Bibliografie tematiche / Geology – South Africa – Namaqualand

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Letteratura scientifica selezionata sul tema "Geology – South Africa – Namaqualand"

Autore: Grafiati
Pubblicato: 4 giugno 2021
Ultima modifica: 18 febbraio 2022

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Articoli di riviste sul tema "Geology – South Africa – Namaqualand"

1

de Beer, C. H., e P. H. Macey. "Lithostratigraphy of the Mesoproterozoic Windpoort Granite (Spektakel Suite), western Namaqualand, South Africa". South African Journal of Geology 122, n. 2 (1 giugno 2019): 249–56. http://dx.doi.org/10.25131/sajg.122.0017.

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AbstractThe Windpoort Granite is a porphyritic, leucocratic granite belonging to the Spektakel Suite, a group of late- to post-tectonic granites intruded into the orthogneisses and supracrustal metamorphic rocks in western Namaqualand. Like other granites of this type, it is devoid of penetrative tectonic foliation, at most displaying a magmatic foliation parallel to the boundaries of the intrusion. Its main characteristic setting it apart from other Spektakel Suite granites in western Namaqualand is its tightly packed arrangement of small stubby alkali feldspar phenocrysts. Its U-Pb LA-ICPMS age of 1087 ± 11 Ma agrees with the age of other Spektakel Suite granites showing similar field relationships. It classifies geochemically as a highly potassic monzogranite with more evolved compositions than all other plutons of the Spektakel Suite.
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Brandt, D. "Mesozoic fluvial deposits on a rifted continental margin near Vaalputs, Namaqualand, South Africa". South African Journal of Geology 106, n. 1 (1 marzo 2003): 11–16. http://dx.doi.org/10.2113/1060011.

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3

WATERS, D. J. "Partial melting and the formation of granulite facies assemblages in Namaqualand, South Africa". Journal of Metamorphic Geology 6, n. 4 (luglio 1988): 387–404. http://dx.doi.org/10.1111/j.1525-1314.1988.tb00430.x.

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4

Moore, John M., e David J. Waters. "Geochemistry and origin of cordierite-orthoamphibole/orthopyroxene-phlogopite rocks from Namaqualand, South Africa". Chemical Geology 85, n. 1-2 (luglio 1990): 77–100. http://dx.doi.org/10.1016/0009-2541(90)90124-p.

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RAITH, J. G., e S. L. HARLEY. "Low‐P / high‐Tmetamorphism in the Okiep Copper District, western Namaqualand, South Africa". Journal of Metamorphic Geology 16, n. 2 (marzo 1998): 281–305. http://dx.doi.org/10.1111/j.1525-1314.1998.00131.x.

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Kisters, Alexander F. M., Roger L. Gibson, E. Guy Charlesworth e Carl R. Anhaeusser. "The role of strain localization in the segregation and ascent of anatectic melts, Namaqualand, South Africa". Journal of Structural Geology 20, n. 2-3 (febbraio 1998): 229–42. http://dx.doi.org/10.1016/s0191-8141(97)00081-3.

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Madi, Kakaba. "Seismicity and neotectonic uplift in the Augrabies Falls National Park, Namaqualand, Northern Cape, South Africa". Earthquake Science 29, n. 5 (ottobre 2016): 281–89. http://dx.doi.org/10.1007/s11589-016-0166-z.

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Ballouard, Christophe, Marlina A. Elburg, Sebastian Tappe, Christian Reinke, Henriette Ueckermann e Shane Doggart. "Magmatic-hydrothermal evolution of rare metal pegmatites from the Mesoproterozoic Orange River pegmatite belt (Namaqualand, South Africa)". Ore Geology Reviews 116 (gennaio 2020): 103252. http://dx.doi.org/10.1016/j.oregeorev.2019.103252.

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MAIER, W. D., M. A. G. ANDREOLI, D. I. GROVES e S. J. BARNES. "PETROGENESIS OF CU-NI SULPHIDE ORES FROM O'OKIEP AND KLIPRAND, NAMAQUALAND, SOUTH AFRICA: CONSTRAINTS FROM CHALCOPHILE METAL CONTENTS". South African Journal of Geology 115, n. 4 (1 dicembre 2012): 499–514. http://dx.doi.org/10.2113/gssajg.115.4.499.

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Yuhara, M., T. Miyazaki, J. Ishioka, S. Suzuki, H. Kagami e N. Tsuchiya. "Rb-Sr and Sm-Nd Mineral Isochron Ages of the Metamorphic Rocks in the Namaqualand Metamorphic Complex, South Africa". Gondwana Research 5, n. 4 (ottobre 2002): 771–79. http://dx.doi.org/10.1016/s1342-937x(05)70912-6.

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Più fonti

Tesi sul tema "Geology – South Africa – Namaqualand"

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Moodley, Jason Anthony. "Petrogenesis of the Bysteek and Koenap Formation Migmatites, Central Namaqualand". Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1001574.

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Abstract (sommario):
The Mesoproterozoic rocks of the Bysteek and Koenap Formations of the Arribees Group are exposed within a NW-SE striking antiformal structure comprised of mafic granulites and metapelitic diatexites, and a number of marble and calc-silicate rock layers. The mafic granulites of the Bysteek Formation show a typological variety of anatectic features, including nebulitic, stromatitic mesosomes, melanosomes, quartz syenitic leucocratic vein networks and syenitic pools. Melanosomes consist of hedenbergitic to diopside-rich clinopyroxene (XMg: 0.40), anorthitic plagioclase (An90), with some quartz, minor apatite and titanite. Anatexis was caused by biotite dehydration melting and formed a melt of probably granitic composition. The leucosome composition ranges from either alkali-feldspar-granitic to plagioclase rich or granitic. This variation is interpreted as a result of variable extraction of melt from the source to granitic pools. The diatexites of the Koenap Formation are most likely of metapelitic or meta-greywacke origin. They are texturally variable but always contain high modal contents of alkali feldspar and quartz which generally form magmatic textures. Almandine-rich garnet (XMg: 0.18-0.25), cordierite (XMg: 0.71) form secondary biotite, sillimanite and magnetite during retrograde breakdown. Thermodynamic modelling of mafic granulite compositions suggests peak P-T conditions of ~865 °C and 8.6 kbar. Occasionally, garnet rich in ferric iron (XAdr: 0.55) forms by plagioclase-clinopyroxene breakdown under oxidising conditions at ~6 kilobar and ~ 800 °C. At the same stage amphibole forms in some melanosomes. P-T estimations for the diatexites based on thermodynamic modelling suggest the equilibration of the assemblage garnet, cordierite, alkali feldspar and melt at ~860 °C and 5.5 kbar. Conditions comparable to the peak pressure in the mafic granulites could not be established. However, since the diatexites and the mafic granulites are closely related in the field and no evidence of juxtaposition after the thermal peak exists, the P-T record of the diatexites might be incomplete
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Booth, Peter William King. "Pan-African imprint on the early mid-proterozoic Richtersveld and Bushmanland sub-provinces near Eksteenfontein, Namaqualand, Republic of South Africa". Doctoral thesis, University of Cape Town, 1990. http://hdl.handle.net/11427/26232.

