Mineralogical Constraints on the Potassic and Sodic-Calcic Hydrothermal Alteration and Vein-Type Mineralization of the Maronia Porphyry Cu-Mo ± Re ± Au Deposit in NE Greece

Vasilios Melfos,Matías G Sánchez,Reiner Klemd,Anestis Filippidis,Alexandre Tarantola,Constantinos Mavrogonatos,Lambrini Papadopoulou,Panagiotis Voudouris,Paul G Spry,Margarita Melfou,Anna Schaarschmidt,Karsten M Haase

doi:10.3390/min10020182

Abstract

The Maronia Cu-Mo ± Re ± Au deposit is spatially related to a microgranite porphyry that intruded an Oligocene monzonite along the Mesozoic Circum-Rhodope belt in Thrace, NE Greece. The magmatic rocks and associated metallic mineralization show plastic and cataclastic features at the south-eastern margin of the deposit that implies emplacement at the ductile-brittle transition, adjacent to a shear zone at the footwall of the Maronia detachment fault. The conversion from ductile to brittle deformation caused a rapid upward magmatic fluid flow and increased the volume of water that interacted with the host rocks through high permeable zones, which produced extensive zones of potassic and sodic-calcic alteration. Potassic alteration is characterized by secondary biotite + K-feldspar (orthoclase) + magnetite + rutile + quartz ± apatite and commonly contains sulfides (pyrite, chalcopyrite, pyrrhotite). Sodic-calcic alteration consists of actinolite + sodic-calcic plagioclase (albite/oligoclase/andesine) + titanite + magnetite + chlorite + quartz ± calcite ± epidote-allanite. The high-oxidation state of the magmas and the hydrothermal fluid circulation were responsible for the metal and sulfur enrichments of the aqueous fluid phase, an increase in O2 gas content, the breakdown of the magmatic silicates and the production of the extensive potassic and sodic-calcic alterations. Brittle deformation also promoted the rapid upward fluid flow and caused interactions with the surrounding host rocks along the high temperature M-, EB-, A- and B-type veins.

Highlights

Hydrothermal alteration in porphyry type deposits refers to modifications in the primary chemistry, mineralogy and texture of the host rocks in response to fluid-rock interactions [1,2,3]
The Maronia porphyry Cu-Mo ± Re ± Au mineralization is hosted in microgranite porphyry, which intruded the Oligocene monzonite, at the footwall of a detachment fault
This fault formed as a result of the extensional geotectonic regime in the Rhodope massif, which produced magmas in a subduction-related magmatic arc

Summary

Introduction

Hydrothermal alteration in porphyry type deposits refers to modifications in the primary chemistry, mineralogy and texture of the host rocks in response to fluid-rock interactions [1,2,3]. Late meteoric waters commonly mix with magmatic fluids and react with the wall rocks resulting in sericitic and argillic alterations at lower temperatures. Several hydrothermal minerals, such as actinolite, calcite, biotite, epidote, chlorite, kaolinite, K-feldspar, magnetite, sericite and titanite, replace earlier-formed primary magmatic minerals, and are indicators of the various alteration zones in porphyry Cu deposits [3]

Results

Discussion

Conclusion