Dynamics of Ore MEtal TRansport in Alkaline Porphyry systems (DOMETRAP)

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Our project aims at investigating the detailed transport mechanisms of ore metals including their pathways and carriers in alkaline porphyry-epithermal systems. The study will focus on the Ladolam deposit on Lihir (Papua New Guinea) representing one of the largest and most representative deposits of this kind. South of Lihir, a young submarine volcanic field has been interpreted as an early analogue of the volcanic system hosting Ladolam. Only here, less evolved rocks and eruption at >1 km water depth allow to study the metal transport in the magmatic system least affected by magmatic differentiation and degassing at shallow crustal levels. Epithermal-style mineralization similar to Ladolam occurs at Conical Seamount and mantle and crustal xenoliths recording igneous processes from the mantle source to eruption are abundant in lavas from the nearby Tubaf Seamount. Our research project focuses on a detailed reconstruction of the thermobarometric evolution during melt ascent and how it affects melt oxidation state and metal transport capability of the magma. For this purpose, we plan to combine the initial basic characterization of the petrology and geochemistry of the rock samples with the high-precision analyses of volatiles and trace metals and microthermobarometry using fluid and glass (formerly melt) inclusions. With this data we aim at an improved understanding of the mechanisms that trigger subvolcanic intrusions or volcanic eruptions in this specific setting. Integrating these insights into the deep magmatic plumbing system with the evolution of these silica-undersaturated, highly alkaline magmas that have been proven to be highly fertile for the formation of economically important porphyry systems is of great relevance. Furthermore, our constraints on the pressures of melt stagnation, ascent rates, eruptions triggers and potentially melt-volatile exsolution depth will feed directly into a project led by PD Dr. Philipp Weis that aims at modelling the physical properties of porphyry formation at Ladolam. Further links within the SPP 2238 are provided to the project by Dr. Andreas Audétat that focuses on petrological experiments related to alkaline porphyries in continental settings.