Volume 18, Issue 55 (6-2001)
Abstract
Three granitoid bodies, Shirkuh batholith, Kaffe Abad and Ader Bolandan are exposed in NW Yazd, Cutting across the Naiband formation (Upper Triassic), and overlain by Cretaceous formations. Shirkuh batholith is most likely of Jurassic age. It seems to be the first and the most significant episode of magmatism in studied area which occurred in Middle Jurassic (Late Cimmerian) time. On the other hand, contact metamorphism of Cretaceous limestone arround the Kaffe Abad and Ader Bolandan intrusive bodies due to intrusion of granites and dioritic dikes and also the formation of various skarns indicate that the Kaffe Abad and Ader Bolandan intrusive bodies were emplaced during the later orogenic phases. Therefore, Shirkuh granitoid batholith has a wide range of Plutonic activity during Jurassic time, the most important episode of which has occurred in Middle Jurassic. Because of metamorphism of surrounding Cretaceous limestons, the Kaffe Abad and Ader-Bolandan intrusive bodies are at least younger than Lower Cretaceous and it is also possible that they are Oligo Miocene in age. Quartz, plagioclase and orthoclase are the major minerals, while garnet, biotite, pyroxene, amphibole, tourmaline, apatite, zircon, cordierite, andalusite, magnetite and hematite are found as accessory minerals in these rocks. SiO2, Na2O, K2O and CaO content are variable in different parts of the intrusive bodies. Spider diagrams clearly demonstrate Ba, K, Rb enrichment and Ti, Sr, Nb depletion in these rocks. Geochemically, two types of granites, I and S, are recognized, S type granites of which are more abundant in the region. Marble, skarn, Fe Cu Pb Zn. mineralization and non metalic minerals, such as kaolinite exist as economic potentials.
