Geological significance of high-resolution magnetic data in the Quesnel terrane, Central British Columbia1This article is one of a series of papers published in this Special Issue on the theme of New insights in Cordilleran Intermontane geoscience: reducing exploration risk in the mountain pine beetle-affected area, British Columbia.2Geological Survey of Canada Contribution No. 20100225.

2011 ◽  
Vol 48 (6) ◽  
pp. 1065-1089 ◽  
Author(s):  
M.D. Thomas ◽  
M. Pilkington ◽  
R.G. Anderson
Keyword(s):  
British Columbia ◽  
High Resolution ◽  
Mountain Pine Beetle ◽  
Gravity Data ◽  
Sedimentary Cover ◽  
Volcanic Rocks ◽  
Geological Mapping ◽  
Magnetic Data ◽  
Structural Variations ◽  
High Resolution Data

The ability of airborne sensors to image the magnetic signatures of prospective Quesnel terrane rocks through ubiquitous Quaternary glacial sedimentary cover in central British Columbia helps target new areas for mineral exploration. Newly acquired high-resolution data provide new perspectives on the nature and probable areal distribution of many geological units, revealing detail and information unattainable by conventional geological mapping. In combination with gravity data, these magnetic data indicate the presence of a granitic intrusion and a development of Nicola Group volcanic rocks, both potential hosts for porphyry- and (or) vein-type mineralization, under younger Tertiary volcanic cover. At a finer scale, magnetic patterns and fabrics permit discrimination between volcanic rocks of the Tertiary Chilcotin and Kamloops groups, and detection of subtle compositional and (or) structural variations within the groups. Contacts between volcanic cover and basement rocks and between basement units are more accurately defined, significantly reducing locally the areal extent of volcanic cover and opening up more ground for exploration. The high resolution of features in images of magnetic vertical derivatives reveals the Naver pluton to be more complex than currently mapped, comprising several integral elements, one of which may be a large roof pendant. Internal subdivisions of the Thuya batholith are defined, and annular marginal phases are proposed within two large granodioritic intrusions. Several new intrusions are proposed within the extensive, mainly sedimentary Devonian–Triassic terrain northeast of Kamloops, internal composition variation is suggested for some larger mapped intrusions, and areas underlain by some intrusions are enlarged.

Volcanoes geological mapping and structural geology with UAS High Resolution Digital Terrain Model : the Kuei-Shan Tao case example (Eastern Taiwan).

2021 ◽  
Author(s):  
Benoit Deffontaines ◽  
Kuo-Jen Chang ◽  
Samuel Magalhaes ◽  
Gérardo Fortunato
Keyword(s):  
High Resolution ◽  
Okinawa Trough ◽  
Volcanic Rocks ◽  
Digital Terrain Model ◽  
Structural Features ◽  
Point Of View ◽  
Geological Mapping ◽  
Lava Flows ◽  
Aerial Photographs ◽  
Structural Scheme

<p>Volcanic areas in the World are often difficult to map especially in a structural point of view as (1) fault planes are generally covered and filled by more recent lava flows and (2) volcanic rocks have very few tectonic striations. Kuei-Shan Tao (11km from Ilan Plain – NE Taiwan) is a volcanic island, located at the soutwestern tip of the South Okinawa trough (SWOT). Two incompatible geological maps had been already published both lacking faults and structural features (Hsu, 1963 and Chiu et al., 2010). We propose herein not only to up-date the Kuei-Shan Tao geological map with our high resolution dataset, but also to create the Kuei-Shan Tao structural scheme in order to better understand its geological and tectonic history.</p><p>Consequently, we first acquired aerial photographs from our UAS survey and get our new UAS high resolution DTM (HR UAS-DTM hereafter) with a ground resolution <10cm processed through classical photogrammetric methods. Taking into account common sense geomorphic and structural interpretation and reasoning deduced form our HR UAS-DTM, and the outcropping lithologies situated all along the shoreline, we have up-dated the Kuei-Shan Tao geological mapping and its major structures. To conclude, the lithologies (andesitic lava flows and pyroclastic falls) and the new structural scheme lead us to propose a scenario for both the construction as well as the dismantling of Kuei-Shan Tao which are keys for both geology and geodynamics of the SWOT.</p>

Crustal velocity structure of the southern Nechako basin, British Columbia, from wide-angle seismic traveltime inversion1This article is one of a series of papers published in this Special Issue on the theme of New insights in Cordilleran Intermontane geoscience: reducing exploration risk in the mountain pine beetle-affected area, British Columbia.

