This study reports the first measurements of sulphur and boron isotopic compositions in olivine-hosted melt inclusions (MI) from basaltic lava and scoria deposits from the 1941 Tolbachik eruption, Kamchatka, Russia. The primary aim of the present study is to constrain the origin of sulphur in relation to silicate-sulphide immiscibility that occurred in the Tolbachik mafic magmas. Melt inclusions fall into two compositionally distinct groups based on their S- and B-isotope systematics, the first is hosted by olivine from lava and the second in olivine from lapilli and scoria. The upper ends of the concentration ranges for CO₂ (3660–4200 μg/g) and H₂O (4.5–5.9 wt%) imply the onset of magma crystallization between ~25 and ~30 km for both MI groups, i.e., close to the Moho discontinuity. After filtering the compositions of melt inclusions experienced H₂O-loss due to the diffusion of H from olivine hosts, both lava- and scoria-related melt inclusions are characterized by similar fractionation depths between ~15 and ~30 km. The inclusions from scoria show no signs of sulphur degassing at depth and, along with the most S-rich inclusions from lava, exhibit enrichment in S. Strong positive correlations of S/K₂O with H₂O/K₂O, Cl/K₂O and F/K₂O, as well as the correlations of these ratios with δ³⁴S also preclude significant S-loss by degassing and point towards mixing of at least two magmas containing contrasting volatile concentrations and isotopic compositions. Slab-derived ¹¹B-enriched fluids and, to a minor extent, ¹¹B-depleted melts could be major agents controlling the composition of the mantle wedge and, consequently, the chemical and isotopic variability of its derivative melts. A subducted serpentinized peridotite could serve as a possible source of the ¹¹B- and probably the ³⁴S-rich signature of the studied primitive Tolbachik magmas.

这项研究报告了对来自1941年俄罗斯堪察加半岛托尔巴奇克火山喷发的玄武岩熔岩和火山灰沉积物中橄榄石质熔体包裹体（MI）中硫和硼同位素组成的首次测量。本研究的主要目的是限制与托尔巴奇克铁镁质岩浆中发生的硅酸盐与硫化物不混溶有关的硫的起源。根据熔体的S和B同位素体系，熔体夹杂物分为两个成分不同的组，第一组由熔岩中的橄榄石组成，第二组由lapilli和scoria中的橄榄石组成。CO ₂（3660-4200μg/ g）和H ₂的浓度范围上限O（4.5–5.9 wt％）表示两个MI组的岩浆结晶开始在〜25 km〜〜30 km之间，即接近Moho间断。在过滤熔体夹杂物的成分后，由于H从橄榄石基质中扩散而经历了H ₂ O损失，与熔岩和火山灰有关的熔体夹杂物的特征是约15至30 km之间的相似分馏深度。火山灰中的夹杂物没有显示出深度脱硫的迹象，并且与熔岩中最富S的夹杂物一起，富集了S。S/ K ₂ O与H ₂ O / K ₂ O，Cl /的强正相关ķ ₂ ö和F / K ₂ O，以及所述与这些比率的相关性δ ³⁴S还通过脱气排除了显着的S损失，并指向至少两个含对比挥发物浓度和同位素组成的岩浆混合。板坯衍生的富含¹¹ B的流体以及少量的¹¹ B贫化的熔体可能是控制地幔楔成分的主要因素，因此，也可以控制其衍生熔体的化学和同位素变异性。俯冲的蛇纹岩橄榄岩可能是研究的原始托尔巴奇克岩浆的¹¹ B富集特征（可能是³⁴ S富集特征）的可能来源。