Cretaceous high-pressure metamorphism and low pressure overprint in the Sistan Suture Zone, eastern Iran: Additional temperature estimates for eclogites, geological significance of U-Pb zircon ages and Rb-Sr constraints on the timing of exhumation

Kurzawa, Timon; Bröcker, Michael; Rad, Gholamreza Fotoohi; Berndt, Jasper; Lisker, Frank

doi:10.1016/j.jseaes.2017.07.051

Cited by 15 publications

(9 citation statements)

References 39 publications

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“…Relatively small occurrences of oceanic HP/LT rocks are commonly associated with the ophiolitic suture zones surrounding the microcontinental fragments and have been reported, for example, from the Alborz, Sabzevar, Sistan, Makran, and Zagros areas as well as from several occurrences to the west of the CIM (Nain, Jandagh and Chupanan) (e.g. Agard et al, 2006Agard et al, , 2011Angiboust et al, ,2013Angiboust et al, , , 2016Bröcker et al, 2013;Davoudian et al, 2016;Fotoohi Rad et al, 2005;Hunziker et al, 2017;Kurzawa et al, 2017;Omrani, Moazzen, Oberhänsli, Altenberger, et al, 2013;Omrani et al, ,2017;Omrani, Moazzen, Oberhänsli, Tsujimori, et al, 2013;Rossetti et al, 2017;Sepidbar et al, 2020;Shafaii Moghadam et al, 2017;Torabi, 2011;Torabi & Arai, 2013;Zanchetta et al, 2018).…”

Section: Geological Settingmentioning

confidence: 99%

“…Early 40 Ar/ 39 Ar ages for Sistan rocks indicated a considerable age range (c. 139-116 Ma;Fotoohi Rad et al, 2009). The geological significance of these data were challenged by Rb-Sr, 40 Ar/ 39 Ar, and U-Pb ages of HP/LT rocks from the same area documenting much younger ages (c. 87-85 Ma; Bonnet et al, 2018;Bröcker et al, 2013;Kurzawa et al, 2017). This led to the conclusion that the earlier Sistan data are erroneous and most likely compromised by analytical issues (Bröcker et al, 2013).…”

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confidence: 99%

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Unravelling metamorphic ages of suture zone rocks from the Sabzevar and Makran areas (Iran): Robust age constraints for the larger Arabia–Eurasian collision zone

Bröcker

Omrani

Berndt

et al. 2021

Journal Metamorphic Geology

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In this study we establish a time frame for metamorphic processes affecting Neotethyan suture zones at the northern (Sabzevar) and southern (Makran) margin of the Central Iranian Microcontinent. For this purpose, we have applied Rb-Sr and U-Pb geochronology to blueschist-and amphibolite facies rocks from these occurrences. So far, no isotopic ages are available for high-P/low-T rocks from the Sabzevar area which are exposed in the Govain and Chili mountains near Soltanabad. Three newly dated blueschists from the Govain mountain yielded Rb-Sr ages of 56.52 ± 0.32, 57.20 ± 0.32, and 55.12 ± 0.33 Ma respectively. These ages provide the first unambiguous evidence for late Palaeocene to early Eocene high-P metamorphism in the Sabzevar zone and confirm the accuracy of earlier age assignments that were derived indirectly. The clearly confirmed age difference between late Palaeocene-early Eocene blueschists of the Govain mountain and kilometre-scale dismembered HP granulites with Early Cretaceous (Albian) metamorphic ages from outcrops c. 60 km to the west of Soltanabad further corroborates interpretations that these rocks are not related to the same subduction zone complex. The blueschists record closure of an Albian to Late Cretaceous back-arc basin, whereas the granulites formed due to subduction of older oceanic lithosphere. Uranium-Pb zircon dating of an amphibolite from the Iranshahr region in the Makran Zone yielded an intercept age of 87.8 ± 1.8 Ma and weighted mean age of 88.1 ± 1.7 Ma. Rb-Sr mineral isochrons for seven blueschistand amphibolite facies samples from the same area generated very consistent ages of c. 84 Ma (± <1-3 Ma), regardless of metamorphic grade. The apparent contradiction that rocks recording different P-T conditions have identical metamorphic ages either indicates tectonic mixing of rocks during exhumation that originally had formed at the same time at different depths of the subduction system, or very rapid exhumation so that differences in closure temperatures became indistinguishable. The new data are similar, but much more precise, than previously reported K-Ar ages and suggest that most of the existing data had not been significantly compromised by contamination with extraneous Ar. Potassium-Ar indications for older blueschist-and/or amphibolite facies metamorphism (>85 Ma) have not yet been confirmed but can be

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Section: Geological Settingmentioning

confidence: 99%

mentioning

confidence: 99%

Unravelling metamorphic ages of suture zone rocks from the Sabzevar and Makran areas (Iran): Robust age constraints for the larger Arabia–Eurasian collision zone

