The Emergence of Global Continental Collision and the Onset of Massive Crustal Eclogitization

Academic Background

The evolution of Earth’s crust is closely related to the development of plate tectonics, particularly the compositional changes in continental crust, which provide key evidence for understanding the evolution of plate tectonics. However, uncertainties remain regarding the compositional changes in the lower crust, especially during the transition from the Proterozoic to the Phanerozoic. The differences in crustal composition between the Proterozoic and Phanerozoic, particularly the preservation and disappearance of mafic lower crustal layers, are critical issues in understanding the evolution of plate tectonics. By analyzing seismic profile data from 29 orogenic belts globally, this study reveals significant differences in crustal composition between the Proterozoic and Phanerozoic and proposes that the onset of global continental collision and eclogitization is the primary cause of this change.

Source of the Paper

This paper was co-authored by Bing Xia (China University of Geosciences), Irina M. Artemieva (Chinese Academy of Geological Sciences and GEOMAR Helmholtz Centre for Ocean Research, Germany), and Hans Thybo (Chinese Academy of Geological Sciences and Istanbul Technical University, Turkey). The paper was published online on October 18, 2024, in the journal Geology, with the DOI 10.1130/G52647.1.

Research Process and Results

1. Data Collection and Processing

The research team digitized seismic refraction/wide-angle reflection profiles from 29 orogenic belts globally, totaling over 18,000 kilometers. These profiles were sampled every 10 kilometers to ensure comprehensive and accurate data. Poor-quality seismic models were excluded to ensure data reliability.

2. Analysis of Crustal Velocity Structure

By analyzing the seismic P-wave velocity (Vp) structure, the research team linked crustal composition to Vp values. Experimental data show that crustal layers with Vp values between 6.8 and 7.4 km/s are typically mafic crustal layers (SiO2 content between 44% and 53%). The team found that Proterozoic orogenic belts generally preserve thick mafic lower crustal layers, whereas Phanerozoic orogenic belts lack this layer.

3. Changes in Crustal Composition

The research team found that the lower crust in Proterozoic orogenic belts accounts for 26% to 42% of the total crustal thickness, while in Phanerozoic orogenic belts, the lower crust thickness is significantly reduced, accounting for less than 7%. This change indicates a significant increase in SiO2 content in Phanerozoic crust, making the crust more felsic overall. The team attributes this change to widespread eclogitization during the Phanerozoic.

4. The Role of Eclogitization

Eclogite is a rock formed under high-pressure and low-temperature conditions, with a density typically higher than mantle peridotite. The research team proposes that continental collision and subduction during the Phanerozoic led to widespread eclogitization of the lower crust, triggering the delamination or dripping of high-density eclogite bodies. This process resulted in the large-scale recycling of mafic crustal material into the mantle, reducing the overall crustal density and causing the rise of continental crust, forming extensive continental areas.

5. The Modern Style of Plate Tectonics

The research team suggests that the formation and delamination of eclogite are key drivers of the modern style of plate tectonics. The formation of eclogite increases the downward pull on continental plates until the dense material is removed, creating a feedback mechanism. This process not only alters crustal composition but also promotes the rise of continents and the emergence of large land areas, leading to the Neoproterozoic Oxidation Event and the explosion of life in the Phanerozoic.

Conclusions and Significance

Through the analysis of global seismic profile data, this study reveals significant differences in crustal composition between the Proterozoic and Phanerozoic and proposes that the onset of global continental collision and eclogitization is the primary cause of this change. This research provides new evidence for understanding the evolution of plate tectonics and offers a new explanation for the formation of continents and the explosion of life in Earth’s history.

Highlights of the Research

1. Global Data Analysis: The research team systematically analyzed seismic profiles from 29 orogenic belts globally, providing comprehensive and reliable results.
2. Key Role of Eclogitization: The study is the first to propose the critical role of eclogitization in the compositional changes of Phanerozoic crust, offering a new perspective on the modern style of plate tectonics.
3. Link Between Crustal Composition and Life Evolution: The study reveals the close connection between changes in crustal composition and the formation of continents, the oxidation event, and the explosion of life in Earth’s history, with significant scientific implications.

Additional Valuable Information

The research team also notes that the formation and delamination of eclogite not only alter crustal composition but also affect the density structure of the mantle. The mantle density in Phanerozoic orogenic belts is significantly higher than in Proterozoic orogenic belts, a change that may be related to the remnants of eclogite. Additionally, the team proposes the rapid nature of the eclogitization process, suggesting that short-term tectonic events may promote the formation and delamination of eclogite.

By systematically analyzing global seismic data, this study reveals significant differences in crustal composition between the Proterozoic and Phanerozoic and highlights the key role of eclogitization in the modern style of plate tectonics. This research provides a new perspective on the formation of continents and the evolution of life in Earth’s history, offering significant scientific value.