AGE AND TECTONIC SIGNIFICANCE OF THE MAFIC DYKE SWARM IN THE KURUKTAGREGION, XINJIANG

The mafic dykes are composed of a series of northwest-trending diabase in Kuokesu of the Kuruktag region, Xinjiang. Four whole-rock samples of the mafic dykes in the region give an Ar-40 / Ar-36-K-40 / Ar-36 is ochron age of 282 Ma with the initial Ar-40 / Ar-36 = 507. The charact eristics of the major, trace and rare earth elements of the dyke rocks indicate that they belong to the calc-alkaline series and were emplac ed in extensional structures at an intermediate depth of the crust. Th is shows that there was a large-scale extension in the Permian Period, which might be associated with the post-collisional extension of the ancient Tianshan Mountains.