Upper crustal structure of Deception Island area (Bransfield Strait, Antarctica) from gravity and magnetic modelling

Deception Island is a young, active volcano located in the south-western part of Bransfield Strait, between the Antarctic Peninsula and the South Shetland archipelago. New gravity and magnetic data, from a marine geophysical cruise (DECVOL-99), were analysed. Forty-eight survey lines were processed and mapped around Deception Island to obtain Bouguer and magnetic anomaly maps. These maps show well- defined groups of gravity and magnetic anomalies, as well as their gradients. To constrain the upper crustal structure, we have performed 2+1/2D forward modelling on three profiles perpendicular to the main anomalies of the area, and taking into account previously published seismic information. From the gravity and magnetic models, two types of crust were identified. These were interpreted as continental crust (located north of Deception Island) and more basic crust (south of Deception Island). The transition between these crustal types is evident in the Bouguer anomaly map as a high gradient area trending NE–SW. Both magnetic and gravity data show a wide minimum at the eastern part of Deception Island, which suggests a very low bulk susceptibility and low density intrusive body. With historical recorded eruptions and thermal and fumarolic fields, we interpret this anomaly as a partially melted intrusive body. Its top has been estimated to be at 1.7 km depth using Euler deconvolution techniques.

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The geophysical signature of Oyut deposits, Oyu Tolgoi, Mongolia

Mongolian Geoscientist ◽

10.5564/mgs.v26i52.1323 ◽

2021 ◽

Vol 26 (52) ◽

pp. 80-96

Author(s):

Erdene Batbaatar ◽

Munkhjargal Todbileg ◽

Otgonbayar Sansar ◽

Baatar Bataa

Keyword(s):

Gravity Data ◽

Porphyry Copper ◽

Mineral Deposits ◽

Magnetic Data ◽

The South ◽

Porphyry Cu ◽

Gravity And Magnetic ◽

Integrated Interpretation ◽

Ground Magnetic ◽

Gravity And Magnetic Data

The well-known Oyu Tolgoi Cu-Au group deposits can be divided into three main deposits: Hugo Dummett deposit (Hugo North and Hugo South), Oyut deposits (South Oyu, Southwest Oyu and Central Oyu), and Heruga deposit in the south. These deposits sit along 26 km long, north-northeast trending belt termed as the Oyu Tolgoi trend. This paper reviews investigations on geophysical signatures of the South Oyu, Southwest Oyu and Central Oyu deposits and compares geophysical models of the mineral deposits with their lithology, alteration, mineralization, and structures. A variety of datasets including induced polarization, ground magnetic, gravity survey are used in the study and generated inversion products of ground magnetic and gravity data with integrated interpretation. Typical responses from the Oyut deposits are: up to 0.1 mGal positive gravity anomaly above background, 100–200 nT low or high magnetic anomaly compared to background depending on the geological situations, and from 12 mV/V to 30 mV/V chargeability anomalies and low resistivity signatures from 100 ohm.m to 400 ohm.m. The interpreted geological-geophysical models of porphyry Cu-Au deposits presents in this study have emphasis on integrated interpretation of geophysical techniques, and inversions of gravity and magnetic data in gold rich porphyry copper system.

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Application of gravity and magnetic methods to assess geological hazards and natural resource potential in the Mosida Hills, Utah County, Utah

Geophysics ◽

10.1190/1.1444840 ◽

2000 ◽

Vol 65 (5) ◽

pp. 1514-1526 ◽

Cited By ~ 12

Author(s):

Alvin K. Benson ◽

Andrew R. Floyd

Keyword(s):

Gravity Data ◽

Magnetic Data ◽

Geological Hazards ◽

Mafic Lava ◽

Subsurface Geology ◽

Gravity And Magnetic ◽

Geophysical Surveys ◽

Utah County ◽

Gravity And Magnetic Data ◽

Hills Area

Gravity and magnetic data were collected in the Mosida Hills, Utah County, Utah, at over 1100 stations covering an area of approximately 58 km2 (150 mi2) in order to help define the subsurface geology and assess potential geological hazards for urban planning in an area where the population is rapidly increasing. In addition, potential hydrocarbon traps and mineral ore bodies may be associated with some of the interpreted subsurface structures. Standard processing techniques were applied to the data to remove known variations unrelated to the geology of the area. The residual data were used to generate gravity and magnetic contour maps, isometric projections, profiles, and subsurface models. Ambiguities in the geological models were reduced by (1) incorporating data from previous geophysical surveys, surface mapping, and aeromagnetic data, (2) integrating the gravity and magnetic data from our survey, and (3) correlating the modeled cross sections. Gravity highs and coincident magnetic highs delineate mafic lava flows, gravity lows and magnetic highs reflect tuffs, and gravity highs and magnetic lows spatially correlate with carbonates. These correlations help identify the subsurface geology and lead to new insights about the formation of the associated valleys. At least eight new faults (or fault segments) were identified from the gravity data, whereas the magnetic data indicate the existence of at least three concealed and/or poorly exposed igneous bodies, as well as a large ash‐flow tuff. The presence of low‐angle faults suggests that folding or downwarping, in addition to faulting, played a role in the formation of the valleys in the Mosida Hills area. The interpreted location and nature of concealed faults and volcanic flows in the Mosida Hills area are being used by policy makers to help develop mitigation procedures to protect life and property.

