Identifying Gaps in the Investigation of the Vredefort Granophyre Dikes: A Systematic Literature Review

Elizaveta Kovaleva,Matthew S. Huber

doi:10.3390/geosciences10080306

Abstract

The Vredefort impact structure is among the oldest and largest impact structures preserved on Earth. An understanding of its key features can serve as a guide for learning about the development of basin-sized impact structures on Earth and other planetary bodies. One of these features is the so-called Vredefort granophyre dikes, which formed when molten material from the impact melt sheet was emplaced below the crater floor. The importance of these dikes has been recognized since the earliest studies of the Vredefort structure, nearly 100 years ago. The present study is a systematic literature review to determine the extent to which peer-reviewed scientific publications have generated unique data regarding the granophyre dikes and to investigate how scientific methods used to investigate the granophyre have changed over time. In total, 33 unique studies have been identified. Of those, more studies have been performed into the core-collar dikes than the core dikes. The majority of the studies have focused on field analyses, bulk geochemistry, and the studies of mineral components. The granophyre has long been recognized as a product of post-deformational processes and thus has been a target of age dating to constrain the minimum age of the impact event. In the last 25 years, studies of stable isotopes and shock deformation of minerals in lithic clasts within the dikes have taken place. A small number of geophysical studies relevant to the granophyre dikes have also been undertaken. Overall, there has been a relatively small number of studies on this important rock type, and the studies that have taken place tend to focus on two particular dikes. Several of the dikes have only been investigated by regional studies and have not been specifically targeted. The use of modern techniques has been lacking. More fieldwork, as well as geophysical, isotopic, microstructural studies, and application of novel techniques, are necessary for the granophyre dikes to be truly understood.

Highlights

Impact cratering is a fundamental process in the Solar System, with impact craters being abundant on the surfaces of the vast majority of terrestrial bodies that have been observed (e.g., [1])
The types of research on the granophyre dikes have changed over time
The early work on the granophyre focused on the basic properties of the dikes, such as field mapping, petrography, and bulk geochemistry

Summary

Introduction

Impact cratering is a fundamental process in the Solar System, with impact craters being abundant on the surfaces of the vast majority of terrestrial bodies that have been observed (e.g., [1]). The process of impact cratering results in such effects as structural deformation, shock metamorphism, melting, and vaporization of the target materials [2]. Basin-forming impact events cause sufficient melting to form voluminous melt sheets that can be up to several kilometers thick [2]. On terrestrial bodies, such as the Moon or Mars, large multi-ring basins with melt sheets are selected for scientific exploration missions (e.g., [3]). The three structures have a different level of exposure and preservation state, which makes them complementary to each other in terms of developing our understanding of impact events, and allows us to study different aspects of Geosciences 2020, 10, 306; doi:10.3390/geosciences10080306 www.mdpi.com/journal/geosciences

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