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Combined geophysical, structural geological, metamorphic, geochronological, and stable isotope information is employed to elucidate the Neoarchaean thermo-tectonic evolution of the Southern Marginal Zone (SMZ) within the Limpopo Complex (South Africa) during the Limpopo orogeny (2.72 to 2.62 Ga). The complex evolutionary history of the SMZ was controlled by an allochthonous SMZ granulite nappe that was extruded from a rising granulite diapir through a process of mid-crustal heterogeneous channel flow. This granulite nappe with its embedded structures (steeply plunging reclined folds and steep shear zones) was formed during emplacement of the diapir to mid-crustal level (6 kbar, 20 km depth) from where it was thrust south-westwards along the Hout River shear zone (HRSZ) sole thrust against the Kaapvaal Craton (KVC) at 2.72 to 2.69 Ga. Evidence for the thermo-tectonic interaction of the granulite nappe with the KVC includes (1) thrust complexes (referred to as hot-iron zones) that are developed at the frontal ramp sections of the HRSZ juxtaposed against the granite-greenstone belts of the KVC, and (2) strike-slip shear deformation associated with the lateral ramp section of the HRSZ, which developed against the KVC devoid of greenstone belts. The emplacement of the post-tectonic Matok granitic pluton at ~2.68 Ga into the SMZ signified the end of the thermo-tectonic event that established the regional fold- and shear deformational framework of the granulite facies SMZ. Post-Matok secondary shear zones reflect evidence for HRSZ-linked tectonism that continued intermittently to 2.65 to 2.62 Ga. Low H2O-activity fluids (H2O activity of 0.1 to 0.3) released from devolatilisation of underthrust greenstone material passively infiltrated and interacted with the overlying cooling granulites. This established a retrograde anthophyllite-in isograd at ~6 kbar and ~620°C that subdivides the SMZ into a northern granulite domain and a southern retrograde hydrated granulite domain. Simultaneously, gold-bearing fluids focused into these minor shear zones established shear zone-hosted orogenic gold mineralisation at 2.65 to 2.62 Ga. Emplacement of the posttectonic Palmietfontein granite at ~2.46 Ga and associated sub-volcanic granitic dykes into both the retrograde hydrated granulite domain and the granulite domain signifies the end of all thermo-tectonic activity in the SMZ. A Palaeoproterozoic thermal overprint at ~2.1 Ga is recorded by Rb-Sr biotite and phlogopite ages derived from various rocks from the SMZ and adjacent KVC. This thermal event is not associated with deformation and did not result in the formation of new mineral assemblages. Integrated data presented and discussed in this paper contradict the interpretation of age and petrological data utilised to support alternative models for the evolution of the SMZ, including a proposed ~2.1 Ga Palaeoproterozoic polymetamorphic amphibolite-grade thermo-tectonic event. [ABSTRACT FROM AUTHOR]

This paper addresses the credibility of published data utilised to underpin conflicting models recently proposed for the geodynamic evolution of the Limpopo Complex (LC), Southern Africa, in the Neoarchaean and Palaeoproterozoic. We are mainly focused on the tectonic and metamorphic processes that affected the Central Zone (CZ) of the LC, but also consider the significance of the timing of the thermo-tectonic interaction of the Southern Marginal Zone (SMZ) of the LC with the granite-greenstone terrane of the Kaapvaal Craton (KVC) at the position of the steep north-dipping Hout River Shear Zone (HRSZ). HRSZ-linked tectonism at the contact with the KVC is expressed as a narrow "hot-iron zone" directly dated at 2.72 to 2.69 Ga and developed in the footwall of the north-dipping HRSZ. HRSZ-linked tectonic activity intermittently continued up to 2.65 to 2.62 Ga with no structural-metamorphic or geochronological evidence that the SMZ and the rest of the KVC were affected by regional thermo-tectonic (orogenic) activity after ca. 2.68 Ga. The complementary This paper addresses the credibility of published data utilised to underpin conflicting models recently proposed for the geodynamic evolution of the Limpopo Complex (LC), Southern Africa, in the Neoarchaean and Palaeoproterozoic. We are mainly focused on the tectonic and metamorphic processes that affected the Central Zone (CZ) of the LC, but also consider the significance of the timing of the thermo-tectonic interaction of the Southern Marginal Zone (SMZ) of the LC with the granite-greenstone terrane of the Kaapvaal Craton (KVC) at the position of the steep north-dipping Hout River Shear Zone (HRSZ). HRSZ-linked tectonism at the contact with the KVC is expressed as a narrow "hot-iron zone" directly dated at 2.72 to 2.69 Ga and developed in the footwall of the north-dipping HRSZ. HRSZ-linked tectonic activity intermittently continued up to 2.65 to 2.62 Ga with no structural-metamorphic or geochronological evidence that the SMZ and the rest of the KVC were affected by regional thermo-tectonic (orogenic) activity after ca. 2.68 Ga. The complementary [ABSTRACT FROM AUTHOR]

