Abstract Melt inclusions record the depth of magmatic processes, magma degassing paths, and volatile budgets of magmas. Extracting this information is a major challenge. It requires determining melt volatile contents at the time of entrapment when working with melt inclusions that have suffered post-entrapment modifications. Several processes decrease internal melt inclusion pressure, resulting in nucleation and growth of a vapor bubble and, time permitting, diffusion of volatiles (especially CO2) into the vapor bubble. Previous studies have shown how this process may lead to most of the CO2 in the bulk melt inclusion being lost to the bubble. Without reconstruction, most of the melt inclusion data in the literature vastly underestimate the CO2 concentrations of magmas by measuring the glass phase only. Methods exist that attempt to reconstruct the entrapped CO2 contents, but they can be difficult to apply and do not always yield consistent results. Here, we explore bubble growth, evaluate CO2 reconstruction approaches, and develop improved experimental and computational approaches. Piston-cylinder experiments were conducted on olivine-hosted melt inclusions from Seguam (Alaska, U.S.A.) and Fuego (Guatemala) volcanoes at the following conditions: 500–800 MPa, 1140–1200 °C for Seguam and 1110–1140 °C for Fuego, 4–8 wt% H2O in the KBr brine filling the experimental capsules, and run durations of 10–120 min. Heated melt inclusions form well-defined S-CO2 trends consistent with degassing models. CO2 contents are enriched by a factor of ~2.5, on average, relative to those of the glasses in unheated melt inclusions, whereas S contents of heated and unheated melt inclusion glasses overlap, indicating that insignificant amounts of S partition into the vapor bubble. For naturally quenched melt inclusions, relatively low closure temperatures for CO2 diffusion enables some CO2 to enter vapor bubbles during quench, whereas higher closure temperatures for S diffusion limits its loss to vapor bubbles. We evaluate the timescales of post-entrapment processes and use the results to develop a new computational model to restore entrapped CO2 contents: melt inclusion modification corrections (MIMiC). Heated melt inclusion data are used as a benchmark to evaluate the results from MIMiC and other published methods of CO2 reconstruction. The methods perform variably well. Key advantages to our experimental technique are accurate measurements of CO2 contents and efficient rehomogenization of large quantities of melt inclusions. Our new computational model produces more accurate results than other computational methods, has similar accuracy to the Raman method of CO2 reconstruction in cases where Raman can be applied (i.e., no C-bearing phases in the bubble), and can be applied to the vast body of published melt inclusion data. To obtain the most robust data on bubble-bearing melt inclusions, we recommend taking both experimental- and MIMiC-based approaches.

中文翻译：

---

橄榄石熔体包裹体中的汽泡生长

摘要 熔体包裹体记录了岩浆过程的深度、岩浆脱气路径和岩浆的波动收支。提取这些信息是一项重大挑战。在处理夹带后发生变化的熔体夹杂物时，需要确定夹带时的熔体挥发物含量。几个过程会降低内部熔体夹杂物压力，导致蒸汽泡的成核和生长，并且在时间允许的情况下，挥发物（尤其是 CO2）扩散到蒸汽泡中。先前的研究表明，这个过程可能会导致大量熔体包裹体中的大部分 CO2 流失到气泡中。如果没有重建，文献中的大部分熔体包裹体数据仅通过测量玻璃相就大大低估了岩浆的 CO2 浓度。存在尝试重建截留的 CO2 含量的方法，但它们可能难以应用并且并不总是产生一致的结果。在这里，我们探索气泡生长，评估 CO2 重建方法，并开发改进的实验和计算方法。在以下条件下对来自 Seguam（美国阿拉斯加州）和 Fuego（危地马拉）火山的橄榄石熔体包裹体进行了活塞缸实验：Seguam 为 500-800 MPa，Seguam 为 1140-1200 °C，Fuego 为 1110-1140 °C , 填充实验胶囊的 KBr 盐水中的 4–8 wt% H2O，运行时间为 10–120 分钟。加热的熔体夹杂物形成与脱气模型一致的明确定义的 S-CO2 趋势。相对于未加热熔体夹杂物中的玻璃，CO2 含量平均增加约 2.5 倍，而加热和未加热的熔体夹杂物玻璃的 S 含量重叠，表明少量的 S 分配到蒸汽泡中。对于自然淬火的熔体夹杂物，相对较低的 CO2 扩散闭合温度使一些 CO2 在淬火过程中进入蒸气泡，而较高的 S 扩散闭合温度限制了其向蒸气泡的损失。我们评估了截留后过程的时间尺度，并使用结果开发了一个新的计算模型来恢复截留的 CO2 含量：熔体夹杂物改性校正 (MIMiC)。加热的熔体夹杂物数据被用作评估 MIMiC 和其他已发表的 CO2 重建方法的结果的基准。这些方法的表现各不相同。我们的实验技术的主要优势是准确测量 CO2 含量和大量熔体夹杂物的有效再均化。我们的新计算模型比其他计算方法产生更准确的结果，在可以应用拉曼的情况下（即气泡中没有含 C 相）与 CO2 重建的拉曼方法具有相似的精度，并且可以应用于大量已发布的熔体夹杂数据的主体。为了获得有关含气泡熔体夹杂物的最可靠数据，我们建议同时采用基于实验和基于 MIMiC 的方法。气泡中没有含碳相），并且可以应用于大量已发表的熔体夹杂物数据。为了获得有关含气泡熔体夹杂物的最可靠数据，我们建议同时采用基于实验和基于 MIMiC 的方法。气泡中没有含碳相），并且可以应用于大量已发表的熔体夹杂物数据。为了获得有关含气泡熔体夹杂物的最可靠数据，我们建议同时采用基于实验和基于 MIMiC 的方法。