Date: 12-2003
Electrical conductivity of continental lithospheric mantle from integrated geophysical and petrological modeling: Application to the Kaapvaal Craton and Rehoboth Terrane, southern Africa
Publisher: American Geophysical Union (AGU)
Date: 11-10-2011
DOI: 10.1029/2011JB008544
Three-dimensional galvanic distortion of three-dimensional regional conductivity structures: Comment on “Three-dimensional joint inversion for magnetotelluric resistivity and static shift distribution
Publisher: American Geophysical Union (AGU)
Date: 14-12-2011
DOI: 10.1029/2011JB008665
A new methodology for the acquisition and processing of audio-magnetotelluric (AMT) data in the AMT dead band
Publisher: Society of Exploration Geophysicists
Date: 09-2005
DOI: 10.1190/1.2073889
Abstract: Distant lightning activity, the natural energy source for the audio-magnetotelluric (AMT) method, has a signal minimum between 1 and 5 kHz, the so-called AMT dead band. The energy in this band exhibits both diurnal and annual variation magnetic-field litudes during the daytime are often well below the noise levels of existing sensors (coil magnetometers), thus reducing the effectiveness of the method for quantitative high-resolution studies of near-surface targets. To overcome this deficiency, we propose a hybrid acquisition and processing methodology based on combining the telluric-telluric (T-T) and telluric-magnetotelluric (T-MT) methods in this frequency range. Our method records the telluric channels at several sites and at base and remote reference stations during the day and records the full magnetotelluric (MT) components at the base and remote stations only during the night. Applying a tensor multiplicative relationship between these responses, we obtain the T-MT AMT transfer functions for the sites these transfer functions can represent a reasonable approximation of the real AMT impedance tensors. To test the approach, a T-MT experiment was carried out in Sudbury, northern Ontario, during summer 2000. We compare the processed daytime data using the conventional MT approach to those obtained from our T-MT approach. The results demonstrate that our method can determine high-quality estimates in the dead band, although the estimates can be severely affected by noise.
Water in cratonic lithosphere: Calibrating laboratory‐determined models of electrical conductivity of mantle minerals using geophysical and petrological observations
Publisher: American Geophysical Union (AGU)
Date: 06-2012
DOI: 10.1029/2012GC004055
High‐resolution electromagnetic images of conducting zones in an upthrust crustal block
Publisher: American Geophysical Union (AGU)
Date: 15-08-1994
DOI: 10.1029/94GL01106
Tectonic evolution of the Superior Boundary Zone from coincident seismic reflection and magnetotelluric profiles
Publisher: American Geophysical Union (AGU)
Date: 06-1999
DOI: 10.1029/1999TC900002
Strike-angle determination from the magnetotelluric impedance tensor in the presence of noise and local distortion: rotate at your peril!
Publisher: Oxford University Press (OUP)
Date: 05-1993
Beyond chi-squared: Additional measures of the closeness of a model to data
Publisher: Society of Exploration Geophysicists
Date: 27-08-2018
Geoelectric structure of the Proterozoic Wopmay Orogen and adjacent terranes, Northwest Territories, Canada
Publisher: Canadian Science Publishing
Date: 06-2005
DOI: 10.1139/E05-042
Abstract: Magnetotelluric (MT) soundings were made along a transect in northern Canada crossing the Proterozoic Wopmay Orogen, Fort Simpson basin, and adjacent parts of the Slave craton and the Nahanni terrane. The results are used to define the geoelectric structure and constrain the crustal and lithospheric structure and evolution. Across the Wopmay Orogen, geoelectric strikes at crustal depths average N34°E and are interpreted to be related to transcurrent faulting that occurred during late distal collisions at the western margin of the orogen. Weak two-dimensionality in the Fort Simpson basin is interpreted to be due to the sedimentary rocks in the basin. At longer periods, geoelectric strikes across the Wopmay Orogen rotate from ∼N43°E at uppermost mantle penetration to ∼N62°E at a depth of 100 km. The uppermost mantle strikes are interpreted to be due to ductile shearing linked to the transcurrent faulting in the overlying crust. The deeper strikes may be caused by shearing at the base of the present-day lithosphere. Within the Wopmay Orogen, the MT results image a conductor at the margin of the Fort Simpson and Hottah terranes interpreted to be related to the collision of these terranes. Conductive crust beneath the western margin of the Great Bear magmatic arc suggests correlative rocks of the Coronation margin extend south of the Slave craton. Lastly, decreased resistivity in the Hottah terrane at mantle depths is interpreted to be caused by the introduction of graphitic or sulphidic rocks during subduction prior to the HottahSlave and Fort Simpson Hottah collisions.
TOPO-EUROPE: The geoscience of coupled deep Earth-surface processes
Publisher: Elsevier BV
Date: 07-2007
Regional electrical resistivity structure of the southern Canadian Cordillera and its physical interpretation
Publisher: American Geophysical Union (AGU)
Date: 10-12-2001
DOI: 10.1029/2001JB000358
Partial melt or aqueous fluid in the mid-crust of Southern Tibet? Constraints from INDEPTH magnetotelluric data
Publisher: Oxford University Press (OUP)
Date: 05-2003
An objective real‐time data‐adaptive technique for efficient model resolution improvement in magnetotelluric studies
Publisher: Society of Exploration Geophysicists
Date: 1986
DOI: 10.1190/1.1442043
Abstract: A scheme is described whereby the error associated with the least well‐resolved model eigenparameter in a magnetotelluric survey is reduced by focusing data collection on a specific range of frequencies. The scheme also gives a quantitative estimate of the statistical error associated with the least well‐resolved model parameter, and thus provides an objective criterion to the operator regarding when to cease data collection at that location. The scheme is based on a linearization of the relationship between variations in the model parameters and the changes thereby introduced to the computed response function. The matrix of partial derivatives describing this linearization is factored orthogonally by a singular value decomposition. The scheme is illustrated by applying it to a synthetic data set. Also, the algorithm has been coded in Basic on an HP9845 and employed in the field. An ex le is given of its field operation in a sedimentary basin environment.