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The present investigation examines the relationship between the Proterozoic Richtersveld and Bushmanland Subprovinces in the westernmost part of the Namaqua Province, near Eksteenfontein, Republic of South Africa. There is a controversy about this relationship because isotopic data contrast with field evidence. On a regional scale the Richtersveld Subprovince is separated from the Bushmanland Subprovince by the northward-dipping Groothoek Thrust. North of the thrust the Richtersveld Subprovince is comprised of low grade volcano/ plutonic rocks of the Vioolsdrif Terrane and medium grade volcano sedimentary sequences of the Pella Terrane. Medium grade rocks of the Steinkopf Terrane (Bushmanland Subprovince) lie immediately south of the thrust. Late Proterozoic strata of the Stinkfontein Formation (Gariep Group) overlie the Namaqua Province in the west; Cambrian Nama Group outliers occur east of the Stinkfontein Formation. Isotopic data show that lithologies of the Richtersveld Subprovince formed between 2000 - 1730 Ma, whereas those of the Bushmanland Subprovince are younger. It is not clear whether the Namaqua metamorphic imprint (at 1200 - 1100 Ma), which is manifest in terranes south of the Groothoek Thrust, extended as far as the Vioolsdrif Terrane in the north. Early Proterozoic structural and metamorphic imprints are inferred to have been obliterated during this event. The westernmost part of the Namaqua Province was overprinted for a distance of 100 km from the coast, during the Pan-African event at 700 Ma and 500 Ma. An area measuring nearly 500 km2 , traversing the western extremity of the boundary between the Richtersveld and Bushmanland Subprovinces was mapped on a scale of 1:36,000. Field mapping was carried out with the aid of aerial photographs, whereas laboratory techniques included map compilation, structural analysis, X-ray diffractometry, geochemical (XRF) and electron microprobe analyses. Supracrustal units of the Richtersveld Subprovince are composed of quartzo-feldspathic gneisses, schists, and minor meta-pelites. Supracrustals of the Bushmanland Subprovince are less diverse than those of the Richtersveld Subprovince and have a disconformable relationship with them. Most intrusive rock-types are thick granitic sheets, except the Early Proterozoic Vioolsdrif Granodiorite which forms part of a batholithic pluton in the north. The Sabieboomrante adamellite gneiss, Kouefontein granite gneiss and Dabbieputs granite gneiss could not be correlated with lithologies commonly occurring in the Richtersveld and Bushmanland Subprovinces. They have been given the new rock names. Mafic and ultramafic rocks of the Klipbok complex occur along the strike of the Groothoek Thrust. They form part of the Richtersveld Subprovince.
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Wynn, Timothy James. "Proterozoic analogues of mid crustal deformation from NW Scotland and Namaqualand, South Africa". Thesis, Imperial College London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320409.

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Smithies, Robert Hugh. "The geology and alteration/mineralization of the Van Rooi's vley W/Sn deposit, Namaqua metamorphic complex, South Africa". Thesis, Rhodes University, 1987. http://hdl.handle.net/10962/d1004526.

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Scheelite, wolfram Ite and cassIterIte mIneralizat ion is hosted wIthin numerous quartz-tourmaline-feldspar-fluorite veins at Van Rooi's Vley, N.W. Cape Province . MineralizatIon and hydrothermal alteration within, and around, these veins is hIghly complex and reflects the intricate interaction of hydrotherma l activity upon a structurally deformed sequence of ProterozoIc med ium to high-grade gneisses. Four distinct stages of alteration and mineralization occurred, including a l ate 'epithermal stage'. Although the location of mineralization was strongly controlled by st ructure, the concentration of mineralizati on was controlled by physicochemical variables, of which host-rock geochemistry was particularly important . Further W/Sn mineralization occurs on a local scale, some of which is spatia lly related to minor leucogranite dykes. Leucogranite bodies are not uncommon within the region and some are enriched in Wand Sn. By comparing FIB ra tio s,W/Sn ratios, the alteration mineralogy, the ore mineralogy and the Fe-content of tourmaline, the deposits within the Van Rooi's Vley area can be placed into a 'proximal' to 'distal' classification, with respect to a common source of mineralizing hydrothermal fluids. The Van Rooi's Vley deposit, whilst affiliated to greisen-style deposits, represents a ' distal' quartz-vein lode deposit.
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Stalder, Marcel. "Petrology and mineral chemistry of sulphide ores and associated metalliferous rocks of the Gamsberg Zn-Pb deposit, South Africa : implications for ore genesis and mineral exploration". Thesis, Stellenbosch : University of Stellenbosch, 2004. http://hdl.handle.net/10019.1/16072.

