The latest study, published in Science Advances on Aug. 14, explores the complex relationship between Earth's evolving mantle, crust, and tectonic processes over time. It also sheds light on key questions regarding the onset of plate tectonics, the operation of subduction dynamics billions of years ago, and the development of Earth's crust.
Led by Duncan Keller and Cin-Ty Lee from Rice University, the research team focused on studying the Marcy and Morin anorthosites, well-known examples from North America's Grenville orogen, which are approximately 1.1 billion years old. The team aimed to test hypotheses about the magmatic processes responsible for these formations.
Through the analysis of isotopes of boron, oxygen, neodymium, and strontium in the rocks, coupled with petrogenetic modeling, the researchers discovered that the magmas responsible for these anorthosites were enriched with melts derived from oceanic crust that had been altered by seawater at low temperatures. Additionally, they identified isotopic signatures typical of subduction zone rocks, such as abyssal serpentinite.
"Our research indicates that these giant anorthosites likely originated from the extensive melting of subducted oceanic crust beneath convergent continental margins," said Keller, the Clever Planets Postdoctoral Research Associate, Earth, Environmental and Planetary Sciences and the study's lead author. "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."
The study, which incorporates traditional approaches with the innovative use of boron isotopic analysis in studying massif-type anorthosites, suggests that these rocks were formed during intense subduction conditions that may have been common billions of years ago.
As massif-type anorthosites no longer form on Earth today, the new findings linking these formations to high-temperature subduction in Earth's early history open new avenues for interdisciplinary research into how these rocks document the physical changes of our planet over time.
"This research advances our understanding of ancient rock formations and sheds light on the broader implications for Earth's tectonic and thermal history," said Lee, the Harry Carothers Wiess Professor of Geology, professor of Earth, environmental and planetary sciences and study co-author.
The study's co-authors include William Peck from Colgate University's Department of Earth and Environmental Geosciences; Brian Monteleone from the Department of Geology and Geophysics at Woods Hole Oceanographic Institution; Celine Martin from the American Museum of Natural History's Department of Earth and Planetary Sciences; Jeffrey Vervoort from the School of the Environment at Washington State University; and Louise Bolge from the Lamont-Doherty Earth Observatory at Columbia University.
Research Report:Mafic slab melt contributions to Proterozoic massif-type anorthosites
Related Links
Rice University
Explore The Early Earth at TerraDaily.com
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