Sand provenance in the Kwanza Basin, Angola, is assessed using conventional and varietal heavy mineral analysis. There are contrasting heavy mineral signatures in the north and south of the basin separated by a hybrid zone. These contrasts are attributed to different hinterland geology. Heavy mineralogy, sand body distribution and prominent structures allowed the subdivision of the Kwanza Basin into five depositional domains. Heavy mineral indices filter important provenance signatures in space and time in addition to providlng tectonic and geomorphologic information. Quantitative and qualitative thermal and composition information was obtained from fluid inclusions using UV fluorescence and microthermometry. There were at least two pulses of hydrocarbon generation and migration from source rocks in the basin based on homogenization temperatures of 52-129°C, geochemical characterization of oil shows from proprietary data, and Genesis basin modelling: 1) during Albian time, rift-related high heat flow triggered the first pulse, and 2) high rates of sedimentation led to a burial-induced pulse during the Neogene-Quaternary. There are three main controls on diagenesis: stratigraphy and facies; thermal history; and provenance. Significant authigenic minerals (illite, smectite, dolomite, quartz and feldspar) were only noted in Cenomanian or older rocks. Apatite fission track analysis (AFTA) yields a record of the temperature regime experienced by the basin and basement through the pre-rift, syn-rift and post-rift stages. There were three main tectono-thermal events in the basin: 1) pre-rift and early syn-rift cooling; 2) a post-rift period of tectonic quiescence (Cretaceous to early Tertiary); interrupted by 3) a rapid cooling (denudation) due to epeirogenic uplift of the Inner Kwanza Basin and hinterland at ca. 23 Ma. Miocene denudation of the Inner Kwanza Basin and the hinterland is mirrored by a burial-related temperature increase in the Outer Kwanza Basin. This source to sink correlation indicates a period of bypassed sedimentation into the Outer Kwanza Basin and possibly onto the abyssal plain of Angola. Keywords: Kwanza Basin, diagenesis, provenance, heavy minerals, fluid inclusion, microthermometry, AFTA, basin modelling, hydrocarbon charge.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:485387 |
| Date | January 2007 |
| Creators | Machado, Vladimir Alberto Gouveia |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=225701 |
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