Authigenic carbonate and barite crusts were analyzed from recently discovered cold seeps on the Lofoten-Vesterålen (LV) continental slope, northern Norway. Carbonate phases in these crusts are methane-derived Mg-calcite and aragonite. Scanning electron microscopy (SEM) was used to petrographically characterize cold seep crusts, and secondary ion mass spectrometry (SIMS) was used to measure the microscale sulfur isotope composition (${\delta }^{34}$S values) of authigenic barite. The mean ${\delta }^{34}$S_BaSO4 value from SIMS spot analyses is 70‰ (n = 303), significantly elevated with respect to seawater sulfate (∼21‰). The ${\delta }^{34}$S values can vary more than 40‰ within individual barite aggregates (< 250 μm) and more than 50‰ within cm-scale samples. ${\delta }^{34}$S_BaSO4 values in layered barite aggregates are most variable parallel to growth axes, with minimal variability in the perpendicular direction; fluctuations in ${\delta }^{34}$S_BaSO4 values along growth axes are inferred to record temporal changes in sulfate distillation during barite precipitation. In layered barite aggregates, ${\delta }^{34}$S_BaSO4 values frequently approach ∼90‰, but at these high ${\delta }^{34}$S values, barite dissolution features become increasingly prevalent and may reflect an upper limit for porewater ³⁴S_SO4 enrichment while maintaining barite saturation in this system. We suggest the primary forcing affecting sulfate distillation is varying activity of anaerobic oxidation of methane coupled to sulfate reduction (AOM-SR) due to temporal changes in cold seep methane flux. These findings provide the first semi-continuous geologic proxy for paleo-methane flux on the Lofoten-Vesterålen continental margin and suggest methane advection rates varied considerably over the course of carbonate-barite crust formation. In addition to systematic microscale changes in ${\delta }^{34}$S_BaSO4 values, periodic intra-aggregate dissolution features indicate a dynamic seepage environment with two or more periods of enhanced methane flux in recent geological history.

从最近在挪威北部 Lofoten-Vesterålen (LV) 大陆坡上发现的冷渗流中分析了自生碳酸盐和重晶石结壳。这些地壳中的碳酸盐相是甲烷衍生的镁方解石和文石。使用扫描电子显微镜 (SEM) 对冷渗结壳进行岩相学表征，并使用二次离子质谱法 (SIMS) 测量微尺度硫同位素组成。${\delta }^{34}$S 值）的自生重晶石。均值${\delta }^{34}$SIMS 现场分析的S _BaSO4值为 70‰ (n = 303)，相对于海水硫酸盐 (~21‰) 显着升高。这${\delta }^{34}$S 值在单个重晶石聚集体 (< 250 μm) 内变化超过 40‰，在厘米级样品内变化超过 50‰。 ${\delta }^{34}$层状重晶石聚集体中的S _BaSO4值在平行于生长轴的方向上变化最大，在垂直方向上的变化最小；波动${\delta }^{34}$推断沿生长轴的S _BaSO4值记录重晶石沉淀过程中硫酸盐蒸馏的时间变化。在层状重晶石聚集体中，${\delta }^{34}$S _BaSO4值经常接近 ~90‰，但在这些高${\delta }^{34}$S 值、重晶石溶解特征变得越来越普遍，并且可能反映了孔隙水³⁴ S _SO4富集的上限，同时保持该系统中的重晶石饱和。我们认为影响硫酸盐蒸馏的主要强迫是由于冷渗甲烷通量的时间变化而导致的甲烷厌氧氧化与硫酸盐还原 (AOM-SR) 耦合的不同活动。这些发现为 Lofoten-Vesterålen 大陆边缘的古甲烷通量提供了第一个半连续地质代理，并表明甲烷平流率在碳酸盐-重晶石地壳形成过程中变化很大。除了系统性的微观变化${\delta }^{34}$S _BaSO4值、周期性的骨料内溶解特征表明在最近的地质历史中具有两个或更多个时期的甲烷通量增强的动态渗流环境。