Gruzdeva Yulia, Weis Philipp
GFZ Helmholtz Centre for Geosciences, Telegrafenberg, 14473, Potsdam, Germany.
Institute of Geosciences, University of Potsdam, Karl-Liebknecht-Straße 24/25, 14476, Potsdam, Germany.
Sci Rep. 2025 Aug 15;15(1):29949. doi: 10.1038/s41598-025-15335-8.
Volatile degassing from hydrous magma reservoirs controls the formation of porphyry copper deposits. Geochemical studies suggest that water-rich magmas may be more prone for ore formation, with fluid-melt partitioning potentially producing particularly metal-rich fluid stages. However, the coupled physicochemical processes at the magmatic-hydrothermal transition remain elusive, because they depend on non-linear properties of magmas, fluids and rocks. For this study, we further developed a numerical model for magma convection, volatile degassing, hydraulic fracturing and fluid flow by modifying its permeability response to brecciation and introducing chemical fluid-melt partitioning. We investigate the role of intrusion depth, water content and distribution coefficients on degassing and ore formation. The results show how magmas can self-organize into distinct degassing stages with contrasting timescales of metal fluxes. Depth and water content control the amount of fluids released by an initial short-lived tube-flow outburst event, leading to brecciation and a first mineralization event in shallow porphyry-epithermal levels for high distribution coefficients. Further cooling leads to continuous fluid release at lower rates, producing a second mineralization event at deeper levels. Our results suggest that near-saturated water contents of voluminous magma reservoirs in combination with low fluid-melt distribution coefficients support the formation of large porphyry deposits.
含水岩浆库的挥发性气体脱气控制着斑岩铜矿的形成。地球化学研究表明，富水岩浆可能更有利于成矿，流体 - 熔体分配可能产生特别富含金属的流体阶段。然而，岩浆 - 热液转变过程中的耦合物理化学过程仍然难以捉摸，因为它们取决于岩浆、流体和岩石的非线性特性。在本研究中，我们通过修改其对角砾化的渗透率响应并引入化学流体 - 熔体分配，进一步开发了一个用于岩浆对流、挥发性气体脱气、水力压裂和流体流动的数值模型。我们研究了侵入深度、含水量和分配系数对脱气和成矿的作用。结果表明岩浆如何自组织成具有不同金属通量时间尺度的不同脱气阶段。深度和含水量控制着由初始短暂的管流爆发事件释放的流体量，对于高分配系数而言，这会导致角砾化以及浅部斑岩 - 浅成热液层位的首次矿化事件。进一步冷却导致以较低速率持续释放流体，在更深层位产生第二次矿化事件。我们的结果表明，大量岩浆库的近饱和含水量与低流体 - 熔体分配系数相结合有利于形成大型斑岩矿床。