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Thesis (PhD)--University of Stellenbosch, 2004.
ENGLISH ABSTRACT: The Gamsberg Zn-Pb deposit is a metamorphosed and multiply deformed sediment-hosted base metal deposit in the central Namaqua Province of South Africa. The deposit is hosted by the Bushmanland Group, a late Palaeoproterozoic (2000-1600 Ma) supracrustal succession of quartzite, metapelitic schist and interbedded metavolcanic rocks. Mineralisation occurs within the central part of the Gams Formation, a heterogeneous sequence of metamorphosed metalliferous sediments and fine-grained organic-rich shales. The ore horizon is subdivided into a lower unit of metapelite-hosted ore, an intermediate layer of phosphorite-hosted ore, and an upper unit of banded garnet-apatite ore. The ore body is enveloped by unmineralised silicate-, carbonate- and oxide-facies metalliferous rocks, which originally represented mixtures of Fe-Mn-rich hydrothermal precipitates, authigenic carbonate, and variable concentrations of detrital material. Based on mineralogical and geochemical characteristics, the metalliferous host rocks are subdivided into iron formations, coticules, Fe-Mn silicates, impure marbles and barite/Ba-rich quartzite. Minerals of the Gams Formation mostly represent solid solution between the Fe and Mn end-members of garnet, pyroxene, pyroxenoid, amphibole, olivine, spinel and ilmenite. Calcium-rich rock types are a typical feature and characterized by the occurrence of manganoan calcite, clinopyroxene, andradite-rich garnet and titanite. A successive increase in the (Mn+Ca):Fe value of rocks and minerals is evident with increasing distance from the ore horizon. Amphibole is restricted to Fe-rich ore-bearing assemblages, whereas orthopyroxene, clinopyroxene, Fe-rich pyroxenoid and olivine are present in intermediate assemblages, and Mn-rich rhodonite and pyroxmangite in the most manganiferous assemblages. These variations are mimicked by an increase in the Mn:Fe value of coexisting garnet and ilmenite group minerals with increasing distance from ore. LA-ICP-MS analyses have been used to constrain the REE patterns of garnet and apatite. In the ore-body, these minerals display a positive Eu anomaly, which is interpreted to reflect a distinct hydrothermal signature. In contrast, garnet and apatite in unmineralised metalliferous rocks display nil or a negative Eu anomaly. Primary features of the Gams Formation, such as REE patterns, the banded nature of garnet-apatite ore, the presence of diagenetic apatite nodules, and the distribution of the redox-sensitive elements Ba and Mn have been used to constrain palaeo-environmental conditions. The results indicate that metapelitehosted ore has been deposited in a stratified ocean that was characterised by anoxic bottom waters and precipitation of Fe and Zn sulphides into organic matter-rich shales. These rocks were superceded by phosphorite-hosted ore, garnet-apatite ore and metalliferous host rocks that developed in a suboxic to oxic environment. The large size of the deposit, the internal lamination of the ores and the predominance of sphalerite and barite are consistent with a vent-distal setting and precipitation of the ore-forming constituents from dense and reduced hydrothermal fluids, which originated due to reactivation of dormant growth faults. Collectively, the geological evidence indicates that Gamsberg is bridging the gap betweenthe SEDEX and BHT classifications. The relationships demonstrate that differences between these two classes of sediment-hosted Zn-Pb deposits are predominantly related to environmental conditions within localised third order basins and not to fundamental differences in ore-forming processes.
AFRIKAANSE OPSOMMING: Die Gamsberg Zn-Pb afsetting is ‘n meerfasig vervormde en gemetamorfiseerde sedimentgesetelde onedel metaal afsetting in die sentrale Namakwa Provinsie van Suid Afrika. Die afsetting word geherberg deur die Boesmanland Groep, ‘n laat Paleoproterosoïse (2000 – 1600 Ma) bokors-opeenvolging van kwartsiet, metapelitiese skis en tussengelaagde metavulkaniese gesteente. Mineralisasie word gevind in the sentrale deel van die Gams Formasie. Die Gams Formasie is ‘n heterogene opeenvolging van gemetamorfiseerde metaalhoudende sediment en fynkorrelrige organiese skalie. Die erts horison word onderverdeel in ‘n onderste laag van metapeliet-gesetelde erts, n sentrale laag van fosforiet-gesetelde erts, en ‘n boonste laag van gebande granaat-apatiet erts. Die erts-liggaam word omhuls deur ongemineraliseerde silikaat-, karbonaat- en oksied-fasies metal-ryke rotse. Hierdie gesteentes word geinterpreteer as oorspronklike mengsels van Fe-Mn-ryke hidrotermale partikels, outigeniese karbonaat, en verskeie hoeveelhede detritale materiaal. Gebaseer op mineralogiese en geochemiese kenmerke word hierdie rotse onderverdeel in ysterformasies, „coticules“, Fe-Mn silikate, onsuiwer marmer en barite/Ba-ryke kwartsiet. Minerale van die Gams Formasie form meestal soliede oplossingsreekse tussen die Fe en Mn endlede van granaat, pirokseen, piroksenoid, amfibool, olivien, spinel en ilmeniet. Kalsium-ryke rots tipes is ‘n tipiese kenmerk van die Gams Formasie en word gekenmerk deur mangaan-ryke kalsiet, klinopirokseen, andradiet-ryke granaat en sfeen. Daar word ‘n stapsgewyse vergroting van die (Mn+Ca):Fe verhouding in gesteentes en minerale gevind met toeneemende afstand van die erts horison. Amfibool is beperk tot Fe-ryke ertsdraende gesteentes, ortopirokseen, klinopirokseen, Fe-ryke piroksenoid en olivien tot intermediêre gesteentes, en Mn-ryke rodoniet en piroksmangiet tot Mn-ryke gesteentes. Hierdie variasies gaan gepaard met vergroting van die Mn:Fe verhouding in granaat en ilmeniet-groep minerale met toeneemende afstand van die erts. LA-ICP-MS analises was gebruik om die skaars-aarde element patrone van granaat en apatiet te bepaal. In die erts-liggaam wys hierdie minerale ‘n positiewe Eu anomalie, wat geinterpreteerd word as ‘n hidrotermale kenmerk. In ongemineraliseerde gasheer gesteentes wys granaat en apatiet geen of ‘n negatiewe Eu anomalie. Primêre kenmerke van die Gams Formasie, soos skaars-aarde patrone, the gebande voorkoms van granaat-apatiet erts, die teenwoordigheid van diagenetiese apatiet knolle, en die verspreiding van die redox-sensitiewe elemente Ba en Mn, was gebruik om afleidings oor die paleo-omgewing te maak. Die resultate het gewys dat metapeliet-gesetelde erts afgeset was onder anoksiese bodem water deur presipitasie van Fe en Zn sulfiedes in organiese skalie. Hierdie erts gaan oor in fosforiet-gesetelde erts, granaat-apatiet erts en metaal-ryke gasheer gesteente wat in ‘n suboksiese tot oksiese omgewing ontstaan het. Die grootte van die afsetting, die interne gelaagdheid van die erts, asook die teenwoordigheid van sfaleriet en bariet dui op ‘n distale omgewing relatief tot die hidrotermale bron en presipitasie van die ertsuit digte en gereduseerde hidrotermale vloeistowwe, wat ontstaan het deur die heraktiveering van rustende groeiverskuiwings. Gesaamentlik bewys die geologiese kenmerke van Gamsberg dat gemetamorfiseerde SEDEX en Broken Hill-tipe mineralisasie binne die perke van ‘n enkele afsetting kan voorkom. Die geologiese verhoudings dui aan dat verskille tussen hierdie twee tipes van sedimentgesetelde afsettings meestal veroorsaak word deur omgewings-toestande binne in gelokaliseerde derde orde komme en nie deur fundamentele verskille in ertsvormende prosesse nie.
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Pether, John. "The sedimentology, palaeontology and stratigraphy of coastal-plain deposits at Hondeklip Bay, Namaqualand, South Africa". Master's thesis, University of Cape Town, 1994. http://hdl.handle.net/11427/22469.

