High-resolution Aeromagnetic Data Research Articles

Modeling geothermal energy potential in the Ruwan-Zafi hot spring region of northeastern Nigeria using high-resolution aeromagnetic data

Modeling geothermal energy potential in the Ruwan-Zafi hot spring region of northeastern Nigeria using high-resolution aeromagnetic data

Groundwater Exploration Within Shallow Depths Around Distinct Litho-Petrological Contact Zones

The world’s increasing demand for freshwater has put a strain on existing reserves in recent years, necessitating further exploration of new groundwater reserves. However, geologic provinces located within the contact boundary of Sedimentary Basin-Basement Complex region are somewhat faced with the problem of shallow sediment thickness. As a result, exploring for groundwater poses a challenge as the sediment thickness might be insufficient to host productive aquifers. Hence, exploring for faults and fractures zones that are embedded on the hard rock underneath the sediment is very essential and complimentary. In this study, high resolution aeromagnetic data over a litho-petrological contact zone of the Middle Benue Trough (MBT) and the Adamawa Massif were analyzed to delineate groundwater exploration areas using a simplified qualitative and quantitative approach. Visual inspection of isolated and aggregate anomalies is performed by analyzing their shapes, dimensions, lateral extents, and discontinuities. Lineaments were then extracted from the residual magnetic map to determine faults, fractures, and joints. A two-source-depth model is indicated by the Spectral Analysis technique used to determine the thickness of the sediments in the area. The deeper source (Z1) has a thickness of 0.9 - 3.6 km, while the shallow source (Z2) has a thickness of 0.1 - 0.8 km. While in some areas the overburden thickness may be sufficient for groundwater exploration, in others it was not, as indicated by the shallow magnetic depth, Z2. Nonetheless, areas of shallow thickness but with aggregates of faults, fractures, and joints were identified as possible locations for groundwater accumulation through magnetic lineament exploration.

Geological Structure and Possible Mineralized Zones in Ikungi – Manyoni Area, Tanzania: Delineated from High-resolution Aeromagnetic Data

Understanding geological structures is important in mineral exploration. Delineating subsurface geological structures, structural intersections, and complexities of potential geological settings for the formation of hydrothermal mineral deposits, such as gold requires using magnetic data, particularly, high-resolution aeromagnetic data. To define possible targets for mineral exploration, this study used linear detection and the Centre for Exploration Targeting (CET) techniques on high-resolution aeromagnetic data for structural delineation and interpretation. The study's conclusions indicate that the majority of geological features, such as faults, shears, fault intersections, and fracture systems, trend NE-SW, N-S, and occasionally NW-SE. These structures create potentially large areas that have a strong chance of becoming mineralized. The CET grid analysis technique defined mineralized zones, particularly the structural intersections which are potential targets in mineral exploration. The effectiveness of the CET technique in mineral prospecting was demonstrated by the correlation between the results and existing mineral occurrences (such as Shanta Gold Mine, abandoned pits, and the operating pits of small-scale miners in Muhintiri). Based on the findings reported herein, any sites that share characteristics with those that have demonstrated gold mineralization should be prioritized for ground follow-up

Integrated groundwater exploration in basement complex terrain for sustainable regional water supply in Abuja, Nigeria

This study integrates geophysical and geological analyses to identify potential areas for regional water supply in newly developed sites and regions lacking coverage from the lower Usuma Dam. Covering an expanse of approximately 5200 km2, high-resolution aeromagnetic data were collected, analyzed, and interpreted alongside thirty-five (35) vertical electrical sounding (VES) data points, utilizing the Schlumberger array with current electrode separations (AB/2) ranging from 100 to 140 m and potential spacing MN/2 varying from 0.25 to 5m. The aeromagnetic data, reduced to the equator, reveal anomalies characterized by variations in magnetic susceptibility, indicative of changes in rock composition. Total magnetic field intensity ranges from 435.7 nT to 568.3 nT, with variations attributed to the presence of diamagnetic materials, specifically magnetite and quartzite in basement rocks. Residual data, ranging from −92 to 41.4 nT and high residual values correspond to granite gneiss and coarse porphyritic biotite hornblende granite. First vertical derivative results expose lineaments with lengths ranging from 894.4m to 11.627 km, supported by tilt derivative lineaments of 1.131–11.400 km these delineate potential zones for urban and regional groundwater supply, emphasizing the role of lineaments and faults in controlling structural geometry for groundwater flow. Geological mapping affirms high fracturing with conjugate faults in the area. Interpreted VES curves identify 65.7% as H-type, 22.9% as KH, and 5.7% as QH curves, with HK- and A-type curves at 2.9%. Overburden thickness varies from 6 to 44 m at specific VES points. Iso-resistivity maps exhibit high resistivity values (6000 to 9000 Ωm) due to geological outcrops, while low resistivity values result from a partially or highly fractured basement. Recommendations include drilling 31 VES points for regional water supply in Abuja's urban area, offering a diversified water source and reducing dependence on potentially vulnerable surface water supplies.

