The Tectono-Metamorphic Evolution of the Namaqua Metamorphic Province

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Geochemistry and Geochronology".

Deadline for manuscript submissions: closed (20 August 2021) | Viewed by 4315

Special Issue Editors

Department of Geology, Rhodes University, Grahamstown (Makhanda), South Africa
Interests: tectonometamorphic evolution of high-grade metamorphic crust; formation of pegmatites and hydrothermal gold deposits; origin of kimberlite magma
Department of Earth Sciences, University of the Western Cape, Bellville 7535, Western Cape, South Africa
Interests: igneous and metamorphic petrology; lithogeochemistry; economic geology
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Special Issue Information

Dear colleagues

The Namaqua Metamorphic Province (NMP) in Southern Africa is one of the largest Mesoproterozoic metamorphic belts on Earth, with prolonged and intense magmatic and metamorphic episodes between ~1300 and 950 Ma. Large parts of the NMP consist of granites, most of which were emplaced between ~1230 and 1100 Ma into hot middle continental crust, part of which reaches ultrahigh-temperature conditions at pressures not exceeding ~500 MPa. Typically, the metamorphic peaks are followed by near-isobaric P–T paths. Intense, commonly contractional deformation has taken place in several tectonic episodes. The Namaqua Sector exposed in western South Africa and Southern Namibia, and the Natal Sector in southeastern South Africa, developed at roughly the same time but according to the available data appear to be different from each other in some possibly significant respects, particularly with regard to the abundance of Palaeoproterozoic heritage and the tectonic position and setting in Mesoproterozoic time. Further, the mineral endowment differs, with several significant ore deposits or occurrences in the Namaqua Sector (base metal, lithium, REE) but much less mineralization in the Natal Sector.

The traditional literature over the last four decades has mostly seen this history in the context of the Grenvillian orogeny and the assembly of the Rodinia supercontinent, postulating the amalgamation of continental fragments that in the early and mid-Mesoproterozoic were separated by several oceanic basins. Increasing evidence, however, suggests widespread and uniform Palaeoproterozoic lithospheric heritage in all parts of the NMP, which show similarity with those domains of the belt that have formed in Paleoproterozoic time and remained largely unaffected by tectonic, metamorphic, and magmatic episodes in Mesoproterozoic time.

In recent decades, the database for the NMP has steadily grown, particularly with regard to geochronological data. However, this has not necessarily improved the overall understanding of regional crustal evolution, nor has it confirmed the traditional tectonic models in which the NMP is supposed to have formed. In some instances, new data were fitted into the traditional model, even where they do not appear to support, or even may contradict it, rather than seeking new avenues of data interpretation.

In this Special Issue, we invite original or review papers that provide new perspectives on the tectonometamorphic evolution of the Namaqua Metamorphic Province. Such papers may be based on new data, re-interpret published data, or present reviews on existing data sets that provide key insight into crustal evolution.

The Special Issue will include publications on the following topics:

  • The timing and conditions of regional tectonic episodes;
  • The nature and significance of domain boundaries in the NMP;
  • The abundance and sources of granitoid and mafic magmatism over time and space in the NMP;
  • The formation episodes of the juvenile Mesoproterozoic crust and Paleoproterozoic precursors;
  • The relationships between Paleoproterozoic crustal entities in the Richtersveld, the Sperrgebiet, and the Kheis with each other and with Mesoproterozoic domains;
  • Studies on the metamorphic evolution and the critical assessments of the metamorphic evolution in relation to tectonic processes and settings;
  • The differences and commonalities between crustal evolution in the Namaqua Sector and the Natal Belt;
  • The deposition and tectonic setting of sedimentary rocks in the NMP in Mesoproterozoic time;
  • The context of ore forming processes and the regional tectonometamorphic evolution of the NMP.

Dr. Steffen Büttner
Dr. Russell Bailie
Guest Editors

Manuscript Submission Information

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Keywords

  • Mesoproterozoic crustal evolution
  • Paleoproterozoic heritage
  • magma sources
  • tectonic settings
  • P–T–t–d paths
  • southern Africa
  • Rodinia
  • continental back-arc vs. collisional models

Published Papers (1 paper)

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Research

29 pages, 9497 KiB  
Article
Polyphase Deformation of the High-Grade Metamorphic Rocks along the Neusspruit Shear Zone in the Kakamas Domain: Insights into the Processes during the Namaquan Orogeny at the Eastern Margin of the Namaqua Metamorphic Province, South Africa
Minerals 2021, 11(7), 759; https://doi.org/10.3390/min11070759 - 14 Jul 2021
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Abstract
The central part of the Namaqua Metamorphic Province was subjected to intense deformation under high-grade metamorphic conditions up to granulite facies, but also shows greenschist facies overprints denoting the metamorphic nature during the 1.2–1.0 Ga Namaquan Orogeny. This study examines the structural development [...] Read more.
The central part of the Namaqua Metamorphic Province was subjected to intense deformation under high-grade metamorphic conditions up to granulite facies, but also shows greenschist facies overprints denoting the metamorphic nature during the 1.2–1.0 Ga Namaquan Orogeny. This study examines the structural development of the central Kakamas Domain of the eastern Namaqua Metamorphic Province, which has not been extensively studied previously. The compressional orogenic phase is associated with D1 and D2 deformation events during which northeast–southwest-directed shortening resulted in southwest-directed thrusting illustrated by an intra-domain thrust and southwest-verging isoclinal folds. The post-tectonic Friersdale Charnockite of the Keimoes Suite is emplaced during the D3 deformation event. Late reactivation of the intra-domain thrust in the Kakamas Domain to form the Neusspruit Shear Zone during the D4 event is of a monoclinic nature and is described as a deeply rooted structure with shear direction towards the east. This structure, together with the more local Neusberg Thrust Fault, forms part of an intensely flattened narrow basin in the eastern Namaqua Metamorphic Province. Strain and vorticity indices suggest a transpressional shearing across the Neusspruit Shear Zone and adjacent regions probably initiated during the reactivation of the intra-domain thrust. The ~1.2 to 1.8 km-wide, northwest–southeast striking dextral-dominated Neusspruit Shear Zone constitutes a western regional boundary for the supracrustal Korannaland Group and is composed of steep, narrow zones of relatively high strain, characterised by ductile deformation and penetrative strain. Full article
(This article belongs to the Special Issue The Tectono-Metamorphic Evolution of the Namaqua Metamorphic Province)
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