Sains Malaysiana 51(3)(2022): 657-677

http://doi.org/10.17576/jsm-2022-5103-03

Curie-point Depths, Geothermal Gradients and Sub-Surface Heat Flow Estimation from Spectral Analysis of High-Resolution Aeromagnetic Data over Gongola Basin and Its Environs, Northeastern Nigeria

(Kedalaman Titik Curie, Kecerunan Geoterma dan Anggaran Aliran Haba Sub-Permukaan daripada Analisis Spektrum Data Aeromagnetik Resolusi Tinggi di Lembangan Gongola dan Sekitarnya, Timur Laut Nigeria)

ABUBAKAR YUSUF^1,2, LIM HWEE SAN^1,* & ISMAIL AHMAD ABIR¹

¹Exploration Geophysics Section, School of Physics, Universiti Sains Malaysia, 11800 Penang, Malaysia

  ²Department of Geology, Faculty of Science, Gombe State University, P.M.B. 0127, Gombe, Nigeria

Diserahkan: 20 Mac 2021/Diterima: 31 Julai 2021

Abstract

Geothermal energy resources have been established globally to be among the sustainable and environmentally harmless means of energy generation. Curie-point depths (CPD), temperature gradients, and heat flow data over the study area were computed using a spectral analysis method in order to have a preliminary view of the geothermal implications (prospect) of the current area. Aeromagnetic data acquired by the Nigerian Geological Survey Agency (NGSA) in the year 2009 was used for the research. The results showed the minimum, maximum, and the average CPD values as 8.18 km, 31.48 km, and 13.0 km, respectively. The minimum, maximum and average thermal gradients obtained were 18.42 °C/km, 70.91 °C/km, and 50.2 °C/km, respectively. The heat flow data obtained ranged from 33.15 mW/m² to 177.28 mW/m², with an average value of 110.65 mW/m². Locations depicting shallow CPDs anomalies (Alkaleri, Darazo, Dukku, Misau, Wuyo, Deba, and Tula), also showed conformity with high heat flow areas. As such, they are regarded as areas of promising geothermal prospects and are recommended for further detailed investigation. Locations depicting a high magnetic susceptibility contrast from a generated analytic signal map, as well as high temperature gradients, high heat flow, and shallow CPDs are attributed to crustal thinning along the sedimentary basin and magmatic intrusions along basement areas, respectively. The magnetic depth to the basement calculated for the study area using the source parameter imaging (SPI) method ranges from 0.610 km to 3.055 km. The present study has provided an insight on preliminary information, regarding new areas of possible geothermal prospects for further detailed investigation.

Keywords: Aeromagnetic; Curie-point depth; heat flow; spectral analysis; temperature gradients

Abstrak

Sumber tenaga geoterma telah ditubuhkan secara global untuk menjadi antara kaedah penjanaan tenaga yang mampan dan tidak berbahaya kepada alam sekitar. Kedalaman titik Curie (CPD), kecerunan suhu dan data aliran haba ke atas kawasan kajian telah dihitung menggunakan kaedah analisis spektrum untuk mendapatkan pandangan awal tentang implikasi (prospek) geoterma bagi kawasan semasa. Data aeromagnet yang diperoleh oleh Agensi Kajian Geologi Nigeria (NGSA) pada tahun 2009 digunakan untuk penyelidikan. Keputusan menunjukkan nilai CPD minimum, maksimum dan purata masing-masing 8.18 km, 31.48 km dan 13.0 km. Kecerunan terma minimum, maksimum dan purata yang diperoleh ialah 18.42 °C/km, 70.91 °C/km dan 50.2 °C/km, masing-masing. Data aliran haba yang diperoleh adalah antara 33.15 mW/m2 hingga 177.28 mW/m2, dengan nilai purata 110.65 mW/m2. Lokasi yang menggambarkan anomali CPD cetek (Alkaleri, Darazo, Dukku, Misau, Wuyo, Deba dan Tula), juga menunjukkan pematuhan dengan kawasan aliran haba yang tinggi. Oleh itu, ia dianggap sebagai kawasan prospek geoterma yang menjanjikan dan disyorkan untuk kajian terperinci lanjut. Lokasi yang menggambarkan kontras kerentanan magnet yang tinggi daripada peta isyarat analitik yang dijana, serta kecerunan suhu tinggi, aliran haba yang tinggi dan CPD cetek dikaitkan dengan penipisan kerak di sepanjang lembangan sedimen dan pencerobohan magmatik di sepanjang kawasan bawah tanah. Kedalaman magnet ke ruang bawah tanah yang dihitung untuk kawasan kajian menggunakan kaedah pengimejan parameter sumber (SPI) berjulat dari 0.610 km hingga 3.055 km. Kajian ini telah memberikan gambaran tentang maklumat awal, mengenai kawasan baharu prospek geoterma untuk kajian terperinci lanjut.

Kata kunci: Aeromagnetik; aliran haba; analisis spektrum; kecerunan suhu; kedalaman titik Curie

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^*Pengarang untuk surat-menyurat; email: hslim@usm.my