A team from Rice University and collaborators uncovered the origins of massif-type anorthosites, linking these ancient rock formations to early Earth’s subduction processes and thermal dynamics.
Researchers led by Rice University have made significant progress in solving one of geology’s enduring mysteries — the origins of massif-type anorthosites. These enigmatic rock formations, rich in plagioclase feldspar, predominantly formed during Earth’s Proterozoic Eon and have long puzzled scientists due to conflicting theories about their creation.
A groundbreaking study, published in Science Advances, delves into the connections between Earth’s evolving mantle and crust, providing fresh perspectives on the early tectonic forces that shaped our planet. The findings offer new avenues for exploring when plate tectonics commenced, the dynamics of ancient subduction zones and the development of Earth’s crust over billions of years.
Led by Duncan Keller and Cin-Ty Lee from Rice University, the research team focused on studying the Marcy and Morin anorthosites, prominent examples from North America’s Grenville orogen dating back approximately 1.1 billion years. By examining isotopes of boron, oxygen, neodymium and strontium in these rocks and conducting petrogenetic modeling, the team decoded vital clues about their formation.
“Our research indicates that these giant anorthosites likely originated from the extensive melting of subducted oceanic crust beneath convergent continental margins,” Keller, a postdoctoral researcher at Rice University, said in a news release. “Because the mantle was hotter in the past, this process directly connects the formation of massif-type anorthosites to Earth’s thermal and tectonic evolution.”
This study, supported by NASA and the U.S. National Science Foundation, uniquely combines classical methods with the innovative application of boron isotopic analysis to comprehend massif-type anorthosites. The research suggests these rock formations emerged from exceptionally hot subduction processes prevalent billions of years ago. This significant revelation enhances our understanding of ancient rock formations and their role in chronicling Earth’s physical evolution.
“This research advances our understanding of ancient rock formations and sheds light on the broader implications for Earth’s tectonic and thermal history,” added Lee, the Harry Carothers Wiess Professor of Geology at Rice University.
The collaborative effort also included contributors from institutions such as Colgate University, Woods Hole Oceanographic Institution, the American Museum of Natural History, Washington State University and Columbia University’s Lamont-Doherty Earth Observatory.
By extending our knowledge about the origins of these massive anorthosite formations, this research not only resolves longstanding geological debates but also opens new interdisciplinary pathways for exploring Earth’s early history and its dynamic geological processes.