Subsurface Qualitative Investigation for Mineral Exploration using Aeromagnetic Data

This research investigated the subsurface qualitative investigation for mineral exploration of Ibadan Southwest Nigeria, using high resolution aeromagnetic data. The data acquired from Nigeria Geological Survey Agency (NGSA) were subjected to different filtering processing techniques to produce magnetic anomaly maps which were analyzed to detect the subsurface geologic features that are indicative of the potential mineral deposits in the study area. The processing techniques applied in this study to delineate the magnetically active regions were Total Horizontal Derivative (THD), Analytic Signal Amplitude (ASA) and Upward Continuation (UP) method at 150 m and 250m. The results obtained show THD values ranged between 0.002 nT and 0.039 nT connoting regions between non-magnetic body region and high magnetic anomaly regions. The ASA technique revealed susceptibility contrast region between 0.0022 and 0.1472 nT/m; these depict region of geologic body housing the mineralized zones. Thus, there is potential for mineral exploration in the study area.

Investigation of iron ore potential in north-central Nigeria, using high-resolution aeromagnetic dataset and remote sensing approach

The instability of fuel prices in the international market has adversely affected the economy of Nigeria, which is a developing country that solely relies on crude oil. This has led the country to consider diversifying its economy into mineral resources. The consideration of iron ore as an important mineral for global infrastructure, steel production, and wealth creation has prompted this study to consider its potential within north-central Nigeria. Additionally, no geophysical reports considering the regional distribution of iron ore potential in both the Basement Complex and the sedimentary basins within north-central Nigeria have been previously carried out. This study employs an analytical hierarchy process (AHP) and weighted overlay to integrate the analyses of the high-resolution aeromagnetic data set (HRAMD) and Landsat 8 OLI/TIRS to assess the iron ore potential of the different geological terrain in north-central Nigeria. The ferrous mineral band ratio technique was adopted in processing the Landsat data, and several signal enhancement techniques were performed on the HRAMD, including the first vertical derivative (1VD), analytical signal, center for exploration targeting (CET) grid analysis, Euler deconvolution, and radially averaged power spectrum (RAPS). The shallowest magnetic sources and the high amplitude zones were delineated, and the dominant structural trend of the area was revealed to be WNW-ESE and NE-SW, and both orientations appeared to be favorable for mineralization. The apparent depth estimates of shallow and deep-seated magnetic structures obtained from Euler deconvolution ranged from 127.65 to 3540.64 m, whereas RAPS delineated a range of 285–3710 m. The analytical signal (AS) categorized the magnetism of the area into low, intermediate, and high magnetic zones. The higher magnetic zones were considered to be favorable for mineralization. The ferrous mineral ratio map reveals areas of higher reflectance, which depict zones of iron ore potential. The iron ore potential map was validated using known iron ore mines and deposits, which showed a perfect correlation, and new sites of probable iron ore mineralization within north-central Nigeria were revealed. This article will serve as a guide for stakeholders in the exploration of iron ore deposits.

Contrasting structures of the Southern Benue trough and the contiguous crystalline basement as observed from high-resolution aeromagnetic data

