Tourmaline Composition of the Kışladağ Porphyry Au Deposit, Western Turkey: Implication of Epithermal Overprintстатья
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Аннотация:The Kı¸slada ˘g porphyry Au deposit occurs in a middle Miocene magmatic complex
comprising three different intrusions and magmatic-hydrothermal brecciation related to the multiphase
effects of the different intrusions. Tourmaline occurrences are common throughout the deposit,
mostly as an outer alteration rim around the veins with lesser amounts disseminated in the intrusions,
and are associated with every phase of mineralization. Tourmaline mineralization has developed
as a tourmaline-rich matrix in brecciated zones and tourmaline-quartz and/or tourmaline-sulfide
veinlets within the different intrusive rocks. Tourmaline was identified in the tourmaline-bearing
breccia zone (TBZ) and intrusive rocks that had undergone potassic, phyllic, and advanced argillic
alteration. The tourmaline is present as two morphological varieties, aggregates of fine crystals
(rosettes, fan-shaped) and larger isolated crystals and their aggregates. Four tourmaline generations
(tourmaline I to IV) have different compositions and substitutions. Tourmaline I in TBZ and INT#1
is distinguished by the highest Fetot and enriched in Fe3+. Tourmalines II and III occur as fine
aggregates, accompanied by the formation of isolated crystals and are characterized by lower Fetot
and Fe3+. Tourmaline IV is characterized by the lowest Fetot, enriched in Cl, and has the highest
proportion of X-site vacancy among all the tourmalines. Tourmaline I may be attributed to the
potassic stage in INT#1 and early tourmaline in TBZ. Tourmalines II and III from INT#1 and the TBZ
could be referred to the phyllic stage. The low Fe content in tourmaline is caused by the simultaneous
deposition of sulfide minerals. Tourmaline IV from the TBZ and tourmaline II from INT#3 are
distinguished by the high X-site vacancy proportion up to the formation of X-site vacant species
as well as enriched in Cl; they can be attributed to the argillic stage of the hydrothermal process.
The textural and especially chemical data of the tourmaline from the Kı¸slada ˘g Au deposit provide
information on the physico-chemical conditions during the porphyry to epithermal transition and
subsequent epithermal overprinting.