Abstract

The depth to the Curie isothermal point (CPD) was estimated using aeromagnetic data from northern Cameroon. The CPD was estimated using a two-dimensional power density spectral analysis of nineteen 30 × 30 km blocks over a series of Neoproterozoic lithologies associated with the Pan African orogeny. The results show that there are two main regions characterized by the CPD analysis: 1) Shallow depths (~6.37 - 10.09 km) which are located in several regions including the northern portions of the study area (toward the regions of Hina Marbak, Gawel and northern Moutouroua), the southeast (Kaele region), the south (Guider) and the southwest (Mayo Oulo), and 2) deeper depths (~10.68 - 13.72 km) are located in the northeast (Mindif) and southwest (southern Moutouroua, Guider and Bossoum). The shallow depths can be related to two tectonic regimes: 1) the West-Central African Rift System with northeast-trending strike-slip faults emanating from the Gulf of Guinea and 2) the Cameroon Volcanic Line. However, the ultimate source of these shallow regions is interpreted to be related to the Cameroon Volcanic Line based on low seismic velocities imaged by recent broadband seismic studies which are concentrated along the northeast-trending strike-slip faults. An additional finding using the CPD depths, a Curie isothermal temperature of 580&#176C and a one-dimensional heat flow model, was heat-flow values ranging from 105.68 to 227.63 mW/m2, which are above average global heat flow values and are therefore indicative of potential geothermal resources.

Highlights

  • The thermal structure of the lithosphere is required for many geodynamic investigations, including the deformation of rocks, boundaries of mineral phase changes, and rates of geochemical reactions [1]

  • The shallow depths can be related to two tectonic regimes: 1) the West-Central African Rift System with northeast-trending strike-slip faults emanating from the Gulf of Guinea and 2) the Cameroon Volcanic Line

  • The reduced to the equator (RTE) map contains mainly northeast trending minima and maxima anomalies that are roughly parallel to the strike-slip tectonic episodes that related to the Proterozoic collisional events [26]

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Summary

Introduction

The thermal structure of the lithosphere is required for many geodynamic investigations, including the deformation of rocks, boundaries of mineral phase changes, and rates of geochemical reactions [1]. Geothermal gradients are commonly estimated from near-surface heat-flow measurements, but heat-flow measurements are commonly unavailable [2] [3], are distributed randomly, and may be affected by local thermal anomalies. In regions where heat-flow data are sparse or unavailable, geophysical and geochemical methods can be used to estimate the thermal structure. One can use magnetotellurics, magnetics, and seismic velocity to indirectly determine the presence of high heat flow values. Magnetotellurics and seismic velocity only indirectly infer the presence of higher temperatures by low electrical conductivities or low seismic velocities but do not provide temperature estimations. The magnetic method can determine the depth to the Curie point depth (CPD) where these depths can be used to estimate the regional heat flow [4]

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