Geochemistry of the Early Cretaceous Koegel Fontein Anorogenic Igneous Complex, South Africa

Curtis, C.; Trumbull, Robert B.; Beer, C.H. de; Harris, Chris; Reid, David L.; Romer, Rolf L.

doi:10.2113/gssajg.114.3-4.353

Cited by 10 publications

(2 citation statements)

References 38 publications

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“…Post-Karoo igneous rocks, coeval with Atlantic rifting (approximately 160-130 Ma), can be found in the most southern region of the study area ( Figure 2). The Koegel Fontein complex near the towns of Kotzesrus and Biesiesfontein is composed of a variety of intrusive bodies including tholeiitic basalt plugs, syenite and granite plutons, and dykes of varying composition [de Beer, 2002;Curtis et al, 2011]. A suite of NNW-SSE trending dolerite dykes crosscut the Koegel Fontein complex and is believed to have the same origin as the False Bay dolerite suite in the Southern Cape based on their age and composition [Day, 1987;Reid, 1990;Reid et al, 1991;Trumbull et al, 2007;de Beer, 2010].…”

Section: Synrift and Postrift Intrusive Activitymentioning

confidence: 99%

The chronology and tectonic style of landscape evolution along the elevated Atlantic continental margin of South Africa resolved by joint apatite fission track and (U‐Th‐Sm)/He thermochronology

et al. 2016

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Atlantic-type continental margins have long been considered "passive" tectonic settings throughout the entire postrift phase. Recent studies question the long-term stability of these margins and have shown that postrift uplift and reactivation of preexisting structures may be a common feature of a continental margin's evolution. The Namaqualand sector of the western continental margin of South Africa is characterized by a ubiquitously faulted basement but lacks preservation of younger geological strata to constrain postrift tectonic fault activity. Here we present the first systematic study using joint apatite fission track and apatite (U-Th-Sm)/He thermochronology to achieve a better understanding on the chronology and tectonic style of landscape evolution across this region. Apatite fission track ages range from 58.3 ± 2.6 to 132.2 ± 3.6 Ma, with mean track lengths between 10.9 ± 0.19 and 14.35 ± 0.22 μm, and mean (U-Th-Sm)/He sample ages range from 55.8 ± 31.3 to 120.6 ± 31.4 Ma. Joint inverse modeling of these data reveals two distinct episodes of cooling at approximately 150-130 Ma and 110-90 Ma with limited cooling during the Cenozoic. Estimates of denudation based on these thermal histories predict approximately 1-3 km of denudation coinciding with two major tectonic events. The first event, during the Early Cretaceous, was driven by continental rifting and the development and removal of synrift topography. The second event, during the Late Cretaceous, includes localized reactivation of basement structures as well as regional mantle-driven uplift. Relative tectonic stability prevailed during the Cenozoic, and regional denudation over this time is constrained to be less than 1 km.

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Section: Synrift and Postrift Intrusive Activitymentioning

confidence: 99%

The chronology and tectonic style of landscape evolution along the elevated Atlantic continental margin of South Africa resolved by joint apatite fission track and (U‐Th‐Sm)/He thermochronology

et al. 2016

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“…Tholeiitic dolerite dikes of composition, enriched in augite and pigeonite, intruded Namaqualand Metamorphic Province rocks near Brand-se-baai during the Jurassic (190-150 Ma;De Beer et al, 2002). The Early Cretaceous (144-134 Ma) Koegel Fontein Complex is a granite-syenite intrusive suite with minor plugs and dikes of felsic and mafic composition that intruded the basement north of the Namakwa Sands deposit (Curtis et al, 2011). The mafic dikes are tholeiitic in composition and contain high concentrations of augite and ilmenite.…”

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Geology of the Cenozoic Namakwa Sands Heavy Mineral Deposit, West Coast of South Africa: A World-Class Resource of Titanium and Zircon

Philander

Rozendaal

2015

Economic Geology

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Exploration for heavy minerals along the coastal strip of southwest Africa led to the discovery and subsequent delineation of the Namakwa Sands deposit near Brand-se-baai in 1987. Currently, Tronox Limited controls the Namakwa Sands operation, which has developed into a significant, global producer of titanium slag, pig iron, ceramics quality zircon and rutile concentrates. The Namakwa Sands deposit is classified as a megaresource with 1.17 billion tons (Bt) of in situ ore, containing an estimated 92.6 million metric tons (Mt) of total heavy minerals and the equivalent of 23.9 Mt TiO2 units and 9.4 Mt zircon.The siliciclastic, arenaceous deposit is divided into two adjacent orebodies, referred to as Graauwduinen West and Graauwduinen East. The Graauwduinen West orebody consists of three strandline-dune couplets set in a transitional shallow marine-aeolian environment, whereas the Graauwduinen East orebody comprises a largely unrelated dune deposit. Superimposed onto the ore-bearing sequence is a pseudostratigraphy of duricrust that effectively cemented the bulk of the mineralized sands to various degrees of hardness. The two orebodies are profoundly different in many aspects. Spatially, the planar mineralization bears northeasterly in the Graauwduinen West orebody, strikingly perpendicular to the southeasterly trend observed in the Graauwduinen East orebody. Contrasts in their bulk chemistry and mineralogy are statistically significant. The Graauwduinen West orebody features noticeably better total heavy mineral grades, accompanied by conspicuously high proportions of the gangue minerals garnet and pyroxene.The valuable mineral fraction is predominated by ilmenite (FeTiO3), followed in abundance by zircon (ZrSiO4), leucoxene (an alteration product of ilmenite), and rutile (TiO2). Their geochemistry, mineralogy, and petrography are extremely variable, but the bulk of the current valuable mineral fraction is recoverable to premium-grade products. The proximal, Mesoproterozoic Namaqualand Metamorphic Province is considered the main contributor to the current heavy mineral population. The Graauwduinen West orebody received source sediment via established fluvial-marine courses, whereas the source of the Graauwduinen East orebody is considered to originate from a distinct fluvial-aeolian corridor. The genesis of the Namakwa Sands deposit is strongly entrenched in the geomorphic evolution of the west coast of southern Africa since the Cenozoic, which was driven by regional tectonism, fluctuating sea levels, and alternating climatic patterns.

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Petrogenesis of low-δ18O quartz porphyry dykes, Koegel Fontein complex, South Africa

Harris

Sarkar

Whitehead

et al. 2018

Contrib Mineral Petrol

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Geochemistry of the Early Cretaceous Koegel Fontein Anorogenic Igneous Complex, South Africa

Cited by 10 publications

References 38 publications

The chronology and tectonic style of landscape evolution along the elevated Atlantic continental margin of South Africa resolved by joint apatite fission track and (U‐Th‐Sm)/He thermochronology

The chronology and tectonic style of landscape evolution along the elevated Atlantic continental margin of South Africa resolved by joint apatite fission track and (U‐Th‐Sm)/He thermochronology

Geology of the Cenozoic Namakwa Sands Heavy Mineral Deposit, West Coast of South Africa: A World-Class Resource of Titanium and Zircon

Petrogenesis of low-δ18O quartz porphyry dykes, Koegel Fontein complex, South Africa

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