Petrological Characteristics on NW of Ladakh Batholith and its enclaves around the Trans-Himalayan Belt (India)

The Ladakh Batholith is part of the Trans-Himalayan Plutonic Belt (a Cretaceous-Palaeogene Andean-type arc) extending over 2500 km along the southern margin of the Eurasian continent. Although extensive studies have performed in Ladakh (geotectonic implications and geochronology of the granitic rocks) mineralogy and petrogenesis of source area have remained poorly studied. Here we present the petrography and petrology of Taru and Umla granites, which is located about 50 to 60 km Westside of Leh district of Ladakh region (NW India). The intrusive rocks are medium- to coarse-grained and porphyritic with feldspar. They are composed of biotite granodiorite, hornblende granodiorite, quartz granodiorite, leucogranite, biotite-hornblende granite and amphibole biotite monzodiorite. The predominant minerals are alkali feldspar, plagioclase, quartz, biotite, and hornblende. The accessory minerals consist of apatite, zircon, microcline, rutile, monazite, allanite, titanite and opaques. Secondary minerals are mainly chlorite, sericite, epidote, and muscovite. Growth zones of plagioclase are accentuated by secondary sericite, muscovite, clay minerals and epidote. The process of alteration is sericitization, saussuritization and epidotization. Biotite or amphibole is completely altered by chlorite and subordinate epidote. Fine prismatic zircons are surrounded by apatite and having inclusions in biotite and plagioclase. Intergrowth textures (i.e. antiperthitic, perthitic, graphic, granophyric, myrmekites). Mafic enclave having sharp, crenulate and rounded to elongate structures ranges from 5 to 10 cm in length. Plagioclase xenocrysts, quartz and acicular apatite indicate the formation of hybridization. Field observation indicates that the Ladakh Batholith and their enclaves could be the products of multistage mixing and mingling processes consequent fractional differentiation of various batches of mafic and felsic magmas are formed in open magma chamber of subduction setting.