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报告题目：Geological Cycles and the Evolution of the Continental Crust

撰稿：发布时间：2015-05-30

各位老师、同学：您们好！
应王强研究员的邀请，英国圣安德鲁斯大学教授Chris Hawkesworth近期将访问我所，并将于7月8日（周三）上午 10：00做学术报告，欢迎大家参加。
报告题目：Geological Cycles and the Evolution of the Continental Crust
报告专家:Prof. Chris Hawkesworth
英国圣安德鲁斯大学教授
英国皇家学会院士
苏格兰皇家学会院士
中国科学院“国际杰出学者”
报告时间: 7月8日（周三）上午 10：00
报告地点: 标本楼1楼阶梯会议室

报告摘要：
Geological Cycles and the Evolution of the Continental Crust

The continental crust is the archive of Earth history, and the apparently cyclical nature of geological evolution is a feature of the geological record. The advent of radiometric ages has highlighted that the continental crust is characterised by distinctive peaks and troughs in the distribution of ages of igneous crystallization, metamorphism, continental margins and mineralization. It is argued that the temporal distribution largely reflects the different preservation potential of rocks generated in different tectonic settings, rather than fundamental pulses of activity, and the peaks of ages are linked to the timing of supercontinent assembly.

Less than 5% of the geological record consists of rocks older than 3 Ga, and there no known rocks older than 4 Ga. The sedimentary record is biased by preferential sampling of relatively young material in their source terrains. The implication is that there were greater volumes of continental crust in the Archaean than might be inferred from the compositions of detrital zircons and sediments. Recent studies based on the U-Pb, Hf and O isotope ratios of detrital zircons suggest that at least ~60-70% of the present volume of the continental crust had been generated by 3 Ga. The growth of continental crust was a continuous process, but there was a decrease in the rate of crustal growth at ~3 Ga. Before 3 Ga the rates of continental growth were high (~3.0 km3.yr-1), broadly similar to the rates at which new crust is generated and destroyed at the present time. Since 3 Ga the net growth rate was much lower (~0.8 km3.yr-1), perhaps because of higher rates of destruction of crustal materials. It is inferred that subduction-driven plate tectonics and discrete subduction zones have been dominant since ~3 Ga.

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报告题目：Geological Cycles and the Evolution of the Continental Crust

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