The North Australian Craton 3D Gravity and Magnetic Inversion Models: A trial for first pass modelling of the entire Australian continent

2021 ◽  
Author(s):  
J.A. Goodwin ◽  
R.J.L. Lane
Keyword(s):  
The North ◽  
Gravity And Magnetic ◽  
Magnetic Inversion ◽  
Australian Continent ◽  
First Pass ◽  
3D Gravity

Late Quaternary change in the mountains of New Guinea

Antiquity ◽  
1995 ◽  
Vol 69 (265) ◽  
pp. 818-830 ◽  
Author(s):  
Geoff Hope ◽  
Jack Golson
Keyword(s):  
Late Quaternary ◽  
New Guinea ◽  
Mountainous Areas ◽  
The South ◽  
Environmental Sequence ◽  
The North ◽  
Australian Continent

At the south and north limits of our region are mountainous areas very different from the open arid spaces of the Australian continent between. In the north, the high country of New Guinea offers a complex and well-studied environmental sequence as the arena for early and puzzling human adaptations, precursor of the extraordinary societies of the island today.

Metamorphic Gradient: A Regional-Scale Area Selection Criterion for Gold in the Northeastern Superior Province, Eastern Canadian Shield

SEG Discovery ◽  
2007 ◽  
pp. 1-15
Author(s):  
Michel Gauthier ◽  
Sylvain Trépanier ◽  
Stephen Gardoll
Keyword(s):  
Regional Scale ◽  
Selection Criterion ◽  
Superior Province ◽  
James Bay ◽  
Area Selection ◽  
The North ◽  
First Pass ◽  
Abitibi Subprovince ◽  
Frontier Region ◽  
Metamorphic Gradient

ABSTRACT One hundred years after the first gold discoveries in the Abitibi subprovince, the Archean James Bay region to the north is experiencing a major exploration boom. Poor geologic coverage in this part of the northeastern Superior province has hindered the application of traditional Abitibi exploration criteria such as crustal-scale faults and “Timiskaming-type” sedimentary rocks. New area selection criteria are needed for successful greenfield exploration in this frontier region, and the use of steep metamorphic gradients is presented as a possible alternative. The statistical robustness of the metamorphic gradient area selection criterion was confirmed by using the curve of the receiver operating characteristic (ROC) to estimate the correlation between metamorphic fronts and the distribution of known Abitibi orogenic gold producers. The criterion was then applied to the James Bay region during a first-pass craton-scale exploration program. This was part of the strategy that led to the discovery of the Eleonore multimillion-ounce gold deposit in 2004.

Integration of gravity, magnetic, and seismic data for subsalt modeling in the Northern Red Sea

2021 ◽  
Vol 9 (2) ◽  
pp. T507-T521
Author(s):  
Camille Le Magoarou ◽  
Katja Hirsch ◽  
Clement Fleury ◽  
Remy Martin ◽  
Johana Ramirez-Bernal ◽  
...  
Keyword(s):  
Red Sea ◽  
Seismic Reflection ◽  
Magnetic Data ◽  
Gravity Inversion ◽  
Gravity And Magnetic ◽  
3D Gravity ◽  
Thin Crust ◽  
Gravity And Magnetic Data ◽  
Refraction Data ◽  
Northern Red Sea

Rifts and rifted passive margins are often associated with thick evaporite layers, which challenge seismic reflection imaging in the subsalt domain. This makes understanding the basin evolution and crustal architecture difficult. An integrative, multidisciplinary workflow has been developed using the exploration well, gravity and magnetics data, together with seismic reflection and refraction data sets to build a comprehensive 3D subsurface model of the Egyptian Red Sea. Using a 2D iterative workflow first, we have constructed cross sections using the available well penetrations and seismic refraction data as preliminary constraints. The 2D forward model uses regional gravity and magnetic data to investigate the regional crustal structure. The final models are refined using enhanced gravity and magnetic data and geologic interpretations. This process reduces uncertainties in basement interpretation and magmatic body identification. Euler depth estimates are used to point out the edges of high-susceptibility bodies. We achieved further refinement by initiating a 3D gravity inversion. The resultant 3D gravity model increases precision in crustal geometries and lateral density variations within the crust and the presalt sediments. Along the Egyptian margin, where data inputs are more robust, basement lows are observed and interpreted as basins. Basement lows correspond with thin crust ([Formula: see text]), indicating that the evolution of these basins is closely related to the thinning or necking process. In fact, the Egyptian Northern Red Sea is typified by dramatic crustal thinning or necking that is occurring over very short distances of approximately 30 km, very proximal to the present-day coastline. The integrated 2D and 3D modeling reveals the presence of high-density magnetic bodies that are located along the margin. The location of the present-day Zabargad transform fault zone is very well delineated in the computed crustal thickness maps, suggesting that it is associated with thin crust and shallow mantle.

