Triassic granitic rocks exposed in Dan Chang area are northern and southern granitic units. These granites intruded Silurian-Devonian clastic sedimentary rocks of Bo Phloi Formation and Ordovician limestones of Thung Song Group. Fifteen representative samples were collected for petrography, whole-rock geochemistry, and mineral chemistry studies. These granites show porphyritic texture and comprise quartz, K-felspar, plagioclase, biotite, and muscovite as the major compositions, with the minor compositions of ilmenite, zircon, and apatite. Moreover, aplite and pegmatite are associated with the southern granite as dikes. Aplite and pegmatite are composed of mainly K-feldspar, quartz, tourmaline, and plagioclase. Based on the whole-rock geochemistry, these rocks can be classified as peraluminous S-type granite to granodiorite, originating from high-K calc-alkaline and derived from an upper crustal source. The geotectonic discrimination diagrams show that these granitic rocks are significantly related to syn-collision to late-orogenic. The mineral chemistry of the granites shows a close relationship of their compositions and magma genesis, which can imply that aplite might be the last stage of the granitic crystallization. Moreover, the crystallization Pressure-Temperature (P-T) conditions of the northern and the southern granites are 3.4-3.7 kbar, 571-630°C and 3.3-3.8 kbar, 624-656°C, with calculated intrusion depths of 12-13 km and 12-14 km, respectively. These granitic rocks are comparable to the S-type granite of the Central Belt Granite of Thailand, resulted from syn-collisional crustal thickening and subsequent post-collision after the closure of the Paleotethyan during the Late Triassic.

<p>Granitic rocks in Thailand and South East Asia have been divided into Eastern belt granite, Central belt granite, and Western belt granite.The Central belt granite widely expose in Thailand including Dan Chang area. According to the field investigation, there are two granitic bodies in Dan Chang area. The main granitic body is composed of mainly K-feldspar, plagioclase, quartz, and biotite with some accessory minerals of opaque mineral and zircon. The granitic rocks are obviously characterized by porphyritic texture of coarse-grain K-feldspar.Another granitic body is small body which is similar mineral assemblage to those granite in the main body with different proportion of K-feldspar. The amount of K-feldspar in the small body granite is less than the main body granite. However, both granitic bodies are generally characterized by porphyritic texture of K-feldspar. Moreover, aplite and pegmatite are associated with both of them. The results of field investigation and petrographic study of the granitic rocks in Dan Chang District, Suphan Buri Province, Thailand can be compared with the Central belt granite which may be resulted from the Sibumasu and Indochina collision in Late Triassic.</p>