The Singhbhum Craton in India has well-preserved Palaeoarchaean greenstone belts, but their stratigraphic make-up is a mystery.
Cratons are fragments of ancient continents that existed billions of years ago. Their research sheds light on how processes within and on the surface of the Earth worked in the past. As they house a range of rock assemblages such as greenstones and granites, they preserve the vestiges of our young Earth.
Greenstones are rock assemblages composed mostly of submarine volcanic rocks with some sedimentary rocks. They are the most valuable archives for studying early Earth surface processes.
A new study published in Precambrian Research by a team of researchers led by Dr. Jaganmoy Jodder of the University of Witwatersrand’s Evolutionary Studies Institute shows that the Singhbhum Craton in India contains remarkably well-preserved volcanic and sedimentary rocks dating back as far as 3.5 billion years and that it has a geologic history similar to that of parts of South Africa and Australia.
Jodder and his colleagues evaluated the geology of the old greenstone rocks using thorough field surveys and exact Uranium-Lead (U-Lb) radiometric-age dating. The researchers used their findings to create crucial geological timelines showing the Daitari greenstones’ tectonic history.
Jodder said, “The Daitari greenstone belt shares a similar geologic make-up compared to the greenstones exposed in the Barberton and Nondweni areas of South Africa and those from the Pilbara Craton of north-western Australia.”
Submarine volcanic eruptions were prevalent between 3.5 and 3.3 billion years ago, and they have been preserved mainly as pillowed lava within the greenstones of the Singhbhum, Kaapvaal, and Pilbara cratons.
Submarine turbidity current deposits formed when the volcanic vent went under, yielding an age estimate for the sub-marine sedimentary rocks deposited roughly 3.5 billion years ago, based on exact detrital U-Pb zircon data.
Studies of ancient greenstones are significant for understanding the various volcanic processes and preserving minor sedimentary rocks that originated in sub-marine environments.
He said, “These volcano-sedimentary rocks provide clues related to habitable environments on the young Earth and can be regarded as time capsules to help us better understand the evolutionary tale of the planet in its early stages.”
Jodder and his colleagues suggest that these ancient continents were subjected to geologically similar activities 3.5 billion years ago.
He said, “However, we are not certain about their palaeo-geographic positioning. And thus, cannot validate that they once formed part of a supercontinent.”
He added, “The current research has led to a broader understanding of the ancient volcano-sedimentary rocks exposed in the Daitari area in India. This study resulted in unique recognition of felsic magmatic processes common to the Archaean cratons of India, South Africa, and Australia during the Palaeoarchaean times. It opens up newer avenues for research on early Earth processes.”