PLATE TECTONICS AND THE EVOLUTION OF THE TIMOR SEAR NORTHWEST AUSTRALIA

1973 ◽  
Vol 13 (1) ◽  
pp. 13 ◽  
Author(s):  
B. J. Warris
Keyword(s):  
Early Cretaceous ◽  
Rift Valley ◽  
Plate Tectonics ◽  
Ocean Basin ◽  
Complete Separation ◽  
The North ◽  
Australian Continent ◽  
Early Palaeozoic ◽  
Oceanic Plates ◽  
Shelf Sedimentation

The Browse and Bonaparte Gulf Basins in northwestern Australia contain sedimentary sections which range in age from early Palaeozoic to Recent. These basins developed as a result of the rifting and break up of Gondwanaland into two continents. The sedimentary and tectonic histories of these basins clearly reflect the relative movements of these continents.In pre-Permian times, the earliest postulated rifting may have been early Palaeozoic associated with the north-south separation of Gondwanaland from Eurasia which produced the Tethyan Sea. This was followed by Middle Palaeozoic rifting which affected the Bonaparte Gulf Basin, Fitzroy Graben and perhaps also the Browse Basin.A Late Carboniferous-Early Permian rift valley developed between the Kimberley Block and a western landmass. Alternate marine and fluvio-deltaic deposits characterised sedimentation in this rift valley until Early Jurassic time. Marine transgressions inundated from the north where the rift valley opened into the Tethyan Sea.During the Late Jurassic and Early Cretaceous, the western landmass was detached from the Australian continent along a major right lateral wrench fault. At this time the Indian Ocean Basin appeared as a distinct morphological unit and inundated the Browse Basin. Associated with these movements were the emergence of the Ashmore-Sahul Block and Northeast Londonderry Ridge and the development of the Scott Reef-Buccaneer trend. Marine volcanics at Scott Reef and Ashmore Reef may be related to the formation of new ocean crust.At the end of the Early Cretaceous, tectonic events associated with the complete separation of the western landmass from Australia, resulted in a regional northwesterly tilt of the basin and a major marine transgression.During the Tertiary, Australia moved north, away from Antarctica, and eventually collided with the Southeast Asian and West Pacific oceanic plates. Timor uplifted as a Tertiary melange of Australian sediments behind a north-dipping sub-duction zone along the Timor Trough. The Timor Sea remained relatively stable and was the site of carbonate shelf sedimentation.

Bright spots, milligals, and gammas

Geophysics ◽  
1982 ◽  
Vol 47 (12) ◽  
pp. 1693-1705
Author(s):  
Alan O. Ramo ◽  
James W. Bradley
Keyword(s):  
Seismic Data ◽  
Magnetic Data ◽  
Amplitude Analysis ◽  
Seismic Amplitude ◽  
The North ◽  
Gravity And Magnetic ◽  
Amplitude Anomaly ◽  
North Edge ◽  
Gravity And Magnetic Data ◽  
Seismic Anomaly

Spatially discontinuous high‐amplitude seismic reflections were encountered in seismic data acquired in the early 1970s in northeast Louisiana and southwest Arkansas. Large acoustic impedance contrasts are known to result from gaseous hydrocarbon accumulations. However, amplitude anomalies may also result from large density and velocity contrasts which are geologically unrelated to hydrocarbon entrapment. A well drilled on the northeast Louisiana amplitude anomaly encountered 300 ft of rhyolite at a depth of 6170 ft. Subsequent gravity and total field magnetic profiles across the feature revealed the presence of 0.2 mgal and 17 gamma anomalies, respectively. The measured magnetic susceptibility of the rhyolite was 0.0035 emu and the measured density contrast was [Formula: see text]. Model studies based on the seismically determined areal extent of the anomaly and the measured thickness of rhyolite accounted for the observed gravity and magnetic anomalies. The southwest Arkansas amplitude anomaly was a sheet‐like reflection which terminated to the north and west within the survey area. Two north‐south gravity profiles exhibited a negative character over the sheet‐like reflector but did not exhibit a clear spatial correlation with the north limit of the seismic anomaly. Two north‐south magnetic profiles exhibited tenuous 4 gamma anomalies which appeared to be spatially correlated with the interpreted north edge of the seismic anomaly. A subsequent wildcat well encountered no igneous material but did penetrate 200 ft of salt at about 7500 ft. Reassessment of the gravity and magnetic data indicated that this seismic amplitude anomaly is not attributable to an intrasedimentary igneous source; it suggested a salt‐related 0.2 to 0.3 mgal minimum coextensive with the observed seismic amplitude anomaly. Present amplitude analysis technology would treat these seismic data with suspicion. However, gravity and magnetic data acquisition can provide a relatively inexpensive means for evaluation and verification of amplitude anomalies and thus should be an adjunct for land seismic exploration utilizing amplitude analysis.

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