Earth’s Mantle Underwent a Dramatic Transformation 300 Million Years Ago
New research reveals a significant shift in the composition of Earth’s mantle, startingaround 300 million years ago, coinciding with the onset of modern plate tectonics and leading to global chemical heterogeneity.
The constant movement of tectonic plateson Earth’s surface, known as plate tectonics, plays a crucial role in shaping our planet. As plates collide, one dives beneath the other in a process calledsubduction, carrying crustal material deep into the Earth’s mantle. This process continuously alters the chemical composition of the convecting mantle, creating diverse mantle sources that have been extensively studied.
However, the extent to which Earth’sdynamic evolution has influenced the chemical composition of the convecting mantle, and when global chemical heterogeneity in the convecting mantle first emerged in Earth’s history, remained unclear.
Now, researchers from the Institute of Oceanology, Chinese Academy of Sciences(IOCAS), in collaboration with colleagues from Australia, Switzerland, and the United States, have addressed these questions through a comprehensive compilation of geochemical and isotopic data from intracontinental basalts over the past billion years. This study sheds light on the long-term cycle of Earth’s internal matter over geological timescales.
Published recently in Science Advances, the study reveals a dramatic shift in the composition of Earth’s mantle around 300 million years ago.
A Shift in Mantle Composition
Statistical analysis of the composition of intracontinental basalts revealed that basalts with enriched neodymium (Nd) isotopic characteristics (εNd\u003c 0) only appeared around 300 million years ago (Figure 1). This period coincides with the emergence of kimberlites, a type of rock that carries signatures of crustal material involvement (Figure 1). These findings suggest a global change in the composition of the convecting mantle.
Ancient Subduction Events
The paleogeographic locations of enriched intracontinental basalts and kimberlites indicate that mantle enrichment was not influenced by proximity to subduction zones (Figure 2). This led the researchers to propose that the enriched characteristics in these rocks originated from older, more distant subduction events.
Implications for Earth’s Evolution
This research provides compelling evidence for a significant change in Earth’s mantle composition around 300 million years ago. This shift, likely driven by ancient subduction events, has profound implications for understanding the evolution of our planet. It highlights the interconnectedness of Earth’s surface andinterior, and the long-term impact of tectonic processes on the composition and dynamics of the mantle.
References:
- Original Research: https://www.science.org/doi/10.1126/sciadv.adg8945
- SciTechDaily Article: https://scitechdaily.com/earth-mantle-underwent-a-dramatic-transformation-300-million-years-ago/
Figure Captions:
- Figure 1: εNdi in intracontinental basalts and kimberlites over the past billion years. Source: IOCAS
*Figure 2: Relationship between εNdi of intraplate magmas and subduction zone distance. Enriched plate
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