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Abstract (sommario):
Bibliography: pages 295-307.
The exposures in diamond mines on the Namaqualand west coast of South Africa provide a rare opportunity to examine a record that is normally inaccessible beneath a thick cover of aeolian sands. This study presents the main results of fieldwork in mine excavations on the farms Hondeklip and Avontuur-A, near Hondeklip Bay. Sections in the deposits were described in detail and the vertebrate and invertebrate faunas were sampled. The buried topography of the gneiss bedrock, obtained by prospecting, is complex, with the main feature consisting of a coast-parallel ridge flanking a wide palaeochannel on its landward side. Advanced kaolinitic weathering affected both the bedrock and a diamondiferous, basal kaolinitic sediment patchily preserved in the channel. The incision of the channel is related to the Oligocene regression and the basal kaolinitic sediment is interpreted as a fluvial arkose deposited in the channel. Both the bedrock and the deposit in the channel were then kaolinized during humid climatic conditions in the late Oligocene and early Miocene. Weathering-profile silcrete also developed in the basal kaolinitic sediment. It is tentatively proposed that this weathering period may be represented in the Namib Desert by the thick laterite capping Eocene sediments at Kakaoberg. Subsequently, the palaeochannel was exhumed and was ultimately filled by late Tertiary marine deposits. The marine deposits were laid down in shallowing-upwards sequences of the shore face environment. Two regressive, progradational packages (alloformations) are recognized. The older extends seawards from at least -50 m asl. and is the "45-50 m Complex" of Carrington and Kensley (1969), now called the 50 m Package. East of the channel, on the exposed coast, high-wave-energy storm-deposition in the lower shoreface dominates the preserved record. With lowering of sea-level, the bedrock ridge emerged to the seaward of the prograding palaeoshoreline, reduced the level of incident wave energy and profoundly influenced the development of sub-environments within the progradational regime. Ultimately, low-energy bay deposits filled the palaeochannel in the bedrock. On the basis of vertebrate evidence and correlation with global sea-level trends, the age of the 50 m Package is middle Pliocene. The upper facies of the 50 m Package (foreshore and upper shoreface) have been extensively removed by later subaerial erosion. The subsequent transgression truncated the seaward extent of the 50 m Package, reached ~30 m asl. and prograded seaward from that elevation. It is called the 30 m Package and combines the "29-34 m Beach" and "17-21 m Complex" of Carrington and Kensley (1969). A late Pliocene age is envisaged. The upper-shoreface facies of the 30 m Package is usually preserved, but may be disguised by pedogenesis. The diamondiferous marine gravels mined in the area are mainly lower-shoreface storm deposits and pre-existing transgressive lags and shelf deposits have generally been reworked during regression. Enigmatic, muddy and/or phosphatic units, previously called "E-stage," are patchily preserved in the base of the 50 m Package and are revealed to be distal storm deposits laid down in the transitional shoreface to offshore environment. They are part of the overlying regressive sequence, but may include a fragmentary , petrified, mixed, vertebrate remanie. Nevertheless, eroded remnants of older deposits must also occur in places.
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Moore, John Michael. "A comparative study of metamorphosed supracrustal rocks from the western Namaqualand metamorphic complex". Doctoral thesis, University of Cape Town, 1986. http://hdl.handle.net/11427/22585.

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Abstract (sommario):
Bibliography: pages 346-370.
A regional study of highly metamorphosed supracrustal rocks was undertaken in the western portions of the Namaqualand Metamorphic Complex. The study area was essentially restricted to a north-south section some 50 kilometres wide and 220 kilometres long. Eight east-west-trending belts of supracrustal rocks were examined, together with several smaller paragneiss remnants, in an area dominated by quartzo-feldspathic gneisses of granitic composition. The supracrustal rocks were classified into seven major lithological groups: quartzitic rocks, metapelitic and metapsammitic rocks, quartzo feldspathic rocks, metabasites, metacarbonate rocks, magnesium-rich cordierite rocks and iron formations. Further subdivision, based on variations in mineral constituents within each group, also occurred, as well as the presence of lithologies with compositions transitional between certain groups. The various supracrustal sequences were subdivided into formations containing minor distinctive members on an informal lithostratigraphic basis. Correlation between the major supracrustal belts was then undertaken. Four subgroups were identified across the study area, comprising a quartzo feldspathic gneiss subgroup and an overlying feldspathic quartzite/garnetcordierite gneiss subgroup that both predominate in the southern and central part of the area, a glassy quartzite/mica- sillimanite schist subgroup that predominates in the northern part, and a cordierite gneiss/metacarbonate subgroup that is restricted to the Geselskapbank synform. The supracrustal rocks appear to have been emplaced on a basement of augen gneisses. This relationship is, however, complicated by the intrusion of granit i c rocks within the contact zone.
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Elferink, Lisa. "The cenozoic stratigraphy and associated heavy mineral palaeo-placer deposit on Geelwal Karoo : West Coast, South Africa". Thesis, Stellenbosch : Stellenbosch University, 2005. http://hdl.handle.net/10019.1/21452.

