Igneous activity in the Bornu Basin, onshore NE Nigeria; implications for opening of the South Atlantic

Abstract

The structure of igneous plumbing systems in circum-South Atlantic, intra-continental rift basins, e.g., the West and Central African Rift Systems (WCARS), remains enigmatic due to poor subsurface data coverage and quality. How magmatism in these basins related to the opening of the South Atlantic is thus poorly understood. We 14 integrate 2D and 3D seismic reflection data (c. 27600 km 2), data from 23 boreholes, 15 and field observations from the Bornu Basin and Upper Benue Trough, onshore NE 16 Nigeria to examine the timing and development of igneous bodies possibly related to 17 opening of the South Atlantic. We identify numerous sills, which typically have saucer-18 shaped and en-echelon morphologies, and extrusive volcanic cones. The igneous rocks 19 are alkali basalts and dolerites. Seismic-stratigraphic relationships indicate that 20 emplacement occurred in the Early Cretaceous (Albian-to-Cenomanian; ca. 120 Ma), 21 Late Cretaceous (Santonian-to-early Campanian; ca. 83 Ma), and Cenozoic (Miocene; 22 ca. 22 Ma). Magmatism was broadly coeval with major plate boundary interactions, 23 characterized by major azimuthal changes in fracture zones in the developing South 24 Article text Click here to download Article text Adamu Paper Manuscript_CM_II.docx Atlantic Ocean. The broad temporal correlation between intra-continental rift basin 25 magmatism and plate boundary interactions suggests that periods of magma 26 emplacement may have, in some way, been instigated by stress dissipation into intra-27 continental rift basins. 28

Assessment of the interval heat flow and thermal resistance at the Faltu-1 well, Borno basin, NE Nigeria

“…The first type occurred at the two depth ranges of 1274 to 1384 and 1838 to 1900 m, and has limiting interval heat flow values of 103 and 111 mW m . This suggests two episodes of the intrusion events in line with the work of Suleiman et al (2017). The maturation of organic matter in oil and gas in sedimentary basins is impacted by the heat released by intruding magmatic bodies (White & McKenzie, 1989;Ali et al 2005).…”

“…Magmatic intrusions with thicknesses ranging between 5 and 220 m that may be either doleritic or gabbroic have been identified in the basin (GeoEngineering International, 1994 (White & McKenzie, 1989). Using both 2-and 3-D seismic data, Suleiman et al (2017) have mapped saucer-shaped and strata-concordant sills and volcanic plugs geometries in the basin, and based on seismic stratigraphy and host rocks enhancements, their emplacements have been dated to corresponding to the timing of major plate boundary interactions, namely, Early Cretaceous (Albian to Cenomanian; c. 120 Ma), Late Cretaceous (Santonian to early Campanian; c. 83 Ma) or Cenozoic (Miocene; c. 22 Ma). These intrusives have gamma ray intensities of between 20 and 50 API, resistivities of more than 20 ohm-metre, bulk densities of 2700 to 2900 kg m -3 and interval transit times of 230 μs m -1 and less.…”

Variation in style of magmatism and emplacement mechanism induced by changes in basin environments and stress fields (Pannonian Basin, Central Europe)

“…With the advancement of 3D seismic cubes a great number of studies have been published on various subvolcanic features from well‐studied different continental margins (Hansen & Cartwright, ; Holford, Schofield, Macdonald, Duddy, & Green, ; Jackson, ; Jackson, Schofield, & Golenkov, ; Lee, Young, Yoon, Kim, & Yoo, ; Magee Jackson, & Schofield, ; Planke, Rasmussen, Rey, & Myklebust, ; Suleiman, Magee, Jackson, & Fraser, ; Zhao et al, ). Papers mainly focused on identifying and characterizing various intrusive and extrusive features and their implications on the evolution of sedimentary basins and petroleum systems (Holford et al, ; Klarner & Klarner, ; Lee et al, ; Planke et al, ).…”

The shallow depth emplacement of mafic intrusions on a magma-poor rifted margin: An example from the Bight Basin, southern Australia

“…Magma is also commonly transported from larger "feeder" lobes towards smaller lobes at the periphery of the intrusion (e.g. Schofield et al, 2012a;Suleiman et al, 2017). Based on these observations, we infer that the saucer-shaped sills were emplaced via flow of magma upwards and radially outwards from a source region found at their deepest points (e.g.…”