Bhopal, July 23: A rare granite formation in Madhya Pradesh’s Pichhore region has been dated to approximately 2.56 billion years old, making it the second oldest known orbicular granite formation in the world according to a new international study.
The research, conducted by scientists from Banaras Hindu University, IIT Kanpur, the University of Campinas (Brazil), the Japan Advanced Institute of Science and Technology, IISER Berhampur and AllGeo Solutions Pvt. Ltd., examined the Pichhore orbicular granite near Kutawali village in the Bundelkhand Craton.
Researchers found that the granite contains distinctive spherical structures, known as orbicules, formed by rapid crystallisation during a sudden thermal pulse in a prehistoric magma chamber. These structures, some measuring up to 30 centimetres in diameter, preserve evidence of geological processes that occurred during the Neoarchean era, when Earth’s continental crust was beginning to stabilise.
Using uranium lead (U-Pb) zircon dating, the team determined the granite crystallised around 2.56 billion years ago. The analysis also identified inherited zircon grains dating back 3.5 billion years, indicating that ancient continental crust was already being recycled to form new landmasses during Earth’s early history.
The study provides new insights into the geological evolution of the Bundelkhand Craton and confirms that the magma originated from melting existing continental crust rather than directly from the Earth’s mantle.
Researchers noted that the site designated a national geoheritage site, is vulnerable to agricultural expansion and called for stronger conservation measures to protect the globally significant geological formation. They said preserving the Pichhore granite is essential for understanding the evolution and stabilisation of Earth’s early continental crust.