The Kliphoek Granite is a mesocratic, porphyritic post-tectonic granite in the western Namaqualand sector of the Mesoproterozoic Namaqua-Natal Belt. It was mapped as one of 26 different types of granite of the Spektakel Suite by Council for Geoscience geologists. The granite is differentiated from other members of the suite on grounds of its greenish colour, dark-brown weathering outcrops and stubby phenocrysts. Its composition is that of a lesser evolved, shoshonitic monzogranite with no evidence of metamorphism. It has been dated at 1078 ± 5 Ma and 1060 ± 9 Ma. The granite is mined for dimension stone (Verde Bitterfontein).
Abstract The 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.
Historically, the Western and Southern Branches have always been considered different entities of the Cape Fold Belt with regard to both their origin and mechanism of formation. Deformation in the Western Branch was generally considered to be the older of the two. A review of the sparse evidence that led earlier authors to the above conclusions has indicated many shortcomings : the Witteberg-Dwyka unconformity in the western Karoo does not imply an early phase of folding in the west ; and evidence of pre-Dwyka folds is clearly lacking. The monoclinal folding in the Western Branch obviously originated from horizontal compression. This, together with indications that the NW-trending folds do not die out westwards, eliminates the need for a vertical tectonics model for the Western Branch. Soft sediment tectonic structures in outcrops of the Witteberg Group in both branches indicate similar states of diagenesis during the main fold phases
Research Article| March 01, 2019 The age of the Koegel Fontein anorogenic complex, South Africa, and its relationship to the regional timing of magmatism and breakup along the South Atlantic rifted margin R.B. Trumbull; R.B. Trumbull GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany e-mail: bobby@gfz-potsdam.de Search for other works by this author on: GSW Google Scholar M. Sudo; M. Sudo Institute of Geosciences, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany e-mail: msudo@geo.uni-potsdam.de Search for other works by this author on: GSW Google Scholar C. Harris; C. Harris Department of Geological Sciences, University of Cape Town, Rondebosch, 7700 South Africa e-mail: chris.harris@uct.ac.za Search for other works by this author on: GSW Google Scholar R.A. Armstrong; R.A. Armstrong Research School of Earth Sciences, Australian National University, Canberra, Building 142, Mills Road, ACT 0200, Australia e-mail: richard.armstrong@anu.edu.au Search for other works by this author on: GSW Google Scholar C.H. de Beer C.H. de Beer Council for Geoscience, 3 Oos Street, Bellville, 7535 South Africa e-mail: cdebeer@geoscience.org.za Search for other works by this author on: GSW Google Scholar South African Journal of Geology (2019) 122 (1): 69–78. https://doi.org/10.25131/sajg.122.0007 Article history first online: 03 Mar 2019 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation R.B. Trumbull, M. Sudo, C. Harris, R.A. Armstrong, C.H. de Beer; The age of the Koegel Fontein anorogenic complex, South Africa, and its relationship to the regional timing of magmatism and breakup along the South Atlantic rifted margin. South African Journal of Geology 2019;; 122 (1): 69–78. doi: https://doi.org/10.25131/sajg.122.0007 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySouth African Journal of Geology Search Advanced Search Abstract The early Cretaceous Koegel Fontein intrusive complex is situated near the Atlantic coast in South Africa, about 350 km northwest of Cape Town. The complex comprises felsic units of granite and syenite with compositionally related dykes, and a single intrusive plug of diorite. Existing zircon U-Pb ages of 144 ± 2 Ma for the syenite and 133.9 ± 1.3 Ma for the granite suggest that the emplacement of the complex took place over a period of about 10 My. This study provides additional and independent ages of the Koegel Fontein complex by 40Ar/39Ar dating to confirm the onset and duration of magmatism and better define the sequence of igneous units that comprise it.New laser step-heating 40Ar/39Ar ages on plagioclase and biotite from the main intrusive units in the complex are presented here, including samples previously dated by U-Pb dating. The 40Ar/39Ar ages for the granite and syenite units (131.1 ± 0.9 Ma and 143.3 ± 0.9, respectively) are