The stratovolcano Mt. Pelée, Martinique, exhibits eruptive styles ranging from dome formation to sustained, highly violent explosive activity. Historical eruptions have produced lava domes and pyroclastic density currents, collectively termed Peléan activity. In pre-colonial times, several Plinian eruptions took place. Here, we explore physical controls on the proportions of fine particles produced—i.e., the fragmentation efficiency—during primary fragmentation. Samples were collected from ignimbrites from the 1929–1932 and 1902–1905 Peléan eruptions and the P1 (1300 CE), P2 (280 CE), and P3 (79 CE) Plinian eruptions. All samples are andesitic in bulk composition and contain a rhyolitic groundmass glass. The Peléan materials are more crystalline and less porous than their Plinian counterparts, a consequence of more extensive outgassing during dome formation. Representative blocks were cored and experimentally fragmented following rapid decompression (> 1 GPa·s⁻¹ from initial pressure between 5 and 20 MPa). Dry sieving allowed for determining grain size distributions, from which the fractal dimensions, D_f, were calculated as a quantification of fragmentation efficiency. Our results indicate different behaviors for Peléan and Plinian samples. While fragmentation efficiency is positively correlated with applied potential energy for Peléan samples, this relationship is not observed for the Plinian samples, possibly due to syn-fragmentation gas escape above a certain porosity. The rapid decompression experiments were designed to minimize secondary fragmentation by shear along the walls or impact while preserving the entirety of produced materials. Thus, our experimental grainsize data are physically linked to sample textures and overpressure. By comparison with natural pyroclastic products—commonly incompletely preserved—we can approach quantitatively constraining the energetic conditions underlying individual eruptions.

马提尼克岛的成层火山 Pelée 呈现出从圆顶形成到持续、高度剧烈的爆炸活动的喷发类型。历史上的火山喷发产生了熔岩穹丘和火山碎屑密度流，统称为贝利火山活动。在前殖民时期，发生过几次普林尼式火山喷发。在这里，我们探索了对初级破碎过程中产生的细颗粒比例（即破碎效率）的物理控制。样品是从 1929-1932 年和 1902-1905 年 Peléan 喷发以及 P1（公元 1300 年）、P2（公元 280 年）和 P3（公元 79 年）普林尼式喷发的熔结岩中采集的。所有样品的整体成分均为安山岩，并含有流纹岩基质玻璃。与普林尼材料相比，Peléan 材料的结晶度更高，孔隙更少，这是圆顶形成过程中更广泛排气的结果。快速减压（> 1 GPa·s）后，对代表性区块进行取芯和实验破碎⁻¹（初始压力在 5 至 20 MPa 之间）。干筛可以确定粒度分布，从中得出分形维数D _f，被计算为碎片效率的量化。我们的结果表明 Peléan 和 Plinian 样本具有不同的行为。虽然对于 Peléan 样品来说，碎裂效率与所施加的势能呈正相关，但对于 Plinian 样品却没有观察到这种关系，这可能是由于在一定孔隙率以上发生同步碎裂气体逸出。快速减压实验的目的是最大限度地减少沿壁剪切或冲击造成的二次破碎，同时保留所生产的材料的整体性。因此，我们的实验粒度数据与样品纹理和超压有物理联系。通过与通常不完全保存的天然火山碎屑产物进行比较，我们可以定量地限制单个喷发背后的能量条件。