Comment on “Deep resistivity cross section of the intraplate Atlas Mountains (NW Africa): New evidence of anomalous mantle and related Quaternary volcanism”
Publisher: American Geophysical Union (AGU)
Date: 10-2012
DOI: 10.1029/2011TC003051
Conductivity structure and rheological property of lithosphere in Southern Tibet inferred from super-broadband magnetotelluric sounding
Publisher: Springer Science and Business Media LLC
Date: 02-01-2010
Geoelectric structure of the northeastern Williston basin and underlying Precambrian lithosphereEarth Science Sector (ESS) Contribution 20080509.
Publisher: Canadian Science Publishing
Date: 06-2009
DOI: 10.1139/E09-028
Abstract: Magnetotelluric (MT) measurements were made in southern Manitoba, Canada, as part of the Portable Observatories for Lithosphere Analysis and Research Investigating Seismicity (POLARIS) project, to image the northeastern part of the Williston basin and underlying Precambrian lithosphere. Data collected at 21 sites along a 400 km east–west profile at 49.5°N and a 300 km north–south profile at 100°W were analyzed using robust spectral analysis, tensor decomposition, and two-dimensional inversion. The resulting resistivity models allow sub ision of the Williston basin into three layers: an upper layer of 1–5 Ω·m corresponding to Mesozoic and upper Paleozoic rocks, a 20–50 Ω·m layer corresponding to lower Paleozoic carbonate rocks, and a 2–3 Ω·m layer corresponding to the Ordovician Winnipeg Formation. Deeper penetrating MT responses, interpreted with other MT data, reveal a region in the westernmost Superior craton with a southwest–northeast geoelectric fabric that is oblique to subprovince boundaries. The observations can be explained by Proterozoic deformation extending several hundred kilometres east of the Superior boundary zone or by a separate Archean terrane adjacent to the boundary. The Thompson belt (TOBE) conductor in the south of the study area has previously been interpreted as part of the Superior boundary zone (SBZ). However, MT results show that the conductor does not extend continuously along the margin of the zone and MT studies to the north define conductors on the margin of the Sask craton. The results suggest the TOBE conductor is associated with the Sask craton margin. The MT results indicate significant along-strike variation of the SBZ in southern Manitoba.
A Reduced Order Approach for Probabilistic Inversions of 3D Magnetotelluric Data II: Joint Inversion of MT and Surface‐Wave Data
Publisher: American Geophysical Union (AGU)
Date: 12-2021
DOI: 10.1029/2021JB021962
Abstract: Joint probabilistic inversions of magnetotelluric (MT) and seismic data have great potential for imaging the thermochemical structure of the lithosphere as well as mapping fluid/melt pathways and regions of mantle metasomatism. In this contribution, we present a novel probabilistic (Bayesian) joint inversion scheme for 3D MT and surface‐wave dispersion data particularly designed for large‐scale lithospheric studies. The approach makes use of a recently developed strategy for fast solutions of the 3D MT forward problem (Manassero et al., 2020, 0.1093/gji/ggaa415 ) and combines it with adaptive Markov chain Monte Carlo (MCMC) algorithms and parallel‐in‐parallel strategies to achieve extremely efficient simulations. To demonstrate the feasibility, benefits and performance of our joint inversion method for imaging the temperature and conductivity structures of the lithosphere, we apply it to two numerical ex les of increasing complexity. The inversion approach presented here is timely and will be useful in the joint analysis of MT and surface wave data that are being collected in many parts of the world. This approach also opens up new avenues for the study of trans‐lithospheric and trans‐crustal magmatic systems, the detection of metasomatized mantle, and the incorporation of MT into multi‐observable inversions for the physical state of the Earth's interior.
Electromagnetic images of regional structure in the southern Canadian Cordillera
Publisher: American Geophysical Union (AGU)
Date: 24-12-1992
DOI: 10.1029/92GL01457
Magnetotelluric observations across the Juan de Fuca Subduction System in the EMSLAB Project
Publisher: American Geophysical Union (AGU)
Date: 10-10-1989
Electrically Conductive Crust in Southern Tibet from INDEPTH Magnetotelluric Surveying
Publisher: American Association for the Advancement of Science (AAAS)
Date: 06-12-1996
DOI: 10.1126/SCIENCE.274.5293.1694
Abstract: The crust north of the Himalaya is generally electrically conductive below depths of 10 to 20 km. This conductive zone approaches the surface beneath the Kangmar dome (dipping north) and extends beneath the Zangbo suture. A profile crossing the northern Yadong-Gulu rift shows that the high conductivity region extends outside the rift, and its top within the rift coincides with a bright spot horizon imaged on the INDEPTH CMP (common midpoint) profiles. The high conductivity of the middle crust is atypical of stable continental regions and suggests that there is a regionally interconnected fluid phase in the crust of the region.
