The Saghand Region, Central Iran: U-Pb geochronology, petrogenesis and implications for Gondwana Tectonics

Abstract

The Saghand area of East-Central Iran exposes rocks that comprise the substratum of the Central Iranian continental terrane, as part of the larger Alpine-Himalayan orogenic system. Our new U-Pb ages and geochemical data from the magmatic, metamorphic and siliciclastic rocks of the Saghand area unravel three main episodes of orogenic activity in the latest Neoproterozoic-Early Cambrian, the Late Triassic, and the Eocene. Geologic events in the oldest episode include in chronological order, low-to medium-grade metamorphism, calc-alkaline plutonism, rhyolitic to andesitic volcanism, and widespread trondhjemite emplacement, from 547 Ma to 525 Ma. The Late Triassic event (approximately 220-213 Ma) is characterized by the emplacement of granite-tonalite plutons. The extensive, high-grade metamorphic rocks, migmatites and post-kinematic intrusions of Eocene age (47-44 Ma) occur in a distinct domain, in the western part of the Saghand area. These rocks previously were thought to represent the Precambrian basement of the Central Iranian Terrane. The terminal Neoproterozoic-Early Cambrian orogeny in central Iran was related to a broad-scale magmatic arc that developed along the Proto-Tethyan margin of the Gondwanaland supercontinent. The fragmented remains of that margin occur as displaced terranes, including the Central Iranian Terrane, now embedded within the Alpine-Himalayan orogenic system. The newly recognized Late Triassic intrusions of the Saghand area are indicative of a tectonomagmatic episode of possible collisional nature, in accord with the previously identified Early Kimmerian (Cimmerian) event in the region. The extensive Eocene metamorphic and magmatic activities correspond to the early Alpine Orogeny, which resulted from the convergence between Arabian and Eurasian plates, and the Cenozoic closure of the Tethys oceanic tract(s) by subduction.

Salt domes of the UAE and Oman: Probing eastern Arabia

“…There is therefore reliable evidence of crustal extension between 720-640 Ma, followed by widespread but slow subsidence unaffected by tectonics from 640 to 547 Ma, which is best explained by a model of continental stretching. 525 Ma (Ramezani and Tucker, 2003) suggests subduction of proto-Tethyan crust beyond the continental margin, which converted the Oman and UAE regions into a retro-arc setting on the NE Arabian margin. Thick evaporites and black shales were deposited in a number of 'salt' basins while structural highs focussed carbonate deposition.…”

Identification of mineralized zones in the Zardu area, Kushk SEDEX deposit (Central Iran), based on geological and multifractal modeling

“…Although the block was originally thought to have formed during the Pan-African intra-continental extension [50][51][52], it has recently been redefined as a magmatic arc ( Fig. 1) developed along the Proto-Tethyan margin of the Gondwanan supercontinent [45,[53][54][55]. Some authors have reported geological features, predominantly bimodal alkaline volcanism, suggestive of an extensional back-arc regime in the eastern portion of the area [47,48,56].…”

“…The Bafq district, in which the Kushk deposit occurs, is located within the central part of the Kashmar-Kerman Tectonic Zone [45], also known as the Posht-e-Badam Block [46], of the Central Iranian Zone (CIZ: Fig. 1).…”

Porphyry copper assessment of the Tethys region of western and southern Asia: Chapter V in <i>Global mineral resource assessment</i>

“…In the Kashmar-Kerman Terrane to the west, a 52-Ma high-grade metamorphic gneissic and migmatitic complex is intruded by large late-to post-kinematic calc-alkaline dioritegranite plutons and aplitic dikes of early Eocene age (47-44 Ma; Ramezani and Tucker, 2003). The metamorphic complex is largely the product of anatexis followed by exhumation associated with extensional cordilleran metamorphic core complex formation (Verdel and others, 2007).…”