Ancient rocks reveal two stages of underground journey in Türkiye

Researchers at Istanbul Technical University identified two distinct phases of geological movement for granitic rocks in northwestern Anatolia, Türkiye.

By studying three specific granitic bodies near the Marmara Sea, the team traced how these rocks moved from deep within the Earth's crust to the surface over millions of years. The team used a combination of mineral-based dating methods to act as geological clocks. These clocks allowed them to track the cooling of the rocks from approximately 800°C down to 60°C.

The findings show that the rocks first crystallized at mid-crustal depths between 8.8 to 13.6 kilometers deep during the Eocene period, roughly 48 to 37 million years ago. The study revealed that the rocks underwent two major cooling events. The first occurred during the Eocene, where the rocks cooled rapidly from 800°C to 350°C. This was followed by a period of much slower cooling.

A second rapid cooling phase happened during the early Oligocene, about 32 to 28 million years ago. The researchers suggest these two phases were caused by different processes: the first by deep-seated transformations in the crust and the second by a broader regional tectonic shift involving the retreat of the African plate.