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Geophysical magnetic data analyses of the geological structures with mineralization potentials over the southern part of Kebbi, NW Nigeria

Augie Abdulrahaman Idris, Salako Kazeem Adeyinka, Rafiu Adewuyi Abdulwaheed, Jimoh Mufutau Owolabi

Mining Science

2022

Vol. 29

179--203

This study used geophysical data analysis to map and provide useful estimates of the geometry, depth, and magnetization of the magnetic sources, as a continuation and improvement over the earlier analyses in the area. Fugro airborne surveys collected aeromagnetic data for the Nigeria Geological Survey Agency (NGSA) between 2009 and 2010. The study area’s data were processed and analyzed using an improved tilt derivative (TDR) technique and 2D magnetic structural modelling. The result of TDR reveals the horizontal location and extent of the edges of various magnetic sources that formed lineaments. The results from 2D modelling for the selected profiles (PI, P2, P3, P4, and P5) identify zones with a high magnetic anomaly responding to fractures. These fracture regions of the basement complex area could be caused by fault/shear zones. Fault-induced areas on these sub-basin floors are important hosts for hydrothermal mineralization. In comparison to the geological setting, these regions are underlain by quartz-mica schist, biotitehornblende, granite, biotite, gneiss, diorite, migmatite, medium coarse-grained sandstone, ironstones, laterite, siltstones, and clay. These regions could be suitable for mineral exploration and correspond to the Ngaski, Yauri, Magama, Shanga, and Rijau. However, in comparison to the SPI results, the depth/thickness of the sediments that crossed the areas of the sedimentary basin and basement complex zones did not match the results of 2D forward modelling. The SPI technique usually provides an average depth of the magnetic source and is unable to accurately map the undulating basement. While the aforementioned results of 2D forward modelling provide sediment thickness by accurately reflecting basement topography.

Interpretation of gravity anomaly to delineate thrust faults locations at the northeastern part of India and its adjacent areas using source edge detection technique, tilt derivative and Cos(θ) analysis

Ghosh Gopal K.

Acta Geophysica

2019

Vol. 67, no. 5

1277--1295

The Northeast India and its adjacent areas converge among the three diferent plates, viz. Eurasia, India and Sunda plates. The tectonic interaction of Northeast India and underlying dynamics of the Himalayas as well as the Indo-Burma Ranges might cause the Assam Syntaxis. The area of study is located between latitude 23°–28°N and longitude 88°–96°E and situated in one of the most seismically active tectonic provinces in the world with seismic zone-V. This area had demonstrated several thrust faults activities and tectonic evident accomplishments during the recent past. The complicated geotectonic setups inspirits various smaller magnitude earthquakes, and the current seismicity shows seismic activities are still enduring in the Shillong Plateau, Arakan-Yoma fold belt, Bengal Basin, Naga Hills, Mikir Hills, Upper–Lower Brahmaputra Valley and Mismi Hills of Himalayan foothills. It is imperative to obtain wide-ranging learning tectonic confguration, thrust faults delineation for improved geoscientifc study. Parts of the areas are extremely unreachable, and very limited thrust faults were marked by studying GIS map received from the various agencies and feld geological study. During the past studies, most of the prominent lineaments/thrusts are marked; however, many active and hidden thrust faults are still unidentifed. Seismic data can provide better information about the thrust faults locations, but due to small number of seismic data, the information is not adequate. In this paper, attempt has been made to study and reinterpret the available ground gravity data of northeastern parts of India for understanding thrust fault locations using various applications of gravity derivatives like analytical signal, horizontal gravity gradient, tilt derivative, horizontal tilt angle derivative and Cos(θ) analysis. Source edge detection technique has also been premeditated to categorize thrust fault locations. It is understandable that the low gravity is observed at Assam Valley which contributed sediment accumulations and higher gravity anomaly observed at Shillong Plateau and Bengal Basin containing denser formations. Bouguer gravity data is used after isostatic correction assuming Airy’s isostasy root depth model and frst-order trend removal using least square technique. The derived thrust fault locations from the present study are superimposed with the existing thrust-fault locations for correlation. Some additional thrust faults are narrated which are not previously mapped. It is also suggested that Brahmaputra Thrust, Dauki Fault, Naga Thrust, Disang Thrust and Kopili Fault have key responsibility for high seismicity and tectonic movement causing upliftment and depression that encouraged some anticlockwise rotation in the area.