Mineral-Mineral chemistry of biotite in the porphyry Cu system in Fakos area, Linmos

Graduate Thesis uoadl:2938105 143 Read counter

Unit:
Department of Geology and Geoenviromment
Library of the School of Science
Deposit date:
2021-03-07
Year:
2021
Author:
Stamopoulos Paraskevas
Louloudaki Pinelopi
Supervisors info:
Παναγιώτης Βουδούρης, Καθηγητής, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος ,Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών
Original Title:
Ορυκτολογική-Ορυκτοχημική μελέτη βιοτίτη από το σύστημα πορφυρικού χαλκού του Φακού της Λήμνου.
Languages:
Greek
Translated title:
Mineral-Mineral chemistry of biotite in the porphyry Cu system in Fakos area, Linmos
Summary:
Porphyry copper mineralization in the Fakos area, Limnos island, is genetically related to the emplacement of monzonitic dikes, being part of the Miocene shoshonitic magmatism in Northeastern Aegean area. The porphyry-type mineralization is introduced during potassic alteration of the intrusives, characterized by a hydrothermal assemblage composed of biotite-magnetite-quartz-apatite, and accompanied by chalcopyrite, pyrite and bornite.
Mineral-chemical studies in hydrothermal biotites (phlogopites) analyzed during this stydy, and compared with magmatic biotites from the literature, indicate that: (a) hydrothermal biotites are more enriched in Si (between 5.8 and 6 apfu) and Mg resulting in a lower Fe / (Fe + Mg) ratio, in relation to the magmatic ones (Si <5.7 apfu); (b) hydrothermal biotites show much lower concentrations of Ti (<0.2 apfu) than magmatic biotites, having between 0.5 and 0.6 apfu; (c) hydrothermal biotites are distinguished from magmatic biotites by higher values of XMg and octahedral Al (AlVI); (d) finally, the phlogopite from Fakos, present zero values in F, and Cl varying between 0.17 and 0.22 wt.%. The above geochemical characteristics indicate increasing oxidation during crystallization and cooling of the monzonite intrusions under magmatic-hydrothermal conditions. This oxidation is associated with release of fluid phases from the magma that led to the formation of porphyry type mineralization.
The mineralogical studies carried out on biotites from the Fakos area, are in agreement with studies in biotites from porphyry-type mineralization in W. Thrace (Kassiteres, Pagoni Rachi Maronia), and indicates similar physicochemical conditions for the generation of porphyry-style ores, and of biotite formation. In contrast, the biotites from Fakos show extremely low F content (<0.02% by weight), and lower values in Cl (0.17-0.22 wt.%), compared to biotites of W. Thracian porphyry systems, which incorporate significant amounts of F and Cl. The reason for this differentiation is not yet clear, but it is possibly related to both the various composition of the intrusives in each area, as well as by specific magmatic-hydrothermal processes during the deposition of biotite.
Main subject category:
Science
Keywords:
Limnos, Fakos, Porphyry, biotite, Minerology
Index:
No
Number of index pages:
0
Contains images:
Yes
Number of references:
68
Number of pages:
56
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