{"id":{"repo_id":"cape-town","oai_identifier":"oai:open.uct.ac.za:11427/9239"},"canonical_url":"https://search.dev.ndltd.org/etd/cape-town/oai:open.uct.ac.za:11427/9239","repository":{"repo_id":"cape-town","name":"University of Cape Town","base_url":"https://open.uct.ac.za/oai/request"},"display":{"title":"Determining the physico-chemical conditions on the early earth : Barberton scientific drilling project, South Africa","abstract":"Low-grade metabasites and hydrothermally altered ultramafic rocks comprise most of the ca. 3.5-3.2 Ga, Paleoarchean Barberton Greenstone Belt (BGB) of South Africa. However, PT-constraints and detailed petrological information on the variably altered mafic-ultramafic rocks are sparse and the nature of greenschist facies metamorphism is poorly characterized. In addition, alteration and silicification associated with distinct emerald green, fuchsite-(Crmica)- carbonate-quartz alteration zones is commonly found beneath chert horizons in the mafic-ultramafic rocks of the Onverwacht Group of the BGB. The origin of this silicification is highly debated and has important bearing on the nature of Paleoarchean geodynamic models, crustal geothermal gradients, hydrothermal oceanic regimes, as well as potential early life-sustaining environments. Over the past four decades, widely varying interpretations have been reported for the origin of these silica-rich fuchsitic alteration zones in the BGB, ranging from very low temperature (less than 60oC) atmospheric weathering of komatiites (Lowe and Byerly, 1986; 1999); low-temperature (less than 125oC) seafloor alteration (Hofmann and Harris, 2008); to bedding-parallel ‘flaser-banded gneissesschists’ in oceanic ‘extensionaloverthrust glide planes’ (de Wit, 1982a; 1986a,b; de Wit et al., 1982b; 1987b; 2011). Consequently, these fuchsitic-alteration zones have been at the centre of much debate surrounding stratigraphy models and the possible operation of early Paleoarchean platetectonic processes in the BGB.","abstract_html":"Low-grade metabasites and hydrothermally altered ultramafic rocks comprise most of the ca. 3.5-3.2 Ga, Paleoarchean Barberton Greenstone Belt (BGB) of South Africa. However, PT-constraints and detailed petrological information on the variably altered mafic-ultramafic rocks are sparse and the nature of greenschist facies metamorphism is poorly characterized. In addition, alteration and silicification associated with distinct emerald green, fuchsite-(Crmica)- carbonate-quartz alteration zones is commonly found beneath chert horizons in the mafic-ultramafic rocks of the Onverwacht Group of the BGB. The origin of this silicification is highly debated and has important bearing on the nature of Paleoarchean geodynamic models, crustal geothermal gradients, hydrothermal oceanic regimes, as well as potential early life-sustaining environments. Over the past four decades, widely varying interpretations have been reported for the origin of these silica-rich fuchsitic alteration zones in the BGB, ranging from very low temperature (less than 60oC) atmospheric weathering of komatiites (Lowe and Byerly, 1986; 1999); low-temperature (less than 125oC) seafloor alteration (Hofmann and Harris, 2008); to bedding-parallel ‘flaser-banded gneissesschists’ in oceanic ‘extensionaloverthrust glide planes’ (de Wit, 1982a; 1986a,b; de Wit et al., 1982b; 1987b; 2011). Consequently, these fuchsitic-alteration zones have been at the centre of much debate surrounding stratigraphy models and the possible operation of early Paleoarchean platetectonic processes in the BGB.","abstract_has_math":false,"creators":["Grosch, Eugene Gerald"],"institution":"Department of Geological Sciences","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Richardson, Steve"],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011","date_published":"2011","updated_at":"2026-07-24T01:34:09Z","subjects":[],"languages":["eng"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/11427/9239","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Richardson, Steve"]},{"key":"dc:creator","label":"Author","values":["Grosch, Eugene Gerald"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2014-11-05T17:30:47Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2014-11-05T17:30:47Z"]},{"key":"dc:date.issued","label":"Date","values":["2011"]},{"key":"dc:publisher.department","label":"Dc Publisher Department","values":["Department of Geological Sciences"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["University of Cape Town"]},{"key":"dc:type","label":"Dc Type","values":["Doctoral Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["Doctoral"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["PhD"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["eng"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/11427/9239"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Includes bibliographical references (leaves 146-162)."]