Petrology and geochemistry of clastic sedimentary rocks as evidences for provenance of the Late Palaeozoic Madzaringwe Formation, Tshipise-Pafuri Basin, South Africa

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• 作者：Ntokozo Malaza ; KuiWu Liu ; BaoJin Zhao
• 关键词：Tshipise ; Pafuri Basin ; Karoo Supergroup ; Sediment petrography ; Geochemistry ; Provenance ; Tectonic setting
• 刊名：Science China Earth Sciences
• 出版年：2016
• 出版时间：December 2016
• 年：2016
• 卷：59
• 期：12
• 页码：2411-2426
• 全文大小：
• 刊物主题：Earth Sciences, general;
• 出版者：Science China Press
• ISSN：1869-1897
• 卷排序：59

文摘

Petrography and geochemistry (major, trace and rare earth elements) of clastic rocks from the Late Palaeozoic Madzaringwe Formation, in the Tshipise-Pafuri Basin, Northern South Africa, have been investigated to understand their provenance. Sandstone petrography and detrital modes indicates that the Late Palaeozoic succession was derived from craton interior and recycled orogen provenance. Sandstones in the Madzaringwe Formation are sub-arkosic to sub-litharenite. The sediments may represent a recycled to craton interior provenance. The geochemical data of major elements show that sandstone and shales have the same source. The study of paleoweathering conditions based on modal composition, chemical index of alteration (CIA) and A-CN-K (Al₂O₃-CaO+Na₂O-K₂O) relationships indicate that probably chemical weathering in the source area and recycling processes have been more important in shale and sandstone rocks. The relatively high CIA values (70–90%) indicates moderate to high weathering conditions of the samples and the paleoclimate of the source area was warm. K₂O/Na₂O versus SiO₂ and Na₂O-CaO-K₂O tectonic setting discrimination plots, suggest a passive continental margin. In the study of trace elements, triangular Th-Sc-Zr/10 and La-Th-Sc plots both suggest a passive margin setting of the basin. Petrographic and geochemical results of the samples suggest uplifted basement source areas dominated by sedimentary rocks and/or granite-gneiss rocks. The source rocks might have been the recycled pre-Soutpansberg Karoo Supergroup rocks and the metasedimentary rocks of the Soutpansberg Group. Other source rocks may have been the pre-Beit-Bridge basement rocks (granites and gneisses).