Okak Bay AMT data‐set case study: Lessons in dimensionality and scale
Publisher: Society of Exploration Geophysicists
Date: 2003
DOI: 10.1190/1.1543195
Abstract: Electromagnetic (EM) exploration for base metals using the natural‐source audio‐magnetotelluric (AMT) technique has increased significantly during the last five years due to enhancements in all aspects of AMT and to the demand for imaging deeper than conventional controlled‐source EM methods. However, regional currents induced by natural sources can be problematic in certain situations, and the appropriate interpretational dimensionality must be known. Herein we demonstrate that a two‐dimensional (2D) interpretation is valid for a defined frequency band, but that the effects of large‐scale three‐dimensional (3D) structures must be considered at lower frequencies. Using an AMT dataset from an area located north of Voisey's Bay, Labrador, Canada, we analyse the responses to determine the appropriate dimensionality and to test them for internal consistency. Maps of the distortion‐corrected data identify the lateral extent of connected conducting mineralization intersected by a drilling program. One‐dimensional (1D) inversions of the corrected data from those sites on top of the mineralized zone show the resolution properties of the data. We constructed a pseudo‐3D model from 2D inversions of the data in the frequency band 1000–10~Hz from all profiles, and this model images the mineralized body sufficiently for exploration purposes. We suggest that the anomalous low‐frequency responses observed at sites close to the mineralized zone are possibly due to charges impinged on the mineralized body's boundaries by currents induced in the Atlantic Ocean some 50 km away. Although 3D numerical modeling studies exhibit some of the effects observed, we are unable to reproduce numerically the observed behavior.
The elusive lithosphere–asthenosphere boundary (LAB) beneath cratons
Publisher: Elsevier BV
Date: 04-2009
Calculations of voltages for magnetotelluric modelling of a region with near-surface inhomogeneities
Publisher: Elsevier BV
Date: 03-1989
A quantitative methodology to extract regional magnetotelluric impedances and determine the dimension of the conductivity structure
Publisher: Oxford University Press (OUP)
Date: 12-1993
Crustal structure of the India–Asia collision zone, southern Tibet, from INDEPTH MT investigations
Publisher: Elsevier BV
Date: 05-2005
Deep electrical conductivity structures of the Appalachian Orogen in the southeastern U.S.
Publisher: American Geophysical Union (AGU)
Date: 15-06-1996
DOI: 10.1029/95GL03601
Coincident conductive and reflective middle and lower crust in southern British Columbia
Publisher: Oxford University Press (OUP)
Date: 1995
Conductivity discontinuities in the upper mantle beneath a stable craton
Publisher: American Geophysical Union (AGU)
Date: 23-12-1993
DOI: 10.1029/93GL02833
Electromagnetic images of a strike‐slip fault: The Tintina fault—Northern Canadian
Publisher: American Geophysical Union (AGU)
Date: 04-2002
DOI: 10.1029/2001GL013408
Lithospheric geometry of the Wopmay orogen from a Slave craton to Bear Province magnetotelluric transect
Publisher: American Geophysical Union (AGU)
Date: 2009
DOI: 10.1029/2007JB005326
Abstract: Two‐dimensional inversions of lithospheric‐probing magnetotelluric (MT) data at a total of 20 sites acquired along an approximately east–west 300‐km‐long profile across the Wopmay orogen in the Northwest Territories, Canada, provide electrical resistivity models of the boundary between the Archean Slave craton and the adjacent Proterozoic Bear Province. An analysis of distortion effects and structural dimensionality indicates that the MT responses are primarily one‐dimensional or only weakly two‐dimensional with a depth‐independent geoelectric strike angle of N32°E, consistent with regional structural geology. The regional‐scale model, generated from the longer period responses from all of the sites along the profile, reveals significant lateral variations in the lithospheric mantle. Resistive cratonic roots are imaged to depths of ∼200 km beneath both the Slave craton and the Hottah terrane of the Bear Province. These are separated by a less resistive region beneath the Great Bear magmatic zone, which is speculatively interpreted as a consequence of a decrease in the grain size of olivine in the Wopmay mantle, caused by localized shearing, compared to its neighboring cratonic roots. Focused two‐dimensional models, from higher frequency responses at sites on specific sections of the profile, reveal the resistivity structure at crustal depths beneath the region. These suggest that the root of the Slave craton crosses beneath the Wopmay orogen, and that the Wopmay fault zone does not penetrate into the lower crust. A comparison of these results with those obtained during the Lithoprobe project farther south shows striking along strike variations in the conductivity structure associated with the Wopmay orogen.
Detection of Widespread Fluids in the Tibetan Crust by Magnetotelluric Studies
Publisher: American Association for the Advancement of Science (AAAS)
Date: 27-04-2001
Abstract: Magnetotelluric exploration has shown that the middle and lower crust is anomalously conductive across most of the north-to-south width of the Tibetan plateau. The integrated conductivity (conductance) of the Tibetan crust ranges from 3000 to greater than 20,000 siemens. In contrast, stable continental regions typically exhibit conductances from 20 to 1000 siemens, averaging 100 siemens. Such pervasively high conductance suggests that partial melt and/or aqueous fluids are widespread within the Tibetan crust. In southern Tibet, the high-conductivity layer is at a depth of 15 to 20 kilometers and is probably due to partial melt and aqueous fluids in the crust. In northern Tibet, the conductive layer is at 30 to 40 kilometers and is due to partial melting. Zones of fluid may represent weaker areas that could accommodate deformation and lower crustal flow.