The present study investigated crustal structures and geological bodies within selected areas of the southern Benue trough and the adjacent crystalline basement. It utilized high-resolution aeromagnetic data to provide original insights into the contrasting structures and geological bodies within the area, while also identifying promising areas for further mineral and hydrocarbon investigations. The aeromagnetic anomaly data were analyzed using various techniques, including total gradient magnitude, pseudo-gravity transformation, tilt derivative, and source parameter imaging. The total gradient magnitude anomalies revealed a considerable component of the basin affected by block faulting which may have resulted from severe tectonic and structural deformation of the metamorphic basement and the subsequent injection into the sedimentary sequence, a few intrusions. The pseudo-gravity transformation identified a large igneous body in the sedimentary basin which is characterized by positive pseudo-gravity anomalies and surrounded on both sides by linear negative anomalies that signify a rift zone. The positive amplitude of the tilt derivative identified subtle linear magnetic minerals associated with the geologic structure and igneous bodies that suggest considerable mineral exploration prospects. A two-dimensional model of the source parameter imaging reveals the basement below the sedimentary basin to be intensely fragmented and variably subsided with the floor of the basin forming irregular upward and downward folds. In conclusion, the findings suggest promising prospects for mineral exploration along the margin of the sedimentary basin and potential hydrocarbon resources in the northeastern segment of the basin, which is characterized by fewer intrusions.

Ancient silicic volcanism and incipient rift propagation during Gondwana breakup; geophysical insights from the Bumbeni ridge, South Africa

A detailed understanding of the association between magmatism and rift initiation is key to defining the prevailing tectonic conditions active during the initial break-up of Gondwana. The Bumbeni Complex in northern KwaZulu-Natal, South Africa represents an early Cretaceous silicic volcanic centre exposed at the southwestern termination of a linear zone of magnetic anomalies which are buried beneath sedimentary cover. Newly acquired high resolution aeromagnetic data combined with legacy seismic and borehole data is analysed to define the structural architecture of the basement beneath the Zululand Basin in northern KwaZulu-Natal. Multiple prominent positive and negative anomalies ranging from −200 nT to +300 nT based on International Geomagnetic Reference Field (IGRF) and corrected Reduced to Pole (RTP) data are resolved and form a distinct geophysical lineament. Geophysical and borehole core data indicate that the lineament represents a chain of silicic central volcanoes developed as a ridge feature, the Bumbeni Ridge, along the axial zone of an incipient rift structure. Detailed geological mapping and high resolution geophysical data are analysed and compared with analogous contemporary continental rift environments, as well as published data within the adjacent offshore Northern Natal Valley. Results are presented which propose a continental rift evolutionary model for Gondwana breakup in the Zululand Basin in northern KwaZulu-Natal.

Evaluation of Geothermal Energy Potential of Parts of Upper Benue Trough Nigeria Using High Resolution Aeromagnetic Data

Evaluation of Geothermal Energy Potential of Parts of Upper Benue Trough Nigeria Using High Resolution Aeromagnetic Data

Structural and Tectonic Interpretation of Nkalagu and Environs Using High-Resolution Aeromagnetic Data

Structural and Tectonic Interpretation of Nkalagu and Environs Using High-Resolution Aeromagnetic Data

An integrated approach of advanced methods for mapping geologic structures and sedimentary thickness in Ukelle and adjoining region (Southeast Nigeria)

High-resolution aeromagnetic data were enhanced using recent and advanced filters to map the geologic structures of the Ukelle and adjoin region (Southeast Nigeria). Aeromagnetic data were reduced to the equator (RTE) and upward continued to 100 m. Subsequently, enhancement operations like the tilt angle of the horizontal gradient (TAHG), logistic function of the horizontal gradient (LTHG), and fast sigmoid function (FSED) operations were carried out. The results from these filters indicated that the ENE-WSW, NE-SW, NNE-SSW, and NNW-SSE orientations dominate the structural pattern of the Ukelle region. In addition, the edge filters delineated NE-SW trending synclinal structures that match the location of thick (500-1400 m) sedimentation obtained by the tilt-depth (TD) method. Furthermore, the structural map obtained from remote sensing data validated the lineament orientations and position of the NE-SW trending synclinal structure. The results also showed that the study location’s southeastern and northwestern flanking portions, controlled by extensive Santonian igneous intrusions and metamorphisms, are characterized by high lineaments and thin (0-500 m) sedimentation. The observed thin sedimentation is believed to be caused by widespread Santonian tectonic events in the area. At the same time, related geologic structures served as migration pathways and accumulation zones for rift mineralization.

