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Steynsdorp Gneiss

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(A) Steynsdorp gneisses and layer-parallel leucogranite sheets. (B) Sharp tectonic contact between the Steynsdorp gneiss complex and the overlying amphibolite layers of the Theespruit Formation. The contact is exposed in a river section in NE sector of the dome. (C) Breccia-like clasts of strongly foliated, partly banded amphibolites that are hosted by the Steynsdorp gneisses. The fabric in the amphibolites is sharply truncated by the host rock. The presence of these foliated amphibolites into the Steynsdorp gneisses is consistent with a high-grade tectonometamorphic event that predated the emplacement of Steynsdorp gneisses at ca. 3509 Ma. (D) Layer-parallel granodiorite sheet intruded into the foliated Steynsdorp gneisses. These sheets occur predominantly in the southern part of the core of the Steynsdorp pluton.

(A) Steynsdorp gneisses and layer-parallel leucogranite sheets. (B) Sharp t... Available to Purchase

Published: 01 January 2010
Figure 3. (A) Steynsdorp gneisses and layer-parallel leucogranite sheets. (B) Sharp tectonic contact between the Steynsdorp gneiss complex and the overlying amphibolite layers of the Theespruit Formation. The contact is exposed in a river section in NE sector of the dome. (C) Breccia-like clasts
Journal Article

A LA-ICPMS zircon record of magmatic crystallization and compositional alteration in meta-igneous rocks of the eastern Kaapvaal Craton Available to Purchase

R. Bolhar, A. Hofmann, C.M. Allen, R. Maas
Published: 01 September 2021
South African Journal of Geology (2021) 124 (3): 761–782.
DOI: https://doi.org/10.25131/sajg.124.0042
... during igneous zircon crystallization and subsequent compositional alteration. Four rock samples previously dated by SIMS U-Pb using zircon were selected: 3.56 Ga Ngwane Gneiss, 3.55 Ga Theespruit felsic metavolcanic, 3.50 Ga Steynsdorp Gneiss and 2.98 Ga Nhlangano Gneiss. LA-ICP-MS U-Pb zircon ages...
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View PDF for article title, A LA-ICPMS zircon record of magmatic crystallization and compositional alteration in meta-igneous rocks of the eastern Kaapvaal Craton
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Three-dimensional (3-D) surface created by interpolation of dip angles measured at 190 structural stations across Steynsdorp. The surface is draped over a digital elevation model as in Figure 2B. The topography is highlighted with black lines. Insets i, ii, and iii are lower-hemisphere projections of the foliation and lineation in the (i) Theespruit rocks, (ii) Steynsdorp gneisses, and (iii) sheeted zone.

Three-dimensional (3-D) surface created by interpolation of dip angles meas... Available to Purchase

Published: 01 January 2010
-hemisphere projections of the foliation and lineation in the (i) Theespruit rocks, (ii) Steynsdorp gneisses, and (iii) sheeted zone.
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(A) Boudinaged pyroxenite (pyx) layer at the base of the Theespruit Formation. The pyroxenite is wrapped around by relatively darker amphibolite (amp) layers. (B) Strongly developed, NE-plunging stretching lineation in felsic bands of the Steynsdorp gneisses. (C) Example of F1 intrafolial folds in chert layers of the Theespruit Formation. These folds plunge predominantly NE. (D) Chlorite-filled tension gashes in the foliation plane of the Theespruit felsic schist. The tension gashes are mainly perpendicular to the mineral lineation. (E) Asymmetric feldspar porphyroclast in the Steynsdorp foliated gneiss. (F) Extensional S-C′ fabric in the Theespruit felsic schist. The asymmetric feldspars, S-C′ features, and rotated garnets are consistent with the downward movement of the greenstone belt relative to the trondhjemite-tonalite-granodiorite (TTG) gneisses.

(A) Boudinaged pyroxenite (pyx) layer at the base of the Theespruit Formati... Available to Purchase

Published: 01 January 2010
Figure 6. (A) Boudinaged pyroxenite (pyx) layer at the base of the Theespruit Formation. The pyroxenite is wrapped around by relatively darker amphibolite (amp) layers. (B) Strongly developed, NE-plunging stretching lineation in felsic bands of the Steynsdorp gneisses. (C) Example of F1
Image
(A) Simplified lithological and structural map of the Steynsdorp dome. Image in the background is an orthorectified, gray-scale aerial photograph, provided by the Council of Geosciences of South Africa. (B) Block diagram of the Steynsdorp dome, created from combined 30-m-resolution digital elevation model and 10-m-resolution aerial photograph. The geological contacts and structural features are derived from the lithological and structural map in A. Note that there is a slight decrease in dip angle from the supracrustal rocks to the sheeted zone and that the horizontal Mpuluzi sheet is overlying the NE-dipping layer-parallel sheets. The variation in dip angle is shown in more detail in Figure 5. (C) Sketch of a NE-SW cross section showing S1 in the Theespruit Formation, overlying in the Steynsdorp gneisses.