Two-dimensional interpretation of three-dimensional magnetotelluric data: an example of limitations and resolution
Publisher: Oxford University Press (OUP)
Date: 07-2002
Influence of Deformation and Fluids on Ti Exchange in Natural Quartz
Publisher: American Geophysical Union (AGU)
Date: 12-2021
DOI: 10.1029/2021JB022548
Abstract: Using a combination of microstructural, spectroscopic, and geochemical analyses, we investigate how subgrain rotation recrystallization and fluid migration affect Ti concentration [Ti] in naturally deformed quartz veins from the Prijakt Nappe (Austroalpine Unit, Eastern Alps). These coarse‐grained quartz veins, that formed at hibolite facies conditions, were overprinted by lower greenschist facies deformation to different degrees. During the overprint, subgrain rotation recrystallization was dominant during progressive deformation to ultramylonitic stages. The initial [Ti] (3.0–4.7 ppm) and cathodoluminescence (CL) signature of the vein crystals decrease during deformation mainly depending on the availability of fluids across the microstructure. The amount of strain played a subordinate role in resetting to lower [Ti] and corresponding darker CL shades. Using a microstructurally controlled analysis we find that the most complete re‐equilibration in recrystallized aggregates ([Ti] of 0.2–0.6 p.m.) occurred (a) in strain shadows around quartz porphyroclasts, acting as fluid sinks, and (b) in localized microshear zones that channelized fluid percolation. [Ti] resetting is mainly observed along wetted high angle boundaries (misorientation angle –15°), with partial [Ti] resetting observed along dry low angle boundaries ( –15°). This study shows for the first time that pure subgrain rotation recrystallization in combination with dissolution‐precipitation under retrograde condition provide microstructural domains suitable for the application of titanium‐in‐quartz geothermobarometry at deformation temperatures down to 300–350°C.
Central Baffin electromagnetic experiment (CBEX): Mapping the North American Central Plains (NACP) conductivity anomaly in the Canadian arctic
Publisher: Elsevier BV
Date: 05-2005
The geometry of the Iapetus Suture Zone in central Ireland deduced from a magnetotelluric study
Publisher: Elsevier BV
Date: 04-2007
Improving Bahr's invariant parameters using the WAL approach
Publisher: Oxford University Press (OUP)
Date: 10-2005
Internal structure of the western flank of the Cumbre Vieja volcano, La Palma, Canary Islands, from land magnetotelluric imaging
Publisher: American Geophysical Union (AGU)
Date: 20-07-2010
DOI: 10.1029/2009JB006445
Mining for net zero: The impossible task
Publisher: Society of Exploration Geophysicists
Date: 04-2023
Abstract: If current predictions of anthropogenically induced climate change are accurate, and they are becoming more robust and prescient with time, the world must transition away from fossil fuels and embrace transportation, energy generation, and energy storage from renewables so that future generations are not in peril. More than 190 countries have each signed the Paris Agreement, which has as its goal a reduction of global greenhouse gas emissions to limit the global temperature increase in this century to 2°C while pursuing efforts to limit the increase even further to 1.5°C. Additionally, more than 70 countries, including the biggest polluters, have set a net-zero greenhouse gas emissions target, which covers about 76% of global emissions — a commendable and laudable goal. However, a number of fundamental challenges make achieving this goal difficult, perhaps impossible. One such challenge is the lack of a broad appreciation that there needs to be much more mining of metals and minerals, in excess of already mining more than at any other time in prior human history. For ex le, one estimate is that there needs to be as much copper mined over the next 20–25 years as has been mined to date. Many countries have become aware of the need for access to “critical minerals” for futureproofing, but they appear to be unaware of the fundamental issues that will h er that access. This is a fast-moving issue. Some of the specific details raised here will become less relevant, and new ones will appear. However, the core issues raised, of the need for a more positive public perception of mining, of the need for more mining, and of the need for far more skilled talent, will not change.
Partially Molten Middle Crust Beneath Southern Tibet: Synthesis of Project INDEPTH Results
Publisher: American Association for the Advancement of Science (AAAS)
Date: 06-12-1996
DOI: 10.1126/SCIENCE.274.5293.1684
Abstract: INDEPTH geophysical and geological observations imply that a partially molten midcrustal layer exists beneath southern Tibet. This partially molten layer has been produced by crustal thickening and behaves as a fluid on the time scale of Himalayan deformation. It is confined on the south by the structurally imbricated Indian crust underlying the Tethyan and High Himalaya and is underlain, apparently, by a stiff Indian mantle lid. The results suggest that during Neogene time the underthrusting Indian crust has acted as a plunger, displacing the molten middle crust to the north while at the same time contributing to this layer by melting and ductile flow. Viewed broadly, the Neogene evolution of the Himalaya is essentially a record of the southward extrusion of the partially molten middle crust underlying southern Tibet.
A pioneering geophysicist: Rosemary Hutton
Publisher: Geological Society of London
Date: 25-09-2020
Europe from the bottom up: A statistical examination of the central and northern European lithosphere–asthenosphere boundary from comparing seismological and electromagnetic observations
Publisher: Elsevier BV
Date: 11-2010
Seismic reflections and electrical conductivity: A case of Holmes's curious dog?
Publisher: Geological Society of America
Date: 1995
Joint inversion of long-period magnetotelluric data and surface-wave dispersion curves for anisotropic structure: Application to data from Central Germany
Publisher: American Geophysical Union (AGU)
Date: 10-03-2011
DOI: 10.1029/2010GL046358
The electric Moho
Publisher: Springer Science and Business Media LLC
Date: 2001
DOI: 10.1038/35053053
Abstract: Since Mohorovicić discovered a dramatic increase in compressional seismic velocity at a depth of 54 km beneath the Kulpa Valley in Croatia, the 'Moho' has become arguably the most important seismological horizon in Earth owing to its role in defining the crust-mantle boundary. It is now known to be a ubiquitous feature of the Earth, being found beneath both the continents and the oceans, and is commonly assumed to separate lower-crustal mafic rocks from upper-mantle ultramafic rocks. Electromagnetic experiments conducted to date, however, have failed to detect a corresponding change in electrical conductivity at the base of the crust, although one might be expected on the basis of laboratory measurements. Here we report electromagnetic data from the Slave craton, northern Canada, which show a step-change in conductivity at Moho depths. Such resolution is possible because the Slave craton is highly anomalous, exhibiting a total crustal conductance of less than 1 Siemens--more than an order of magnitude smaller than other Archaean cratons. We also found that the conductivity of the uppermost continental mantle directly beneath the Moho is two orders of magnitude more conducting than laboratory studies on olivine would suggest, inferring that there must be a connected conducting phase.
