The Grenvillian Namaqua-Natal fold belt adjacent to the Kaapvaal Craton: 1. Distribution of Mesoproterozoic collisional terranes deduced from results of regional surveys and selected profiles in the western and southern parts of the fold belt

Colliston, W.P.; Schoch, A.E.; Cole, Janine

doi:10.1016/j.jafrearsci.2014.05.017

Cited by 16 publications

(3 citation statements)

References 52 publications

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“…What is more pertinent in the context of this study is the tectonic fabric that was established at this time, as this basement structure may have been important in controlling the style of prerift, synrift, and postrift deformation [e.g., Daly et al, 1989;Clemson et al, 1997;Ziegler and Cloetingh, 2004;Corti et al, 2007;Frimmel et al, 2013]. At least four compressional deformation events have been documented in gneissic foliations and folds and are thought to have been driven by processes coeval with the regional Kibaran Orogeny (approximately 1200-1000 Ma) and global Grenville Orogeny (approximately 1300-950 Ma) [Jacobs et al, 1993;Clifford et al, 2004;Eglington, 2006;Viola et al, 2012;Colliston et al, 2014]. These deformation events were followed by a phase of extension in western Namaqualand that has been attributed to the collapse of the Namaqualand orogenic belt [Dewey et al, 2006].…”

Section: Tectonic Setting Of the Namaqualand Basement Rocksmentioning

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: Tectonic Setting Of the Namaqualand Basement Rocksmentioning

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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“…The Namaqualand Metamorphic Complex forms part of a Proterozoic orogenic belt on the southern margin of the Kaapvaal craton in southern Africa (Colliston, Schoch, & Cole, 2014;Hartnady, Joubert, & Stowe, 1985). It experienced high-grade, granulite facies metamorphism at 1,030-1,040 Ma during the Namaqua thermal event (Robb, Armstrong, & Waters, 1999).…”

Section: Namaqualand Metamorphic Complex South Africamentioning

confidence: 99%

A comparison of observed and thermodynamically predicted phase equilibria and mineral compositions in mafic granulites

Forshaw

Waters

Pattison

et al. 2018

Journal Metamorphic Geology

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Recently published activity–composition (a–x) relations for minerals in upper amphibolite‐ and granulite facies intermediate and basic rocks have expanded our ability to interpret the petrological evolution of these important components of the lower continental crust. If such petrological modelling is to be reliable, the abundances and compositions of phases calculated at the interpreted conditions of metamorphic equilibration should resemble those in the sample under study. Here, petrological modelling was applied to six granulite facies rocks that formed in different tectonic environments and reached different peak metamorphic pressure–temperature (P–T) conditions. While phase assemblages matching those observed in each sample can generally be calculated at P–T conditions that approximate those of peak metamorphism, a consistent discrepancy was found between the calculated and observed compositions of amphibole and clinopyroxene. In amphibole, Si, Ca and A‐site K are underestimated by the model, while Al and A‐site Na are overestimated; comparatively, in clinopyroxene, Mg and Si are generally underestimated, while Fe2+ and Al are typically overestimated, compared to observed values. One consequence is a reversal in the Fe–Mg distribution coefficient (KD) between amphibole and clinopyroxene compared to observations. Some of these mismatches are attributed to the incorrect partitioning of elements between the predicted amphibole and clinopyroxene compositions; however, other discrepancies are the result of the incorrect prediction of major substitution vectors in amphibole and clinopyroxene. These compositional irregularities affect mineral modal abundance estimates and in turn the position and size (in P–T space) of mineral assemblage fields, the effect becoming progressively more marked as the modal abundance of hornblende increases; hence, this study carries implications for estimating P–T conditions of high‐temperature metabasites using these new a–x relations.

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“…The Namaqua metamorphic complex comprises granulite facies, dominantly quartzofeldspathic, rocks; however, because they do not crop out in this area, their exact composition and structure are unknown. In comparison with observations further north, where outcrops exist, the fabric of the Namaqua metamorphic complex is likely to be dominated by gently north-to-northeast-dipping foliations (Colliston et al, 2014). The Malmesbury group comprises lower greenschist facies siliciclastic sedimentary and volcanic rocks, deformed in the Pan-African Saldania orogeny, in which thrust and strike-slip faults have a predominant northwesterly strike (Belcher and Kisters, 2003).…”

Section: Geology Of the Ceres-tulbagh Areamentioning

confidence: 89%

Microseismic Activity and Basement Controls on an Active Intraplate Strike‐Slip Fault, Ceres–Tulbagh, South Africa

Smit

Fagereng

Braeuer³

et al. 2015

Bulletin of the Seismological Society of America

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Earthquakes far from plate boundaries are poorly understood, because of few well-studied examples and uncertainty of what controls the location of these events. In 1969 a damaging local magnitude (M L ) 6.3 strike-slip earthquake, with no surface expression, occurred in the Ceres-Tulbagh region in the South African stable continental interior. Here, we present a microseismic study of the Ceres-Tulbagh area, conducted over three months in 2012, in which 172 events recorded on at least three stations follow a Gutenberg-Richter relationship for −1:5 < M L < 0:5. The events delineate a 5 km wide, subvertical zone that is microseismically active to a depth of 15 km. This fault zone is subparallel to the 1969 aftershock zone and at low angle to the regionally inferred greatest horizontal stress. We argue that the microseismically active zone is guided by inherited structures in the basement geology. This and similar structures may represent significant earthquake hazard in plate interiors.Online Material: Tables of station and event parameters, and P-and S-wave arrival times.

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The Grenvillian Namaqua-Natal fold belt adjacent to the Kaapvaal Craton: 1. Distribution of Mesoproterozoic collisional terranes deduced from results of regional surveys and selected profiles in the western and southern parts of the fold belt

Cited by 16 publications

References 52 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

A comparison of observed and thermodynamically predicted phase equilibria and mineral compositions in mafic granulites

Microseismic Activity and Basement Controls on an Active Intraplate Strike‐Slip Fault, Ceres–Tulbagh, South Africa

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