近日，中国科学院地质与地球物理研究所翟明国报道了锆石扩散年代测定揭示了一个延长的古元古代造山带的短暂超高温变质作用。2025年12月29日出版的《地质学》杂志发表了这项成果。

超高温变质作用（≥900°C）代表了大陆地壳中最极端的热状态。这种条件是否如在某些显生宙造山带中观察到的那样，在前寒武纪时期以短暂脉冲形式（<1百万年）出现，目前仍未明确。

研究组综合运用相平衡模拟、温压计、高分辨率纳米二次离子质谱微量元素成像及锆石扩散模拟，对华北克拉通古元古代胶辽吉造山带中泥质麻粒岩的锆石进行分析。岩石记录了约850°C时约1.30 GPa的峰值压力，随后在减压过程中升温至≥940°C和约0.65 GPa，继而冷却至约600°C。锆石保留了具有振荡性Dy、Yb和Ti分带的太古代碎屑核，其外围增生约1.85 Ga的变质边。对碎屑核内这些元素剖面的扩散模拟显示，加热持续时间为0.02−0.62百万年，超高温状态驻留时间在0.05−1.3百万年之间，为古元古代存在超短时（约0.1百万年）超高温脉冲提供了首个坚实证据。

Ti分带研究进一步首次获得了地壳温度下天然锆石中Ti扩散速率的经验约束，显示其扩散速率比实验外推值快3至5个数量级。该事件与约1.85 Ga镁铁质侵入体的时空关联表明，瞬态地幔上涌是其热源。这些发现证明，活跃的古元古代壳幔相互作用产生了可与现代造山带相比的短期超高温事件，凸显了纳米二次离子质谱引导的锆石扩散年代学在解析前寒武纪热力学与构造过程时序方面的强大能力。

附：英文原文

Title: Zircon diffusion chronometry reveals brief ultrahigh-temperature metamorphism in a prolonged Paleoproterozoic orogen

Author: Yi Zou, Junxing Chen, Xu Chu, Lei Zhao, Jinghui Guo, Mingguo Zhai

Issue&Volume: 2025-12-29

Abstract: Ultrahigh-temperature (UHT) metamorphism (≥900°C) represents the most extreme thermal regime in the continental crust. Whether such conditions occurred as brief pulses (<1 m.y.) during the Precambrian, as observed in some Phanerozoic orogens, remains unresolved. Here we integrate phase equilibria modeling, thermobarometry, high-resolution nanoscale secondary ion mass spectrometry (NanoSIMS) trace-element mapping, and diffusion modeling in zircon from pelitic granulites in the Paleoproterozoic Jiao-Liao-Ji orogen, North China craton. The rocks record peak pressures of ～1.30 GPa at ～850°C, followed by heating during decompression to ≥940°C and ～0.65 GPa, and subsequent cooling to ～600°C. Zircons preserve Archean detrital cores with oscillatory Dy, Yb, and Ti zoning, overgrown by ca. 1.85 Ga metamorphic rims. Diffusion modeling of these elemental profiles within the detrital cores reveals heating durations of 0.020.62 m.y. and UHT residence times within 0.051.3 m.y., providing the first robust evidence for ultrafast (～0.1 m.y.) UHT pulses in the Paleoproterozoic. Ti zoning further yields the first empirical constraints on Ti diffusivity in natural zircon at crustal temperatures, showing rates three to five orders of magnitude faster than experimental extrapolations. The spatial and temporal links to ca. 1.85 Ga mafic intrusions suggest transient mantle upwelling as the heat source. These findings demonstrate that vigorous Paleoproterozoic crust-mantle interactions generated short-lived UHT events comparable to those in modern orogens, highlighting the power of NanoSIMS-guided zircon diffusion chronometry in resolving the tempo of Precambrian thermal and tectonic processes.

DOI: 10.1130/G53740.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G53740.1/723849/Zircon-diffusion-chronometry-reveals-brief