Basaltic lavas provide a window into their mantle sources and the associated geodynamic processes associated with them. Obtaining absolute chronology on young basalt flows is often challenging. Some gypsum crusts in pyro-duct (lava tube) caves crystallize during the last “cooling” stages of tube formation probably at relatively low temperatures (i.e., <100 °C). Here we propose uranium-series dating of these ‘speleogenetic’ gypsum crusts as a way to establish the ages of young basalt flows. We demonstrate the technique using cave crusts from four young basalt flows in El Malpais National Monument, New Mexico, three of which are moderately well-dated by alternative methods (¹⁴C, ³⁶Cl, and ³He ages). They all exhibit well-formed lava tube systems that contain gypsum crust speleothems interpreted to be remnant of the volcanic sulfur or sulfate processes when the tube systems were active during their terminal stages. δ¹⁸O_SO4, δ³⁴S, ⁸⁷Sr/⁸⁶Sr, and δ²³⁴U values for the gypsum crusts have near-basaltic signatures, and the crusts contain uranium concentrations suitable for uranium-series dating in three of these four basalt flows. Analyses of gypsum from caves of two well-dated basalt flows yielded uranium-series ages that agree with the ages determined by other techniques showing that absolute ages of young basalt flows can be achieved by this method. The fourth flow, the Hoya de Cibola basalt, previously undated by other absolute means has a U–Th gypsum crust isochron age of 16.9 ± 0.9 ka. The uranium-series age and isotopic analyses of these gypsum crusts should be useful in geologic applications involving young basalt flows.

玄武岩熔岩提供了进入其地幔源以及与之相关的相关地球动力学过程的窗口。要获得年轻玄武岩流的绝对年代，通常是有挑战性的。在管道形成的最后“冷却”阶段，热释药（熔岩管）洞中的一些石膏硬壳会结晶，可能是在相对较低的温度下（即<100°C）。在这里，我们建议对这些“造山型”石膏壳进行铀系列定年，以此来确定年轻玄武岩流的年龄。我们演示了使用新墨西哥州El Malpais国家纪念碑中的四个年轻玄武岩流的地壳的技术，其中三个通过替代方法（¹⁴ C，³⁶ Cl和³他老了）。它们都表现出结构良好的熔岩管系统，其中包含石膏底壳鞘脂，当该管系统在其末端阶段处于活动状态时，它们被解释为火山硫或硫酸盐过程的残余。δ ¹⁸ ø _SO4，δ ³⁴ S，⁸⁷ SR / ⁸⁶ Sr和δ ²³⁴石膏地壳的U值具有接近玄武岩的特征，地壳中的铀浓度适合于这四个玄武岩流中的三个中的铀系列测年。从两种日期合适的玄武岩流的洞穴中进行的石膏分析得出的铀系列年龄与其他技术确定的年龄一致，表明该方法可以实现年轻玄武岩流的绝对年龄。第四次流动，霍亚德西博拉玄武岩，以前通过其他绝对方式未打捞，U-Th石膏地壳的等时年龄为16.9±0.9 ka。这些石膏壳的铀系列年龄和同位素分析在涉及年轻玄武岩流的地质应用中应该是有用的。