2011 ◽  
Vol 48 (6) ◽  
pp. 1050-1063 ◽  
Author(s):  
A.L. Stephenson ◽  
G.D. Spence ◽  
K. Wang ◽  
J.A. Hole ◽  
K.C. Miller ◽  
...  
Keyword(s):  
British Columbia ◽  
Mountain Pine Beetle ◽  
Velocity Structure ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Velocity Model ◽  
Seismic Profile ◽  
Wide Angle ◽  
Seismic Velocities ◽  
Coast Mountains

In the BATHOLITHSonland seismic project, a refraction – wide-angle reflection survey was shot in 2009 across the Coast Mountains and Interior Plateau of central British Columbia. Part of the seismic profile crossed the Nechako Basin, a Jurassic–Cretaceous basin with potential for hydrocarbons within sedimentary strata that underlies widespread volcanic rocks. Along this 205 km-long line segment, eight large explosive shots were fired into 980 seismometers. Forward and inverse modelling of the traveltime data were conducted with two independent methods: ray-tracing based modelling of first and secondary arrivals, and a higher resolution wavefront-based first-arrival seismic tomography. Material with velocities less than 5.0 km/s is interpreted as sedimentary rocks of the Nechako Basin, while velocities from 5.0–6.0 km/s may correspond to interlayered sedimentary and volcanic rocks. The greatest thickness of sedimentary rocks in the basin is found in the central 110 km of the profile. Two sub-basins were identified in this region, with widths of 20–50 km and maximum sedimentary depths of 2.5 and 3.3 km. Such features are well-defined in the velocity model, since resolution tests indicate that features with widths greater than ∼13 km are reliable. Beneath the sedimentary rocks, seismic velocities increase more slowly with depth — from 6.0 km/s just below the basin to 6.3 km/s at ∼17 km in depth, and then to 6.8–7.0 km/s at the base of the crust. The Moho is found at a depth of 33.5–35 km beneath the profile, and mantle velocities are high at 8.05–8.10 km/s.

Seismic reflection constraints on upper crustal structures in the volcanic-covered central Nechako basin, British Columbia1This article is one of a series of papers published in this Special Issue on the theme of New insights in Cordilleran Intermontane geoscience: reducing exploration risk in the mountain pine beetle-affected area, British Columbia.

2011 ◽  
Vol 48 (6) ◽  
pp. 1021-1037 ◽  
Author(s):  
A.J. Calvert ◽  
N.E. Hayward ◽  
J.E. Spratt ◽  
J.A. Craven
Keyword(s):  
British Columbia ◽  
Seismic Data ◽  
Seismic Reflection ◽  
Mountain Pine Beetle ◽  
Volcanic Rocks ◽  
Seismic Survey ◽  
Volcanic Stratigraphy ◽  
Exploration Risk ◽  
Good Signal ◽  
Lower Crustal

