Hydrothermal corundum, topaz, diaspore and alunite supergroup minerals in the advanced argillic alteration lithocap of the Kassiteres-Sapes porphyry-epithermal system, western Thrace, Greece

Hydrothermal corundum, topaz, diaspore and alunite supergroup minerals in the advanced argillic alteration lithocap of the Kassiteres-Sapes porphyry-epithermal system, western Thrace, Greece

Voudouris, P.C.

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Επιστημονική δημοσίευση - Άρθρο Περιοδικού (EL)

Scientific publication - Journal Article (EN)

2014

The Kassiteres-Sapes area is a telescoped porphyry Cu-Mo-Re ± Au and epithermal Au-Ag-Cu-Te system, hosted within Oligocene calc-alkaline to high-K calc-alkaline granodiorite-tonalite, microdiorite and quartz-feldspar porphyries and their volcanic equivalents. High- And intermediate sulfidation epithermal mineralization was deposited in advanced argillic lithocaps that overprint sodic/potassic and sericitic alteration of the intrusive rocks. Deep level, corundum-sericite-feldspar-, corundum-quartz-, and quartz-diaspore-topaz-APS minerals-pyrophyllite-sericite bearing assemblages occur in close proximity to porphyry-style mineralization at the Koryfes, Konos Hills and St Demetrios deposits. Rapid cooling of ascending magmatic-hydrothermal solutions at pressures below 0.6 kb and temperatures above 370 ?C could dilute quartz resulting in silica undersaturation and the formation of corundum-sericite at Koryfes Hill. The corundum-quartz assemblage at St Demetrios was likely derived from previous diasporebearing advanced argillic alteration at moderate temperature ( 400 °C) and low pressure, followed by rapid depressurization accompanying boiling of the hydrothermal fluid. The disequilibrium assemblage quartz+diaspore+topaz (± pyrophyllite ? sericite) formed between 285? and 320 ?C by vapor saturation pressure from acid solutions after condensation of vapors released from the porphyries. The presence of topaz reflects the presence of fluorine in the fluid. Alumino-phosphates-sulfates (woodhouseite, Sr-rich woodhouseite and Sr-Ce-rich woodhouseite) are present as pseudocubic crystals enclosed within diaspore and natroalunite. High level lithocaps include natroalunite/alunite-kaolinite/dickite-pyrite bearing assemblages of both replacement- And vein-type, which deposited at 300° to 200 °C by increasing acidity of the fluid at higher topographic levels and/or from direct input of magmatic vapors. Episodic magmatic-hydrothermal activity in the district is characterized by several stages of advanced argillic alteration and associated Au-Ag-Cu-Te high-sulfidation mineralization. ©2014 E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany. (EN)

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Άρθρο Περιοδικού (Journal Article)