Aluminum-phosphate-sulfate (APS) minerals in the sericitic-advanced argillic alteration zone of the Melitena porphyry-epithermal Mo-Cu ± Au ± Re prospect, western Thrace, Greece
Voudouris, Panagiotis C.; Melfos, Vasilios
published: Nov 1, 2012
ArtNo. ESP154019001002, Price: 29.00 €
The Melitena porphyry-epithermal Mo-Cu ± Au ± Re prospect, in western Thrace, Greece, is genetically related to a calcalkaline, subvolcanic body of granodioritic composition that was emplaced during Tertiary within the high-grade metamorphic rocks of the Rhodope Massif. The molybdenite mineralization occurs within quartz stockworks crosscutting a transitional sericitic-advanced argillic alteration zone of the intrusive, including quartz, sericite, pyrophyllite, diaspore, aluminum-phosphates-sulfates (APS) and pyrite. This alteration zone is exposed in the deeper levels of an advanced argillic lithocap composed of quartz, natroalunite, and minor diaspore and pyrophyllite. The APS minerals are Ca-Sr-Ba-Pb-rich phosphates-sulfates and represent solid solutions within the beudantite- and plumbogummite groups: among the most interesting phases are Sr-Ca-Ba hinsdalite and cerian crandallite occurring as cores within woodhouseite, as well as Pb-Ca-Ba svanbergite occurring as cores within Ca svanbergite and Sr woodhouseite. To our knowlegde this is the first occurrence of hypogene strontian hinsdalite and certain crandallite in Greece. At Melitena the molybdenite mineralization was contemporaneous to the development of transitional sericitic-advanced argillic alteration from vapor condensates. This assemblage was formed at temperatures between 285° and 320 °C from acid solutions derived after condensation of HCl- and SO2-rich gases released from the granodiorite porphyry. Changes in the acidity of the fluid with decreasing temperature resulted in the deposition of alunite and Na-rich alunite at higher topographic levels.