In 2008, a Vibroseis seismic reflection survey was acquired by Geoscience BC across the eastern part of the volcanic-covered Nechako basin in central British Columbia, where Cretaceous sedimentary rocks have been exhumed along a NNW trend. Good signal penetration through the volcanic cover is indicated by lower crustal reflections at 8–12 s, which were recorded by the entire seismic survey. Comparison of the 2008 seismic survey with data from a previous survey indicates that the lack of reflectivity in the earlier surveys is generally representative of the subsurface geology. The seismic data show that ∼1700 and ∼2900 m thick sub-basins are present at the northern and southern ends of this trend, but the intervening Cretaceous rocks are discontinuous and relatively thin. The creation of a passive-roof duplex by Campanian or later low-angle thrusting is inferred within the thickest Cretaceous strata, but elsewhere faulting is likely related to Eocene extension or transtension. Seismic reflections are also recorded from folded volcanic stratigraphy, the base of the surface volcanic rocks, an underlying volcaniclastic stratigraphy, and intrusions projecting into a Quaternary volcanic cone. Seismic interpretation is complemented by coincident audiofrequency magnetotelluric surveys, from which faulting is inferred at offsets in a regional conductor. No regionally extensive stratigraphy can be identified within the seismic data, and the central Nechako basin appears to be a complex network of small, deformed sub-basins, rather than a single large basin.

Predictive Geological Mapping from Geophysical Data Using Self-Organizing Maps: A Case Study from Baie Verte, NL, Canada

Geophysics ◽  
2021 ◽  
pp. 1-55
Author(s):  
Angela Carter-McAuslan ◽  
Colin Farquharson
Keyword(s):  
Gravity Data ◽  
Geological Mapping ◽  
Magnetic Data ◽  
Self Organizing Maps ◽  
Predictive Mapping ◽  
Legacy Data ◽  
Geological Units ◽  
Radiometric Data ◽  
Self Organizing

Self-organizing maps (SOMs) are a type of unsupervised artificial neural networks clustering tool. SOMs are used to cluster large multi-variate datasets. They can identify patterns and trends in the geophysical maps of an area and generate proxy geology maps, known as remote predictive mapping. We applied SOMs to magnetic, radiometric and gravity datasets compiled from multiple modern and legacy data sources over the Baie Verte Peninsula, Newfoundland, Canada. The regional and local geological maps available for this area and the knowledge from numerous geological studies allowed for assessing the accuracy of the SOM-based predictive mapping. Proxy geology maps generated by primary clustering directly from the SOMs and secondary clustering using a k-means approach reproduced many geological units identified by previous traditional geological mapping. Of the combinations of datasets tested, the combination of magnetic data, primary radiometric data and their ratios, and Bouguer gravity data gave the best results. We found that using reduced-to-the-pole residual intensity or analytic signal as the magnetic data were equally useful. The SOM process was unaffected by gaps in the coverage of some of the datasets. The SOM results could be used as input into k-means clustering as k-means clustering requires no gaps in the data. The subsequent k-means clustering resulted in more meaningful proxy geology maps than were created by the SOM alone. In regions where the geology is poorly known, these proxy maps can be useful in targeting where traditional, on-the-ground geological mapping would be most beneficial which can be especially useful in parts of the world where access is difficult and expensive.

Integration and spatial analysis of high-resolution geophysical and geological data, eastern Gaspé Peninsula

2004 ◽  
Vol 41 (5) ◽  
pp. 603-618 ◽  
Author(s):  
Christine St-Laurent ◽  
Daniel Lebel ◽  
Denis Lavoie ◽  
Michel Malo ◽  
Camille St-Hilaire
Keyword(s):  
High Resolution ◽  
Sedimentary Cover ◽  
Volcanic Rocks ◽  
Aeromagnetic Survey ◽  
Near Surface ◽  
Low Pass ◽  
Gravimetric Data ◽  
Significant Intensity ◽  
Geophysical Anomalies ◽  
The Town

In the vicinity of the Town of Gaspé, the relationships between the Silurian-Devonian sedimentary succession of the Gaspé Belt and the Humber and the Dunnage zones are complex. To unravel these relationships, we used high-resolution aeromagnetic data and regional gravimetric data coupled with field tectonostratigraphic information. The magnetic vertical derivative located several magnetic anomalies associated with near-surface features in the Silurian–Devonian cover sequence. In particular, a conglomerate with magnetic fragments that overlies the Late Silurian Salinic Unconformity is clearly recognizable. Large ovoid anomalies of significant intensity located in the Silurian–Devonian sedimentary cover area cannot be associated with any known geological feature. The interpretation of the high-pass and low-pass filtered aeromagnetic survey indicates that the ovoid anomalies originate below the Silurian–Devonian cover sequence. The most significant of the ovoid anomalies is associated with a gravimetric anomaly. It is proposed that these geophysical anomalies are probably associated with ultramafic and (or) volcanic rocks correlative in the subsurface with outcrops of the Cambrian–Ordovician lithologies of the Lady Step Complex and (or) the Shickshock Group.

