The thermal structure of the Earth is an important parameter used to determine the tectonic environment/modes of deformation/extension, depths extent of brittle and ductile deformation zones/behavior of the lithosphere, regional heat flow variations and maturity of organic matter in sedimentary basins of a region (Dolmaz et al., 2005; Hussein et al., 2013; Leseane et al., 2015; Tanaka, 2017). Thermal structure also plays a major role in hydrocarbon exploration (Tissot et al., 1987), mineral exploration (Cathles & Smith, 1983), and geothermal exploration (Muffler & Cataldi, 1978). Thermal anomalies resulting from and/or accompanying tectonic deformation of the lithosphere have been used to constrain the mechanisms responsible for continental rifting and deep rifting processes (McKenzie, 1978; Morgan, 2006). Therefore, the thermal structure is one of the important parameters that can be used to infer mechanisms responsible for strain localisation during continental extension/rifting (Leseane et al., 2015).
The thermal structure/gradient of the lithosphere is generally estimated from the near surface heat-flow measurements (Davies, 2013; Furlong et al., 1995; Ross et al., 2006). However, heat flow measurements of high quality do not cover the whole globe, non-uniformly distributed, and often affected by local thermal anomalies contamination (Davies, 2013; Ross et al., 2006). In regions where there are few or inadequate heat flow measurements, one of the methods of investigating the thermal structure of the crust is the estimation of Curie point depth (CPD), using aeromagnetic data. The CPD corresponds to a depth at which the ferromagnetic minerals in the crust loses their capability to acquire spontaneous magnetisation state/nature to a paramagnetic state under the influence of increasing temperature. Therefore, the basal depth of a magnetic source from aeromagnetic data is considered to be the Curie point depth (Dolmaz et al., 2005; Ravat et al., 2016). The CPD has been largely used to estimate the thermal structure of the crust in different tectonic settings (Arnaiz-Rodríguez & Orihuela, 2013; Bhattacharyya & Leu, 1975a, 1975b; Blakely, 1988; Blakely & Hassanzadeh, 1981; Chiozzi et al., 2005; Dolmaz et al., 2005; Hussein et al., 2013; Leseane et al., 2015; Okubo et al., 2005, 1985; Ravat et al., 2007; Serson & Hannaford, 1957; Shuey et al., 1977; Stampolidis & Tsokas, 2002; Tanaka, 2007; Tanaka et al., 1999; Vacquier & Affleck, 1941). The CPD is strongly depended on the thermal properties (geothermal gradient and heat flow) of a specific region and the mineralogical composition of rocks (Arnaiz-Rodríguez & Orihuela, 2013).
The CPD is normally shallow in the volcanic regions and areas with high heat flow than those areas that are not affected by thermal processes (Arnaiz-Rodríguez & Orihuela, 2013; Hussein et al., 2013; Mickus & Hussein, 2016; Stampolidis & Tsokas, 2002). This is also true in areas where the crustal thinning (either tectonically or thermally driven) has been observed (Arnaiz-Rodríguez & Orihuela, 2013; Dolmaz et al., 2005; Leseane et al., 2015) while in isostatically and tectonically stable regions, or low heat flow areas the CPD tend to be deeper (Arnaiz-Rodríguez & Orihuela, 2013; Chiozzi et al., 2005). This is has been demonstrated in different isostatically stable and low heat flow cratonic regions such as the West African Craton (Toft & Haggerty, 1988) , Guayana shield (Arnaiz-Rodríguez & Orihuela, 2013) and the Yangze Craton (Chang, 2008). The wide variations of the CPD in these regions may be contributed by the variations in crustal thickness and the geochemical compositions of rocks surrounding these tectonic provinces (Arnaiz-Rodríguez & Orihuela, 2013; Trifonova et al., 2009).
In this paper/chapter we investigate the thermal structure of the Rukwa Rift Basin, based on the Curie point depth estimation. A Curie point depth map of the area was constructed from aeromagnetic data and a corresponding heat-flow map was produced. Rukwa Rift Basin is a site of extensive continental extension with the possibility of elevated heat flow.
Due to the lack of heat flow data within or nearby Rukwa Rift Basin (Fig. 1), any elevated heat flow that may be caused by the potential magma chamber is unknown. The results of the 2D spectral methods will be analysed to determine if there is higher heat flow within and surrounding Rukwa Rift Basin and relate these findings to their cause of the higher heat flow. Heat flow measurements provide a direct estimate of the thermal structure of the uplifted lithosphere thereby providing evidence on the extent to which the lithosphere may have been thermally perturbed (Nyblade, 1997).
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