Geology of Angola - Essay Example

Geology of Angola s Introduction Angola is located in Africa’s southern parts on the Atlantic coast. In Africa, it isthe second largest producer of oil after Nigeria. Due to the recent explorations of oil it is believed it will surpass Nigeria in Oil production in the coming decade. It has an area of about 1,246,700 square Kilometers and a population of about 20 million individuals. It can be effectively subdivided into mainly five regional geological units. Of all this units, each of them contains mineral deposits of various combinations. The entire eastern part and nearly half of Angola is extended by tertiary to quaternary sedimentary cover rocks that that mainly comprise of quartzic sandstone, sand, clay and gravel. In the coastal basin series that are found on Angola’s western margin, there lies cretaceous to Pleistocene marine sediments. Geology of Angola Angola’s most mineral potential apart from the gas reserve, and its oil, has a relationship to the Precambrian shield, and these has been found to outcrop over a larger parts throughout the country. After oil and gas, Angola’s next most important resource is diamond (Arthur, et.al, 2003). The Precambrian basement also has a relationship by which the diamonds are distributed. The kimbelite pipes that are of crustaceous age have been instrumental in bringing the diamonds close to the surface. The kimberlite pipes are arranged along a structural trend of about 1200 km in length and in the north easterly direction, they have been witnessed to intersect the Precambrian shield. There have also been found to the existence of carbonates that have been instrumental in offering the exploration of minerals that are associated with carbonates such as the rare earths and the fluorites. Along certain parts of Angolan pre Cambrian shield, there has been found the occurrence of fold belts that are three in number. This fold belts have been found to be associated with ores such as polymetallic copper of the copper belt type (Fullagar, West & National Science Teachers Association 2011). Angola’s important gas and oil reserves are mainly hosted by the presence of marine coastal basins. These basins are mainly of lower Quaternary to Cretaceous age. In addition, these coastal basins are also associated with other mineral deposits such as copper, bitumen, and various chemical and industrial deposits such as potash, phosphate, sulphur, gypsum and limestone. In the south eastern parts of Angola the area is extensively covered by deposits of Kalahari sand. These deposits have been found to mainly contain lignite seams. Oil exploration has greatly been able to provide borehole data hence facilitating the knowledge of the Cretaceous coastal basins (Arthur, et.al, 2003). The areas that are mainly virtually unknown include the Moxico and the Cuando Cubango and it is mainly due to the reason that they are covered by the Kalahari sand that is rarely exploited or mined Oil in Angola According to Reed (2009), the main reason why there is oil in Angola is due to the presence of pre salt as well as post salt that include cretaceous age Pinda carbonates that are salt rafted, reservoirs that are clastic turbidite of the Tertiary- age and also the existence of pre-salt microbalitic carbonates. Angola’s important gas and oil reserves are mainly hosted by the presence of marine coastal basins. These basins are mainly of lower Quaternary to Cretaceous age (van der Weijden, de Lange & Pruysers Peter, 2013).The pre- salt microbalitic carbonates have been found to contain high similarity with the giant Tupi oil discovery in Brazil. The amount of oil production in Angola is expected to dramatically increase since most of these oil potential areas have been discovered in the new century. Some of the areas with oil deposits include the Bentiaba region in southern Angola that is characterized with spectacular outcrops with an underlying unit that is reddish brown in color. This unit consists of terrestrial sediments that are cretaceous and believed to have been deposited in the initial break up that occurred in the south- western Gondwana. What unconformable overlays this is the Cretaceous Albian carbonates (Reed, 2009). The other region is near the town of Sumbe at the gorge of River Cubai where there exists the cretaceous carbonates of the Albian age outcropping. They are approximated to be of the same age as the prolific carbonate oil reservoirs of Pinda. Additionally, there is the Libongo oil seeps near Caxito around 60 kilometers from Lwanda that are believed to have existed for over several hundred years. How did the land form? The land commonly referred to as the Angola basin is believed to have formed by the break up that occurred on the supercontinent that was known Pangaea. These led to the creation Angola, Atlantic Ocean, and the argentine