Tectono-magmatic controls on fluid flow in a detachment-related porphyry system: Insights from magnetic petrofabric analyses at the Maronia deposit, NE Greece

The circulation of magmatic-hydrothermal fluids along crustal-scale fault systems plays a fundamental role in the formation of porphyry-type ore deposits, as these structures control magma emplacement, fluid pathways, and associated rock alteration. In the Rhodope magmatic-metallogenic belt of northern Greece, numerous Oligocene-Miocene porphyry-type ore deposits formed in an extensional back-arc environment. One example is the Maronia Cu-Mo±Re±Au porphyry deposit in the Mesozoic Circum-Rhodope metamorphic belt, where plutonic intrusion occurred during detachment fault activation. Despite this, the detailed sequence and timing of magmatic-hydrothermal fluid circulation related to ore formation remain poorly constrained.

In this study, we aim to unravel the relationship between magmatic and tectonic events to decipher the mechanisms of magmatic-hydrothermal fluid circulation along detachment faults associated with ore formation processes. A total of 20 rock samples were collected across the exposed detachment fault zone at Maronia, ranging from unaltered monzonite to the porphyry microgranite intrusion. We combined highly sensitive Anisotropy of Magnetic Susceptibility and Remanence (AMS and ARM) petrofabric tools with geochemical analyses (e.g., EPMA, LA-ICP-MS/MS). Petrofabric analyses identified multiple magnetic fabrics within individual samples, providing insights into magmatic intrusion emplacement, deformation, and fluid flow, as well as into whether magmatic and tectonic processes occurred concurrently or successively.

Preliminary geochemical and magnetic analyses of minerals and whole rocks constrain the genetic relationship between microgranite intruding the mylonitic rocks within the detachment fault. Petrofabric data are coaxial with observed field fabrics, whereas preliminary ARM results indicate that higher coercivity mineral phases deviate from both field observations and AMS results. Petrographic observations reveal the nature of mineralization and allow evaluation of textural changes related to fluid-rock interaction. We suggest that the combined dataset reflects a strain archive of multi-stage tectonomagnetic processes that drove fluid flow and possibly mineralisation in this sector of the Circum-Rhodope belt.

This study further demonstrates the potential of integrating petrofabric data with geochemical methods to better resolve fluid flow processes and tectono-magmatic evolution in detachment-controlled porphyry systems, providing new insights into the structural controls on mineralization at Maronia.