Robust processing of magnetotelluric data in the AMT dead band using the continuous wavelet transform
Publisher: Society of Exploration Geophysicists
Date: 11-2008
DOI: 10.1190/1.2987375
Abstract: The energy sources for magnetotellurics (MT) at frequencies above [Formula: see text] are electromagnetic waves generated by distant lightning storms propagating globally within the earth-ionosphere waveguide. The nature of the sources and properties of this waveguide display diurnal and seasonal variations that can cause significant signal litude attenuation, especially at [Formula: see text] frequencies — the so-called audiomagnetotelluric (AMT) dead band. This lack of energy results in unreliable MT response estimates and, given that in crystalline environments ore bodies located at some [Formula: see text] depth are sensed initially by AMT data within the dead band, this leads to poor inherent geometric resolution of target structures. We propose a new time-series processing technique that uses localization properties of the wavelet transform to select the most energetic events. Subsequently, two coherence thresholds and a series of robust weights are implemented to obtain the most reliable MT response estimates. Finally, errors are estimated using a nonparametric jackknife algorithm. We applied this algorithm to AMT data collected in northern Canada. These data were processed previously using traditional robust algorithms and using a telluric-telluric magnetotelluric (TTMT) technique. The results show a significant improvement in estimates for the AMT dead band and permit their quantitative interpretation.
Upper mantle temperature determined from combining mineral composition, electrical conductivity laboratory studies and magnetotelluric field observations: Application to the intermontane belt, Norther
Publisher: Elsevier BV
Date: 07-2005
Magnetotelluric response and geoelectric structure of the Great Slave Lake shear zone
Publisher: Elsevier BV
Date: 02-2002
Geochemical and geophysical constrains on the dynamic topography of the Southern African Plateau
Publisher: American Geophysical Union (AGU)
Date: 10-2017
DOI: 10.1002/2017GC006908
Crustal structure and rheology of the Longmenshan and Wenchuan Mw 7.9 earthquake epicentral area from magnetotelluric data
Publisher: Geological Society of America
Date: 18-09-2012
DOI: 10.1130/G33703.1
Crustal and upper mantle structure of northern Tibet imaged with magnetotelluric data
Publisher: American Geophysical Union (AGU)
Date: 02-2004
DOI: 10.1029/2002JB002305
Atmospheric sources for audio-magnetotelluric (AMT) sounding
Publisher: Society of Exploration Geophysicists
Date: 03-2002
DOI: 10.1190/1.1468604
Abstract: The energy sources for natural-source magnetotelluric (MT) frequencies 1 Hz are electromagnetic (EM) waves caused by distant lightning storms and which propagate within the Earth–ionosphere waveguide. The properties of this waveguide display diurnal, seasonal, and 11-year solar-cycle fluctuations, and these temporal fluctuations cause significant signal litude attenuation variations—especially at frequencies in the 1- to 5-kHz so-called audiomagnetotelluric (AMT) dead band. In the northern hemisphere these variations increase in litude during the nighttime and the summer months, and they correspondingly decrease during the daytime and the winter months. Thus, one problem associated with applying the AMT method for shallow ( km) exploration can be the lack of signal in certain frequency bands during the desired acquisition interval. In this paper we analyze the time variations of high-frequency EM fields to assess the limitations of the efficient applicability of the AMT method. We demonstrate that magnetic field sensors need to become two orders of magnitude more sensitive than they are currently to acquire an adequate signal at all times. We present a proposal for improving AMT acquisition involving continuous profiling of the telluric field only during the daytime and AMT acquisition at a few base stations through the night.
Geophysical evidence for crustal and mantle weak zones controlling intra-plate seismicity – the 2017 Botswana earthquake sequence
Publisher: Elsevier BV
Date: 2019
Introduction to this special section: Critical minerals exploration
Publisher: Society of Exploration Geophysicists
Date: 04-2023
Abstract: This special section of The Leading Edge focuses on the issue of critical minerals from the perspective of recent progress in mining exploration and anticipated future needs as the global energy economy transitions to higher use of, and reliance on, renewables. The definition of a “critical mineral” is itself context dependent. For ex le, minerals such as lithium, nickel, cobalt, manganese, and graphite each are essential to the development of modern, high-efficiency lithium-ion batteries, and any disruptions to these minerals — whether through supply chain issues or raw, geologic access — ultimately impacts the future of this now-pervasive, and increasingly necessary, energy storage technology. Similarly, rare earth elements (REEs) have long been central to the manufacture of permanent magnets, which themselves are key components of wind turbines and electric vehicles, the latter of which account for 14% of global passenger car sales in 2022, up from 9% in the previous year. In the United States alone, the market forecast for electric vehicles is expected to grow to roughly US$137 billion in 2028, up from $24 billion in 2020. Lastly, the more “common” but still “critical” minerals copper and aluminum are the backbone of the rapidly expanding global energy distribution systems upon which our modern society is built.