basins and it took place in the early cretaceous. Due to its basins rich in Aptian salt that evaporates to form a thick basin it has been found to be a large reservoir of petroleum (van der Weijden, de Lange & Pruysers Peter, 2013). It is generally believed that the rifting that created the Angola Basin took place in three phases and happened in about 110 to 140 million years back between the times of the Jurassic and the Cretaceous. Effect of geology to the community/region The geology of the area has shaped both the community and region in various different ways. During the breakup of the supercontinent that was known as Pangaea, Arthur, et.al, (2003), suggest that it led to formation of various features such as the Atlantic Ocean that resulted to Angola having coastal basins. With the formation of the Atlantic Ocean, the region currently occupied by the ocean seized to be habitable and with the existence of a coastal basin the neighboring communities on the shores of the ocean started engaging in activities such as fishing. Additionally, the rifting led to creation of different regions in Angola such coastal lowland, a vast plain that was known as plateau, the rain forest and mountains and hills. These areas currently experience different climatic conditions hence the communities have been forced overtime to adapt to this. This is mainly characterized by the communities living around hills practicing in agriculture while those living in coastal basins participating in tourism as well as working in oil exploration companies (Reed, 2009). Regional Geological mapping According to Arthur, et.al, (2003), the percentage of Angola that has been geologically mapped is about 31%. He further suggests that reports have been published of 28 geological maps at a scale of 1; 100 000. Furthermore reports of 14 geological maps have been published at a scale of 1: 250 000. Most of the geological sheets containing the scales of 1: 100 000 that have been published have been found to be having relation to the Lupacas corridor transcontinental structure. The Lupaca’s corridor is a zone that is associated with the tectonic magmatic reactivation of acid, alkaline rocks as well as the carbonatites. The main mineral resources include oil, gold, diamonds, Chrome, Nickel, Manganese, Tungsten, tin, Quartz, mineral sands, Potash, Gypsum, Sulphur, Coal and Uranium. Data base of Exploration There exists a 1; 100 000 scale complete coverage map of the whole country. The maps though old are of good quality. In addition, there is the availability of air photos that can be used for almost the whole country with the exception of some few areas in the north and North West that are mainly covered with the tropical forest. These include the areas of Zaire, Cabinda and Uige. For the satellite imagery, they exist at a scale of 1: 1 million but are of poor quality and in black and white. In general the geological map coverage can be termed to be poor for only 31% of the country is covered with geological that are to scale. Additionally, of this 31% only about 50% have been published (Van der Weijde, de Lange, & Pruysers Peter, 2013). Finally, the information that is captured in these geological maps ranges from extremely excellent to poor. Hence the data can be summarized as follows: Geochronology- There exist insufficient data related to this. Geophysical Coverage airborne-There exists only 10 % of Angola’s aeromagnetic coverage. It is among the lowest in many African Countries. Most of its airborne surveys have been conducted for oil exploration around the coastal areas (Reed, 2009). Geophysics of the ground- With oil exploration the geophysics has been adequately used. But on the other issues the geophysics has been utilized in limited areas. Geochemistry- Condiama and Diamang traditionally carried out stream sampling of heavy material such as diamonds. In addition, there have been other organizations and individuals undertaking geochemistry for stream, soil and heavy material. The total compilation resulting to these works is not in existence hence it has been difficult to ascertain the exact levels of the coverage of Geochemistry (Fullagar, West & National Science Teachers Association 2011). References Arthur, T., MacGregor, D. S., Cameron, N. R., & Geological Society of London. (2003). Petroleum geology of Africa: New themes and developing technologies. London: Geological Society. Fullagar, P. D., West, N. W., & National Science Teachers Association. (2011). Geology. Arlington, Va: National Science Teachers Association. Reed, K. (2009). Crude existence: Environment and the politics of oil in Northern Angola. Berkeley: University of California Press. Van der Weijden CH, de Lange GJ, & Pruysers Peter A. (2013). Early diagenetic processes in sediments of the Angola Basin, eastern South Atlantic. Utrecht: Universiteit Utrecht. Read More