The paper reviews published and unpublished geological data pertaining to the structural and metamorphic controls, rock types, characteristic features, source, and timing of hypozonal orogenic gold mineralization in the Giyani Goldfield. The Giyani Goldfield includes the NW domain of the >3.0 Ga Giyani greenstone belt (GGB) at the northern edge of the Kaapvaal Craton and the southern retrograde hydrated domain of the juxtaposed Southern Marginal Zone (SMZ) of the ca. 2.72 Ga Limpopo Complex (LC). Mineralization at all gold mines and gold prospects of the Giyani Goldfield is structurally controlled and closely associated with the Hout River shear zone (HRSZ) and associated smaller shear zones suggesting a specific tectonic setting. This tectonic setting is the direct consequence of thrusting the SMZ of the LC against and over the adjacent GGB at the position of the steeply north-dipping (south verging) HRSZ during the exhumation stage of the ca. 2.72 to 2.69 Ga Limpopo orogeny followed by regional retrograde hydration of the southern part of the SMZ at ca. 2.68 to 2.62 Ga. This tectonic setting offers an explanation for a deep-seated crustal source for gold and for the concentration of orogenic gold mineralization within specific structural features located within the Giyani Goldfield. This tectonic setting also explains the lithological, structural and metamorphic complexity, metasomatic alteration and post-peak metamorphic timing of gold mineralization. Finally, it provides important clues with regards to a crustal source for gold mineralizing fluids and the identification of new potential targets for gold exploration in the Giyani Goldfield. [ABSTRACT FROM AUTHOR]

New field, structural, petrologic, and age data show that tectonic styles and metamorphic histories in the West Alldays area of the Central Zone of the Limpopo Complex, southern Africa, can be linked to neo-Archean and Paleoproterozoic high-grade (granulite facies) tectonometamorphic events. The styles comprise (1) a regionally developed high-grade (S2) gneissic fabric that evolved into a regional (D2) system of sheath folds mapped as circular to oval-shaped structures with lineations plunging steeply to the WSW and (2) a system of mainly N-S-trending and north-verging (D3) shear zones characterized by high-grade tectonites (‘straight gneisses’) with well-developed (S3) gneissic fabrics. In the West Alldays area, the superimposition of D3 onto the regional D2 fold pattern produced the kilometer-scale N-S-trending Baklykraal shear zone, which, before this study, was mapped as the Baklykraal fold and interpreted as part of the regional D2 fold pattern in the Central Zone. The Paleoproterozoic high-temperature D3 shear event is accurately constrained to 2023 ± 11 Ma by a Pb/Pb stepwise leaching garnet date that reflects the syntectonic crystallization of a garnet-cordierite-sillimanite-biotite-quartz paragenesis formed during shearing. This tectonite records a retrograde pressure-temperature (PT) path from 780°C at 5.7 kbar to 600°C at 3.3 kbar. The neo-Archean age of the M2 granulite facies metamorphism, coeval with the tight D2 folding preserved within the Baklykraal shear zone, is evident from several garnet Pb/Pb stepwise leaching experiments that gave dates intermediate between 2000 and 2600 Ma, with large scatter in the data arrays (thus interpreted as mixed ages), and from zircon ages of protoliths of the syn-D2 Singelele-type quartzofeldspathic gneisses. A polymetamorphic garnet-cordierite-orthopyroxene-biotite-quartz paragenesis from a D2 outcrop within the Baklykraal shear zone records two PT paths: a decompression-cooling PT path from ∼850°C at ∼8.5 kbar to ∼675°C at ∼6 kbar at ∼2600 Ma and an isobaric (6 kbar) heating event from ∼675°C to ∼770°C that was immediately followed by a decompression-cooling path that reflects the uplift of the high-grade rocks toward the Earth's surface (to the level of about 8–10 km). Polymetamorphic granulites that resulted from the isobaric heating event introduce new petrologic and geochronologic problems. On the basis of new data, we thus document previously unrecognized N-S-trending high-temperature shear zones and associated polymetamorphic granulites from the Central Zone of the Limpopo Complex. These shear zones developed in the Paleoproterozoic and were superimposed onto older (neo-Archean) regional fold structures. The tectonic history of the Central Zone of the Limpopo Complex is therefore characterized by two high-grade tectonometamorphic events separated by at least 550 m.yr. These data require that existing models for crust formation in the Central Zone, including those that argue for a single granulite facies event linked to an orogeny at ∼2000 Ma, be reconsidered. [ABSTRACT FROM AUTHOR]

Discusses whether the structural and metamorphic characteristics of the Northern and Southern Marginal Zones of the Limpopo Belt can be linked to a collision of the Kaapvaal and Zimbabwe Cratons during the Late Archaean. Salient features of the two Marginal Zones; Discussion of the study; Conclusions.

Introduces the concept of whole-rock/mineral fractionations applied to rocks of the Southern Marginal Zone (SMZ) of the Limpopo Belt. Analytical methods used in study; Geological setting of SMZ of the Limpopo Belt; Results and discussion of the study; Conclusions.

Presents a study demonstrating that metamorphism associated with the second thrust event is pre-Transvaal, post-Platberg in age. Information on the localities studied; Lithologies and structures of thrust slices; Significance of quartz vein formation; Mineralogy of the studied samples; Chemical composition of studied samples.