深部碳循环的锌同位素示踪研究进展

Advances on Application of Zinc Isotope as a Tracer for Deep Carbon Cycles

深部碳循环和地球表层的碳循环一起构成了全球的碳循环.因为地球超过90%的碳都位于深部,深部碳循环研究对于理解地球长期的气候变化具有重要的科学意义.深部碳循环研究涉及多个科学问题,其中最重要的科学问题之一是如何准确识别地幔中的碳是再循环的地表碳.锌作为亲石元素,广泛存在于岩浆岩、地幔和碳酸盐岩中.地幔和地表沉积碳酸盐岩之间锌同位素组成存在显著的差异,而板块俯冲脱水、地幔部分熔融和岩浆结晶分异等过程导致的锌同位素分馏较为有限,因此锌同位素具有示踪深部碳循环的潜力.系统阐述了锌同位素示踪深部碳循环的原理,回顾了目前应用锌同位素示踪深部碳循环取得的阶段性成果,并指出锌、镁同位素联合示踪有望成为未来深部碳循环研究的主流.

The deep carbon cycle and surface’s carbon cycle together constitute the global carbon cycle. Research on deep carbon cycles is of significance for understanding the long-term climate change of the Earth given that >90% of Earth’s carbon is stored in the deep Earth. Research on deep carbon cycles involves many aspects, among which one of the most important scientific issues is how to accurately identify recycled surface carbon in the mantle. Zinc(Zn) is a lithophile element and widely distributed in igneous rocks, mantle and sedimentary carbonates. There is a large Zn isotope difference between marine carbonates and the terrestrial mantle. Also, subduction-related dehydration, partial melting and magmatic differentiation only result in limited Zn isotope fractionation. Thus, Zn isotope has the potential as a novel tracer for deep carbon cycles. In this paper, the principle and potentiality of Zn isotope utilized as a tracer for deep carbon cycle are reviewed and the advances of using Zn isotope to trace deep carbon cycles in previous studies are presented. In addition, the combination between Zn and magnesium(Mg) isotopes is expect to the essential aspect of the deep carbon cycles in the future.