Ph.D. Tezi Görüntüleme

Student: İbrahim Uysal
Supervisor: Prof. Dr. M. Burhan Sadıklar
Department: Jeoloji Mühendisliği
Institution: Graduate School of Natural and Applied Sciences
University: Karadeniz Technical University, Turkey
Title of the Thesis: Petrology of Upper Mantle Peridotite and Ophiolitic Chromitites from the Muğla (SW-Turkey): Implications from Mineral Chemistry, Major-Trace-Rare Earth Elements (REE)-Platinum-Group Elements (PGE) Geochemistry, PGE Mineralogy and Re-Os Isotope Systematics
Level: Ph.D.
Acceptance Date: 27/12/2007
Number of Pages: 288
Registration Number: Di618
Summary:

      Mantle peridotites around the city of Muğla in SW-Turkey are classified into three

subgroups, namely Cpx-harzburgite, depleted harzburgite and dunite, on the basis of their

      modal mineralogy, geochemical features and mineral chemistry. Cpx-harzburgites are

characterized by their higher Ca, Al and REE contents, and contain Al-rich orthopyroxene

      and clinopyroxene with lower Cr# spinel compared to depleted harzburgite and dunite.

Cpx-harzburgites are thought to be the residua left after extraction of MORB-type basalt,

      produced by %10 partial melting of fertile upper mantle, from which high-Al chromitite

with high radiogenic Os content crystallized. However, depleted harzburgites are assumed

      to be residua left after extraction of hydrous boninitic melt, produced by second stage

partial melting of already depleted mantle due to subducting slab, from which high-Cr

      chromitites with lower radiogenic Os content were crystallized as a result of melt-rock

interaction in a suprasubduction environment. Dunites around the chromite deposits are

      considered to be the product of melt-peridotite interaction.

Most of the chromitites contain high-Cr chromite and display enrichment in IPGE

      (Os, Ir, Ru) over PPGE (Rh, Pt, Pd), with concentrations of PGE between 61 and 1305

ppb. Consistently, laurite-erlichmanite serie minerals with various Os contents are found to

      be the most abundant PGM in chromite. In addition to Os-Ir-Ru and Ru-Fe-Os alloys,

irarsite and kashinite, Pt-Fe alloys (isoferroplatinum) which is not common in ophiolitic

      chromitites were also detected as primary inclusions in chromite. In partly altered

chromitite sample, laurite grains were found to be affected by alteration and transformed to

      the Ru-oxide phases. The presence of olivine and clinopyroxene as well as hydrous silicate

inclusions such as amphibole and phlogopite in high-Cr chromitite support the idea that

      high-Cr chromitites were formed in a suprasubduction environment.

Key Words: Muğla, Mantle peridotites, Melt-peridotite interaction, Ophiolitic chromitites,

      Platinum-Group Elements, Platinum-Group Minerals, Re-Os isotope.