Abstract:

Granites occurred in the Gaoligong tectonic belt were controlled by Nujiang deep fault. The granites emplaced in SN direction as long and narrow lens. Far away from the Nujiang fault, the granite is massive structure and medium to coarse-grained texture. Near to the fault, granites are banded structure and mylonitic texture. The SHRIMP age of zircon from granites is 124-118 Ma. As well, the ⁴⁰Ar/³⁹Ar dating of biotite from granitic mylonites is 18-10 Ma, same with the deformed age of mylonitic granites from Chayu, which is on the north location of this tectonic belt. The granite belt changes younger from 76 Ma in northeast to 37 Ma in the southwest. This indicates that these plutonic units intruded in order. All these above proposed that the granites in the tectonic belt from Bomi-Chayu to Gaoligong crystallized in 124-118 Ma. The strike-slip peak time of Nujiang deep fault is 18-10 Ma. In this period, the slide in large scale took place in Atyn Tagh fault, Ailaoshan-Honghe fault. There are also many rifts occurred on the south edge of Lhasa block. These coupled with collision of India-Asia and extrusion of India to NNE direction. The granites in the Gaoligong belt are responsive to the whole process of India-Asia collision.

Key words: Nujiang-Gaoligong belt, deformation of granite, age of strike-slip, India-Asia collision, Neo-Tethys, tectonics