US EPA

4831893 

Journal Article 

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, PC 

2014 

1 

Neues Jahrbuch fuer Mineralogie. Abhandlungen
ISSN: 0077-7757 

191 

2 

117-136 

10.1127/0077-7757/2014/0251 

WOS:000331098000001 

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 degrees 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 degrees 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 degrees and 320 degrees 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 degrees to 200 degrees 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. 

Hydrothermal corundum; topaz; diaspore; aluminum-phosphate-sulfate minerals; alunite; porphyry-epithermal; Kassiteres-Sapes; Greece