},{"key":"dc:description.abstract","label":"Abstract","values":["Low-grade metabasites and hydrothermally altered ultramafic rocks comprise most of the ca. 3.5-3.2 Ga, Paleoarchean Barberton Greenstone Belt (BGB) of South Africa. However, PT-constraints and detailed petrological information on the variably altered mafic-ultramafic rocks are sparse and the nature of greenschist facies metamorphism is poorly characterized. In addition, alteration and silicification associated with distinct emerald green, fuchsite-(Crmica)- carbonate-quartz alteration zones is commonly found beneath chert horizons in the mafic-ultramafic rocks of the Onverwacht Group of the BGB. The origin of this silicification is highly debated and has important bearing on the nature of Paleoarchean geodynamic models, crustal geothermal gradients, hydrothermal oceanic regimes, as well as potential early life-sustaining environments. Over the past four decades, widely varying interpretations have been reported for the origin of these silica-rich fuchsitic alteration zones in the BGB, ranging from very low temperature (less than 60oC) atmospheric weathering of komatiites (Lowe and Byerly, 1986; 1999); low-temperature (less than 125oC) seafloor alteration (Hofmann and Harris, 2008); to bedding-parallel ‘flaser-banded gneissesschists’ in oceanic ‘extensionaloverthrust glide planes’ (de Wit, 1982a; 1986a,b; de Wit et al., 1982b; 1987b; 2011). Consequently, these fuchsitic-alteration zones have been at the centre of much debate surrounding stratigraphy models and the possible operation of early Paleoarchean platetectonic processes in the BGB."]},{"key":"dc:title","label":"Title","values":["Determining the physico-chemical conditions on the early earth : Barberton scientific drilling project, South Africa"]}]}],"canonical_facts":{"dc:contributor.advisor":["Richardson, Steve"],"dc:creator":["Grosch, Eugene Gerald"],"dc:date.accessioned":["2014-11-05T17:30:47Z"],"dc:date.available":["2014-11-05T17:30:47Z"],"dc:date.issued":["2011"],"dc:description":["Includes bibliographical references (leaves 146-162)."],"dc:description.abstract":["Low-grade metabasites and hydrothermally altered ultramafic rocks comprise most of the ca. 3.5-3.2 Ga, Paleoarchean Barberton Greenstone Belt (BGB) of South Africa. However, PT-constraints and detailed petrological information on the variably altered mafic-ultramafic rocks are sparse and the nature of greenschist facies metamorphism is poorly characterized. In addition, alteration and silicification associated with distinct emerald green, fuchsite-(Crmica)- carbonate-quartz alteration zones is commonly found beneath chert horizons in the mafic-ultramafic rocks of the Onverwacht Group of the BGB. The origin of this silicification is highly debated and has important bearing on the nature of Paleoarchean geodynamic models, crustal geothermal gradients, hydrothermal oceanic regimes, as well as potential early life-sustaining environments. Over the past four decades, widely varying interpretations have been reported for the origin of these silica-rich fuchsitic alteration zones in the BGB, ranging from very low temperature (less than 60oC) atmospheric weathering of komatiites (Lowe and Byerly, 1986; 1999); low-temperature (less than 125oC) seafloor alteration (Hofmann and Harris, 2008); to bedding-parallel ‘flaser-banded gneissesschists’ in oceanic ‘extensionaloverthrust glide planes’ (de Wit, 1982a; 1986a,b; de Wit et al., 1982b; 1987b; 2011). Consequently, these fuchsitic-alteration zones have been at the centre of much debate surrounding stratigraphy models and the possible operation of early Paleoarchean platetectonic processes in the BGB."],"dc:identifier.uri":["http://hdl.handle.net/11427/9239"],"dc:language.iso":["eng"],"dc:publisher.department":["Department of Geological Sciences"],"dc:publisher.institution":["University of Cape Town"],"dc:title":["Determining the physico-chemical conditions on the early earth : Barberton scientific drilling project, South Africa"],"dc:type":["Doctoral Thesis"],"dc:type.qualificationlevel":["Doctoral"],"dc:type.qualificationname":["PhD"]},"updated_at":"2026-07-24T01:34:09Z"}