Bröcker

Omrani

Berndt

et al. 2021

Journal Metamorphic Geology

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“…The SSZ in eastern Iran extends as a N-S trending belt over more than 700 km along the border area between Iran and Afghanistan. This zone located between the Afghan block to the east and Lut continental block to the west from Cretaceous to Paleocene times [31] ( Figure 1B). The SSZ exposes a well-preserved subduction zone complex, which provides evidence for the closure of a northward-extending promontory of the Neo-Tethyan Ocean during Early Cretaceous to Paleocene times due to convergence between the Central Iranian Lut block and the Afghan microcontinent [18].…”

Section: Regional Geological Settingmentioning

confidence: 99%

“…Based on studies of [18] the Sistan ocean zone was characterized by deep water facies, In contrast, the shallow water sea governed upon the Lut and Afghan blocks from Cretaceous to Eocene times [12,32]. Both the Neh and the Ratuk complexes comprise ophiolitic melanges, as well as non-metamorphic and metamorphosed deposits [31]. Both consist of a mélange incorporating ophiolitic rocks (about 30% in volume) associated with Cretaceous to Eocene phyllites and Paleogene terrigenous, marine sedimentary rocks [33].…”

Section: Regional Geological Settingmentioning

confidence: 99%

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Tectono-Magmatic Setting of the Divar Deposit, Eastern Iran: Evidences for VMS Mineralzation

Pourkaseb¹,

Zarasvandi²,

Adelpour³

et al. 2017

Preprint

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The Divar VMS deposit is located in the Nehbandan ophiolite complex (NOC). It is hosted in the Sistan suture zone (SSZ) marking the boundary between the Lut and Afghan continental blocks. This area is composed mainly of various ophiolitic rock units representing a tectono-sedimentary mélange, which are commonly interpreted as being the remnants of Sistan oceanic lithosphere. The major host rocks cropping out in the Divar deposit are mantle peridotites include clinopyroxene-(cpx-) rich harzburgites and depleted harzburgites with gabbronorite, cumulate gabbro, basalt and pelagic sediments. They are interpreted as being related to the rifting and subsequent Late Triassic continental break-up of the southern Neothethys. In this study petrographic observations mineral chemistry with whole rock chemistry, and rare earth element (REE) modeling were carried out on the different rocks associated with Divar deposit. The presented data led to the following conclusions: (1) The depleted harzburgites proved to be related to the residual mantle after 18-22% removal of melts. This is comparable with abyssal peridotites; (2) The cpx-rich harzburgites represent the residual mantle after the removal of 11-13% mid-ocean ridge basalt-type (MORB). Subsequently, the residual mantle was enriched in light REE (LREE) by subduction-derived fluids; (3) The gabbronorite and cumulate gabbro represents a portion of oceanic crust generated in a mid-ocean ridge setting; (4) The basalts belong to the N-MORB-type with no considerable crustal contamination. From the top to bottom, the Divar deposit is characterized a gossan zone, a thick massive ore zone, and a poorly developed stockwork zone. In Divar deposit, host rocks are indicated by serpentinized peridotites and severely altered mafic rocks that include disseminated and stockwork ore under massive lenses. These rocks showed a mineral assemblage of carbonate + quartz-jasper + chlorite + albite + epidote that demonstrate greenschist facies ocean floor metamorphism. Moreover, in the footwall rocks, sericitization and hematitization are also observed. Primary mineralization includes bedded ore, sulphide breccias, stockworks and chimney fragments. Ore mineral abundances decrease from pyrite, magnetite, to chalcopyrite, and sphalerite. Highlightly, there are two distinct mineralization phases' namely massive sulphide (stage-1) and massive magnetite (stage-2). The spatial relationships with the host rocks and textural evidence (e.g., magnetite replacing sulphides) indicate that sulphide minerals and magnetite were generated in different stages. The transition from sulphide to magnetite mineralization is interpreted as being related to the variation of H2S content in the ore fluids. The massive sulphide ore (stage 1) might have formed by primary hydrothermal fluids enriched in H2S and Fe. The second stage (massive magnetite) seem to be related to the later hydrothermal fluids enriched in Fe but poor in H2S, replacing the pre-existing sulphide minerals. The lithological features (stockwork/massive or...

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Cumulate rocks of the Dumak ophiolitic mélange, Eastern Iranian Ranges: Composition, origin and tectonic implications

et al. 2024

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Cretaceous high-pressure metamorphism and low pressure overprint in the Sistan Suture Zone, eastern Iran: Additional temperature estimates for eclogites, geological significance of U-Pb zircon ages and Rb-Sr constraints on the timing of exhumation

Cited by 15 publications

References 39 publications

Unravelling metamorphic ages of suture zone rocks from the Sabzevar and Makran areas (Iran): Robust age constraints for the larger Arabia–Eurasian collision zone

Unravelling metamorphic ages of suture zone rocks from the Sabzevar and Makran areas (Iran): Robust age constraints for the larger Arabia–Eurasian collision zone

Tectono-Magmatic Setting of the Divar Deposit, Eastern Iran: Evidences for VMS Mineralzation

Cumulate rocks of the Dumak ophiolitic mélange, Eastern Iranian Ranges: Composition, origin and tectonic implications

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