环境地球化学国家重点实验室知识库

Mansehra Granite (MG) is massive and sheared which contains light-gray to jet-black schistosed and light-gray micaceous quartzite restites. The later possess relatively higher quartz as compared with mica contents whereas the former has predominant quartz and feldspar. Enclosure of apatite and zircon in micas and absence of sillimanite in schistosed and non-foliated facies suggest that these rocks are restite in nature. Presence of abundant and larger mica flakes at contact of restites with MG indicates exposure of these flakes at relatively higher temperature of granitic melt (623.7−886.6 °C) particularly at their margins. However, central part of restites remained unaffected due lesser impact of elevated temperature. Schistose and surmicaceous restites show crenulation cleavage and preserve structural antiquity during amalgamation in felsic melt. Geochemically, restites and Tanawal Formation indicate calc-alkaline to high K calc-alkaline domain with orogenic syn-collisional settings. Geochemical characteristics and modal mineralogy of restites and Tanawal Formation are similar. This study suggests that former has been derived from the later and their field relationships and geochemical signatures provide credible evidence in favour of S-type trait of Mansehra Granite. In geochemical diagrams, MG portrayed calc-alkaline, peraluminous S-type nature and its magma was generated from heterogeneous Tanawal Formation via fractional crystallization.