U-PB AGES OF LA-ICP-MS ZIRCON FROM LATE CRETACEOUS TUFF IN THE SALIN DEPRESSION OF MYANMAR AND THEIR GEOLOGICAL SIGNIFICANCE

Tuff, as a direct product of volcanic activity, is often found along the edge of the plate. Accurate geochronological dating for the tuff formations in the Salin Depression of the pre-Arc Basin in the north-central part of Myanmar may found a reliable basis for stratigraphic division and calibration of the study area. The tectonic movement between blocks, supplemented by geochemical data, may provide time constraints for delineations of tectonic settings. Our data suggest that: 1) The ages of zircons in tuffs are 70±1.0 Ma, 64.2±1.2 Ma, 65±1.0 Ma, and 64±0.8 Ma., indicating that the Pangji Formation is Late Cretaceous in age. 2) The B-type subduction of the Neo-Tethys Ocean led to magmatic activity in the Central Basin of Myanmar. Tuff deposits derived are deposited in the Salin Depression.