Geothermal prospective areas in the Northern sector of Bida Basin and environs, North-Central Nigeria

With the deteriorating electrical power supply in Nigeria, it is imperative that more alternative sources are explored. This research work is carried out to assess part of the Bida basin as a possible source of geothermal energy that will help to augment the electric power generation in the country. The study was carried out within the northern sector of the Bida Basin and environs and the area which lies between Longitudes 5000ʹ00ʺ – 7000ʹ00ʺ E and Latitudes 8030ʹ00ʺ – 10030ʹ00ʺ N. Sixteen (16) half degree high resolution aeromagnetic data in a block grid format was utilised for this research. To enhance data for interpretation the total magnetic intensity (TMI) map was subjected to regional-residual separation using Oasis Montaj (version 7.0.1) software. To minimize the effect of frequency noise caused by tiny structures near ground surface, the residual magnetic map was upward continued and further divided into sixteen square blocks with each block windowed and subjected to spectral analysis using Matlab (version R2010a) software. Surfer 11 surface mapping software was used for data contouring. Results obtained from the analysis revealed a Curie point depths ranges from 9 – 17 km over the study area, a geothermal gradient range from 32 – 65 0C km-1, and heat flow ranges from 83 – 163 mWm-2. From interpretation of heat flow map, the prospective areas with anomalous geothermal conditions recommended for geothermal exploitation are areas around Masamagu, Mokwa, Bokani, Lapai, Agaie and Agena.

Upward continuation of total magnetic field intensity data over Sokoto basin, north-western Nigeria

High-resolution aeromagnetic data covering the Sokoto basin, north-western Nigeria were acquired and analyzed using regional enhancement techniques, upward continuation and second order regional. The objective was to delineate major geological structures. The data, which are in form of a grid, were knitted using Oasis Montaj software to obtain the magnetic total field intensity map. The composite grid was reduced to a magnetic equator to align the peaks of magnetic anomalies over the center of their causative bodies. The reduced grid was continued at various planes of observation to understate anomalies due to shallow features. The planes were at 10 km, 20 km, 30 km, 40 km, 50 km, 70 km, and 100 km above the surface. Upward continuation maps produced greatly enhanced the long-wavelength (low wavenumber) anomalies associated with deeper subsurface regional structures. The continuation revealed a high magnetic intensity anomaly in western parts of the area and low magnetic intensity anomalies in the eastern parts. The low magnetic intensity in the eastern part is interpreted as a sedimentary deposit. The residual field was removed from the total magnetic field data using the second-order least square method to get the second-order regional field. The regional field analysis agrees with the upward continuation result.

Noise Reduction of Aeromagnetic Data Using Artificial Neural Network

The high-frequency content of high-resolution aeromagnetic data is of particular interest to geophysic ists to identify mineral deposits, shallow faults, and dikes. However, high-resolution aeromagnetic data is contaminated by cultural noise generated from aircraft and man-made features. The culture noise must be removed before starting the interpretation process. Manual techniques are more selective of the noise; however slower and more expensive because they require considerable hands-on interaction. The present study develops a novel method for detecting and removing the culture noise from aeromagnetic data based on an artificial neural network (ANN) in an automatic way and comparing the results with a conventional algorithm using the nonlinear filter. The proposed method is tested using a theoretical example that combine a magnetic anomaly due to a dyke with three sources of cultural noise, besides using a practical example to increase the number of training pattern. The network is trained based on the backpropagation training function, where the algorithm updates the weight and bias states as per the Levenberg–Marquardt optimization. The optimization is reached during the training and validation process after 3,000 iterations. The correlation coefficient ( R) is utilized along with the mean squared error (MSE) as performance indices of the ANN. The ANN demonstrates the capability to detect the spiky data based on the optimal weights, thus allowing for removing and replacing them with clean data using the piecewise cubic Hermite interpolating polynomial (PCHIP) function. The practical utility of the two-method is discussed using high-resolution aeromagnetic data from the Tushka area located in the southwestern desert of Egypt. Comparing the denoising results using the two methods shows that the current approach is more effective in processing and more closely recovering the original magnetic data.