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ENGLISH ABSTRACT: The farm Geelwal Karoo is situated some 16km north of the Olifants River mouth on the West Coast of South Africa and hosts fluvial, marine and aeolian deposits of post-Gondwana age. The oldest basal fluvial succession, unconformably overlies Proterozoic and Palaeozoic basement rocks and is in turn capped by aeolianite and littoral packages representing two transgressive cycles. The fluvial channel clay succession is deposited in shallow bedrock-incised channels, has a wedge-shape and is deposited parallel to the present coastline. The flow direction is along the coast and the northwardtapering, angular, poorly sorted basal vein-quartz lag indicates a northward palaeo-flow direction. Less than 1% total heavy minerals (THM) is found in the matrix of these gravel units and the heavy mineral suite is distinguished by zircon, pseudorutile and kyanite. The channel clay unit is dominated by an upper, mediumgrained quartzose sand and kaolin clay facies, which shows advanced post-depositional weathering. The fluvial unit is correlated with the channel clay unit of Hondeklip Bay and a Cretaceous age is proposed for the initial channel incision. The two shallow marine successions have been correlated with the Late Miocene, Early Pleistocene, +30m and +50m packages respectively. These marine sediments were first described by John Pether (1994) in the Hondeklip Bay area and were named according to their transgressive maxima. They are transgressive successions arranged en echelon down the coastal bedrock gradient, from oldest and highest to youngest. The offshore environment of the +50m package consists of fine silty sand, which is moderately sorted. The mineral assemblage is dominated by quartz and the average THM is 18%. The inshore environment is distinguished by a single poorly sorted basal cobble lag which shows an overall fining upward succession. The beachface environment is composed of medium to fine-grained sand, which is moderate to well-sorted. Mineral diversity is greatest in the inshore and beachface environments and the average THM for these two units is greater than 35%. The +30m package has been extensively eroded due to its lower erosion and outcrops were sporadic along the coast. The +30m offshore sediments are recognised by fine sediments with high concentrations of glauconite and organic matter. The inshore environment is distinguished by numerous poorly sorted pebble lags with fining upward successions. Both the inshore and beachface units have higher feldspar concentrations than the corresponding +50m units. The average THM for these two units is less than 3%. The aeolianite unit, which comprises several distinct units, extends over the entire length of the study area and is characterized by calcrete and red bed horizons. Colour variations in the otherwise homogeneous unit are due to heavy mineral enrichment and/or different degrees of in situ weathering and cementation. The unit is composed exclusively of fine- to medium-grained sand and the THM concentration averages 9%. This unit is composed of more than one generation of aeolian sand and forms part of an aeolian transport corridor which transported sand from the beach to the interior. The oldest unit has been equated with the Upper Miocene Prospect Hill Formation, whereas the more recent yellow dune sand is equated with the Pleistocene Springfontyn Formation. At Geelwal Karoo, only the heavy sand placer in the +50m package was deemed to be of any economic significance. The average THM of this placer was calculated to be 40% and some 150 thousand tons of Tibearing material can be expected from this succession. This relatively small volume of heavy minerals and extensive cementation however, make this placer a less attractive prospect than the neighbouring Namakwa Sands operation.
AFRIKAANSE OPSOMMING: Die plaas Geelwal Karoo is ongeveer 16km noord van die Olifantsriviermond aan die Weskus van Suid- Afrika geleë en het voorkomste van fluviale, marine en eoliese afsettings van post-Gondwana ouderdom. Die oudste eenheid, ‘n basale fluviale eenheid, oorlê Proterosoiëse en Paleosoiëse plaaslike vloer gesteentes wat op hulle beurt weer bedek word deur eoliese en littorale eenhede verteenwoordigene ven twee transgressiewe siklusse. Die fluviale kanaalklei-opeenvolging, afgeset in vlak ingesnyde rotsbedding-kanale, is wigvormig en is afgeset parallel aan die huidige kuslyn in ‘n alluviale waaier-afsetting. Die vloeirigting was langs die kus en die noorwaards toespitsende, hoekige, swak gesorteerde basale aar-kwarts bodemgruis dui op ‘n noordwaards palaeo-vloeirigting. Minder as 1% totale swaarminerale (TSM) is gevind in die tussenmassa van hierdie gruis-eenhede en die swaarmineraal reeks word onderskei deur sirkoon, pseudo-rutiel en kianiet. Die kanaalklei eenheid word oorheers deur ‘n boonste, medium-korrelrige kwarts-bevattende sand en kaolien kleifasies was dui op gevorderde verwering na afsetting. Die fluviale eenheid word gekorreleer met die kleikanaal en ‘n Kryt-ouderdom word voorgestel vir die aanvanklike insnyding van die kanaal. Die twee vlak marine opeenvolgings word gekorreleer met die Laat Mioseen, vroeg Pleistoseen, naamlik die +30m en +50m eenhede onderskeidelik. Die aflandige omgewing van die +50m eenhied bestaan uit matiggesorteerde, fyn slikkerige sand. Die mineraalversameling word oorheers deur kwarts en die gemiddelde TSM is 18%. Die subgetysone word onderskei deur ‘n enkele swak-gesorteerde gruislaag en is oorwegende opwaarts fynerwordend. Die strandomgewing is goed verteenwordige en bestaan uit matig tot goedgesorteerde medium- tot fynkorrelrige sand. Die grootste mineraal-diversiteit kom voor in die subgety- en strandomgewings en die gemiddelde TSM vir hierdie eenhede is hoër as 35%. As gevolg van algemene erosie kom die +30m eenheid sporadies voor. Die aflandige omgeving is herken deur fyn kleierige of slikkerige sedimente met hoe konsentrasies gloukoniet en organiese materiaal. Die subgetysone omgewing is gekenmerk deur verskeie gruislae wat almal opwaarts fynwordend is. Altwee die subgety- en strandomgewings het hoer feldspar konsentrasies as die +50m eenhede. Die gemiddelde THM vir hierdie enhede is minder as 3%. Die eolitiese eenheid, bestaan uit verskeie duidelik-onderskeibare eenhede, beslaan die totale lengte van die studiegebied en word kenmerk deur uitgebreide kalkreet en rooi-laag horisonne. Kleurverskille in die andersins homogene eenheid kan verklaar word in terme van lae swaarmineraal konsentrasies en/of as gevolg wan verskillende grade van in situ verwering en sementering. Die eenheid bestaan uitsluitlik uit fyntot medium-korrelrige sand en het ‘n gemiddelde TSM konsentrasie van 9%. Die eenheid bestaan uit meer as een generasie eoliese sand en maak deel uit van ‘n eoliese vervoersisteem wat sand vanaf die strand na die binneland vervoer het. Die oudste sande in hierdie eenheid is gekorreleer met die Laat Mioseen Prospect Hill Formasie terwyl die meer onlangse geelduin sand vergelyk word met die Pleistoseen Springbokfontein Formasie. By Geelwal Karoo is slegs die +50m eenhede beskou as economies van belang. Die gemiddelde TSM van hierdie swaarmineraal-ertsligaam is bereken op 40% met ‘n verwagte 150 duisend ton Ti-draende material van die opeenvolging. Die relatiewe klein volume swaarminerale en uitgebreide sementering het tot gevolg dat dit ‘n minder aanloklike proposisie is as die aanliggende Namakwa Sands aanleg.
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9

Baars, Franciscus Jacobus, e Franciscus Jacobus Baars. "Geologic and petrologic evidence for granulite facies partial melting in the Garies-Platbakkies supracrustal gneiss belt, Namaqualand metamorphic complex, South Africa". Master's thesis, University of Cape Town, 1990. http://hdl.handle.net/11427/23148.

