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As a new kind of renewable and environmental-friendly energy to generate electricity, hot dry rocks (HDR) geothermal reservoirs have been studied, along with the enhanced geothermal system (EGS). Geophysical methods have been used for the geological characterisation in different scales. The small-scale geophysical data are required for the local geological analysis so as to provide prior information for HDR modelling. Gonghe basin is in the northeast margin of the Qinghai–Tibet Plateau. Several drilling records indicate that this basin is a potential HDR prospecting area with high geothermal gradient, high heat flow and widespread igneous rock distribution, especially the Gonghe town (Qiabuqia) along with its neighbouring area. Gravity and magnetic surveys were carried out here. To better understand the areal and vertical distribution of the HDR, the gravity and magnetic data were inverted using 2D manual inversion and 3D cross-gradient joint inversion based on the smooth l0 norm constraint of minimum support functional stabiliser. The 2D model showed the sedimentary cap with a thickness of around 1000–1500 m. Granites of different periods and intrusion process were widely distributed and underlined the sediments accompanied by some deep faults. As for the HDR delineation, 3D models showed a potential area along Gonghe town and Dongba. The density and susceptibility were estimated at over 2.6 g/cm3 and 4 × 10–3 SI separately, when referred with exiting HDR distribution along the geological profile of DR4–QR1–DR3–DR2 wells. The upper boundary of HDR was outlined at the depth of around 2000 m, and the volume of HDR was then estimated around 6100 km3 above 3500 m depth. The appearance of the density and susceptibility models was affected by the lithology, stress and hydrothermal alteration. More precise geophysical methods including the microgravity, seismic and MT (magnetotelluric) surveys would be more applicable at the HDR exploitation stage.

Reducing the fly-height between the head and disk to less than 1 nm with high reliability is necessary to improve the recording density of magnetic disks. Therefore, the mechanism of the head touchdown (TD) phenomenon, particularly the surfing state after the TD, needs to be understood. Assuming that the contact sliding on the sub-nanometer asperities, covered with a monolayer lubricant film, generates the lubrication film forces and reduces the surface forces, the present study shows that numerical simulations of a one-degree-of-freedom slider model can be used to understand various TD phenomena, including surfing conditions. The three different TD behaviors of a commercial head slider were explained by the differences in the rate of generation of the lubrication film force after the TD and initial surface force. The parametric studies demonstrated that surfing states could be generated at a separation of more than three times the standard deviation of the asperity height by increasing the surface force and magnitude of the disk-waviness, thereby suggesting the possibility of quasi-contact recording.

Subsurface characterization is a crucial aspect of geophysical exploration, enabling the identification and understanding of valuable geological bodies and resources. In this context, joint inversion of gravity and magnetic data has emerged as a powerful geophysical exploration technique, allowing for a more coherent and consistent interpretation of subsurface structures. The study focuses on understanding residual gravity and magnetic anomalies by employing the gradient descent-based joint inversion approach. A MATLAB program was developed to determine the inverse gravitational and magnetic anomalies using the gradient descent approach. We explored the potential of 2D rectangular prisms as a popular geometry to represent mineralized bodies and oil and gas structures. To overcome the non-uniqueness issues, we designed code for joint inversion of gravity and magnetic data. Synthetic data was inverted using the gradient descent technique and compared with the least-squares approach. Numerical simulations and real data application successfully reconstructed the geometry of the prisms. An illustrative example of a prism fault was used for further evaluation. Real data from the Oka complex in Quebec, Canada, was collected from the literature and subjected to joint and individual gravity and magnetic modelling. The results highlighted the influence of heterogeneous mass distribution on matching forward anomalies. The high gravity anomaly in the Oka complex was attributed to carbonatite and silicate rocks. The presence of two intrusive centres within the complex caused the magnetic high. This work demonstrates the effectiveness of the gradient descent approach as it consistently outperformed the conventional method, offering a robust solution for subsurface characterization in geophysical exploration.