Electromagnetic images of a volcanic zone
Publisher: Elsevier BV
Date: 12-1993
Multisite, multifrequency tensor decomposition of magnetotelluric data
Publisher: Society of Exploration Geophysicists
Date: 2001
DOI: 10.1190/1.1444891
Abstract: Accurate interpretation of magnetotelluric data requires an understanding of the directionality and dimensionality inherent in the data, and valid implementation of an appropriate method for removing the effects of shallow, small‐scale galvanic scatterers on the data to yield responses representative of regional‐scale structures. The galvanic distortion analysis approach advocated by Groom and Bailey has become the most adopted method, rightly so given that the approach decomposes the magnetotelluric impedance tensor into determinable and indeterminable parts, and tests statistically the validity of the galvanic distortion assumption. As proposed by Groom and Bailey, one must determine the appropriate frequency‐independent telluric distortion parameters and geoelectric strike by fitting the seven‐parameter model on a frequency‐by‐frequency and site‐by‐site basis independently. Although this approach has the attraction that one gains a more intimate understanding of the data set, it is rather time‐consuming and requires repetitive application. We propose an extension to Groom‐Bailey decomposition in which a global minimum is sought to determine the most appropriate strike direction and telluric distortion parameters for a range of frequencies and a set of sites. Also, we show how an analytically‐derived approximate Hessian of the objective function can reduce the required computing time. We illustrate application of the analysis to two synthetic data sets and to real data. Finally, we show how the analysis can be extended to cover the case of frequency‐dependent distortion caused by the magnetic effects of the galvanic charges.
Proton conduction and hydrogen diffusion in olivine: an attempt to reconcile laboratory and field observations and implications for the role of grain boundary diffusion in enhancing conductivity
Publisher: Springer Science and Business Media LLC
Date: 25-02-2016
Electromagnetic images of modern and ancient subduction zones
Publisher: Elsevier BV
Date: 03-1993
Electrical lithosphere beneath the Kaapvaal craton, southern Africa
Publisher: American Geophysical Union (AGU)
Date: 20-04-2011
DOI: 10.1029/2010JB007883
Velocity–conductivity relationships for mantle mineral assemblages in Archean cratonic lithosphere based on a review of laboratory data and Hashin–Shtrikman extremal bounds
Publisher: Elsevier BV
Date: 04-2009
Lithospheric structure in the Baikal-central Mongolia region from integrated geophysical-petrological inversion of surface-wave data and topographic elevation
Publisher: American Geophysical Union (AGU)
Date: 08-2012
DOI: 10.1029/2012GC004138
The North American Central Plains conductivity anomaly and its correlation with gravity, magnetic, seismic, and heat flow data in Saskatchewan, Canada
Publisher: Elsevier BV
Date: 1990
Source field effects in the auroral zone: Evidence from the Slave craton (NW Canada)
Publisher: Elsevier BV
Date: 09-2007
A multi-station magnetotelluric study in southern Scotland -- II. Monte-Carlo inversion of the data and its geophysical and tectonic implications
Publisher: Oxford University Press (OUP)
Date: 02-1979
Electrical signature of modern and ancient tectonic processes in the crust of the Atlas mountains of Morocco
Publisher: Elsevier BV
Date: 04-2011
Electric lithosphere of the Slave craton
Publisher: Geological Society of America
Date: 2001
Electromagnetic constraints on strike-slip fault geometry—The Fraser River fault system
Publisher: Geological Society of America
Date: 1992
Electromagnetic imaging of a complex ore body: 3D forward modeling, sensitivity tests, and down-mine measurements
Publisher: Society of Exploration Geophysicists
Date: 03-2007
DOI: 10.1190/1.2437105
Abstract: This study investigated the capability of audio-magnetotellurics (AMT) not only to detect, but also to delineate complex conductive ore bodies at minable depths. A detailed 3D numerical-electrical resistivity model of the Bathurst no. 12 deposit (New Brunswick, Canada) was constructed using available geologic and geophysical information. Different geologic and data acquisition conditions were simulated: presence of overburden different geometries, dimensions, and positions of the ore body and different data s ling regimes. The behavior of the surface 3D electromagnetic fields was compared with that from bodies of infinite strike extent. The 3D and 2D AMT responses were similar at high frequencies, so 2D modeling was shown to be both valid and sufficient. However, at low frequencies only those responses for current flow perpendicular to the body (the transverse magnetic mode in a 2D case), were reasonably similar. The 2Dinversions showed that the position and the top of the 3D ore body were well resolved, but the bottom of the ore body's resis-tivity were poorly resolved. To increase resolution at depth below ore bodies, and to possibly extend mine life, we recommend that AMT measurements are taken from within mines. Simple mod-els of ore bodies were simulated to show responses at depth, and to undertake body stripping of the overlying structures. The tests showed that conductive structures above the measurement level can have a strong influence on imaging of conducting zones below, and can produce distortion effects in apparent resistivity and phase. Although the body-stripping approach reduces these effects and gives an indication of whether there are conductive structures below, the resulting image is considerably different from that of a model without overlying conductive structures. Full 3D inversion, holding known structures at constant, is required.
Penetration of crustal melt beyond the Kunlun Fault into northern Tibet
Publisher: Springer Science and Business Media LLC
Date: 22-04-2012
DOI: 10.1038/NGEO1449
Lithospheric anisotropy structure inferred from collocated teleseismic and magnetotelluric observations: Great Slave Lake shear zone, northern Canada
Publisher: American Geophysical Union (AGU)
Date: 10-2004
DOI: 10.1029/2004GL020939
Geophysical transect across a Paleoproterozoic continentcontinent collision zone: The Trans-Hudson Orogen
Publisher: Canadian Science Publishing
Date: 04-2005
DOI: 10.1139/E05-002
Abstract: A summary and comparison of geophysical data and models for the Trans-Hudson Orogen in northern Manitoba and Saskatchewan are presented. Magnetic total field and Bouguer gravity maps are used to define the along-strike extension of geological domains of the orogen exposed on the Canadian Shield, and a two-dimensional density model is produced, which accounts for the observed variations of the Bouguer gravity field across the orogen. An 800-km-long crustal section across the entire continentcontinent collision zone, including the edges of the bounding cratonic blocks, is presented. It incorporates seismic reflectivity, seismic velocities, resistivity, and density models. Key results include (1) evidence for west-vergent crustal stacking and exhumation in the eastern Trans-Hudson Orogen in the form of preserved Moho topography and the presence of higher grade (higher velocity) rocks in the hanging wall of an east-dipping crustal stack (2) definition of the eastward extent of the Archean Sask craton in the subsurface based on distinct lower crustal properties and (3) 400 m of present-day surface topography and 68 km of relief on the Moho are isostatically compensated mainly within the upper mantle by a westward increase in upper mantle temperatures by 40155 °C and (or) 16107 km of thinning of the mantle lithosphere.
