Flood Basalt Impact on Hydrocarbon Systems Project 2016-2018

Six reports issued during this project phase focussed on the Mekele and Blue Nile basins, Ethiopia, as analogues to exploration in other volcanically affected basins. Ar–Ar geochronology was used to constrain the ages of intra-volcanic fluvio–lacustrine sedimentary sequences in these basins (#11). The data provided a new and robust age interpretation for the volcanism in the Blue Nile Basin, which is significantly younger than the volcanism recorded in the north of Ethiopia. A diatom assessment of the intra-volcanic lacustrine units, in conjunction with the new ages, suggest these are potentially the oldest nonmarine diatom record on continental Africa as well as providing palaeoenvironmental interpretations during flood basalt volcanism (#12).

The impact of volcanism on the development of the syn-volcanic sedimentary systems was investigated through two provenance studies. The first investigated the geochemistry of volcanic clasts (#15) whereas the second, focussed on the petrographies, heavy mineral assemblages and single grain chemistry of intra-volcanic sandstones (#17). Three volcanic sources were identified as well as a non-volcanic (metamorphic) source that suggests volcanism did not, initially at least, shutdown pre-existing drainage systems. The provenance characteristics of the sub-volcanic Mesozoic sedimentary succession was also investigated to provide context to the overlying intra-volcanic sedimentary units. The inundation of the Blue Nile River drainage network by Quaternary lava flows was also investigated through field mapping and Ar–Ar geochronology (#13). These data provided insights on the impact of volcanism on river pathways and lake establishment as well as constraining incision rates since the Oligocene. The incision rates and provenance data also have implications for the arrival and nature of volcanic debris reaching the productive Nile Delta, offshore Egypt.

We have also investigated the source rock potential of sub- and intra-volcanic mudstones in the Blue Nile and Mekele basins and carried out bitumen-typing of an intra-volcanic bitumen seep. This report (#16) provides TOC, Rock Eval pyrolysis and organic reflectance data and an assessment of the prospectivity of the mudstones analysed.

The remaining report (#14) investigated the relationship between secondary mineralisation and the petrophysical characteristics of volcaniclastic rocks from three different Flood Basalt Provinces (East Greenland, Faroe Islands and Ethiopia). This was achieved by comparing Mercury Injection Capillary Pressure (MICP) data with Quantitative X-Ray Diffraction (QXRD) results for 33 volcaniclastic rocks. This work has wide-ranging implications for assessing the sealing capacity and reservoir potential of volcaniclastic rocks.

Reports Issued in This Project

• Multi-proxy provenance study of sub- and intra-volcanic sandstones of the Northwestern Highlands, Ethiopia: implications for the impact of volcanism on the development of syn-volcanic sedimentary systems CASP.FBP2016-18.17
• Source rock potential of sub- and intra-volcanic mudstones and bitumen-typing of seep bitumen: Mekele, Blue Nile and Chilga basins, NW Ethiopia CASP.FBP2016-18.16
• Provenance of volcanic clasts from the Ethiopian Flood Basalt Province, Blue Nile Basin, Ethiopia CASP.FBP2016-18.15
• Secondary mineralisation of volcaniclastic rocks and its impact on sealing capacity and reservoir potential CASP.FBP2016-18.14
• Inundation of the Blue Nile River drainage network, Ethiopia, by Quaternary lava flows. Implications for river pathways, lake establishment and incision rates CASP.FBP2016-18.13
• Diatom assessment of the Ethiopian Flood Basalt Province, Ethiopia CASP.FBP2016-18.12
• Dating the Ethiopian Flood Basalt Province in the Blue Nile And Mekele Basins, Ethiopia CASP.FBP2016-18.11