This paper analyzed satellite and aeromagnetic data over Osun State, Southwestern, Nigeria with a view to assessing the surface and subsurface structural settings that may favour mineralization in the study area. To accomplish this goal, airborne magnetic data, Aster Digital Elevation Map, and Landsat-7 ETM + scenes of Osun State were acquired and processed. Several enhancement techniques were applied to improve the quality of the various remotely sensed data sets for visualization and interpretation. The preferential orientations of structural features in the investigated area are northeast–southwest, north–northeast–south–southwest, and northwest–southeast. The northeast–southwest orientation characterized the primary geologic events in the area. The lineament's density analysis revealed that the rocks were affected by high lineament concentration. Remarkable correlations exist between regions of high lineament density and the areas of known mineral occurrences. The lineament seems to play a significant role in providing favorable pathways for the migration and ascent of mineralized fluids to depositional sites. The findings of the present study provide significant information on the linear features and their influence on mineral occurrence in the study area.

Results of a depth-to-basement study are presented for the westernmost Polish Outer Carpathians. The gravity data are inverted for the top of the Precambrian basement using horizons from 2-D gravity and magnetic forward models and well tops as input depth measurements. 2-D models, used in the study, are built upon depth converted seismic profiles. The results are visualized as an isobath map for the top of the Precambrian basement, complemented with the qualitative structural interpretation of gravity and magnetic anomaly maps. The outcome of 3-D joint inversion of the gravity data and depth measurements shows the Precambrian crystalline basement deepening southward from c. 1 to almost 7 km b. s. l. Consequently, an approximately 2 km thick wedge of autochthonous sediments, thickening southward, is embraced between the crystalline basement and a sole detachment of the Carpathian fold-and-thrust belt, imaged by seismic data. Since the modelled top of the crystalline basement is roughly parallel to the Moho, suggesting no extension-related thinning in Mesozoic, the autochthonous sediments are likely of pre-Permian age. A positive magnetic anomaly in the south of the study area is presumably associated with the presence of an elongated body of intermediate to mafic rocks in the basement of the Brunovistulian Terrane. These rocks may represent a relic of a Cadomian magmatic arc comparable to that existing in the Brno Massif of southern Moravia.

Compilation of gravity maps from Romania and Bulgaria provided geophysical data with very good regional coverage, making possible enhanced data processing and cross-border geological interpretation of gravity data on the Moesian Platform. By merging the available gravity data into a unique dataset, a Bouguer gravity anomaly map of the Moesian Platform in Romania and Bulgaria was produced. When applying filtering techniques, the residual gravity anomaly map of the Moesian Platform provided valuable information on the Intramoesian Fault segments in both Romania and Bulgaria. Large and deep geological structures of the Moesian Platform were interpreted on gravity anomalies at crustal depths based on density contrasts as compared with the neighbouring background. Aeromagnetic data processing using different filtering methods in Oasis montaj software, resulted in a series of other magnetic maps and offered new possibilities of interpreting the available data.

High resolution airborne magnetic data of parts of the southern Benue Trough were digitally processed and analyzed in order to estimate the depth of magnetic sources and to map the distribution and orientation of subsurface structural features. Enhancement techniques applied include, reduction to pole/equator (RTP/RTE), first and second vertical derivatives, horizontal gradients and analytic signal. Results from these procedures show that at least 40% of the sedimentary basin contain shallow (<200 m) magmatic bodies, which in most cases are intermediate to mafic intrusive and hyperbysal rocks, and may occur as sills, dikes or batholiths. Magnetic lineaments with a predominant NE–SW trend appear to be more densely distributed around the basement rocks of the Oban Hills and metamorphosed rocks around the Workum Hills. 3D standard Euler deconvolution and Source Parameter Imaging (SPI TM ) techniques were employed for depth estimation. Results from the two methods show similar depth estimates. The maximum depth to basement values for 3D Euler and SPI are 4.40 and 4.85 km with mean depths of 0.42 and 0.37 km, respectively. Results of 2D modelling of magnetic profiles drawn perpendicular to major anomalies in the study area reveal the existence of deep seated faults which may have controlled the emplacement of intrusive bodies in the basin. The abundance of intrusive bodies in the study area renders this part of the southern Nigerian sedimentary basins unattractive for petroleum exploration. However, the area possesses high potential for large accumulation of base metal mineralization.

