近日，英国朴茨茅斯大学Catherine M. Mottram及其团队利用U-Pb碳酸盐定年法追踪斑岩—浅成热液成矿的转变。这一研究成果发表在2024年7月3日出版的国际学术期刊《地质学》上。

来自加拿大Yukon地区一个受断层控制的斑岩—浅成热液系统的41个新的U-Pb测年结果，揭示了一个大于50m.y.碳酸盐沉积记录，大约在ca.77和19Ma之间，结果支持了一个脉冲式、偶发性流体流动模型，而不是一个单一的演化系统。浅成热液碳酸盐沉淀在ca.74-67Ma与白垩纪与斑岩有关的岩浆活动同时发生，且明显晚于白垩纪。

发生在ca.62-56 Ma，ca.51-47Ma和小于40Ma的叠加事件不是原生金属沉积的原因，但可能有助于金属富集。碳酸盐岩年代与角砾岩化作用和断层滑动时期一致。因此，断层运动通过浅成热液矿化、金属的迁移和(再)富集金属实现了幕式叠加。本研究对长期岩浆热液系统的全面重建追踪了从斑岩到浅成热液环境的转变，结果强调了碳酸盐U-Pb定年在关键矿物研究中的作用。

据悉，对绿色能源转换至关重要的关键金属在岩浆—热液过程中富集。在斑岩矿床中，浅成热液成矿可以叠加在更早期的高温体系之上。目前还不清楚矿化是发生在一个单一的演化系统中，还是在脉冲式、幕式叠加事件中形成。因此，流体流动的时间和持续时间仍然是矿床模型中关键的数据缺口，但它们是理解金属(再)迁移和富集过程的重要因素。碳酸盐是流体流动过程中沉淀的常见脉石矿物，可以用U-Pb法对其进行定年，从而直接对热液过程进行定年。

附：英文原文

Title: Tracking the porphyry-epithermal mineralization transition using U-Pb carbonate dating

Author: Catherine M. Mottram, Dawn A. Kellett, Tony Barresi, Glenn G. Chapman, Jesse Halle

Issue&Volume: 2024-07-03

Abstract: Key metals important for the green energy transition concentrate during magmatic-hydrothermal processes. In porphyry deposits, epithermal mineralization can overprint earlier higher-temperature systems. It is not well understood whether mineralization occurs in a single evolving system or forms during pulsed, episodic overprinting events. The timing and duration of fluid flow therefore remain key data gaps in deposit models, but they are essential factors for understanding metal (re)mobilization and concentration processes. Carbonates are common gangue minerals that precipitate during fluid flow and can be dated using the U-Pb method, thereby directly dating hydrothermal processes. Here, 41 new U-Pb dates from a fault-controlled porphyry-epithermal system in Yukon, Canada, reveal a >50 m.y. record of carbonate precipitation between ca. 77 and 19 Ma. Results support a model of pulsed, episodic fluid flow, rather than a single evolving system, where epithermal carbonate precipitation at ca. 74-67 Ma was both coeval with and significantly postdated Cretaceous porphyry-related magmatism. Overprinting events at ca. 62-56 Ma, ca. 51-47 Ma, and younger than 40 Ma were not responsible for primary metal deposition but may have contributed to metal enrichment. Carbonate dates coincide with periods of brecciation and fault slip. Fault movement therefore enabled episodic overprinting by epithermal mineralization, mobilizing and (re)concentrating metals. This comprehensive reconstruction of a long-lived magmatic-hydrothermal system tracks the transition from porphyry to epithermal environments, demonstrating the power of carbonate U-Pb dating for critical minerals research.

DOI: 10.1130/G52211.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G52211.1/645289/Tracking-the-porphyry-epithermal-mineralization