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MAGMATIC, STRUCTURAL, AND METALLOGENIC FRAMEWORK OF THE KASSANDRA MINING DISTRICT, CHALKIDIKI PENINSULA, NORTHERN GREECE

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Abstract

The Kassandra Mining District in northern Greece hosts the Skouries porphyry Au-Cu deposit and intrusion-related carbonate-hosted replacement sulfide orebodies at the Madem Lakkos, Mavres Petres, and Olympias deposits. Igneous suites of late Oligocene (25-27 Ma) and early Miocene (19-20 Ma) age are defined through zircon U-Pb geochronology and whole-rock geochemistry. Both suites exhibit high-K calc-alkaline geochemistry, but the early Miocene porphyries have a shoshonitic affinity. Normalized rare earth element patterns indicate that the late Oligocene suite was influenced by plagioclase fractionation, whereas amphibole-garnet fractionation was important during the early Miocene event. The location and morphology of the sulfide deposits are controlled by a preexisting ductile structural architecture with ductile to brittle faults interacting with chemically reactive marble host rocks. The sulfide orebodies at the Olympias and Madem Lakkos deposits resulted from the intersection of ductile fabrics and fold hinges with extensional mylonites and semi-brittle shear zones. Ore lenses at the Mavres Petres deposit are restricted to fault-imbricated marbles contained within the Stratoni fault zone. Hydrothermal alteration associated with sulfide deposition occurred between 24 Ma and 22 Ma based on 40Ar-39Ar muscovite ages. Kinematic fault-slip analysis and field relationships suggest that sulfide mineralization within the Stratoni fault zone was controlled by north-south extension, whereas a younger phase of mineralization was influenced by east-west extension. The early Miocene Skouries porphyry stock, hosted by a folded gneiss-schist sequence, was localized within the steeply dipping limb of a preexisting district-scale antiform. Northeast-striking porphyry dikes and sheeted veins within the stock indicate that Au-Cu mineralization occurred in response to northwest-southeast directed extension. Structural crosscutting relationships, geochronological ages, carbon-oxygen isotopes, fluid inclusions, and metal distribution patterns suggest that the late Oligocene hydrothermal system within the Stratoni fault zone was centered to the southeast of the Madem Lakkos deposit with an isolated hydrothermal system located to the east of the Olympias deposit. Porphyry Au-Cu mineralization culminated about 4 m.y. later, but was restricted to the Skouries stock. Polymetallic carbonate replacement sulfide and porphyry Au-Cu ore formation corresponds to late Oligocene and early Miocene magmatic events that manifested within the back arc environment in a post-collisional tectonic setting.

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2018-05-30

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Geochemistry; Geochronology; Greece; Kassandra Mining District; Metallogeny; Structural Geology; Geology

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Thompson, John Hugh

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Allmendinger, Richard Waldron
Derry, Louis A.

Degree Discipline

Geological Sciences

Degree Name

Ph. D., Geological Sciences

Degree Level

Doctor of Philosophy

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Government Document

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dissertation or thesis

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