The number of quartz and feldspar rich surfaces identified in northwestern Syrtis Major has been extended beyond previously reported results to a region of about 230 by 125 km. Thermal Emission Imaging System infrared data were used to locate surfaces spectrally identical to previously reported central peak units in Syrtis Major. These surfaces are indicative of the production of highly differentiated magmas. Though it is possible that the granitoid exposures add to the variety of igneous compositions associated with the Syrtis Major volcanic construct, the geologic context of these exposures suggests a formation that predates Syrtis Major.