Application of Aeromagnetic Data Analysis and Interpretations to Investigate Solid Mineral Potential in Part of Bauchi, Northeast Nigeria

Abstract: The distribution of surface and subsurface magnetic materials within the study area, the delineation of geologic lineaments, and an estimate of the depth to magnetic sources were all determined by interpreting high resolution aeromagnetic data that covered a portion of Bauchi, northeastern Nigeria, lying between Latitudes 9040'00"N to 10010'0"N and Longitudes 900'0"E to 9040'0'E. The Aeromagnetic map, analytical signal, and horizontal derivative filters used on total magnetic intensity data after reduction to the magnetic equator (RTE) show that the Toro and its environs contain highly magnetic minerals thought to be potential deposits of iron ore. The lithological map and the lineament maps have a good connection. Further examination of the findings reveals that the research area has varying degrees of Ferro-, para-, and diamagnetic mineralization (of the iron and non-iron varieties). The geological source bodies are thought to be located between 177.389 and 991.626 meters deep, according to the Euler depth solution. This shows that during the orogenic process, a sequence of strong deformations were present alongside the Toro.

Subsurface Structural Characterization as Deduced from High-Resolution Aeromagnetic Data over The Confluence Zones in Central, Nigeria

This study aimed to delineate the intrusion body that controls the structural setting and formation around the river Niger-Benue confluence zone with particular attention to its solid mineral potentials, this is achieved in mapping subsurface structural features through the analysis of recent high-resolution aeromagnetic (HRAM) data-sets with the purpose of examining their effects on geological structures that characterize the confluence zones from the study area. To obtain the necessary reduction in geomagnetic variation, measurements of regional gradients and time variation were used. After applying the reduction to the magnetic equator (RTE) to the corrected magnetic data that was obtained from the Nigerian Geological Survey Agency, NGSA, it was possible to determine the regional expansions of subsurface structural units for both qualitative and quantitative interpretations. In addition, the edge detection method is used to depict the structures and buried subsurface anomalies. Different handling processes were applied to the (HRAM) data, such as local wavenumber (SPI), power spectrum analysis, and Euler and Werner deconvolution analysis. The RTE magnetic anomaly caused by local structures and anomalous body delineated six sub-basins with low amplitude response, which agrees with the total gradient anomaly (analytic signal) and tilt of angle derivative that clearly outlined and characterize edges of lithostratigraphic of Niger-Benue river confluence zones. The sub-basin delineated are the southern Bida basin and northern Anambra basin. The source parameter imagings as well as the Euler and Werner deconvolution were used to delineate major subsurface structures and determine their source depth. Results showed that the area was affected by different lineament trending NE-SW, E-W, and S-E trends. Directional analysis indicates that the dominant trend agrees with the regional fault orientations. The estimated depth to the top of the lineaments on average varies from 0.3 km to 4.6 km and it is relatively deeper in the basins compared to the surrounding areas giving clues to the amount of sediment infill. A 2D forward model showed a sedimentary thickness ranging from 1 to 7 km, and this estimated depth is consistent with the average of 3.5 km proposed by previous researchers.

Delineation of source magnetization and subsurface discontinuity of Ririwai Ring Complex along Kano, North Western Nigeria

High Resolution Aeromagnetic (HRAM) data of Ririwai (sheet 126) which lies between latitude 10° 30' to 11° 00' N and longitude 8° 30' E to 9° 00' E, was used for this research. The study area, Ririwai is situated along Kano, in the Northwestern part of Nigeria, both qualitative and quantitative interpretation techniques were employed in this study. This procedure was carefully undertaken by employing enhancement filters; vertical derivative, upward continuation, analytical signal amplitude processing, and quantitative approaches such as Euler 3D deconvolution and an apparent susceptibility filter to help further give solutions for depth estimates and magnetization. The Euler deconvolution was able to show that the solution plotted clustered around the region where the geological structures are located with average depths range of <139.8 to >904.5 m, with very few solutions having depths less than 200 m, the most prominent structure particularly the Ririwai ring complex have a depth range of 182.9 to 301.5 m. The magnetic susceptibility reading obtained shows that the area is composed of rocks high in magnetic minerals such as magnetite along the western end of the area, it is also flanked by medium to high magnetic values around the central parts with only regions of low magnetic values predominantly along the Ririwai complex and its adjoining outcrops towards the eastern half of the area under study.

