中国地质大学刘盛遨团队近日发现，超高压大理岩中锌同位素揭示了大陆俯冲带碳守恒。2025年5月29日，《地质学》杂志发表了这一成果。

在地质时期，碳通过俯冲作用从地球表面转移到内部，调节了大气中的二氧化碳浓度。然而，与海洋俯冲带相比，大陆俯冲带的碳转移效率却鲜为人知。锌同位素是碳酸盐溶解的敏感指标，含c流体优先含重锌。

研究组对大陆俯冲形成的大别-苏鲁造山带超高压大理岩锌同位素进行了研究。与沉积原岩相比，方解石大理岩中锌浓度和同位素比值的耦合下降为溶蚀作用提供了直接证据，但方解石碳酸盐的溶蚀作用总体上几乎可以忽略不计。对于白云石大理岩，锌浓度升高和锌同位素比值降低表明溶解的碳酸盐在板内发生了强烈的再固定。

这些发现共同表明，碳酸盐岩在大陆地壳俯冲和随后的发掘过程中表现出保存行为。大陆地壳中绝大多数（>98%）的碳最终储存在被挖出的板块中，这表明大陆俯冲系统中的碳收支接近平衡，对全球碳通量的影响有限。相反，海洋俯冲带在地球外部和内部的碳转移中起着至关重要的作用。

附：英文原文

Title: Carbon conservation in continental subduction zones revealed by zinc isotopes in ultrahigh-pressure marbles

Author: Wan-Yu Sun, Sheng-Ao Liu

Issue&Volume: 2025-05-29

Abstract: Transfer of carbon from Earth’s surface into the interior via subduction regulates atmospheric CO2 concentrations over geologic time. The transfer efficiency of carbon in continental subduction zones, however, is less known than that in oceanic subduction zones. Zinc isotopes are a sensitive proxy of carbonate dissolution, with C-bearing fluids preferentially incorporating heavy zinc. We investigate zinc isotopes in ultrahigh-pressure marbles from the Dabie-Sulu orogenic belt formed via continental subduction. Coupled declines of zinc concentrations and isotope ratios in calcite marbles compared with their sedimentary protoliths provide direct evidence for dissolution, but the dissolution fraction of calcite carbonates, as a whole, is almost negligible. For dolomite marbles, the elevated zinc concentrations and decreased zinc isotope ratios indicate that dissolved carbonates underwent strong refixation within the slab. These findings collectively demonstrate that carbonates exhibit conservation behaviors during continental crust subduction and consequent exhumation. The vast majority (>98%) of carbon in continental crust is ultimately stored in the exhumed slabs, indicating that the carbon budget in continental subduction systems is nearly balanced and has limited impact on the global carbon flux. Instead, oceanic subduction zones play an essential role in carbon transfer between Earth’s exterior and interior.

DOI: 10.1130/G53258.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G53258.1/654868/Carbon-conservation-in-continental-subductionredirectedFrom=fulltext