Abstract:

Volcanic rocks and carbonate-terrigenous sequenences occur extensively in Tu Le area of more than 5,000 km2. Author’s results suggest that the exposed carbonate-terrigenous rocks, in fact, are the remnants of the older sedimentary rocks adjacent to, at domes of, or on top of the volcanic formations. There is an absence of volcanic clasts in the form of extruvise sedimentation inside the exposed areas of these sequences. The volcanic clasts are products of explosive eruptions, sitting on the underlying sedimentary formations. Hot contacts and cutting relations between sedimentary units and volcanic rocks in Tu Le area are observed with presence of low-grade thermal contact metamortamophic rocks. The rocks contain fossils of Permian-Jurassic age, corresponding to Late Paleozoic-Mesozoic sequences that prevalently distribute in the northwest region. The volcanic rocks in Tu Le area, with the forming sequence determined by geological relationships, consist of 3 complexes: 1- basalt, 2- rhyolite, and 3- trachite. According to the forming depth, the rocks are classified as sub-volcanic facies with a small amount of explosive and eruption facies. The geological ages of volcanic and clast rocks in Tu Le area appear to be certainly younger than those of surrounding rocks, and probably after the Jurassic Period