New geoscientific constraints on the hydrocarbon potential of the Nechako–Chilcotin plateau of central British Columbia

2014 ◽  
Vol 51 (4) ◽  
pp. v-ix ◽  
Author(s):  
Andrew J. Calvert ◽  
Graham D.M. Andrews
Keyword(s):  
British Columbia ◽  
Large Scale ◽  
Mountain Pine Beetle ◽  
Geological Mapping ◽  
Hydrocarbon Exploration ◽  
Special Issue ◽  
Near Surface ◽  
Mountain Pine ◽  
Geophysical Surveys ◽  
Pine Beetle

Infestation by the mountain pine beetle, Dendroctonus ponderosae, decimated the forests of central British Columbia from 1999 to 2012, severely impacting the forest industry of the Nechako–Chilcotin plateau. In response, all levels of government recognized the value in developing other areas of economic activity, such as hydrocarbon and mineral exploitation, to support local economies. Exploration for resources beneath the Nechako–Chilcotin plateau has historically been constrained by Tertiary volcanic sequences and Quaternary glacial deposits that obscure the underlying geology and limit geophysical imaging. Thus, a coordinated program comprising additional geological mapping, borehole data analysis, and modern geophysical surveys of the area was initiated in 2006, with the objective of better defining the subsurface geology, solving problems of imaging through the complex near-surface, and developing improved regional geological and tectonic models. An initial set of papers arising from this fieldwork, which focused on issues relevant to mineral and hydrocarbon exploration, was published in June 2011 in a Special Issue of the Canadian Journal of Earth Sciences. This Introduction to the second “Mountain Pine Beetle” Special Issue summarizes a set of scientific papers that focus on topics more related to hydrocarbon exploration and the large-scale structure of the crust. The papers deal with the development, thickness, and present distribution of the most prospective Cretaceous sedimentary rocks, as well as characterizing the physical properties of the near-surface volcanic units.

Integrating ice-flow history, geochronology, geology, and geophysics to trace mineralized glacial erratics to their bedrock source: An example from south-central British Columbia1This article is one of a series of papers published in this Special Issue on the theme of New insights in Cordilleran Intermontane geoscience: reducing exploration risk in the mountain pine beetle-affected area, British Columbia.2Earth Sciences Sector Contribution Number: 20100079.

2011 ◽  
Vol 48 (6) ◽  
pp. 1113-1129 ◽  
Author(s):  
A. Plouffe ◽  
R.G. Anderson ◽  
W. Gruenwald ◽  
W.J. Davis ◽  
J.M. Bednarski ◽  
...  
Keyword(s):  
British Columbia ◽  
Mountain Pine Beetle ◽  
Bulk Material ◽  
Magnetic Data ◽  
Ice Flow ◽  
South Central ◽  
Bedrock Geology ◽  
Zircon Crystallization ◽  
Pine Beetle ◽  
Exploration Risk

This study demonstrates how ice-flow history, geochronology, geology, and geophysics may be integrated to enhance the effectiveness of boulder tracing in glaciated regions affected by multiple ice-flow events. Mineralized felsic granitoid boulders (erratics) were discovered 18 years ago on a claim block located 10 km northwest of Little Fort, in the Bonaparte Lake map area (NTS 092P), in south-central British Columbia. Although the boulders have yielded significant gold concentrations (up to 4.15 g/t), their bedrock source is not known. The till near the boulders contains up to 1382 gold grains per 15 kg of bulk material with 75% of the grains having pristine morphology, suggesting a short distance of glacial transport. A U–Pb zircon crystallization age of 198.1 ± 0.5 Ma on one mineralized boulder indicates derivation from an Early Jurassic intrusion. Using a vector addition model based on regional ice-flow patterns, the most recent and detailed bedrock geology map, and recently acquired airborne radiometrics and magnetic data, the northeast sector of the Thuya Batholith (195–205 Ma) is interpreted as the most likely bedrock source of the mineralized boulders.

