Quantifying the storage conditions and evolution of different magmatic components within sub-volcanic plumbing systems is key to our understanding of igneous processes and products. Whereas erupted magmas represent a portion of the eruptible volcanic system, plutonic xenoliths provide a complementary record of the mushy roots of the plumbing system that cannot be mobilised easily to form lavas and consequently offer a unique record of magma diversity within the sub-volcanic plumbing system. Here, we present a detailed petrological and geochemical study of erupted plutonic xenoliths from the island of Sint Eustatius (Statia), in the northern Lesser Antilles volcanic arc. The plutonic xenoliths are predominantly gabbroic, but vary in texture, mineral assemblage and crystallisation sequence. We report major, trace and volatile (H2O and CO2) concentrations of xenolith-hosted melt inclusions (MIs) and interstitial glass. The MIs have a very large range in major element (49–78 wt% SiO2 and 0.1–6.1 wt% MgO) and trace element concentration (72–377 ppm Sr, 32–686 ppm Ba, 39–211 ppm Zr). Their chemistry varies systematically with host phase and sample type. Significantly, it shows that (1) plutonic xenoliths record a complete differentiation sequence from basalt to rhyolite (2) apatite, but not zircon, saturation was reached during crystallisation, (3) amphibole breakdown reactions play a role in the genesis of shallow gabbronorite assemblages, and (4) mixing between crystal cargos and multiple discrete bodies occurred. Residual melt volatile contents are high (≤ 9.1 wt% H2O and ≤ 1350 ppm CO2), returning volatile saturation pressures of 0–426 MPa. Multiple reaction geobarometry and experimental comparisons indicate that equilibration took place in the upper-middle crust (0–15 km). We infer that the Statia plutonic xenoliths represent portions of a large heterogeneous crystal mush within which a great diversity of melts was stored and mixed prior to eruption. Our data show that compositional variations in magmatic plumbing systems exceed those observed in volcanic products, a likely consequence of the blending that occurs prior to and during eruption.

中文翻译：

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小安的列斯群岛圣尤斯特歇斯岛下方富含挥发物的水晶糊中岩浆分化、混合和储存的深成捕虏体的证据

量化次火山管道系统中不同岩浆成分的储存条件和演化是我们了解火成岩过程和产品的关键。喷发的岩浆代表了可喷发火山系统的一部分，而深成捕虏体提供了管道系统的糊状根部的补充记录，这些根部不能轻易地形成熔岩，因此提供了次火山管道系统内岩浆多样性的独特记录。 。在这里，我们对小安的列斯群岛火山弧北部圣尤斯特歇斯岛（斯塔蒂亚）喷发的深成捕虏体进行了详细的岩石学和地球化学研究。深成捕虏体主要为辉长岩，但其结构、矿物组合和结晶顺序各不相同。我们报告了捕虏体中的熔体包裹体 (MI) 和间隙玻璃的主要、痕量和挥发性（H2O 和 CO2）浓度。MI 的主量元素（49–78 wt% SiO2 和 0.1–6.1 wt% MgO）和微量元素浓度（72–377 ppm Sr、32–686 ppm Ba、39–211 ppm Zr）的范围非常大。它们的化学性质随宿主相和样品类型而系统地变化。值得注意的是，它表明（1）深成捕虏体记录了从玄武岩到流纹岩的完整分化序列（2）磷灰石，但不是锆石，在结晶过程中达到饱和，（3）角闪石分解反应在浅部辉长岩组合的成因中发挥作用，(4)晶体货物和多个离散体之间发生混合。残余熔体挥发物含量较高（≤ 9.1 wt% H2O 和 ≤ 1350 ppm CO2），返回挥发物饱和压力为 0–426 MPa。多重反应地压测量和实验比较表明，平衡发生在中上地壳（0-15 km）。我们推断，Statia 深成捕虏体代表了大型异质晶体糊状物的一部分，其中在喷发前储存并混合了多种熔体。我们的数据显示，岩浆管道系统的成分变化超过了火山产物中观察到的成分变化，这可能是喷发前和喷发期间发生混合的结果。