New detrital zircon U–Pb insights on the palaeogeographic origin of the central Sanandaj–Sirjan zone, Iran

Abstract

New detrital U–Pb zircon ages from the Sanandaj–Sirjan metamorphic zone in the Zagros orogenic belt allow discussion of models of the late Neoproterozoic to early Palaeozoic plate tectonic evolution and position of the Iranian microcontinent within a global framework. A total of 194 valid age values from 362 zircon grains were obtained from three garnet-micaschist samples. The most abundant detrital zircon population included Ediacaran ages, with the main age peak at 0.60 Ga. Other significant age peaks are at c. 0.64–0.78 Ga, 0.80–0.91 Ga, 0.94–1.1 Ga, 1.8–2.0 Ga and 2.1–2.5 Ga. The various Palaeozoic zircon age peaks could be explained by sediment supply from sources within the Iranian microcontinent. However, Precambrian ages were found, implying a non-Iranian provenance or recycling of upper Ediacaran–Palaeozoic clastic rocks. Trace-element geochemical fingerprints show that most detrital zircons were sourced from continental magmatic settings. In this study, the late Grenvillian age population at c. 0.94–1.1 Ga is used to unravel the palaeogeographic origin of the Sanandaj–Sirjan metamorphic zone. This Grenvillian detrital age population relates to the ‘Gondwana superfan’ sediments, as found in many Gondwana-derived terranes within the European Variscides and Turkish terranes, but also to units further east, e.g. in the South China block. Biogeographic evidence proves that the Iranian microcontinent developed on the same North Gondwana margin extending from the South China block via Iran further to the west.

Stratigraphic and volcanic signatures of Miaolingian-Late Ordovician rift pulses in the Alborz Mountains, northern Iran

“…The apparent Cambrian-Ordovician palaeogeographic proximity of the Zagros, Sanandaj-Sirjan, central Iranian and Alborz basins (e.g., Torsvik and Cocks, 2017;Domeier, 2018) and the strong biogeographic links of the Alborz Mountains with South China and the Mediterranean margin of Gondwana (Álvaro et al, 2013) have been, and still are, a continuing matter of discussion. Provenance analysis by Horton et al (2008) and Shakerardakani et al (2021), based on detrital zircon populations from Cambrian sandstones sampled in these tectonostratigraphic units, has yielded similar age peaks at 550, 600 and 950 Ma, including minor peaks at 780 and 860 Ma, and subsidiary peaks at 1020, 1880 and 2500 Ma. These U-Pb ages match detrital zircon results for Ediacaran-Cambrian sandstones of Israel, Jordan and possibly Egypt (Kröner et al, 1990;Wilde and Youssef, 2002;Avigad et al, 2003;Kolodner et al, 2006;Meinhold et al, 2021), reflecting common sediment sources from the Arabian-Nubian Shield of the western Arabian Peninsula and Northeast Africa.…”