(A) Simplified lithological and structural map of the Steynsdorp dome. Imag... Available to Purchase

Published: 01 January 2010
is overlying the NE-dipping layer-parallel sheets. The variation in dip angle is shown in more detail in Figure 5 . (C) Sketch of a NE-SW cross section showing S1 in the Theespruit Formation, overlying in the Steynsdorp gneisses.
Image
(A) Simplified lithological and structural map of the Steynsdorp dome. Image in the background is an orthorectified, gray-scale aerial photograph, provided by the Council of Geosciences of South Africa. (B) Block diagram of the Steynsdorp dome, created from combined 30-m-resolution digital elevation model and 10-m-resolution aerial photograph. The geological contacts and structural features are derived from the lithological and structural map in A. Note that there is a slight decrease in dip angle from the supracrustal rocks to the sheeted zone and that the horizontal Mpuluzi sheet is overlying the NE-dipping layer-parallel sheets. The variation in dip angle is shown in more detail in Figure 5. (C) Sketch of a NE-SW cross section showing S1 in the Theespruit Formation, overlying in the Steynsdorp gneisses.

(A) Simplified lithological and structural map of the Steynsdorp dome. Imag... Available to Purchase

Published: 01 January 2010
is overlying the NE-dipping layer-parallel sheets. The variation in dip angle is shown in more detail in Figure 5 . (C) Sketch of a NE-SW cross section showing S1 in the Theespruit Formation, overlying in the Steynsdorp gneisses.
Journal Article

Exhumation of Mesoarchean TTG gneisses from the middle crust: Insights from the Steynsdorp core complex, Barberton granitoid-greenstone terrain, South Africa Available to Purchase

Cristiano Lana, Alex Kisters, Gary Stevens
Journal: GSA Bulletin
Published: 01 January 2010
GSA Bulletin (2010) 122 (1-2): 183–197.
DOI: https://doi.org/10.1130/B26580.1
...Figure 3. (A) Steynsdorp gneisses and layer-parallel leucogranite sheets. (B) Sharp tectonic contact between the Steynsdorp gneiss complex and the overlying amphibolite layers of the Theespruit Formation. The contact is exposed in a river section in NE sector of the dome. (C) Breccia-like clasts...
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View PDF for article title, Exhumation of Mesoarchean TTG <span class="search-highlight">gneisses</span> from the middle crust: Insights from the <span class="search-highlight">Steynsdorp</span> core complex, Barberton granitoid-greenstone terrain, South Africa
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Block diagrams illustrating tectonic burial and subsequent exhumation of the Theespruit Formation and Steynsdorp gneisses in the southern Barberton terrane. (A) Development of NE-verging thrusts during the 3230 Ma tectonic collision (D2), and burial of the Theespruit Formation (e.g., De Ronde and De Wit, 1994; Dziggel et al., 2002; Diener et al., 2005). Pressure-temperature (P-T) estimates (see text for details) indicate a 30–35 km depth of burial. Thickening of the crust resulted in vertical loading and horizontal stretching of lower-crustal levels. (B) Exhumation of the Theespruit Formation and underlying gneisses taking place along a NE-dipping extensional detachment. During this tectonic denudation, the midcrust was thinned to a point that it was no longer exposed in the southern Barberton terrane. The bulk coaxial flow and crustal extension were accommodated by normal faulting with top-to-the-NE extension at upper-crustal levels. We believe that exhumation of lower-crustal rocks and normal faulting of the upper crusts coincided with the deposition of the Moodies basins into host-and-graben structures. (C) Continued NE-SW extension leading to steepening of the preexisting structures, folding of the Moodies basin in the main greenstone belt, and development of an S2 fabric in the Steynsdorp anticline. TTG—trondhjemite-tonalite-granodiorite.