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Determination of Tectonic and Crustal Structure of the Eastern Pontide Orogenic Belt (NE Turkey) Using Gravity and Magnetic Data

Pure and Applied Geophysics ◽

10.1007/s00024-009-0529-7 ◽

2009 ◽

Vol 166 (12) ◽

pp. 1987-2006 ◽

Cited By ~ 24

Author(s):

Nafiz Maden ◽

Kenan Gelisli ◽

Yener Eyuboglu ◽

Osman Bektas

Keyword(s):

Crustal Structure ◽

Orogenic Belt ◽

Magnetic Data ◽

Gravity And Magnetic ◽

Gravity And Magnetic Data

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Gravity and Magnetic Methods

Continental Shelf Limits ◽

10.1093/oso/9780195117820.003.0018 ◽

2000 ◽

Author(s):

Richard M. Carruthers ◽

John D. Cornwell

Keyword(s):

Large Scale ◽

Gravity Data ◽

Integrated Approach ◽

Rock Properties ◽

Magnetic Data ◽

Satellite Gravity ◽

Fully Integrated ◽

Continental Shelves ◽

Gravity And Magnetic ◽

Gravity And Magnetic Data

Lateral variations in the density and magnetization of the rocks within the crust give rise to "anomalies" in the Earth's gravity and magnetic fields. These anomalies can be measured and interpreted in terms of the geology both in a qualitative sense, by mapping out trends and changes in anomaly style, and quantitatively, by creating models of the subsurface which reproduce the observed fields. Such interpretations are generally less definitive in themselves than the results from seismic surveys (see chapter 12), but the data are widely available and can provide information in areas where other methods are ineffective or have not been applied. As the different geophysical techniques respond to specific rock properties such as density, magnetization, and acoustic velocity, the results are complementary, and a fully integrated approach to data collection and interpretation is generally more effective than the sum of its parts assessed on an individual basis. Gravity and magnetic data have been acquired, at least to a reconnaissance scale, over most of the world. In particular, the release into the public domain of satellite altimetry information (combined with improved methods of data processing) means that there is gravity coverage to a similar standard for most of the offshore region to within about 50 km of the coast. Magnetic anomalies recorded from satellites provide global coverage, but the high altitude of the observations means that only large-scale features extending over many 10s of kilometers are delineated. Reconnaissance aeromagnetic surveys with flight lines 10-20 km apart provide a lateral anomaly resolution similar to that of the satellite gravity data. Oceanographic surveys undertaken by a variety of academic and research institutions are another valuable source of data in remote regions offshore which supplement and extend the more detailed coverage obtained over the continental shelves, for example, by oil companies in areas of hydrocarbon interest. Surveys over land vary widely in terms of acquisition parameters and quality, but some form of national compilation is available from many countries. A number of possible applications of the potential field (i.e., gravity and magnetic) data follow from the terms set out by UNCLOS. Paragraph 4(b) of article 76 states, "In the absence of evidence to the contrary, the foot of the continental slope is to be determined as the point of maximum change in the gradient at its base" (italics added).

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Crustal structure of Mesozoic rifting in the northeastern Gulf of Mexico from integration of seismic and potential fields data

Interpretation ◽

10.1190/int-2018-0259.1 ◽

2019 ◽

Vol 7 (4) ◽

pp. T857-T867 ◽

Cited By ~ 5

Author(s):

Mei Liu ◽

Irina Filina ◽

Paul Mann

Keyword(s):

Gulf Of Mexico ◽

Crustal Structure ◽

Late Jurassic ◽

Phase 1 ◽

Integrated Approach ◽

High Density ◽

Magnetic Data ◽

Data Sets ◽

Gravity And Magnetic ◽

Northeastern Gulf Of Mexico

We have investigated the crustal structure of a 400 km wide zone of thinned continental crust in the northeastern Gulf of Mexico (GOM) using gravity and magnetic modeling along two deeply penetrated seismic transects. Using this approach, we identify two zones of prominent, southward-dipping reflectors associated with 7–10 km thick, dense, and highly magnetic material. Previous workers have interpreted the zones as either coarse clastic redbeds of Mesozoic age that are tilted within half-grabens or seaward-dipping reflectors of magmatic origin. Both seismic reflection lines reveal a 10 km thick and 67 km wide northern zone of high density near the Florida coastline beneath the Apalachicola rift (AR). The southern zone of high density occurs 70 km to the south in the deepwater central GOM along the northern flank of the marginal rift, a 48 km wide, southeast-trending structure of inferred Late Jurassic age that is filled by 3 km of low-density and low-magnetic susceptibility sediments including complexly deformed salt deposits. We propose that these two subparallel rifts and their associated magmatic belts formed in the following sequence: (1) AR formed during Triassic-early Jurassic (210–163 Ma) phase 1 of diffuse continental stretching and was partially infilled on its northern edge by southward-dipping volcanic flows; and (2) the similarly southward-dipping southern magmatic zone formed adjacent to the marginal rift during the early phase 2 of late Jurassic (161–153 Ma) rifting of the GOM continental extension; this southern area of SDR formation immediately preceded the formation of the adjacent oceanic crust that separated the rift-related evaporates into the northern and southern GOM. Our integrated approach combining 2D seismic, gravity, and magnetic data sets results in a more confident delineation of these deep crustal features than from seismic data alone.

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