Sedimentary Rocks from the Barberton Greenstone Belt, South Africa
Sedimentary rocks from the Barberton greenstone belt, South Africa
Abstract
The Barberton greenstone belt in South Africa represents one of the best preserved successions of Archaean rocks. The rock sequences have experienced low grade metamorphism, which makes them ideal to study because the effects of alteration and secondary minerals are relatively small. The sedimentary rocks of the Fig Tree Group obtained through the drilling project “Peering into the cradle of life” are analysed for their geochemical composition . This paper deals with previous research into the geochemical composition of the rocks which can indicate what the environment of deposition may have been. Thin sections of the rock samples have been analysed to define the rock types and mineral phases present. Janet van der Brug – 3665542 Undergraduate Honours Research Project 07-06-2013 The main goal of the research is to establish the environment of deposition using the geochemistry and petrology of the samples as an indication of the processes and conditions. This question leads to other, more detailed questions: is there any chemical trace of early life; what redox processes were going on in original rocks; are sediments affected by hydrothermal overprinting? To answer those questions, the following questions give the data for interpretation: what are the major and trace elements of the rock; what are the main minerals? In this paper, the background of the research and known environmental conditions will be discussed, along with research into the petrology of some thin sections taken from the cores. Some preliminary results from the geochemical analysis are included but will not be discussed. In the discussion tentative interpretations of the literature and results will be taken together.
1. Introduction
The Barberton greenstone Belt located in South Africa provides a window into the Archaean earth. This greenstone belt contains well preserved successions of mid-Archaean (3.5 -3.2 Ga)
Abstract
The Barberton greenstone belt in South Africa represents one of the best preserved successions of Archaean rocks. The rock sequences have experienced low grade metamorphism, which makes them ideal to study because the effects of alteration and secondary minerals are relatively small. The sedimentary rocks of the Fig Tree Group obtained through the drilling project “Peering into the cradle of life” are analysed for their geochemical composition . This paper deals with previous research into the geochemical composition of the rocks which can indicate what the environment of deposition may have been. Thin sections of the rock samples have been analysed to define the rock types and mineral phases present. Janet van der Brug – 3665542 Undergraduate Honours Research Project 07-06-2013 The main goal of the research is to establish the environment of deposition using the geochemistry and petrology of the samples as an indication of the processes and conditions. This question leads to other, more detailed questions: is there any chemical trace of early life; what redox processes were going on in original rocks; are sediments affected by hydrothermal overprinting? To answer those questions, the following questions give the data for interpretation: what are the major and trace elements of the rock; what are the main minerals? In this paper, the background of the research and known environmental conditions will be discussed, along with research into the petrology of some thin sections taken from the cores. Some preliminary results from the geochemical analysis are included but will not be discussed. In the discussion tentative interpretations of the literature and results will be taken together.
1. Introduction
The Barberton greenstone Belt located in South Africa provides a window into the Archaean earth. This greenstone belt contains well preserved successions of mid-Archaean (3.5 -3.2 Ga)
References: A. Hofmann. Accepted 1 September 2005. The geochemistry of sedimentary rocks from the Fig Tree group, Barberton greenstone belt: implications for tectonic, hydrothermal and surface processes during mid-Archaean times. Precambrian research 143 (2005), p. 23 – 49. 14 Appendices Appendix 1. Stratigraphy of the Swaziland supergroup. Hofmann 2005 15