Origin of Magnesite in Turkey, a Stable Isotope Study

Zedef, Veysel (1994) Origin of Magnesite in Turkey, a Stable Isotope Study. PhD thesis, University of Glasgow.

Abstract

This thesis is concerned with the problem of the genesis of the various types of cryptocrystalline magnesite deposits found in western Turkey. Veins and stockworks of cryptocrystalline magnesite deposits are found within the discontinuous ultramafic belts of western Turkey. Sedimentary-hydrothermal lacustrine magnesites and presently forming hydromagnesite deposits lie above these ultramafic rocks. A hot-spring calcite deposit at the northern edge of a Menderes graben is also considered. From the stable carbon and oxygen isotopic signatures of the magnesite, hydromagnesite and calcite formations of western Turkey, three end-members can be distinguished End-member-1: represents the cryptocrystalline, vein-type of magnesite deposits. Decarboxylation of organic-rich sediments may have provided about two thirds of the carbonate in the vein-type of Koyakci Tepe magnesite deposits, Konya, which have ~-13 and ~+27 % of delta13C and delta18O respectively. Stockwork deposits at Helvacibaba, Yunak and Kozagac, all in Konya, have slightly heavier delta13C and delta18O values indicating more involvement of atmospheric carbon dioxide (as bicarbonate in the circulating meteoric water) compared to those of Koyakci Tepe. End-member-2 : represents carbon dioxide of atmospheric origin. Presently forming hydromagnesite deposits at Saida lake, Yesilova, Burdur reflect such a carbon dioxide origin with of delta13C of ~+4‰PDB and delta18O of ~+36‰SMOW. End-member-3 : represents the carbon dioxide of metamorphic origin. Present-day, hot-spring travertine (calcite) deposits at Pamukkale, Denizli, have the heaviest delta13C (~+6 %o,PDB) and extremely light delta13C (~+20‰SMOW) values and these values are probably the result of decarbonation and/or dissolution of limestone formations beneath travertines. Sedimentary magnesite deposits at Hirsizdere, Denizli and stockwork magnesite deposit at Arapomer Deresi have unexpectedly heavy delta13C (~+2 and 0‰PDB respectively), and these deposits probably gained their carbonates from decarbonation and/or dissolution of limestones. The extremely low REE contents of magnesite, hydro magnesite and ultramafic host- rocks indicate that the magnesium is derived from the ultramafic rocks. The Saida lake hydromagnesite deposits are being formed by a microbial community in the lake itself. In terms of isotopic signatures, physical features and geological environment, Saida's hydromagnesite deposits are comparable with the Miocene, lacustrine, sedimentary magnesite deposits elsewhere, perhaps especially to Bela-Stena in Serbia. Therefore Saida's hydromagnesites may be a precursor of magnesite.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: M J Russelll
• Keywords: Geology, Geochemistry
• Date of Award: 1994
• Depositing User: Enlighten Team
• Unique ID: glathesis:1994-75642
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Dec 2019 09:15
• Last Modified: 19 Dec 2019 09:15
• URI: https://theses.gla.ac.uk/id/eprint/75642