A ground magnetic survey was carried out to investigate the presence of iron ore at a location (Lat. 7.99883°N to Lat. 7.99933°N, Long. 3.57900°E to Long. 3.57990°E) in Iseyin, Oyo State, South-wes...A ground magnetic survey was carried out to investigate the presence of iron ore at a location (Lat. 7.99883°N to Lat. 7.99933°N, Long. 3.57900°E to Long. 3.57990°E) in Iseyin, Oyo State, South-western Nigeria. Ten magnetic traverses each 100 m long at a separation of 5 m were run West-East. Magnetic intensity was taken at intervals of 10 m along each traverse line using the proton precession magnetometer (G-856 AX). The measured magnetic field data were corrected for drift and were presented as profiles. The profiles were interpreted by calculating the depth to the top of anomalies. The data obtained were used to construct magnetic anomaly maps in 2D and 3D. The magnetic survey results delineated this location into some high and low magnetic field intensity regions. The regions of high magnetic field anomaly indicated the presence of materials with high susceptibility which was suspected to be iron compounds. The quantitative and qualitative analyses on interpretations of field data collected were given, while these results provided values for the total component measurements of ground magnetic anomaly that widely ranged between a maximum positive peak result of 8 nT and to a minimum negative peak result of —6 nT. Using Peter’s half slope technique, depth to the basement was assessed, which actually provided a maximum depth to basement of 6.25 m. From the knowledge of the geology of the area and also, the magnetic survey employed information, therefore, we can finally conclude that, the study area is under laid by geologic structures which favour the accumulation of iron-ore minerals deposit at Oke-Aro area in Iseyin.展开更多
The construction of modern livable cities faces challenges in karst areas,including ground collapse and engineering problems.Wuhan,with a population of 13.74×10^(6) and approximately 1161 km^(2)of soluble rocks i...The construction of modern livable cities faces challenges in karst areas,including ground collapse and engineering problems.Wuhan,with a population of 13.74×10^(6) and approximately 1161 km^(2)of soluble rocks in the urban area of 8569.15 km^(2),predominantly consists of concealed karst areas where occasional ground collapse events occur,posing significant threats to underground engineering projects.To address these challenges,a comprehensive geological survey was conducted in Wuhan,focusing on major karstrelated issues.Geophysical methods offer advantages over drilling in detecting concealed karst areas due to their efficiency,non-destructiveness,and flexibility.This paper reviewed the karst geological characteristics in Wuhan and the geophysical exploration methods for karst,selected eight effective geophysical methods for field experimentation,evaluated their suitability,and proposed method combinations for different karst scenarios.The results show that different geophysical methods have varying applicability for karst detection in Wuhan,and combining multiple methods enhances detection effectiveness.The specific recommendations for method combinations provided in this study serve as a valuable reference for karst detection in Wuhan.展开更多
文摘A ground magnetic survey was carried out to investigate the presence of iron ore at a location (Lat. 7.99883°N to Lat. 7.99933°N, Long. 3.57900°E to Long. 3.57990°E) in Iseyin, Oyo State, South-western Nigeria. Ten magnetic traverses each 100 m long at a separation of 5 m were run West-East. Magnetic intensity was taken at intervals of 10 m along each traverse line using the proton precession magnetometer (G-856 AX). The measured magnetic field data were corrected for drift and were presented as profiles. The profiles were interpreted by calculating the depth to the top of anomalies. The data obtained were used to construct magnetic anomaly maps in 2D and 3D. The magnetic survey results delineated this location into some high and low magnetic field intensity regions. The regions of high magnetic field anomaly indicated the presence of materials with high susceptibility which was suspected to be iron compounds. The quantitative and qualitative analyses on interpretations of field data collected were given, while these results provided values for the total component measurements of ground magnetic anomaly that widely ranged between a maximum positive peak result of 8 nT and to a minimum negative peak result of —6 nT. Using Peter’s half slope technique, depth to the basement was assessed, which actually provided a maximum depth to basement of 6.25 m. From the knowledge of the geology of the area and also, the magnetic survey employed information, therefore, we can finally conclude that, the study area is under laid by geologic structures which favour the accumulation of iron-ore minerals deposit at Oke-Aro area in Iseyin.
基金jointly supported by the project of Chinese National Natural Science Foundation(42107485)National Key R&D Program(2020YFC1512400,2018YFC800804)China Geological Survey(DD20190282,DD20221734,and DD20230323)。
文摘The construction of modern livable cities faces challenges in karst areas,including ground collapse and engineering problems.Wuhan,with a population of 13.74×10^(6) and approximately 1161 km^(2)of soluble rocks in the urban area of 8569.15 km^(2),predominantly consists of concealed karst areas where occasional ground collapse events occur,posing significant threats to underground engineering projects.To address these challenges,a comprehensive geological survey was conducted in Wuhan,focusing on major karstrelated issues.Geophysical methods offer advantages over drilling in detecting concealed karst areas due to their efficiency,non-destructiveness,and flexibility.This paper reviewed the karst geological characteristics in Wuhan and the geophysical exploration methods for karst,selected eight effective geophysical methods for field experimentation,evaluated their suitability,and proposed method combinations for different karst scenarios.The results show that different geophysical methods have varying applicability for karst detection in Wuhan,and combining multiple methods enhances detection effectiveness.The specific recommendations for method combinations provided in this study serve as a valuable reference for karst detection in Wuhan.
