Regional geology, geochronology and geochemistry of the igneous and metamorphic rock suites of the Saghand area, Central Iran

The Saghand area is underlain by rocks comprising a part of the Central Iranian continental terrane. The Central Iranian terrane records a prolonged history of fragmentation, drift, collision and amalgamation, which reflects the tectonic development of the Alpine-Himalayan orogenic system during Mesozoic and Cenozoic time. Geochronologic, petrologic and geochemical study of the igneous and metamorphic rocks of this terrane help to resolve important regional tectonic problems regarding the evolution of the Alpine-Himalayan orogenic system.;The investigated magmatic and metamorphic rocks in the Saghand area of East-Central Iran record three episodes of orogenic activity in the latest Neoproterozoic-Early Cambrian, the Late Triassic, and the Eocene. Geologic events in the oldest episode include lower-amphibolite facies metamorphism, granite-tonalite plutonism, rhyolitic and andesitic volcanism, and widespread trondhjemite emplacement, from 547 Ma to 525 Ma. The Late Triassic event (ca. 213-220 Ma) is represented by emplacement of granodiorite-granite plutons. The extensive, high-grade metamorphic rocks and granite-diorite intrusions of Eocene age (47 to 44 Ma) occur in a distinct structural domain, the Chapedony uplift, in the western part of the Saghand area. These rocks were once believed to represent the Precambrian basement of the Central Iranian terrane.;The latest Neoproterozoic-Early Cambrian orogeny in Central Iran was related to a broad-scale magmatic arc that developed along the northern (present-day) margin of the Gondwanaland supercontinent, after its final assembly. The fragmented remains of the Gondwanan margin occur as displaced terranes, including the Central Iranian terrane, now embedded within the Alpine-Himalayan orogenic system.