Origin of 1.8 Ga zircons in Post Eocene mafic dikes in the Roshtkhar area, NE Iran

Alizadeh, Elahe; Ghadami, Gholamreza; Esmaeily, Dariush; Ma, Changqian; Lentz, David R.; Omrani, Jafar; Golmohammadi, Abbas

doi:10.1080/00206814.2017.1396259

Cited by 5 publications

(2 citation statements)

References 107 publications

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“…Cadomian crust is important as assimilant for the evolution of Cenozoic magmas. However, we do not rule out that the crust beneath Iran is heterogenous and there may be some older continental ribbons such as NE (Alizadeh et al, 2017), SE (Moghadam, Brocker, et al, 2017), and central Iran (Shakerardakani et al, 2019). Pre‐Cadomian crust, if it exists, has yet to be discovered.…”

Section: Geological Settingmentioning

confidence: 88%

Neotethyan Subduction Ignited the Iran Arc and Backarc Differently

Moghadam

et al. 2020

JGR Solid Earth

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Most arcs show systematic temporal and spatial variations in magmatism with clear shifts in igneous rock compositions between those of the magmatic front (MF) and those in the backarc (BA). It is unclear if similar magmatic polarity is seen for extensional continental arcs. Herein, we use geochemical and isotopic characteristics coupled with zircon U‐Pb geochronology to identify the different magmatic style of the Iran convergent margin, an extensional system that evolved over 100 Myr. Our new and compiled U‐Pb ages indicate that major magmatic episodes for the NE Iran BA occurred at 110–80, 75–50, 50–35, 35–20, and 15–10 Ma. In contrast to NE Iran BA magmatic episodes, compiled data from MF display two main magmatic episodes at 95–75 and 55–5 Ma, indicating more continuous magmatism for the MF than for the BA. We show that Paleogene Iran serves as a useful example of a continental arc under extension. Our data also suggest that there is not a clear relationship between the subduction velocity of Neotethyan Ocean beneath Iran and magmatic activity in Iran. Our results imply that the isotopic compositions of Iran BA igneous rocks do not directly correspond to the changes in tectonic processes or geodynamics, but other parameters such as the composition of lithosphere and melt source(s) should be considered. In addition, changes in subduction zone dynamics and contractional versus extensional tectonic regimes influenced the composition of MF and BA magmatic rocks. These controls diminished the geochemical and isotopic variations between the magmatic front and backarc.

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Section: Geological Settingmentioning

confidence: 88%

Neotethyan Subduction Ignited the Iran Arc and Backarc Differently

Moghadam

et al. 2020

JGR Solid Earth

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“…Archean and Paleoproterozoic zircons (2.5-2.4 Ga) are also present as inherited cores in Cenozoic magmatic rocks of the Urumieh-Dokhtar Magmatic Belt (UDMB) and/or as xenocrysts within the Cenozoic metamorphic rocks. Paleoproterozoic zircons (with peak at 1.9-1.8 Ga) are also reported as xenocrysts within the Eocene magmatic dikes from NE Iran (Alizadeh et al, 2018) and as inherited cores in zircons from the Jurassic granitic plutons from southern Iran , but it seems unlikely that these would be enough to give Paleoproterozoic and Archean peaks in our samples. We think that, although ANS, Afro-Arabian craton and Saharan Metacraton are plausible sources for detrital zircons older than ca 600 Ma, it is unlikely that such zircons could be transported across Tethyan ocean to be deposited in Makran (except for DZ of Triassic sandstones) (see Figure 14).…”

Section: 1029/2019tc005963mentioning

confidence: 81%

Reconstructing the Source and Growth of the Makran Accretionary Complex: Constraints From Detrital Zircon U‐Pb Geochronology

et al. 2020

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We have used U-Pb zircon ages and Hf isotopic compositions for detrital zircons from Eocene and Cretaceous-Triassic sedimentary rocks of the Makran accretionary complex (MAC, Iran) to understand the source and growth of the MAC during Mesozoic and Cenozoic time. The Cenozoic sandstones reveal the main age distribution from Paleocene to Eocene with a peak at 54 Ma and show εHf(t) values of −47.7 to +12.1. Our compiled U-Pb-Hf data from both the Urumieh-Dokhtar Magmatic Belt magmatic zircons and the Paleogene Makran detrital zircons reveal that both Makran continental arc and Urumieh-Dokhtar Magmatic Belt are important suppliers of the Makran detrital zircons. Mesozoic zircons show dominant peaks at 94-91 (Late Cretaceous), 151 (Late Jurassic), and 229 Ma (Triassic). Detrital zircons with peaks at 91 and 151 Ma with εHf(t) values of −42.5 to +15.2 can be supplied by the erosion of Makran ophiolitic rocks, although negative εHf(t) values indicate some Makran detrital zircons came from reworking of the magmatic rocks of the Sanandaj-Sirjan zone of Iran. Late Cretaceous detrital zircons (~94-91 Ma) were also supplied from erosion of the nascent Makran arc. Middle to Late Jurassic zircons (163-151 Ma) can also come from erosion of the rifting-related magmatic rocks within the Bajgan-Durkan complex, although zircon U-Pb ages show middle Jurassic ages (170-165 Ma) for the Bajgan-Durkan magmatic rocks. Triassic zircons with εHf(t) values between −17 and +6.9 probably were supplied by the Bajgan-Durkan complex and/or by Central Iran magmatic rocks. Paleozoic detrital zircons show major peaks at 330 (Carboniferous) and 460 Ma (Ordovician). Their εHf(t) values range from −51 to +18.2 and −9.5 to +4.6, respectively. Carboniferous detrital zircons may have come from the erosion of alkaline gabbros and A-type granites reported from the NW, NE, SE, and central segments of the Sanandaj-Sirjan zone and/or may have been supplied from reworking of Carboniferous strata of the Bajgan-Durkan complex. Late Neoproterozoic-Early Cambrian detrital zircons with εHf(t) values from −42.9 to +32.4 are suggested to be derived from the Cadomian magmatic rocks of Iran and Anatolia. The pre-Cadomian detrital zircons with εHf(t) values of −28.9 to +27.5 are consistent with derivation from magmatic rocks of the Arabian-Nubian Shield. Archean (2.5 Ga) and Paleoproterozoic (2.4-1.8 Ga) detrital zircons probably come from the Afro-Arabian Craton and Saharan Metacraton. New data from detrital zircons imply that the MAC evolved from Triassic to Eocene and incorporated all orogenic elements including the continental lithosphere, oceanic crust, and its nearby continental arcs during its evolutionary cycle. Plain Language Summary U-Pb zircon ages and Hf isotopic compositions for detrital zircons are used to understand the source and growth of the Makran accretionary complex during Mesozoic and Cenozoic time. The Cenozoic sandstones reveal important suppliers from both Makran continental arc and Urumieh-Dokhtar Magmatic Belt, while Mesozoic zircons show reso...

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Tectonic Settings of Potassic Igneous Rocks

Müller¹,

Groves²

2018

Potassic Igneous Rocks and Associated Gold-Copper Mineralization

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Origin of 1.8 Ga zircons in Post Eocene mafic dikes in the Roshtkhar area, NE Iran

Cited by 5 publications

References 107 publications

Neotethyan Subduction Ignited the Iran Arc and Backarc Differently

Neotethyan Subduction Ignited the Iran Arc and Backarc Differently

Reconstructing the Source and Growth of the Makran Accretionary Complex: Constraints From Detrital Zircon U‐Pb Geochronology

Tectonic Settings of Potassic Igneous Rocks

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