Serpentinization and Metasomatism. Constraints to their relationship through mineralogical, petrological and geochemical study of rodingitized dykes intruded ultramafic rocks of Kimi district, Evia, Greece.

Postgraduate Thesis uoadl:2758636 479 Read counter

Unit:
Κατεύθυνση Μεταπτυχιακό Δίπλωμα
Library of the School of Science
Deposit date:
2018-05-13
Year:
2018
Author:
Karkalis Christos
Supervisors info:
Ανδρέας Μαγκανάς, Καθηγητής, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών
Παναγιώτης Πομώνης, Επίκουρος Καθηγητής, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών
Κωνσταντίνος Κυριακόπουλος, Καθηγητής, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών
Original Title:
Serpentinization and Metasomatism. Constraints to their relationship through mineralogical, petrological and geochemical study of rodingitized dykes intruded ultramafic rocks of Kimi district, Evia, Greece.
Languages:
English
Translated title:
Serpentinization and Metasomatism. Constraints to their relationship through mineralogical, petrological and geochemical study of rodingitized dykes intruded ultramafic rocks of Kimi district, Evia, Greece.
Summary:
In Kimi (Central Evia, Greece) the Cretaceous-Paleogene flysch consists of schists, sandstones, cherts and ophicalcites, along with serpentinized peridotite bodies underlying Upper Cretaceous limestone intercalations with peridotite fragments. Serpentinized peridotites are intruded by rodingite dykes of a possibly gabbroic origin and they are thought to represent cretaceous ophiolitic remnants of the Vardar Ocean inside flysch, being obducted onto the Pelagonian platform. Based upon their petrographical, mineralogical and geochemical data Kimi rodingites have been divided into two groups according to the presence of calcite or not. A further discrimination concerns the three distinct zones that have been observed in rodingite dykes from both field and laboratory examination and include chlorite-diopside rich Marginal Zones (ΜΖ), garnet-vesuvianite rich Core Zones (CΖ) and Transitional Zones (TZ) which include the aforementioned mierals in various amounts. Rodingitization was a continuous metasomatic process strongly related with serpentinitzation and occurred under alkaline conditions. It was evolved in two main metasomatic events with low and high XCO2 conditions respectively. Each metasomatic event could further subdivided into several stages as it is confirmed by the existence of distinct zoning within the rodingite dykes. Each stage corresponds to the gradual infiltration of metasomatic fluids through the mafic dyke with a gradual increasing of water/rock ratio and decreasing of CO2/H2O ratio and T conditions. Whole rock chemical analyses exhibit CaO enrichment and silica-alkali depletion. Ca2+ derives from clinopyroxene dissolution and is strongly mobilized during serpentinization, while Si loss is attributed to feldspar breakdown of the mafic protoliths. Vesuvianite formation took part in later metasomatic stages of the first event, when the metasomatic fluids were Ca2+ and OH- rich with low CO2/H2O ratios. Apatite formation is indicative of seawater participation and CO2 increase. These final are followed by the second metasomatic event of lower T and high CO2 conditions. This event coincides with ophicalcite formation in OCT (Ocean Continent Transitional Zone) where brittle conditions cause serpentinite breakdown. These cracks usually begin from the chlorititic margins and crosscut the whole rodingite dyke, permitting the CO2 hydrous rich fluids to crystallize calcite. LREE deposition is observed in apatite and allanite. LREE mobilization took part mainly via CO3-2, while apatite presence and Zr mobility could also support the presence of PO4--LREE and LREE-OH- and complexes as well. Stable isotope chemistry data of C and O in calcite samples form rodingite, ophicalcite and red mudstones of Kimi flysch show a combination of sedimentary and mantle derived processes in the metasomatic fluids. Based upon whole rock chemical data from rodingites and serpentinites, spinel chemistry, the presence of vesuvianite and hydrogarnets we conclude that the metasomatic processes possibly took part in a SSZ geological setting. Chemical similarities of Kimi rodingites with those of Skyros are indicative of an elongated ophiolitic Zone within Vardar Ocean. The closure of this Upper Cretaceous Vardar basin coincides with the flysch formation resulting in the westwards thrusting of Kimi flysch onto the Pelagonian platform and the entrance of peridotitic olistostromes within flysch.
Main subject category:
Science
Keywords:
vesuvianite, grossular, REE, Ca-metasomatism, chloritite, rodingite zoning, carbonization
Index:
Yes
Number of index pages:
8
Contains images:
Yes
Number of references:
241
Number of pages:
164
Serpentinization and Metasomatism.Constraints to their relationship through mineralogical, petrological and geochemical study of rodingitized dykes intruded ultramafic rocks of Kimi district, Evia, Greece..pdf (12 MB) Open in new window