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The Namaqua Province of southwestern Africa is comprised of a number of distinct tectonostratigraphic subprovinces and terranes, which have in common a 1100-1200Ma structural and metamorphic imprint. In the western Bushmanland Subprovince, E-Wtrending belts of supracrustal gneisses are intruded by and infolded with granitic gneisses of varying ages. A central zone of rocks metamorphosed in the granulite facies is bordered to the north and south by amphibolite facies rocks. A portion of the Garies-Platbakkies supracrustal gneiss belt has been mapped on a 1:15 000 scale. The supracrustal succession was deposited on an unconfirmed basement. It is structurally juxtaposed and infolded with three different granitic augen gneisses. Large bodies of orthopyroxene-bearing granite are syntectonically emplaced in the succession. A wide variety of anatectic granites crop out as sills, dykes and pods varying in size between a few metres and a few hundred metres. These bodies commonly truncate pre-existing foliations. The metamorphosed supracrustal succession contains gneissic equivalents of felsic, mafic and intermediate volanics; pelitic, semi-pelitic, magnesian and granitic composition sediments; feldspathic quartzites; and subordinate quartzites, banded iron formation and calc-silicates. The mineral assemblages of all the rocks indicate metamorphism in the granulite facies. A variety of field evidence exists which suggests that the metamorphic peak was responsible for generating significant quantities of partial melt. The rocks of the study area contain an early Dl fabric. This is refolded in tight, E-plunging D2 crenulation folds. D2 mineral fabrics pre-date the metamorphic peak. D3 open, asymmetric folds are N-vergent and fold the crystalline products partial melting. The southern limbs of D3-folds are attenuated in 04 shear zones. The whole belt is cut by steep, N-S-trending faults. A wide variety of thermobarometers are tested for their applicability to mineral assemblages in the supracrustal rocks. The results of this application suggest that the metamorphic peak occurred at 780 ± 30°C and 5.0 ± 0.4 kbar. Assemblages in shear zones indicate an isobaric retrograde cooling path. The phase relations of melting near the solidus are reviewed with reference to common assemblages in the leucosomes of rocks with granitic and peraluminous bulk compositions. Isobaric T-a(H₂O) sections are constructed from available experimental and thermochemical data. Biotite dehydration and dehydration melting reactions are balanced using natural mineral compositions. The predicted results are compared with the modal abundances of natural product assemblages. The results suggest that dehydration melting was responsible for migmatization, and the consequent reduction of water activity. The amount of melt produced was controlled by the amount of water available from the dehydration of biotite. There is no evidence for the control of water activity by an external fluid reservoir. Limited amounts of water-undersaturated melts were extracted from their sites of generation. This process was responsible for the depletion of some leucosome assemblages with respect to K₂O, H₂O and in peraluminous rocks Na₂O. The partial melts were emplaced locally in developing shear zones.
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Foulkes, Susan Elizabeth. "New geochemical constraints on the genesis of the Gamsberg zinc deposit, Namaqualand Metamorphic Province, South Africa". Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1012084.

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The base metal massive sulfide deposits of the Aggeneys-Gamsberg (A-G) District are hosted within the Mesoproterozoic Bushmanland Group of the Namaqua-Natal Metamorphic Complex in the Northern Cape Province of South Africa. The district displays an apparent eastward trend in the economic concentration of base metals (+ barite) from relatively Cu-Pb-rich, Ba-poor mineralisation at Black Mountain to Zn- and Ba-rich ores at Gamsberg. Base metal sulfides at Gamsberg are restricted to the so called Gams (Iron) Formation which comprises a sulfidic mineralized unit (“B”) enveloped within a sequence of meta-sedimentary units (“A” and “C”). The aim of the study was to shed further light on the genesis and chemical evolution of the sulfide mineralisation at Gamsberg in the context of the entire A-G District, by interrogating further the apparent district-wide trend in base metal distribution. The Gams Iron Formation was sampled and studied from one key drill core intersection (“G1”) which intersects the largest part of it as described elsewhere; a small number of additional samples from a second drill core (“G2”) complemented the main sample suite. Minerals that make up the silicate assemblages across the studied section include quartz, garnet, pyroxene, pyroxenoid, phyllosilicates, carbonates, amphiboles, oxides (chiefly magnetite) and graphite. In a stratigraphic context, the mineralogical variations conform directly to those documented in the relevant literature from the Gamsberg locality. These are coupled, where possible, with mineral-chemical profiles of selected silicate species which replicate those of bulk-rock compositions, particularly with respect to Mn, Fe and Ca in the upper C Unit of the studied section. These signals collectively track the characteristic transition from a terrigenous, siliciclastic sediment-dominated footwall to an exhalative sediment-dominated hanging wall to the sulfide mineralisation as also seen in similar deposits elsewhere, particularly with respect to the characteristic Mn-rich signature increasingly observed in the hanging wall C Unit. The foregoing suggests that the examined section faithfully records the interpreted primary stratigraphy of the deposits, despite the complex structural and metamorphic overprint that characterises the region. This facilitates a stratigraphic analytical approach on the sulfidic Unit B, through a combination of mineral-chemical and stable isotope analyses. Dominant sulfides in Unit B are sphalerite and pyrite, with lesser pyrrhotite and minor galena. Sphalerite shows high and generally invariant contents of Fe (mean 12.18wt%, as FeS) whereas Zn anti-correlates with Mn (mean 5.58wt%, as MnS). Isotopic analyses for S, Fe and Zn in hand-picked sphalerite and pyrite separates were used with a view to providing new evidence for chemical and isotopic variation within the sulfide ore-body in a vertical (i.e. stratigraphic) sense, discuss the implications thereof, and ultimately interpret the new data in light of similar existing data from the A-G District and elsewhere. The δ³⁴S data for pyrite (plus a single pyrrhotite grain) and sphalerite from both cores G1 and G2 show comparable compositional ranges between 22.9 and 30.4‰ and between 27 and 30.1‰ respectively. The δ⁵⁶Fe data for pyrite show a range between -1.85 and 0.19‰, whereas seven sphalerite separates have a very narrow range of δ⁶⁶Zn from 0.06 to 0.20‰. The atypically high sulfur isotope data reported in this study are interpreted to reflect sedimentary deposition of primary sulfide ore at Gamsberg from an isotopically highly evolved seawater sulfate source through large-scale Rayleigh fractionation processes. Thermogenic sulfate reduction is proposed to have been the main reductive mechanism from seawater sulfate to sulfide, given the absence of very low δ³⁴S data for sulfides anywhere in the A-G District. By contrast, the δ⁶⁶Zn values for sphalerite are for all intents and purposes invariant and very close to 0‰, and therefore suggest little Zn isotope fractionation from an original exhalative fluid source. On this evidence alone, Zn isotopes therefore appear to hold little promise as a proxy of the chemical and isotopic evolution of SEDEX deposits in space and time, although this can only be verified through further application in the broader A-G District and similar deposits elsewhere. The apparent decoupling of Zn and S isotopes in the Gamsberg sulfide deposit, however, points towards diverse sources of these two components, i.e. ascending metalliferous brines versus seawater respectively. Finally, pyrite δ⁵⁶Fe data do show a stratigraphic trend of generally declining values up-section, which are interpreted to reflect the influence of broadly coeval precipitation of isotopically heavy Fe-oxides on a broader-scale – now preserved as abundant magnetite through metamorphism. Further work on the iron isotope composition of silicate-and oxide-hosted Fe on a local-to-district scale will assist in testing this interpretation.
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Libri sul tema "Geology – South Africa – Namaqualand"

1

Bowles, M. Tungsten mineralisation in the Namaqualand-Bushmanland region, northwestern Cape, South Africa. [Pretoria]: Republic of South Africa, Dept. of Mineral and Energy Affairs, Geological Survey, 1988.

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The archaeology of the coastal desert of Namaqualand, South Africa: A regional synthesis. Oxford: John and Erica Hedges Ltd., 2008.

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Johnson, M. R. A revised Precambrian time scale for South Africa. Pretoria: Dept. of Mineral and Energy Affairs, Geological Survey, Republic of South Africa, 1989.

