Brittle tectonic evolution of Gondwana: implications for shale-gas and groundwater exploration

Abstract

Brittle structures are crucial for enabling several key natural processes in the Earth's Upper Crust. In addition, understanding the 3D characteristics and geological evolution of these features is equally important to support various developmental objectives, such as those, inter alia , linked to natural gas, groundwater, hydrothermal minerals and seismicity. In this study, we map various fractures of Gondwana based on the available geological information, satellite imagery and digital elevation data. The lengths and orientations of more than 10,000 fractures in their present-day position reveal four clearly defined patterns, with those striking NW being predominant. Archean-Paleoproterozoic domains are defined by fractures oriented N and NE, whereas the Mesoproterozoic has dominant NNW striking fractures. In contrast, the Neoproterozoic has mostly NE striking fractures and the Phanerozoic sequences are defined by a predominant NW and a subordinate W fracture patterns. The style and geometry of these structures can be linked to major geodynamic events that led to the formation of Gondwana building blocks during the Eburnean (ca. 2.2-1.8 Ga), Kibaran (ca. 1.4-1.0 Ga) and Pan African-Brasiliano (ca. 800-550 Ma) orogens, and amalgamation of Pangea (ca. 350-250 Ma). Many structures have been reactivated and new faults formed during opening of the Atlantic and Indian Oceans (ca. 180-120 ma), the India-Asia collision and rifting across East Africa since about 40 Ma. Although the changes in paleogeography remain difficult to model with accuracy, major structural orientations are corroborated by the occurrence of major mineral deposits and seismicity. The spatial distribution of mapped patterns across the different continent also correlate well with large shale gas prospects and increased groundwater yields. Thus, Gondwana fractures need to be considered in more detail for informing future development related to water and energy use, especially across regions of Africa.