近日，美国伍兹霍尔海洋研究所Jeffrey S. Seewald团队研究了Von Damm热液喷口区碳酸盐和镁硅酸盐置换的千年周期。2025年5月20日，《地质学》杂志发表了这项成果。

加勒比海中开曼隆起的冯达姆热泉（VDVF）在现代热液系统中是独一无二的，因为“烟囱”和土丘几乎完全由滑石组成。

研究组分析了2020年收集的样品，并报告说，除了可变结晶度的无序滑石外，碳酸盐也是VDVF的主要矿物。碳酸盐矿物包括文石、方解石、富镁方解石和白云石。滑石和碳酸盐矿物结构表明，它们不是代替火山宿主岩石，而是由海底热液和海水的混合沉淀而成，出现在烟囱和周围的碎石中。这种矿物组合的交替沉淀是普遍存在的，碳酸盐矿物通常由滑石接替，并且有迹象表明，在某些情况下，滑石和碳酸盐矿物相互取代。

稳定碳同位素数据表明，碳酸盐矿物来源于海水和热液的混合作用，U-Th数据支持了这一观点。放射性碳方解石年龄和滑石²³⁴U-²³⁰Th等时线年龄表明，矿物年龄跨越10万年至数十年。对这些样本的分析表明，在数千年的时间尺度上，从碳酸盐主导的降水转变为镁硅酸盐主导的降水的动态系统。该观察提出了关于海底沉淀物最终命运的问题，以及在这种环境中的碳酸盐和硅酸盐矿物是否被隔离并在岩石记录中得到体现。

附：英文原文

Title: Kiloyear cycles of carbonate and Mg-silicate replacement at Von Damm hydrothermal vent field

Author: Amy Gartman, Terrence Blackburn, Kiana L. Frank, Susan Q. Lang, Jeffrey S. Seewald

Issue&Volume: 2025-05-20

Abstract: The Von Damm vent field (VDVF) on the Mid-Cayman Rise in the Caribbean Sea is unique among modern hydrothermal systems in that the chimneys and mounds are almost entirely composed of talc. We analyzed samples collected in 2020 and report that in addition to disordered talc of variable crystallinity, carbonates are a major class of mineral at VDVF. The carbonate minerals include aragonite, calcite, magnesium-rich calcite, and dolomite. Talc and carbonate mineral textures indicate that, rather than replacing volcanic host rock, they precipitate from the mixing of hydrothermal fluids and seawater at the seafloor, occurring in chimneys and surrounding rubble. Alternating precipitation of this mineral assemblage is pervasive, with carbonate minerals typically being succeeded by talc, and with indications that in some cases talc and carbonate minerals replace one another. Stable carbon isotopic data indicate the carbonate minerals originate from the mixing of seawater and hydrothermal fluid, which is supported by U-Th data. Radiocarbon calcite ages and talc 234U-230Th isochron ages indicate mineral ages spanning over thousands to tens of thousands of years. Analyses of these samples illustrate a dynamic system that transitions from carbonate-dominated to Mg-silicatedominated precipitation over time scales of thousands of years. Our observations raise questions regarding the eventual fate of seafloor precipitates and whether carbonate and silicate minerals in such settings are sequestered and represented in the rock record.

DOI: 10.1130/G53228.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G53228.1/654494/Kiloyear-cycles-of-carbonate-and-Mg-silicate