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Maclaren, A. H. The geology of the area east of Pofadder with emphasis on shearing associated with the Pofadder lineament, Northwest Cape. [Cape Town]: University of Cape Town, Dept. of Geology, Chamber of Mines Precambrian Research Unit, 1988.

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Harley, M. The mineralisation at Elandshoogte Gold Mine, Eastern Transvaal, South Africa. Johannesburg: University of the Witwatersrand, 1990.

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6

International Union for Quaternary Research. Congress. Proceedings of the VXth INQUA Conference: Durban, South Africa, 3-11 August 1999. A cura di Heine Klaus 1940- e Runge Jürgen 1962-. Exton, (PA): Swets & Zeitlinger Publishers, 2001.

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Belcher, R. W. Geology of the Lebowakgomo area. Silverton, Pretoria: Council for Geoscience, South Africa, 2012.

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Trompette, Roland. Geology of western Gondwana (2000-500 Ma): Pan-African-Brasiliano aggregation of South America and Africa. Rotterdam: A.A. Balkema, 1994.

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Robb, L. J. The nature of the Archaean basement in the hinterland of the Witwatersrand Basin. Johannesburg: Economic Geology Research Unit, University of the Witwatersrand, 1986.

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Robb, L. J. The nature of the Archaean basement in the hinterland of the Witwatersrand Basin. Johannesburg: University of the Witwatersrand, 1986.

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Capitoli di libri sul tema "Geology – South Africa – Namaqualand"

1

Cawthorn, R. Grant. "The Bushveld Complex, South Africa". In Springer Geology, 517–87. Dordrecht: Springer Netherlands, 2015. http://dx.doi.org/10.1007/978-94-017-9652-1_12.

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Dewar, Genevieve, e Brian A. Stewart. "Paleoenvironments, Sea Levels, and Land Use in Namaqualand, South Africa, During MIS 6-2". In Africa from MIS 6-2, 195–212. Dordrecht: Springer Netherlands, 2016. http://dx.doi.org/10.1007/978-94-017-7520-5_11.

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Svensen, Henrik H., Stéphane Polteau, Grant Cawthorn e Sverre Planke. "Sub-volcanic Intrusions in the , South Africa". In Physical Geology of Shallow Magmatic Systems, 349–62. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/11157_2014_7.

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Svensen, Henrik H., Stéphane Polteau, Grant Cawthorn e Sverre Planke. "Sub-volcanic Intrusions in the , South Africa". In Physical Geology of Shallow Magmatic Systems, 349–62. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-14084-1_7.

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Govender-Van Wyk, Sharmla, e Deon Wilson. "13. Sustainable Tourism on Commonages: An Alternative to Traditional Agricultural-based Land Reform in Namaqualand, South Africa". In Sustainable Tourism in Southern Africa, a cura di Jarkko Saarinen, Fritz O. Becker, Haretsebe Manwa e Deon Wilson, 231–52. Bristol, Blue Ridge Summit: Multilingual Matters, 2009. http://dx.doi.org/10.21832/9781845411107-020.

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Visser, J. N. J. "Episodic Palaeozoic Glaciation in the Cape-Karoo Basin, South Africa". In Glaciology and Quaternary Geology, 1–12. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-015-7823-3_1.

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Wabo, H., F. Humbert, M. O. de Kock, G. Belyanin, U. Söderlund, L. P. Maré e N. J. Beukes. "Constraining the Chronology of the Mashishing Dykes from the Eastern Kaapvaal Craton in South Africa". In Springer Geology, 215–61. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-13-1666-1_6.

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Heath, G. J., e S. Constantinou. "Sinkholes and Land Use Regulation in South Africa". In Engineering Geology for Society and Territory - Volume 5, 503–6. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-09048-1_97.

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Steffens, Francois E. "Geostatistical Estimation of Animal Abundance in the Kruger National Park, South Africa". In Quantitative Geology and Geostatistics, 887–97. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1739-5_71.

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Kisters, Alexander, e Richard Belcher. "The Stratigraphy and Structure of the Western Saldania Belt, South Africa and Geodynamic Implications". In Regional Geology Reviews, 387–410. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-68920-3_14.

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Atti di convegni sul tema "Geology – South Africa – Namaqualand"

1

"Hydrochemical Characteristics of Open-Pit Groundwater from a Closed Metalliferous Mine in O'kiep, Namaqualand Region, South Africa". In Nov. 27-28, 2017 South Africa. EARES, 2017. http://dx.doi.org/10.17758/eares.eap1117022.

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"Potentially Toxic Elements Contamination of Soils in O’Kiep, an Arid Region of Namaqualand, South Africa". In Nov. 19-20 2018 Cape Town (South Africa). Eminent Association of Pioneers, 2018. http://dx.doi.org/10.17758/eares4.eap1118238.

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Finkelman, Robert B., Olle Selinus e Hassina Mouri. "MEDICAL GEOLOGY IN AFRICA: AN EXAMPLE OF A SUCCESSFUL MEDICAL GEOLOGY EDUCATIONAL INITIATIVE". In 52nd Annual GSA South-Central Section Meeting - 2018. Geological Society of America, 2018. http://dx.doi.org/10.1130/abs/2018sc-309806.

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A.G. Andreoli, Marco, Giulio Viola, Alexandre Kounov, Johann Scheepers, Oliver Heidbach e Ingrid Stengel. "History of Stress at Vaalputs, Namaqualand, South Africa: Evidence for a Mid-Cretaceous “Wegener-type Orogeny” in Western Southern Africa". In 11th SAGA Biennial Technical Meeting and Exhibition. European Association of Geoscientists & Engineers, 2009. http://dx.doi.org/10.3997/2214-4609-pdb.241.andreoli_paper.

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Ameglio, L., e J. Marsh. "The Elephant’s Head Dyke (South Africa) revisited - An integrated geophysics and geology approach". In 8th SAGA Biennial Technical Meeting and Exhibition. European Association of Geoscientists & Engineers, 2003. http://dx.doi.org/10.3997/2214-4609-pdb.144.31.

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Granath, James, Rolf Rango, Pete Emmet, Colin Ford, Robert Lambert e Michael Kasli. "New Viewpoint on the Geology and Hydrocarbon Prospectivity of the Seychelles Plateau". In SPE/AAPG Africa Energy and Technology Conference. SPE, 2016. http://dx.doi.org/10.2118/afrc-2556681-ms.