Block diagrams illustrating tectonic burial and subsequent exhumation of th... Available to Purchase

Published: 01 January 2010
Figure 8. Block diagrams illustrating tectonic burial and subsequent exhumation of the Theespruit Formation and Steynsdorp gneisses in the southern Barberton terrane. (A) Development of NE-verging thrusts during the 3230 Ma tectonic collision (D2), and burial of the Theespruit Formation (e.g
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Cathodoluminescence (CL) images of selected zircons from samples BA06-2 (Theespruit metavolcanic rock), BA06-3 (Steynsdorp Gneiss), SW06-2 (Ngwane Gneiss) and SW05-1 (Nhlangano Gneiss). Some grains show truncated zoning and embayments (e.g. SW06-2, upper right corner). Other characteristic features include the presence of inherited cores (e.g. SW06-2, upper centre) and fine oscillatory zoning (e.g. BA06-3, upper left corner). Circles (30 μm) indicate the location of trace elemental and U-Pb isotopic analysis by LA-ICPMS, and 207Pb/206Pb (common Pb corrected) dates and concordance are also indicated for each analytical spot. Two dates were obtained for some analytical spots where depth profiling identified distinct zircon domains, but only one date is shown.

Cathodoluminescence (CL) images of selected zircons from samples BA06-2 (Th... Available to Purchase

Published: 01 September 2021
Figure 2. Cathodoluminescence (CL) images of selected zircons from samples BA06-2 (Theespruit metavolcanic rock), BA06-3 (Steynsdorp Gneiss), SW06-2 (Ngwane Gneiss) and SW05-1 (Nhlangano Gneiss). Some grains show truncated zoning and embayments (e.g. SW06-2, upper right corner). Other
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(A–B) Garnets in clinopyroxene (cpx)-rich layers within metamafic rocks. These rocks have undergone boudinage, and, in some layers, garnet is preferentially developed as part of the assemblage in the boudin necks (see Fig. 6A). In these low-pressure domains, the peak metamorphic assemblage is grt + cpx + ep + cc + sph + q + pl. (C) Photograph illustrating the texture developed in association with fractures within garnet. Clinopyroxene (cpx) and epidote (ep) are recrystallized to slightly coarser-grained textures within and adjacent to the fractures. Garnet shows no evidence of retrogression within these sites of fluid saturation, and very small fragments of garnet are preserved in the quartz and calcite that have crystallized to fill the fracture. Thus, these garnet-bearing metamafic rocks contain clear evidence for garnet formation during extension and for the fact that the peak metamorphic assemblage was stable during extension. (D) An image of a scanned thin section showing a large (10–25 mm), zoned, syntectonic garnet porphyroblast developed in discrete layers of garnet-rich rocks of intermediate composition. In these rocks, the peak metamorphic assemblage is grt + hb + bt + pl + q + sph + ep. The foliation is defined by hornblende and biotite. The garnet crystals are texturally zoned with an inclusion-rich core and an inclusion-poor rim. (E) Fine-grained greenschist-facies assemblage in felsic schist that overlies the clinopyroxene-rich layers, some 20 m away from the contact with the Steynsdorp gneisses. (F) Chemical zonation in the large garnet crystals depicted in D, showing complex mineral chemical zonation that may constitute evidence for two metamorphic events (discussed in the text). The three zones marked by the white, dark-gray, and light-gray bands correspond to the core, intermediate core, and rim subdivisions in Table 1, respectively. (G) Average pressure-temperature (P-T) conditions of equilibration calculated for the intermediate core and rim-matrix assemblages, shaded in medium and light gray, respectively. Note that the matrix (higher pressure) and rim zone P-T conditions are identical (within error) and that the field of overlap lies within the field of plagioclase stability. There is no evidence in these rocks that plagioclase was not stable on the prograde path. The P-T conditions for meta-morphism determined for the Steynsdorp rocks are consistent with those determined for the other areas of the granitoid terrane to the south of the Barberton greenstone belt.

(A–B) Garnets in clinopyroxene (cpx)-rich layers within metamafic rocks. Th... Available to Purchase

Published: 01 January 2010
the contact with the Steynsdorp gneisses. (F) Chemical zonation in the large garnet crystals depicted in D, showing complex mineral chemical zonation that may constitute evidence for two metamorphic events (discussed in the text). The three zones marked by the white, dark-gray, and light-gray bands correspond
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U-Pb geochronological (common Pb uncorrected) and trace elemental data for five ablations of BA06-3 (3.51 to 3.50 Ga Porphyritic Gneiss – Steynsdorp Pluton). Colors represent degrees of discordance (%).