Waves of the future: Superior inferences from collocated seismic and electromagnetic experiments
Publisher: Elsevier BV
Date: 03-1998
Magnetotelluric observations along the lithoprobe southeastern Canadian Cordilleran Transect
Publisher: American Geophysical Union (AGU)
Date: 07-1988
Artefacts of isotropic inversion applied to magnetotelluric data from an anisotropic Earth
Publisher: Oxford University Press (OUP)
Date: 05-09-2011
Electrical anisotropy of South African lithosphere compared with seismic anisotropy from shear-wave splitting analyses
Publisher: Elsevier BV
Date: 10-2006
Lithospheric structure, evolution and diamond prospectivity of the Rehoboth Terrane and western Kaapvaal Craton, southern Africa: Constraints from broadband magnetotellurics
Publisher: Elsevier BV
Date: 11-2009
Electromagnetic interrogation of the anisotropic Earth: Looking into the Earth with polarized spectacles
Publisher: Elsevier BV
Date: 10-2006
A comparison of techniques for magnetotelluric response function estimation
Publisher: American Geophysical Union (AGU)
Date: 10-10-1989
The electrical resistivity structure of Archean to Tertiary lithosphere along 3200 km of SNORCLE profiles, northwestern Canada
Publisher: Canadian Science Publishing
Date: 06-2005
DOI: 10.1139/E05-080
Abstract: Magnetotelluric (MT) measurements to image the three-dimensional resistivity structure of the North American continent from an Archean core to a region of Tertiary assembly were recorded at almost 300 sites along 3200 km of profiles on the Lithoprobe Slave Northern Cordillera Lithospheric Evolution (SNORCLE) transect in northwestern Canada. At the largest scale, the MT results indicate significant lithospheric thickness variation, from 260 km at the southwest margin of the Slave craton to significantly 100 km at the southwestern end of the SNORCLE transect in the Cordillera. At intermediate scale, the resistivity results allow broad terrane sub isions to be made. Several anomalously conductive zones along the SNORCLE transect, in rocks ranging in age from Archean to Tertiary, are attributed to the introduction of either water or carbon into the crust and mantle during subduction processes. At the local scale, the MT data image two major faults crossing the study area, the Great Slave Lake shear zone and the Tintina Fault. The resistivity images show that both the Tintina Fault and Great Slave Lake shear zone form crustal-scale features, and that the Tintina Fault has a remarkably uniform resistivity signature over a 400 km strike length in the study area. Arguably the most controversial conclusion reached is that the MT data do not support the western extension of North American autochthonous basement suggested from interpretation of the seismic reflection data.
Magnetotelluric array data analysis from north-west Fennoscandia
Publisher: Elsevier BV
Date: 06-2015
North American Central Plains conductivity anomaly goes east
Publisher: American Geophysical Union (AGU)
Date: 07-1986
Trans-Hudson orogen and Williston basin in Montana and North Dakota: New COCORP deep-profiling results
Publisher: Geological Society of America
Date: 1993
Static shift of magnetotelluric data and its removal in a sedimentary basin environment
Publisher: Society of Exploration Geophysicists
Date: 07-1988
DOI: 10.1190/1.1442533
Abstract: Previous modeling investigations of the static shift of magnetotelluric (MT) apparent resistivity curves have limited appeal in that the electric fields used were point measurements, whereas field observations are of voltage differences. Thus, inhomogeneities of dimension of the order of the electrode line length could not be investigated. In this paper, by using a modeling algorithm that derives point voltages rather than point electric fields, I consider the effect on the MT responses of local near‐surface distorting structures, which are both outside of, and inside, the telluric electrode array. I show that static‐shift effects are of larger spatial size but of less magnitude than would be expected from conventional modeling. Also, the field observation that static shift affects only the apparent resistivity curve but not the phase response can be replicated by the voltage difference modeling. If there exists within the earth a layer whose variation in electrical resistivity along the profile can be treated in a parametric fashion, then static shift of the apparent resistivity curves can be corrected. Deriving the modal value from a sufficient number of observations for the layer resistivity is the most useful approach.
Comment on ‘Geomagnetic depth sounding by induction arrow representation: A review’ by G. P. Gregori and L. J. Lanzerotti
Publisher: American Geophysical Union (AGU)
Date: 11-1981
Joint inversion of teleseismic receiver functions and magnetotelluric data using a genetic algorithm: Are seismic velocities and electrical conductivities compatible?
Publisher: American Geophysical Union (AGU)
Date: 25-08-2007
DOI: 10.1029/2007GL030519
Area selection for diamond exploration using deep-probing electromagnetic surveying
Publisher: Elsevier BV
Date: 09-2004
Electromagnetic images of the Trans-Hudson orogen: the North American Central Plains anomaly revealed
Publisher: Canadian Science Publishing
Date: 04-11-2005
DOI: 10.1139/E05-018
Abstract: 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 ~80100 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.
