HIGH-PRESSURE METAMORPHIC ROCKS OF THE CHARA OPHIOLITE BELT (CAOB): AGE AND EXHUMATION CONDITIONS

Abstract

A critical element in the construction of tectonic models of exhumation of basalts that have undergone high-pressure metamorphism is the diagnosis of synchronicity and the genetic relationship between deformations and high-pressure metamorphic changes. In this report, these issues are discussed on the example of the metabasalts of the Chara ophiolite belt. In the bottom of the basalt block with the separation of pillow lavas near the Burshabulak farm, crack-vein systems with high-pressure mineral associations were discovered and analyzed, which directly indicates their tectonic origin. It is shown that the conditions for the formation of such vein mineral associations correspond to eclogite-like rocks (P=18.5 kbar temperatures of no more than 520 °C). The age of the high-pressure metamorphism basalts of the synchronous type with deformations according to 40Ar/39Ar isotope dating of amphiboles cannot be younger than the boundary of 452±14 million years.

Keywords

• high-pressure metamorphism
• exhumation
• basalts
• ar/ar dating
• chara ophiolite belt