A geophysical interpretation of the onshore and offshore geology of the southern Avalon Terrane, Newfoundland

1987 ◽  
Vol 24 (1) ◽  
pp. 60-69 ◽  
Author(s):  
H. G. Miller
Keyword(s):  
Sedimentary Basin ◽  
Gravity Data ◽  
Volcanic Rocks ◽  
Geophysical Data ◽  
Magnetic Data ◽  
Ultramafic Rocks ◽  
Volcanic Island ◽  
Thrust Faulting ◽  
Geophysical Interpretation ◽  
Avalon Peninsula

This paper presents new land and underwater gravity data for the southern portion of the Avalon Terrane of Newfoundland. These gravity data are combined with existing airborne and marine magnetic data to produce a detailed geophysical interpretation of the geology of the southern Avalon Peninsula and the adjacent portions of Placentia and St. Mary's bays.Qualitative interpretation of the geophysical data in conjunction with the known geology reveals that the major faults previously mapped only on land and inferred beneath St. Mary's Bay can be traced offshore geophysically. In addition, the previously unknown offshore limits of a small sedimentary basin in the southeast part of the area can be delineated.Quantitative modelling demonstrates that (1) Precambrian mafic to ultramafic rocks underlie the whole area, (2) thrust faulting in the St. Mary's Peninsula and elsewhere has led to the juxtaposition of Bull Arm volcanic rocks over Harbour Main volcanic rocks, and (3) the evolution of the area may be explained by a combination of earlier volcanic island and extensional models.The mapping has also revealed the presence of previously unknown northwest–southeast lineations in the geophysical patterns, which may be related to the late wrench faulting.

Neotectonics and landscape characterization in the Gawler Craton, South Australia - Insights through high-resolution remote sensing

2020 ◽  
Author(s):  
Cericia Martinez ◽  
Ulrich Kelka ◽  
Ignacio Gonzalez-Alvarez ◽  
Carmen Krapf
Keyword(s):  
High Resolution ◽  
Large Scale ◽  
Mineral Exploration ◽  
Gravity Data ◽  
South Australia ◽  
Magnetic Data ◽  
Surface Features ◽  
Mineral Potential ◽  
Landscape Characterization ◽  
Digital Elevation

<p>The Gawler Craton hosts significant economic mineralization within South Australia. Due to limited outcrops, deeply weathered profiles, and the absence of a clear variety of landscape surface features, mineral exploration is particularly challenging in this part of Australia. Here we present a workflow of data processing and interpretation to understand the neotectonics and landscape characterization of this region. We explore the potential to delineate surface lineaments and features from newly acquired high-resolution datasets. We aim to automatically identify landform domains based on the analysed data and investigate whether deep seated tectonic lineaments manifest in recognizable surface expressions.</p><p>The data we analyse in this study comprises digital elevation, radiometric, magnetic, and gravity data. We assume that elevation and radiometric data relate to surficial landscape features, whereas gravity and magnetic data represent subsurface basement features. Linking the analysis of both surface and subsurface datasets can potentially yield information on the neotectonic activity, and the association between landforms and basement structures as potential zones of fluid migration. We will show how processed digital elevation data can be used for automatic classification of different landform domains.</p><p>In order to assess mineral potential zones in the area, we compare the generated lineament data in terms of their geometric and topological properties to examine whether there is consistency in the subsurface and surface layers. We postulate that through a line density map, we may be able to quantify a potential relationship between lineaments that are representative in both the surface and subsurface, indicating potential faults or large-scale lineament trends that may link mineral systems in the basement with the landscape surface features. Areas that exhibit large numbers of surface and subsurface lineaments might be areas of enhanced mineral potential. This study contributes to enhance the efficiency of mineral exploration protocols in areas under cover.</p>

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