U-Pb geochronological (common Pb uncorrected) and trace elemental data for ... Available to Purchase

Published: 01 September 2021
Figure 5. U-Pb geochronological (common Pb uncorrected) and trace elemental data for five ablations of BA06-3 (3.51 to 3.50 Ga Porphyritic Gneiss – Steynsdorp Pluton). Colors represent degrees of discordance (%).
Journal Article

Gliding and overthrust nappe tectonics of the Barberton Greenstone Belt revisited: A review of deformation styles and processes Available to Purchase

M.J. Van Kranendonk
Published: 01 March 2021
South African Journal of Geology (2021) 124 (1): 181–210.
DOI: https://doi.org/10.25131/sajg.124.0017
... granitoid is the high strain, ca . 3 515 Ma Steynsdorp Gneiss, a strongly foliated granitoid sheet that, together with adjacent Onverwacht greenstones, was deformed within the core of the north-plunging Steynsdorp antiform, the axial plane of which is intruded by the small, 3 230 ± 1 Ma Vlakplaats...
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View PDF for article title, Gliding and overthrust nappe tectonics of the Barberton Greenstone Belt revisited: A review of deformation styles and processes
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Geochemistry of the Archaean Metavolcanic Rocks of Kolar and Hutti Gold Fields, Karnataka, India Available to Purchase

G. V. Ananta Iyer, V. N. Vasudev
Published: 01 September 1979
Jour. Geol. Soc. India (1979) 20 (9): 419–432.
DOI: https://doi.org/10.17491/jgsi/1979/200901
.... The meta basalts of Kolar and Hutti (Karnataka, South India), Norseman (Eastern Goldfields, Western Australia). Steynsdorp (Barberton, South Africa) and Yellowknife (Canada), plot within the field of mid-ocean ridge basalts (MORB). The marginal basin basalts (MBB) of South Sandwich Islands of Scotia Arc...
View PDF for article title, Geochemistry of the Archaean Metavolcanic Rocks of Kolar and Hutti Gold Fields, Karnataka, India
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Reply to “Paleo- to Mesoarchean polymetamorphism in the Barberton granite-greenstone belt, South Africa: Constraints from U-Pb monazite and Lu-Hf garnet geochronology on the tectonic processes that shaped the belt: Discussion” by M. Brown Available to Purchase

Kathryn A. Cutts, Gary Stevens, Alex Kisters
Journal: GSA Bulletin
Published: 01 November 2015
GSA Bulletin (2015) 127 (11-12): 1558–1563.
DOI: https://doi.org/10.1130/B31304.1
... A.F.M. Stevens G. , 2010 , Exhumation of Mesoarchean TTG gneisses from the middle crust: Insights from the Steynsdorp core complex, Barberton granitoid-greenstone terrain, South Africa : Geological Society of America Bulletin , v. 122 , p. 183 – 197 , doi:10.1130/B26580.1. Lana C...
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View PDF for article title, Reply to “Paleo- to Mesoarchean polymetamorphism in the Barberton granite-greenstone belt, South Africa: Constraints from U-Pb monazite and Lu-Hf garnet geochronology on the tectonic processes that shaped the belt: Discussion” by M. Brown
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Journal Article

Paleo- to Mesoarchean polymetamorphism in the Barberton Granite-Greenstone Belt, South Africa: Constraints from U-Pb monazite and Lu-Hf garnet geochronology on the tectonic processes that shaped the belt: Discussion Available to Purchase

Michael Brown
Journal: GSA Bulletin
Published: 01 November 2015
GSA Bulletin (2015) 127 (11-12): 1550–1557.
DOI: https://doi.org/10.1130/B31198.1
.... 465 – 481 , doi:10.1016/j.epsl.2007.05.046. Lana C. Kisters A.F.M. Stevens G. , 2010a , Exhumation of Mesoarchean TTG gneisses from the middle crust: Insights from the Steynsdorp core complex, Barberton granitoid-greenstone terrain, South Africa : Geological Society of America...
View PDF for article title, Paleo- to Mesoarchean polymetamorphism in the Barberton Granite-Greenstone Belt, South Africa: Constraints from U-Pb monazite and Lu-Hf garnet geochronology on the tectonic processes that shaped the belt: Discussion
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U–Pb and Hf isotope data of detrital zircons from the Barberton Greenstone Belt: constraints on provenance and Archaean crustal evolution Available to Purchase