The Nanling region is located at the intersection of the Yangtze Block and Cathaysia Block and is characterized by complex geological and tectonic processes, as well as distinct W-Sn-REE mineralization. Despite extensive research on the mineralization of W-Sn and REE deposits in the Nanling region, the factors impacting the distribution pattern of eastern tungsten and western tin deposits, as well as the mechanism of REE enrichment in the parent rocks, remain uncertain. Deep structural and tectonic variability plays a crucial role in the formation of mineral deposits in the upper crust. Information on deep structural and tectonic variability is contained in the Moho depth, Curie depth, effective elastic thickness, lithospheric density, and thermal structure derived from the processing and inversion of satellite gravity and magnetic data. In this paper, we comprehensively analyse satellite gravity and magnetic data from the Nanling region, integrating the processing and inversion results with the tectonic evolution of this region and relevant geological information. It is hypothesized that the Chenzhou–Linwu fault serves as a channel for mineral and thermal transfer in the Sn ore aggregation zone, facilitating the material transport from the deep mantle to the surface and ultimately leading to the formation of Sn-enriched granite. The collection area of tungsten ore is more weakly associated with the Chenzhou–Linwu fault, and through deep heat transfer, tungsten components are primarily concentrated in the Earth’s crust to produce W-enriched granite. The primary source of REE enrichment in the parent rocks associated with REE mineralization is predominantly derived from the felsic crust, and the rapid intrusion of deep magma resulting from the subduction and retraction of the Palaeo-Pacific Plate is a contributing factor to the contrasting enrichment of light and heavy rare-earth elements. Mineral crystalline differentiation is relatively high, leading to the formation of ore-forming parent rocks with high heavy rare-earth element contents.

580-km length marine magnetic study was performed at the Northern Marmara Shelf and the Lagoon Küçükçekmece to provide new datasets to understand the submarine structures. The distributions of the relatively complex and differentiated low and high magnetic anomalies indicate that the study area was affected by the multiple tectonic regimes. While the magnetic highs correspond with the folding structures, magnetic low anomalies well match with the lineaments determined from the seismic profiles. Magnetic anomalies support an E-W trending fault, controlling the anticlinorium system and NNE-SSW faults related to the compressional tectonics. These magnetic structures might be associated with Thrace Eskisehir Fault Zone, an older right-lateral strike-slip fault, which was the most dominant tectonic element before the North Anatolian Fault Zone. In addition to three appx, N-S trending faults are defined beneath the Lagoon Küçükçekmece from the total and residual magnetic anomaly grids.

The spreading of droplets of perfluoropolyether lubricants is studied on unlubricated, carbon-overcoated disk surfaces, the type used in magnetic recording disk drives. As the number of hydroxyl end groups on the Fomblin-Z backbone is increased from zero to two to four (Z → Zdol → Ztetraol), the spreading kinetics slows down dramatically for each addition of two hydroxyl end groups, and with eight hydroxyl groups, the lubricant ZTMD no longer spreads. Faster spreading kinetics is observed initially when a central droplet is still available to feed lubricants into the molecularly thin lubricant film. Much slower spreading kinetics is observed once this central droplet has dissipated to form a pancake-shaped film less than a monolayer thickness. During the initial spreading stage with the central droplet, the radius R of the area covered by the spreading film grows as R  ~  t ν , with ν  ~ 1/3, while during the final spreading stage, ν  ~ 0.1. The faster spreading mechanism during the initial spreading stage is attributed to the en masse flow of lubricant molecules in the lubricant film driven by the backing pressure of the lubricant remaining in the droplet. The slower spreading kinetics once the central droplet has dissipated is well described by a thickness-dependent diffusion coefficient D ( h ) obtained by modeling lubricant migration as Poiseuille flow driven by the disjoining pressure gradient.