The Malinche Pumice II is a fallout deposit produced by a Plinian-type eruption during the Pleistocene-Holocene at La Malinche volcano. La Malinche (4461 masl) is an active stratocone located in central Mexico, in the Trans-Mexican Volcanic Belt province. It is 26 km to the NE of the City of Puebla and 22 km to the SE of the City of Tlaxcala. The Malinche Pumice II was produced by one of the largest explosive eruptions of this volcano, involving a dacitic magma (63.6–65.3 wt% SiO₂, anhydrous basis) with a mineral assemblage of plagioclase + amphibole + FeTi oxides and ± biotite phenocrysts. Larger plagioclase crystals are up to 1.2 mm in diameter, with resorbed margins and complex zoning (An₂₆ to An₄₃), whereas microcrysts are euhedral with homogeneous composition (An₄₂ to An₅₅). Amphibole is mainly magnesio-ferri-hornblende (Mg# = 0.65–0.82) and lesser amounts of pargasite. Geothermometry performed using FeTi oxides yields an average temperature of 873 ± 2 °C and oxygen fugacity of 1.8 units above the NNO buffer. Amphibole geothermobarometry yields a lower temperature (809 ± 19 °C) and a pressure of 230 ± 100 MPa, assuming 4.4 wt% of H₂O. Considering an average density of 2650 kg/m³ for the upper crust in central Mexico, the storage region of the Malinche Pumice II dacitic magma was located at 8 ± 2 km depth. Biotite could be antecrystic or xenocrystic in origin, based on its reacted texture, large sizes (0.85–2 mm), and reaction rims. Similarly, pargasite that provides higher temperature estimates (900 ± 18 °C) and low anorthite plagioclase (An₂₆) could also be antecrysts or xenocrysts. The Plinian eruption was likely triggered by an input of a hotter and deeper magma batch that overpressurized the dacitic magma system that eventually provoked vesiculation and fragmentation. The eruption shifted to a hydromagmatic style because of external water's entrainment that decreased the vesicularity of pumice. Our results are in good agreement with recent seismicity recorded at depths of ~7 km probably associated with activity of the Malinche's magmatic system.

Malinche Pumice II 是在更新世-全新世 La Malinche 火山由普林尼式喷发产生的沉降沉积物。La Malinche (4461 masl) 是位于墨西哥中部跨墨西哥火山带省的一个活动平层锥体。距普埃布拉市东北部 26 公里，距特拉斯卡拉市东南部 22 公里。Malinche Pumice II 是由这座火山最大的爆发性喷发之一产生的，涉及英安质岩浆（63.6–65.3 wt% SiO ₂，无水基）与斜长石 + 闪石 + Fe Ti 氧化物和 ± 黑云母斑晶的矿物组合。较大的斜长石晶体直径可达 1.2 毫米，边缘有再吸收，分带复杂（An ₂₆至 An ₄₃)，而微晶是具有均匀成分的自面体 (An ₄₂到 An ₅₅ )。角闪石主要是镁铁角闪石（Mg# = 0.65–0.82）和少量的细闪石。使用 Fe Ti 氧化物进行的地温测量产生 873 ± 2 °C 的平均温度和比 NNO 缓冲液高 1.8 个单位的氧逸度。角闪石地球测温法产生较低的温度 (809 ± 19 °C) 和 230 ± 100 MPa 的压力，假设 H ₂ O为 4.4 wt% 。考虑到平均密度为 2650 kg/m ³对于墨西哥中部的上地壳，Malinche Pumice II 英安质岩浆的储存区位于 8±2 km 深度。根据其反应质地、大尺寸（0.85-2 毫米）和反应边缘，黑云母的来源可能是先晶或异晶。同样，提供较高温度估计值 (900 ± 18 °C) 和低钙长石斜长石 (An ₂₆) 也可能是祖先或异种晶体。普林尼火山喷发很可能是由更热、更深的岩浆的输入引发的，这些岩浆使英安质岩浆系统压力过大，最终引发了气泡和破碎。由于外部水的夹带降低了浮石的水泡性，喷发转变为水岩浆喷发。我们的结果与最近在约 7 公里深度记录的地震活动非常吻合，可能与马林什岩浆系统的活动有关。