Application of the Titanium-In-Quartz Thermobarometer to Eclogites from the Biga Peninsula, NW Turkey

Abstract

Eclogites crop out in the Çamlica metamorphics and beneath the Çetmi melange as a tectonic slice in the Biga Peninsula in northwest Turkey. The Çamlica metamorphics occur in the westernmost part of the Biga Peninsula and are tectonically separated from the Denizgoren ophiolite in the west by the Ovacik fault. The Çetmi melange found on the southern part of the Biga Peninsula is mainly composed of various types of blocks within a detritic matrix. The high-P assemblages in eclogite consist of omphacite + garnet + epidote + glaucophane + quartz + phengite. Typical accessory minerals are rutile, zircon and sphene. Ti-in-quartz thermobarometer (TitaniQ) was applied on eclogites from the Biga Peninsula. The P-T dependencies of Ti-in-quartz solubility can be combined with P-T dependencies of Zr-in-rutile solubility to estimate pressure and temperature of crystallization. Titanium concentrations in quartz from the Çamlica metamorphics range from 0.26 to 0.91 ppm. Zirconium concentrations in rutile range from 26 to 64 ppm. However, Ti contents in quartz from the Çetmi melange vary from 0.47 to 2.19 ppm. Zr contents in rutile range between 50 and 150 ppm. Regional high-P metamorphism with peak conditions of 551 ± 5 oC and 21.5 ± 0.3 kbar in eclogite from the Çamlica region and 624 ± 17 oC and 22.6 ± 1.6 kbar in eclogite from the Çetmi region. Ti- in-quartz thermobarometer gives precise and comprehensible pressure and temperature values when using the Zr-in-rutile thermobarometer, which could be an advantage over classical methods.