Structural Setting and Heterogeneous Deformation of the Mesoproterozoic Granite–Gneisses of North Tianshan with the Example of the Karadjilga Massif (Kyrgyzstan)

Abstract A detailed structural study showed that the Mesoproterozoic Karadjilga granite–gneiss massif of the Kyrgyz North Tianshan represents a sheet intrusion, concordant to the bedding of the host Mesoproterozoic metasedimentary strata. The massif has a complex internal structure with strain gradients from unfoliated granite to mylonite. The boundaries of the mylonite, gneiss, and unfoliated granite zones, as well as the foliation in gneisses, are oriented subparallel to the contacts of the massif and are deformed into a single syncline together with the host sedimentary strata. The obtained U–Th–Pb (SHRIMP) age of unfoliated granite (1121 ± 13 Ma) is close to the previously obtained age estimates for granite–gneisses (~1090–1130 Ma), and indicates that, regardless of the degree of deformation, all the rocks of the massif belong to an unified igneous complex.