Insights into fluid evolution and Re enrichment by mineral micro-analysis and fluid inclusion constraints: Evidence from the Maronia Cu-Mo ± Re ± Au porphyry system in NE Greece

Falkenberg J, Keith M, Melfos V, Hohl M, Haase K, Voudouris P, Höß A, Wenske J, Klemd R, Beier C, Kutzschbach M, Strauss H (2024)

Publication Type: Journal article

Publication year: 2024

Journal

DOI: 10.1007/s00126-024-01273-4

Abstract

Porphyry-epithermal veins hosting Re-rich molybdenite and rheniite (ReS2) from the Maronia Cu-Mo ± Re ± Au porphyry in Thrace, NE Greece, provide new insights into the hydrothermal processes causing extreme Re enrichment. Quartz trace element chemistry (Al/Ti, Ge/Ti), Ti-in-quartz thermometry, and cathodoluminescence imaging reveal multiple quartz generations in consecutive hydrothermal quartz-sulfide veins associated with potassic, sericitic, and argillic alteration. Fluid inclusions in different quartz generations indicate that phase separation and fluid cooling are the main ore-forming processes in the porphyry stage (~ 500 – 350 °C), whereas mixing of a vapor-rich fluid with metalliferous (e.g., Pb, Zn, Au) meteoric water forms the epithermal veins (~ 280 °C). These processes are recorded by trace element ratios in pyrite that are sensitive to changes in fluid temperature (Se/Te), fluid salinity (As/Sb, Co/As), and mixing between fluids of magmatic and meteoric origin (Se/Ge). Highly variable intra-grain δ³⁴S values in pyrite record S isotope fractionation during SO2 disproportionation and phase separation, emphasizing the importance of in situ δ³⁴S analysis to unravel ore-forming processes. High δ³⁴S (~ 4.5‰) values of sulfides are indicative of low SO4²⁻/H2S fluid ratios buffered by the local host rocks and mixing of the magma-derived fluid with meteoric water. The formation of Re-rich molybdenite (~ 6600 ppm) is favored by cooling and reduction of a magma-derived, high-temperature (~400 °C), oxidized, and Re-rich fluid triggering efficient Re precipitation in early veins in the potassic alteration zone. The systematic temporal fluid evolution therefore reveals that coeval cooling and reduction of oxidized Re-rich fluids cause extreme Re enrichment at the Maronia porphyry system.

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Involved external institutions

Helsingin yliopisto / University of Helsinki Finland (FI) Technische Universität Berlin Germany (DE) Westfälische Wilhelms-Universität (WWU) Münster Germany (DE) Aristotle University of Thessaloniki Greece (GR) University of Tasmania (UTAS) Australia (AU) National and Kapodistrian University of Athens Greece (GR)

How to cite

APA:

Falkenberg, J., Keith, M., Melfos, V., Hohl, M., Haase, K., Voudouris, P.,... Strauss, H. (2024). Insights into fluid evolution and Re enrichment by mineral micro-analysis and fluid inclusion constraints: Evidence from the Maronia Cu-Mo ± Re ± Au porphyry system in NE Greece. Mineralium Deposita. https://doi.org/10.1007/s00126-024-01273-4

MLA:

Falkenberg, Jan, et al. "Insights into fluid evolution and Re enrichment by mineral micro-analysis and fluid inclusion constraints: Evidence from the Maronia Cu-Mo ± Re ± Au porphyry system in NE Greece." Mineralium Deposita (2024).

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