in good agreement with the zircon U-Pb ages. Other units not previously dated include the Rooivleitjie alkaline granite (150.7 ± 0.6 Ma), two quartz-porphyry dykes (143.0 ± 0.9 and 139.4 ± 1.7 Ma) and the Zout Rivier diorite plug (133.0 ± 1.0 Ma). The new results confirm an early onset of magmatism at Koegel Fontein relative to that of the Etendeka Province some 1000 km to the north, which is consistent with the regional south-to-north propagation of South Atlantic rifting. The youngest 40Ar/39Ar ages at Koegel Fontein (134 to 131 Ma, Rietpoort Granite and 133 Ma, Zout Rivier diorite) correspond to the age of the first magnetic seafloor-spreading anomaly offshore, and we suggest that the longevity of Koegel Fontein magmatism relates to a superposition of pre-drift magmatism onshore and spreading-related magmatism as continental separation began. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Research Article| December 01, 2011 GEOCHEMISTRY OF THE EARLY CRETACEOUS KOEGEL FONTEIN ANOROGENIC IGNEOUS COMPLEX, SOUTH AFRICA C.G. CURTIS; C.G. CURTIS Department of Geological Sciences, University of Cape Town, Rondebosch, South Africa, e-mail: cath.g.curtis@googlemail.com Search for other works by this author on: GSW Google Scholar R.B. TRUMBULL; R.B. TRUMBULL GFZ German Research Centre for Geosciences, Telegrafenberg, Potsdam, Germany, e-mail: bobby@gfz-potsdam.de Search for other works by this author on: GSW Google Scholar C.H. DE BEER; C.H. DE BEER Council for Geoscience, Bellville, South Africa, e-mail: cdebeer@geoscience.org.za Search for other works by this author on: GSW Google Scholar C. HARRIS; C. HARRIS Department of Geological Sciences, University of Cape Town, Rondebosch, South Africa, e-mail: chris.harris@uct.ac.za Search for other works by this author on: GSW Google Scholar D.L. REID; D.L. REID Department of Geological Sciences, University of Cape Town, Rondebosch, South Africa, e-mail: david.reid@uct.ac.za Search for other works by this author on: GSW Google Scholar R.L. ROMER R.L. ROMER GFZ German Research Centre for Geosciences, Telegrafenberg, Potsdam, Germany, e-mail: romer@gfz-potsdam.de Search for other works by this author on: GSW Google Scholar South African Journal of Geology (2011) 114 (3-4): 353–378. https://doi.org/10.2113/gssajg.114.3-4.353 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation C.G. CURTIS, R.B. TRUMBULL, C.H. DE BEER, C. HARRIS, D.L. REID, R.L. ROMER; GEOCHEMISTRY OF THE EARLY CRETACEOUS KOEGEL FONTEIN ANOROGENIC IGNEOUS COMPLEX, SOUTH AFRICA. South African Journal of Geology 2011;; 114 (3-4): 353–378. doi: https://doi.org/10.2113/gssajg.114.3-4.353 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySouth African Journal of Geology Search Advanced Search Abstract The Koegel Fontein Igneous Complex in the Western Cape Province of South Africa is a high-level granite-syenite intrusive suite with minor plugs and dykes of felsic and mafic composition. Age dating and field relations show that the felsic rocks intruded as two sequential series, beginning with syenites and the Kerskloof suite of felsic dykes (andesite-trachyandesite, trachyte-rhyolite) at about 144 Ma, followed by the Rietpoort granite pluton and quartz-porphyry dykes at about 134 Ma. The intrusion of the mafic dykes and plugs took place between the two felsic series. The early Cretaceous age of the Koegel Fontein associates its formation with Gondwana breakup and establishment of the volcanic rifted margin in southwest Africa. This paper reports results from the first geochemical study of the Koegel Fontein Complex.Two groups of mafic units are distinguished based on mineralogy, field characteristics and chemical composition. The tholeiitic group comprises basalt and basaltic andesites, the alkaline group ranges from basanite-tephrite to phono-tephrite and basaltic trachy-andesite. Distinctions of incompatible element concentrations (K, P, Ti) and ratios (Y/Nb, Zr/Nb) indicate the presence of two separate magma series. Regional dolerite dykes (Gariep dykes and others) associated with contemporary magmatism along the continental margin occur in and near the complex. These regional dolerites are much more homogeneous compositionally than the mafic dykes of Koegel Fontein. Compositionally, they closely resemble the less-differentiated tholeiite dykes.The felsic units at Koegel Fontein show geochemical and isotopic evidence for two magma series, which correspond to the two