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ABSTRACT We have reprocessed, re-imaged, and interpreted 10000+ km of legacy 2D seismic data in the Seychelles, particularly in the western part of the Plateau. Seychelles data have been difficult to image, particularly for the Mesozoic section: volcanics are a major attenuator of low frequency signal, and a hard water bottom contributes to signal problems. Enhanced low frequency techniques were applied to improve the signal fidelity in the 4 to 20 Hz range, and to remove spectral notches of shallow geologic origin. These efforts have allowed a reasonable view of the structure of the Plateau to a depth equivalent to about 3.5 sec TWT, and permit a comparison of areas atop the Plateau to the south coast where the three 1980's Amoco wells were drilled. It is clear that the main Plateau area of the Seychelles (excluding the outlying territories) is comprised of several separate basins, each with similar Karoo, Cretaceous, and Cenozoic sections that relate to the East African and West Indian conjugate margins, but the basins each have nuanced tectono-stratigraphic histories. The previously recognized Correira Basin in the SE and the East and West South Coast Basins face the African conjugate margin; other unimaged ones complete the periphery of the Plateau. The interior of the Plateau is dominated by the Silhouette Basin to the west of the main islands and the Mahé Basin to the east. The co astal basins have harsh tectono-thermal histories comparable to other continental margins around the world; they are typically characterized by stretching, subsidence and breakaway from their respective conjugate margins. In contrast the interior basins are comparable to ‘failed’ rift systems such as the North Sea or the Gulf of Suez. The South Coastal Basins, for example, tend to be more extended which complicated interpretation of the Amoco wells, but they have significant upside, as exemplified by the Beau Vallon structure. The interior basins, on the other hand, have typically simpler structure: the Silhouette Basin contains a system of NW-trending linked normal faults that could easily harbor North Sea-sized hydrocarbon traps with a variety of rift-related reservoir possibilities. Bright, reflective, hard volcanic horizons are less common than usually presumed, but most of the basins may contain considerable pyroclastic material in parts of the section. All of the basins appear to be predominantly oil prone, with considerable upside prospectivity.
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"Geochemical Modelling Data of Groundwater in the O’Kiep, Namaqualand Region, South Africa – 2013 to 2019: A Case of Evidenced Contamination by Historical Mining Activity". In Nov. 16-17, 2020 Johannesburg (SA). Eminent Association of Pioneers, 2020. http://dx.doi.org/10.17758/eares10.eap1120218.

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Duyverman, Henk J., e Emma Msaky. "Shale Oil and Gas in East Africa (Esp.Tanzania) with New Ideas on Reserves and Possible Synergies with Renewables". In SPE/AAPG Africa Energy and Technology Conference. SPE, 2016. http://dx.doi.org/10.2118/afrc-2603293-ms.

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Short Abstract Shale oil and gas in East Africa, with new ideas on reserves and possible synergies with renewables Shale oil and gas production have lately revolutionized the oil and gas industry as a real "game-changer", especially in the US. This has prompted many companies and governments to search for these unconventionals with successes in the UK, Poland and Argentina. These unconventionals do often occur onshore in places, where there is no conventional hydrocarbon production, thus enabling the local government or companies to have a new energy source, which is especially valid in Onshore East Africa. New drilling technologies, which combine shale and geothermal drilling/production, are now being developed. Now it is possible to drill/produce both unconventionals and geothermal from a single well.Gas and oil could be produced from the central pipe, and hot water from the outer tubing, thereby reducing development cost for both methods. In Tanzania a study was performed to look at unconventional oil and gas resources in sedimentary basins. A lot of data on Karoo geology, maturity, TOC's and volumetrics will be presented. In general, one needs a thick sedimentary basin with a lot of shales, good maturity and TOC values, and a fairly unfaulted basin to prevent seismicity when fracking. In East Africa and Southern Africa at large only the Karoo sediments of Permian/Triassic age are a suitable candidate for large shale oil/gas reserves. The possible large Karoo shale gas development in South Africa is a good example. A large heavy oilfield at surface in Madagascar proves an oil source in the Karoo. In S.Kenya and also on Pemba oil shows are known, with a unknown Pre-Jurassic source. Preliminary resource calculations in Tanzania indicate possible resources in place of 50-200 Tcf of gas for the Selous basin, comparable in size with the South-African Karoo Basin. The depth of the source rocks make gas the most likely hydrocarbon phase. One has to note that calculating unconventional resources is much more complicated than with conventional resources, since the adsorbed gas (or oil) needs to be calculated from core or log analyses. An onshore well could also text the synergies with geothermal drilling. Recently, TPDC in Tanzania has started a new evaluation, based on new mapping, rock analyses and maturity studies, into the shale oil and gas potential. Altogether, shale gas (or oil) could be an interesting incentive for onshore Tanzania and East Africa at large.
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Dim, C. I., K. Mosto Onuoha e C. Gabriel Okeugo. "Sequence Stratigraphic, Structural and Reservoir Analyses: An Integrated Approach to Exploration and Development of the Eastern Coastal Swamp Cluster, Niger Delta Basin". In SPE/AAPG Africa Energy and Technology Conference. SPE, 2016. http://dx.doi.org/10.2118/afrc-2538089-ms.

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ABSTRACT Sequence stratigraphic, structural and reservoir analytical tools have been employed in interpreting the geology of the eastern Coastal Swamp Depo-belt of the Niger Delta Basin. The aim was to understand the stratigraphic framework, structural styles and hydrocarbon reservoir distribution for improved regional hydrocarbon exploration across the onshore Niger Delta basin. This interpretative study made use of well logs, biostratigraphic (biofacies and bio-zonation) and petrophysical data obtained from twenty wellbores, integrated with recently merged and reprocessed 3D Pre-Stack Time Migrated regional seismic volume spanning across eight fields (over 960 km2). Results reveal the occurrence of nine key chronostratigraphic surfaces (five maximum flooding surfaces and four sequence boundaries) that were tied to well-established pollen and foram bio-zones for high resolution sequence stratigraphic interpretation. The sediment stacking patterns recognized from gamma ray log signatures were used in delineating the lowstand system tract (LST), transgressive system tract (TST) and highstand system tract (HST) genetic units. Well log sequence stratigraphic correlation reveals that stratal packages within the area were segmented into three depositional sequences occurring from middle to late Miocene age. Furthermore, there is thickening of stratal packages with corresponding decrease in net-to-gross thickness from north to south (basinwards). This is due possibly to the influence of syn-depositional structures on stratigraphy. The combination of reservoir sands (of LST and HST), source and seal shales (of TST and HST) and fault structures allows for good hydrocarbon accumulation and should be targeted during exploration. Reservoir evaluation studies using petrophysical parameters indicates the presence of good quality reservoir intervals, which are laterally continuous and partly compartmentalized. Structural top maps of reservoirs show good amplitude response that are stratigraphically and structurally controlled. Structural analysis revealed the occurrence of back-to-back faulting, collapsed crest structures, simple/faulted rollovers, regional foot wall and hanging wall closures and sub-detachment structures. These structural styles constitute the major hydrocarbon entrapment mechanism in the area. Overall, the study has unraveled the existence of undrilled hydrocarbon leads at deeper depths that should be further revalidated for development and production.
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