introduction to the geology and mineralogy of pegmatites located south of mashhad (first report of li-bearing pegmatites from iran)

the granites south of mashhad are located in the north-east of iran and occur in the suture zone between the binalud and kopeh dagh areas. these s-type granites are peraluminous with an upper triassic age and include intersecting pegmatites. these pegmatites are homogenous and show simple mineralogical combinations which include k-feldspars (microcline and orthoclase), plagioclase, quartz, micas (biotite, muscovite and lepidolite), tourmaline (elbaite, dravite, and schorl) and garnet (almandine-spessartite). the pegmatites south of mashhad belong to the lct (lithium-cesium-tantalum) and msrel-li (muscovite- ree-li).the li-content of these pegmatites ranges between 202-1653 ppm and the ratios k/cs, k/rb and al/ga are high which indicates a low level of differentiation. the mg/ li ratio in these pegmatites lies between 0.2-12.6. all the element ratios indicate that pegmatites are low evolved.