intrusive episodes suggested by geochronology and field relations. The first series comprises the volumetrically minor intrusions of syenites, the Kerskloof dykes and the Rooivleitjie granite, with high values (ɛNd(t) from −0.4 to −1.8) indicating a strong mantle input. Similarities of trace element signatures suggest an affinity with the alkaline mafic units. The second series of felsic magmas makes up the bulk of the Koegel Fontein complex, with the large Rietpoort granite pluton and quartz-porphyry dykes (ɛNd(t) = −4.8 to −6.9). These rocks may be related to the tholeiitic mafic series but their isotopic composition indicates a large crustal component. The granitic rocks at Koegel Fontein have geochemical characteristics regarded as typical for anorogenic (A-type) granites, including high contents of Y, Nb, U and Th. In this and in many other features, the Koegel Fontein complex resembles the contemporary intrusive complexes in the Damaraland of northwest Namibia. Like the Damaraland granites, the Koegel Fontein magmas are of mixed origin, and their isotopic composition reflect the proportion of mantle vs. crustal source contributions. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Research Article| June 01, 2012 EVIDENCE OF NEOGENE TO QUATERNARY FAULTING AND SEISMOGENIC DEFORMATION ALONG THE NAMAQUALAND COAST, SOUTH AFRICA C.H. DE BEER C.H. DE BEER Council for Geoscience, P.O. Box 572, Bellville, 7535, Cape Town, South Africa, e-mail: cdebeer@geoscience.org.za Search for other works by this author on: GSW Google Scholar South African Journal of Geology (2012) 115 (2): 117–136. https://doi.org/10.2113/gssajg.115.2.117 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation C.H. DE BEER; EVIDENCE OF NEOGENE TO QUATERNARY FAULTING AND SEISMOGENIC DEFORMATION ALONG THE NAMAQUALAND COAST, SOUTH AFRICA. South African Journal of Geology 2012;; 115 (2): 117–136. doi: https://doi.org/10.2113/gssajg.115.2.117 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySouth African Journal of Geology Search Advanced Search Abstract This paper reports on the results of a systematic investigation into evidence of near-surface and surface deformation of Late Cenozoic sediments along the West Coast of South Africa. Regional studies were supplemented by the investigation of pit faces in diamond mines owned by De Beers Consolidated Mines (Pty) Ltd between Hondeklip Bay and Kleinsee and inspection of exploratory trench logs kept by Alexkor at Alexander Bay. The results provide the first substantiation for previous unverified reports of neotectonic faulting in Pliocene to Pleistocene formations along the Namaqualand coast. Associated deformation of unconsolidated marine sediments suggests that the faulting was seismogenic. The interpretations of some of the observed features remain preliminary and the age of the structures is in most cases not well constrained. Some of the faulting at Hondeklip Bay is clearly younger that 3 Ma and the youngest surface rupture observed may be of latest Pleistocene age. This style of reactivation of coast-parallel Mesozoic or older faults is similar to that recently described in Namibia, and known Quaternary reactivation of the Kango fault system in the Southern Cape. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
'%3e%3cpath fill='%23001489' d='M0 0v6h9V0z'/%3e%3cpath fill='%23e03c31' d='M0 0v3h9V0z'/%3e%3cg stroke='%23fff' stroke-width='2'%3e%3cpath id='d' d='m0 0 4.5 3L0 6m4.5-3H9'/%3e%3cuse xlink:href='%23b' stroke='%23ffb81c' clip-path='url(%23c)'/%3e%3c/g%3e%3cuse xlink:href='%23d' fill='none' stroke='%23007749' stroke-width='1.2'/%3e%3c/g%3e%3c/svg%3e)
'/%3e%3c/defs%3e%3cpath fill='%23012169' d='M0 0h10080v5040H0z'/%3e%3cpath stroke='%23fff' stroke-width='.6' d='m0 0 6 3m0-3L0 3' clip-path='url(%23b)' transform='scale(840)'/%3e%3cpath stroke='%23e4002b' stroke-width='.4' d='m0 0 6 3m0-3L0 3' clip-path='url(%23c)' transform='scale(840)'/%3e%3cpath stroke='%23fff' stroke-width='840' d='M2520 0v2520M0 1260h5040'/%3e%3cpath stroke='%23e4002b' stroke-width='504' d='M2520 0v2520M0 1260h5040'/%3e%3cg fill='%23fff'%3e%3cuse xlink:href='%23d' x='2520' y='3780'/%3e%3cuse xlink:href='%23a' x='7560' y='4200'/%3e%3cuse xlink:href='%23a' x='6300' y='2205'/%3e%3cuse xlink:href='%23a' x='7560' y='840'/%3e%3cuse xlink:href='%23a' x='8680' y='1869'/%3e%3cuse xlink:href='%23e' x='8064' y='2730'/%3e%3c/g%3e%3c/svg%3e)
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)
