In a recent collaboration, Dr. Wang Jian, postdoctoral fellow at the Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, along with Research Professor Tang Gongjian and Wang Qiang, utilized Zn-Mo isotopic tracing to uncover crucial details of the fate of subducted carbonate in the mantle, shedding light on the deep carbon cycling process. The findings were published in the Geophysical Research Letters.
Using Zn-Mo isotopic tracing to investigate the fate of subducted carbonates in the mantle. Image provided by the interviewee.
Understanding the carbon cycle on Earth is crucial for grasping the origins of life, geological processes, and climate change. Researching the carbon cycle is not only fundamental to shaping a habitable Earth but also aligns with the imperative of carbon neutrality policies. The majority of Earth's carbon is stored in surface sedimentary carbonates and can be subducted into the Earth's interior along convergent plate boundaries. Scientists have long been exploring the fate and impact of subducted carbonates.
For the first time, a systematic study of the Zn-Mo isotopic composition of Cenozoic continental intraplate alkaline basalts in the Tarim region of western China reveals that both western and eastern China's Cenozoic volcanic rocks contain Zn-Mo isotopic compositions higher than those of normal mantle, indicating the presence of recycled carbonate components in these volcanic rock source regions. Simulation results suggest that the source regions of these volcanic rocks may have formed from the melting of oceanic crust containing less than 5% carbonate.
Despite geophysical data indicating no stranded oceanic slab in western China, compositional anomalies suggest the presence of ancient recycled carbon-bearing altered oceanic crustal components. These components may be retained near the mantle transition zone and have participated in the formation of Cenozoic volcanic rocks in western China.
By comparing with Cenozoic basalts in eastern China, this study constrains the depths in the mantle reached by subducted carbonates and their ultimate fate. It also provides new insights into the formation of intraplate volcanic rocks and reveals crucial details of deep carbon cycling processes.
This research was supported by the Second Tibetan Plateau Scientific Expedition and Research Program (STEP), Major Science and Technology Projects of Xinjiang Province, the National Natural Science Foundation of China for Young Scientists, and the Postdoctoral Fund.
Related paper information: https://doi.org/10.1029/2023GL105208
