Jian-Feng Gao

Iron and sulfur isotope geochemistry serves as a powerful tool for probing diverse geological processes, spanning igneous, metamorphic, sedimentary, hydrothermal, and biological systems. Pyrite, a ubiquitous iron and sulfur-bearing mineral in various rock types and the predominant sulfide in hydrothermal ore deposits, is a common product throughout hydrothermal mineralization stages. The coupled Fe-S isotopic system in pyrite offers crucial constraints on fluid sources, fluid–rock interaction, and the physicochemical and redox conditions during mineral precipitation.In contrast to conventional bulk analytical methods, in situ microanalytical techniques—notably laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) and secondary ion mass spectrometry (SIMS, mainly for S isotopes)—permit to investigate Fe and S isotopic variations and fine-scale heterogeneity at high spatial resolution, which is essential for deciphering complex, multistage hydrothermal systems. The broader application of these techniques, however, is currently limited by the lack of matrix-matched reference materials with well-characterized Fe and S isotopic compositions.Here, we assess a natural pyrite sample (IGGPy-1) for its major-element and Fe–S isotopic homogeneity. Bulk analysis by elemental analyzer–isotope ratio mass spectrometry (EA-IRMS) yields a δ34SVCDT value of +17.09 ± 0.30‰. Solution-nebulization MC-ICP-MS (SN-MC-ICP-MS) gives δ56FeIRMM‑014 and δ57FeIRMM‑014 values of –1.31 ± 0.06‰ and –1.94 ± 0.12‰, respectively. These results position IGGPy-1 as a promising candidate reference material for in situ Fe–S isotopic microanalysis of pyrite.

水(H₂O)作为硅酸盐岩浆中含量最高的挥发分, 是控制火山喷发机制、地幔熔融行为及斑岩矿床形成的关键因素。但随着"超湿岩浆"(>6% H₂O)等现象的发现, 指示以往的岩浆H₂O含量估算方法可能还存在着许多问题, 准确测定岩浆的H₂O含量依旧是很大的挑战。本文系统综述了现有的岩浆H₂O含量估算方法的优势、劣势以及适用范围, 将其分为直接测量法和模型计算法两个方面进行讨论。直接测量法依赖研究对象的质量以及测试技术的进步, 基于火山玻璃和熔体包裹体, 通过FTIR、SIMS等技术可以对H₂O含量进行定量分析, 但易受脱气与扩散再平衡影响。模型计算法则更依赖模拟实验的设计、实验数据库的完整度以及统计学方法的合理运用, 如水溶解度模型可以建立H₂O溶解度与压力、温度及熔体成分的关系, 但温度、压力等热力学参数较高的不确定性制约了模型的精度, 而矿物-熔体平衡湿度计利用名义上无水矿物(NAMs)的氢分配系数或元素分配行为(如橄榄石ΔT法、斜长石Ca/Na交换等)进行热力学模型的构建, 但现有实验数据较少、矿物结构分析手段的不足等问题依然制约着模型精确度的进一步提高。随着测试技术的不断进步、实验数据库的进一步完善以及机器学习等人工智能方法的引进, 未来岩浆水含量估算方法还会有巨大突破, 为科学家探明全球水循环乃至挥发分循环问题做出关键贡献。

浪木日岩体位于东昆仑造山带东段, 是区域上目前唯一发现具有铂族元素(PGE)矿化的镁铁-超镁铁质岩体。岩体部分橄榄岩相及辉石岩相中金云母和角闪石含量高达5%~15%, 远高于该造山带内其他矿化岩体。本文针对浪木日岩体中的富水矿物, 通过对其矿物学特征及矿物化学成分进行系统研究, 对岩浆演化过程中的物理条件(温度、压力、氧逸度和水含量)和母岩浆成分进行约束, 并评价了富水矿物对浪木日岩体PGE富集及构造背景的指示意义。浪木日岩体中角闪石和金云母均为幔源岩浆成因, 角闪石种类为韭闪石、镁绿钙闪石、钙镁闪石和镁角闪石, 结晶温度区间为947~1029℃, 压力区间为403~586MPa, 侵位深度在12~16km之间。角闪石结晶时岩浆的含水量较高(3.6%~7.8%), 且具有较高的氧逸度(ΔNNO 0.21~1.91)。角闪石计算的岩体母岩浆成分表明母岩浆为富水的玄武质岩浆, 其微量元素含量相比造山带发育铜镍硫化物矿床的岩体总体较低, 并具有平坦的球粒陨石标准化稀土元素配分模式以及Nb-Ta-Zr-Hf亏损的特征。其矿物组合、富水矿物成分和母岩浆特征均与全球阿拉斯加型岩体类似。结合区域地质资料, 浪木日岩体应形成于原特提斯洋俯冲环境。其富水、高氧逸度的成矿母岩浆就位后较晚发生硫化物熔离, 可能是导致PGE富集成矿的关键机制。

This paper reports a new Os micro-distillation device made of glass. We call this glassware a glass conical vial (GCV). The bottom and cover top of the GVC are designed to be pointed in order to hold small droplets of 3–H₂O-baking procedure to clean the used GCV resulted in background levels of Os and Re below 0.37 and 0.36 pg, respectively, even though micro-distilled solutions in the GCV contained up to 750 ng or 350 ng of Os or Re, respectively. The new device has the advantages of high Os recovery, low Os and Re background, and easy cleaning, and is especially suitable for micro-distillation of samples with a low Os content.