Armin Zeh, Axel Gerdes, Christoph Heubeck
Published: 01 January 2013
Journal of the Geological Society (2013) 170 (1): 215–223.
DOI: https://doi.org/10.1144/jgs2011-162
... collages), which are characterized by distinct granitoid intrusion ages and isotope patterns. The Barberton South Terrane (definition of Zeh et al . 2009 ), comprising the Stolzburg, Steynsdorp and Swaziland subterranes (including large parts of the Onverwacht Group and Ancient Gneiss Complex, Fig. 1...
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View PDF for article title, U–Pb and Hf isotope data of detrital zircons from the Barberton Greenstone Belt: constraints on provenance and Archaean crustal evolution
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Paleo- to Mesoarchean polymetamorphism in the Barberton Granite-Greenstone Belt, South Africa: Constraints from U-Pb monazite and Lu-Hf garnet geochronology on the tectonic processes that shaped the belt Available to Purchase

Kathryn A. Cutts, Gary Stevens, J. Elis Hoffmann, Ian S. Buick, Dirk Frei, Carsten Münker
Journal: GSA Bulletin
Published: 01 March 2014
GSA Bulletin (2014) 126 (3-4): 251–270.
DOI: https://doi.org/10.1130/B30807.1
... of Mesoarchean TTG gneisses from the middle crust: Insights from the Steynsdorp core complex, Barberton granitoid-greenstone terrain, South Africa : Geological Society of America Bulletin , v. 122 , p. 183 – 197 , doi:10.1130/B26580.1 . Lana C. Tohver E. Cawood P. , 2010b , Quantifying...
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View PDF for article title, Paleo- to Mesoarchean polymetamorphism in the Barberton Granite-Greenstone Belt, South Africa: Constraints from U-Pb monazite and Lu-Hf garnet geochronology on the tectonic processes that shaped the belt
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Metamorphic evolution for the Inyoni shear zone: Investigating the geodynamic evolution of a 3.20 Ga terrane boundary in the Barberton granitoid greenstone terrane, South Africa Available to Purchase

K.A. Cutts, K.A. Maneiro, G. Stevens, E.F. Baxter
Published: 01 March 2021
South African Journal of Geology (2021) 124 (1): 163–180.
DOI: https://doi.org/10.25131/sajg.124.0009
... for crust formation between 3.5 and 3.7 Ga . Precambrian Research , 78 , 105 – 124 , doi: https://doi.org/10.1016/0301-9268(95)00072-0 Lana , C. , Kisters , A. and Stevens , G. , 2010 . Exhumation of Mesoarchean TTG gneisses from the middle crust: Insights from the Steynsdorp core...
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View PDF for article title, Metamorphic evolution for the Inyoni shear zone: Investigating the geodynamic evolution of a 3.20 Ga terrane boundary in the Barberton granitoid greenstone terrane, South Africa
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SHRIMP U-Pb zircon ages of granitoids from the Western Domain of the Kaapvaal Craton, Southeastern Botswana: implications for crustal evolution Available to Purchase

R.B.M. Mapeo, R.A. Armstrong, A.B. Kampunzu, L.V. Ramokate
Published: 01 June 2004
South African Journal of Geology (2004) 107 (1-2): 159–172.
DOI: https://doi.org/10.2113/107.1-2.159
... and Davis, 1994 Tonalite Gneiss, Baberton U-Pb zircon 3538+4–2 magmatic Kamo and Davis, 1994 Steynsdorp Pluton U-Pb zircon 3509+8–7 magmatic Kamo and Davis, 1994 Quartz Feldspar Porphyry U-Pb zircon 3458±8 magmatic Kamo and Davis, 1994 Stolzburg Pluton (olderb Phase) U-Pb...
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View PDF for article title, SHRIMP U-Pb zircon ages of granitoids from the Western Domain of the Kaapvaal Craton, Southeastern Botswana: implications for crustal evolution
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Palaeoarchaean TTGs of the Pilbara and Kaapvaal cratons compared; an early Vaalbara supercraton evaluated Available to Purchase

N.J. Gardiner, J.A. Mulder, C.L. Kirkland, T.E. Johnson, O. Nebel
Published: 01 March 2021
South African Journal of Geology (2021) 124 (1): 37–52.
DOI: https://doi.org/10.25131/sajg.124.0010
... high-grade gneiss terranes, which represent Archaean mid-continental crust, or low-grade granite-greenstone belts, which represent relic Archaean upper continental crust. The Palaeoarchaean East Pilbara Terrane (EPT), Pilbara Craton, Western Australia, and the Barberton Granite-Greenstone Belt (BGGB...
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View PDF for article title, Palaeoarchaean TTGs of the Pilbara and Kaapvaal cratons compared; an early Vaalbara supercraton evaluated
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