Geochemistry of volcanics and fluid-rock interactions in hydrothermal systems in the Manus Basin

东部马努斯盆地（EMB）是世界上板块构造最活跃和地球化学最多样化的地区之一。马努斯盆地的许多火山中心都有热液系统，这些热液系统在不同程度上受到岩浆脱气的影响。这些系统的地球化学多样性提供了一个无与伦比的机会来研究岩浆脱气及其对热液系统质量传输的影响。在最近的RV梅尔维尔巡航期间，在EMB的不同区域收集了火山岩以及热液流体和硫化物。岩石覆盖范围从枕状玄武岩到高度泡状的长英质熔岩，其中一些是高度斑状的。流体排放区附近的岩石蚀变也变化很大，从泥质到酸性硫酸盐蚀变。这些样品将有助于评估岩浆分异与岩浆成分进入热液系统的关系以及对流体-岩石相互作用和金属迁移的影响。在模型计算中，将把热液活动区新鲜岩石和蚀变岩石的地球化学数据与喷口流体的化学分析结合起来，目的是解释（1）观察到的相组合和（2）喷口流体的化学性质。我们将使用反应路径模型来模拟流体-岩石的相互作用与岩浆成分的变量输入。研究结果将与NSF资助的同伴项目的数据相结合，以全面了解马努斯盆地岩浆热液系统的质量转移。

The eastern Manus Basin (EMB) is one of world’s most plate-tectonically active and geochemically diverse regions. Many volcanic centers in the Manus Basin host hydrothermal systems that are affected by magma degassing to variable extent. The geochemical diversity of these systems provides an unparalleled opportunity to examine magma degassing and its consequences for mass transport in hydrothermal systems. During a recent RV Melville cruise volcanic rocks as well as hydrothermal fluids and sulfides were collected in different areas of the EMB. The rocks cover a range from pillow basalt to highly vesicular felsic lava, some of which are highly porphyritic. Rock alteration in the immediate vicinity of the fluid discharge area is also strongly variable, ranging from argillaceous to acid-sulfate alteration. These samples will allow the assessment of magmatic differentiation in relation to input of magmatic components into the hydrothermal system and consequences for fluid-rock interactions and metal transport. Geochemical data of fresh and altered rocks from hydrothermally active areas will be combined with chemical analyses of vent fluids in model calculations aimed at explaining (1) the phase assemblages observed and (2) the vent fluid chemistry. We will use reaction path models to simulate fluid-rock interactions with variable input of magmatic components. The results will be combined with data from NSF-funded companion projects in order to obtain a comprehensive understanding of mass transfers in the Manus Basin magmatic-hydrothermal systems.