Electrical-resistivity imaging of the central Trans-Hudson orogen
Publisher: Canadian Science Publishing
Date: 04-2005
DOI: 10.1139/E05-017
Abstract: Magnetotelluric (MT) measurements were made on a profile across the Trans-Hudson orogen in 1992 as part of the Lithoprobe transect. The present study includes analysis of results from a 300 km-long section of the profile in which allocthonous Paleoproterozoic juvenile terranes and arc rocks of the western Trans-Hudson orogen have been juxtaposed against the Archean Sask craton. Impedance tensor decomposition of data from the 40 MT sites in the area indicates a geoelectric strike of N28°E. Two-dimensional inversion of the data using a non-linear conjugate gradient algorithm provided images of the resistivity structure. Resistivity images reveal that the crust of the Sask craton is relatively resistive ( Ω·m). In contrast, the rocks of the Flin Flon belt, Glennie domain, and La Ronge domain are mostly relatively conductive ( 1000 Ω·m). In the east of the study area, the images suggest that the Tabbernor fault juxtaposes more conductive rocks of the Glennie domain in the west against more resistive Archean rocks in the east in the upper 20 km of the crust. In the west of the study area, the images confirm that the North American Central Plains conductor occurs within westward-dipping rocks of the La Ronge domain. The resistivity images also reveal that the lower crust beneath the west of the Glennie domain, within a crustal culmination defined by seismic reflection data, is electrically conductive ( Ω·m). An explanation for the enhanced conductivity is that part of the lower crust beneath the western Glennie domain is of Proterozoic age. In this case, a possible source for the enhanced conductivity, based on its location at the edge of the Sask continental block, is Proterozoic ocean margin rocks.
Electromagnetic image of the Trans-Hudson orogen THO94 transect
Publisher: Canadian Science Publishing
Date: 04-2005
DOI: 10.1139/E05-016
Abstract: The North American Central Plains (NACP) anomaly in enhanced electric conductivity and its relationship with the Paleoproterozoic Trans-Hudson orogen (THO) has been studied under the auspices of Lithoprobe for over a decade. The NACP anomaly was the first geophysical evidence of the existence of the THO beneath the Phanerozoic sediments of the Central Plains. This anomaly, detected geomagnetically in the late 1960s, has been the subject of a number magnetotelluric studies from the early 1980s. The PanCanadian and Geological Survey of Canada experiments in the 1980s and the Lithoprobe experiments in the 1990s together comprise four eastwest and one northsouth regional-scale profiles in Saskatchewan perpendicular to the strike of the orogen. In this paper, data from the northernmost line, coincident with seismic line S2B, are analysed and interpreted, and are shown to be key in determining the northern extension of the NACP anomaly. Dimensionality analysis confirms the rotation of deep crustal structures eastward to Hudson Bay, as earlier proposed on the basis of broad-scale geomagnetic studies. On this profile, as with the profile at the edge of the Paleozoic sediments, the NACP anomaly is imaged as lying within the La Ronge domain, in contact with the Rottenstone domain, and structurally above the Guncoat thrust, a late compressional feature. The location of the anomaly together with the surface geology suggests that the anomaly is caused either by sulphide mineralization concentrated in the hinges of folds, by graphite, or by a combination of both. Our interpretation of the data is consistent with that from other profiles, and suggests that the NACP anomaly was formed as a consequence of subduction and collisional processes involving northward subduction of the internides of the THO beneath the Hearne craton. On the southern part of this profile, a resistive structure is identified as the Sask craton, suggesting that Proterozoic rocks are above Archean rocks in the THO.
Shear‐wave splitting observations in the lower Great Lakes region: Evidence for regional anisotropic domains and keel‐modified asthenospheric flow
Publisher: American Geophysical Union (AGU)
Date: 06-04-2004
DOI: 10.1029/2004GL019438
Lithospheric structures and Precambrian terrane boundaries in northeastern Botswana revealed through magnetotelluric profiling as part of the Southern African Magnetotelluric Experiment
Publisher: American Geophysical Union (AGU)
Date: 03-02-2011
DOI: 10.1029/2010JB007740
Area selection for diamonds using magnetotellurics: Examples from southern Africa
Publisher: Elsevier BV
Date: 11-2009
The collective review papers presented at the 7th IAGA Workshop on Electromagnetic Induction in the Earth and Moon
Publisher: Springer Science and Business Media LLC
Date: 09-1986
DOI: 10.1007/BF01904060
The Slave–Kaapvaal workshop: a tale of two cratons
Publisher: Elsevier BV
Date: 12-2003
Are impact-generated lower-crustal faults observable?
Publisher: Elsevier BV
Date: 09-1987
How the crust meets the mantle: Lithoprobe perspectives on the Mohorovičić discontinuity and crust–mantle transitionThis article is one of a series of papers published in this Special Issue on the the
Publisher: Canadian Science Publishing
Date: 04-2010
DOI: 10.1139/E09-076
Abstract: Application of regional geophysical and geological methods throughout two decades of Canada’s Lithoprobe project provides new opportunities to analyze the Mohorovičić discontinuity (Moho) and crust–mantle transition. The transect format employed during Lithoprobe, in which 10 specified regions of Canada were targeted for approximately a decade each, between 1984 and 2003, permitted teams of scientists to focus on geological, geophysical, and tectonic issues for each transect. As a primary objective was to enhance knowledge of the structure of the crust and lithosphere, an obvious target in each transect was the nature and origin of the Moho and crust–mantle transition. Accordingly, the combined results provide new perspectives on the Moho and the relationship of the Moho to the crust–mantle transition. Perhaps the most important result is that the continental geophysical Moho is a deceptively simple feature it has a variety of signatures at different scales that preclude a single, universally applicable interpretation. In methods that provide large-scale information, such as regional seismic studies, it is a relatively abrupt refraction velocity contrast that often displays a dramatic downward decrease in seismic reflectivity. However, its origin in a geological or tectonic sense is perhaps best determined by careful analyses of structural details near the geophysical Moho, which are complex and varied. In some areas within Canada, it appears that the geophysical Moho may be old and perhaps remains from the time the crust formed in other areas, it appears to be a relatively young feature that was superimposed onto older crustal fabrics.
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