THE AGE OF EARLY COLLISIONAL GRANITOIDS OF WESTERN SANGILEN (SE TUVA): IMPLICATIONS FOR ESTIMATING THE DURATION OF OROGENY AT THE MARGIN OF THE TUVA-MONGOLIAN MASSIF

Abstract

The first U-Pb isotope-geochronological data were obtained on the age of early collisional granitoids of the Matut massif (Western Sangilen, SE Tuva). The rocks that have been studied are assigned to magnesian, calc-alkaline, high-potassium, and low-peraluminious varieties. LA-ICP-MS analysis on two zircon samples showed that the Matut granite massif formation age corresponds to 522 Ma (U/Pb, LA-ICP-MS, zircons, 520±3 Ma (sample KT-1070) and 524±3 Ma (sample KT-1324)). Thus, the Matut massif granitoids are among the most ancient in Western Sangilen and were formed at the early collisional stage of the structural evolution of the region. Based on the data obtained, an assessment was made of the duration of collisional orogeny on the northwestern margin of the Tuva-Mongolian massif. The initiation to collapse period of the orogen is at least 80 million years.

Keywords

• orogeny
• collisional
• u-pb
• zircon
• la-icp-ms
• granitoids
• sangilen
• tuva-mongolian massif
• caob