INTERPRETATION OF HIGH RESOLUTION AEROMAGNETIC AND LAND SATELLITE IMAGE OVER PART OF THE NORTH-CENTRAL BASEMENT COMPLEX: IMPLICATION FOR GROUNDWATER EXPLORATION

Considering the significance of groundwater to population growth, this study interprets high resolution aeromagnetic and land satellite imagery data to explore prospective areas for groundwater occurrence in part of the north-central Basement Complex of Nigeria. The study area lies between longitudes 5030' – 7000' E and latitudes 9030' – 10030' N. To achieve this objective, high resolution aeromagnetic data covering the study area was subjected to magnetic residual separation and analytical signal using Oasis Montaj version 8.4. The Land satellite imagery data was also subjected to false colour composite analysis using ILWISversion 3.3 software. Combination of this analysis aided in mapping of lineaments within the study area. Result of lineaments mapping from analytical signal and land satellite images shows high density lineaments around Wushishi, Zungeru, Tegina Kagara, Pandogari, Alawa, Gurmana and low density lineaments around Bobi, Kuta, Guni, Minna, Tenenge. These lineaments having a dominant trend in the NE-SW and NW-SE, E-W minor directions were interpreted as joints, veins, faults, foliations and lineation of outcrops. Field studies in Tegina, Zungeru and Wushishi falling within areas with high lineament density revealed good groundwater yield from motorized pumps, hand pumps and hand dug wells. This is contrary to what was observed in Gidan Gwari an area attributed to low lineament density where only one hand bore hole out of the seven drilled boreholes was productive.

Using geophysics to follow and model the Precambrian basement terranes beneath the Caledonian nappes in Finnmark, northern Norway: A case study

The bedrock geology of Finnmark, northern Norway, consists primarily of rock complexes dating back to the Precambrian and early Mid Palaeozoic eras and comprises (1) a mid-crustal lithospheric basement which is characterised by granitoid and greenstone complexes dating from Neoarchean to late Paleoproterozoic in age; (2) the Caledonide Orogen, characterised by a series of nappes and thrust sheets. Finnmark forms part of the northern margin of the Fennoscandian Shield, which extends across northern Finland into northwestern Russia. Precambrian rock complexes are also found as thrust slices in Caledonian nappes at several places in Finnmark and Troms, as well as in tectonic windows.Recently acquired high-resolution aeromagnetic data have provided spectacular and confirmatory evidence for the continuation of the diverse Precambrian greenstone belts and granulite terranes beneath the magnetically transparent Caledonian nappes.This study aims at analysing this subsurface continuation of the terranes using potential field data and estimating the depths of the main magnetic sources beneath the nappes. In this study, several geophysical methods are used, including 3D Euler deconvolution and 2D Werner deconvolution. We have focused specifically on the depth-to-basement beneath nappes and purposefully excluded anomalies associated with shallow structures, such as dykes and faults. Different methods have produced similar results and indicate an appreciable increase in the depth of the Precambrian basement rocks from south to north. In the south, Precambrian basement rocks are either exposed on the surface southeast of the Caledonian front or reappear within tectonic windows. A prominent positive magnetic anomaly on the Porsanger Peninsula is thought to represent an extension of the anomaly ascribed to the greenstone belt of the Repparfjord Tectonic Window. A 3D model of this has also been provided. According to estimates, the depths-to-basement below nappes close to the Caledonian front range from less than 500 to 2000 m, whilst in the northern part of the study area the depths generally reach 3000 to 4000 m, and are locally estimated to range between 5000 m and 6000 m.

Concealed anatomy and new geological features beneath desert areas of NW India – Constrained from high resolution aero-geophysical data

The vast swathe of area in the Trans-Aravalli region between the western part of the South Delhi Fold Belt and eastern part of the Barmer basin, north-western India exhibits limited geological information due to thick sand cover of the Thar Desert. The present study is to unravel the hidden architecture of the above area using recently acquired high-resolution aero-magnetic data. Here, our interpreted results brought out a buried ring structure in the northern part and NW-SE trending constellation of linear magnetic highs in the southern part. Considering the regional geological milieu, our study correlates the buried ring structure with a possible remnant volcanic cone of the Neoproterozoic silicic Malani Large Igneous Province. Secondly, the significant NW-SE trending linear magnetic highs in the south possibly represents a humongous dyke swarm activity, facilitated by the intricate network of fractures. The orientation of these magnetic linear are conspicuously similar with the Deccan linked Sarnu-Dandali dykes and regional Barmer-Cambay rift system. The northwestern portion of study area displays high magnetic and gravity responses of long wavelength features indicating crustal heterogeneity. The study for the first time documents two concealed structures, which may hold a link of Neoproterozoic Malani and Mesozoic Deccan magmatic pulses.