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[Display omitted] • First set of zircon ages (∼3.6 Ga to 100 Ma) for the Armenian metamorphic basement. • Major and trace element and Sr-Nd-Pb isotope geochemistry of Mesozoic sills and dykes. • 40Ar/39Ar and zircon U-Pb ages and palaeomagnetism of the Mesozoic magmatism. • Geodynamic evolution of the Gondwana-derived South Armenian Block since the Permian. The geodynamic evolution of the South Armenian Block (SAB) within the Tethyan realm during the Palaeozoic to present-day is poorly constrained. Much of the SAB is covered by Cenozoic sediments so that the relationships between the SAB and the neighbouring terranes of Central Iran, the Pontides and Taurides are unclear. Here we present new geochronological, palaeomagnetic, and geochemical constraints to shed light on the Gondwanan and Cimmerian provenance of the SAB, timing of its rifting, and geodynamic evolution since the Permian. We report new 40Ar/39Ar and zircon U-Pb ages and compositional data on magmatic sills and dykes in the Late Devonian sedimentary cover, as well as metamorphic rocks that constitute part of the SAB basement. Zircon age distributions, ranging from ∼3.6 Ga to 100 Ma, firmly establish a Gondwanan origin for the SAB. Trondhjemite intrusions into the basement at ∼263 Ma are consistent with a SW-dipping active continental margin. Mafic intraplate intrusions at ∼246 Ma (OIB) and ∼234 Ma (P-MORB) in the sedimentary cover likely represent the incipient stages of breakup of the NE Gondwanan margin and opening of the Neotethys. Andesitic dykes at ∼117 Ma testify to the melting of subduction-modified lithosphere. In contrast to current interpretations, we show that the SAB should be considered separate from the Taurides, and that the Armenian ophiolite complexes formed chiefly in the Eurasian forearc. Based on the new constraints, we provide a geodynamic reconstruction of the SAB since the Permian, in which it started rifting from Gondwana alongside the Pontides, likely reached the Iranian margin in Early Jurassic times, and was subject to episodes of intraplate (∼189 Ma) and NE-dipping subduction-related (∼117 Ma) magmatism. [ABSTRACT FROM AUTHOR]

[Display omitted] • Provenance during passive- to active-margin transition at South-Qiangtang Cimmerian margin. • Subduction initiation at ~222 Ma, oceanic fringing arc at ~210 Ma and continental arc at ~190 Ma. • Initial Mesotethys subduction coeval along Cimmerian margins, a response to Paleotethys closure. The South Qiangtang terrane (SQT), the Tibetan representative of the Cimmerian continent, is bounded in the south by the Bangong-Nujiang suture zone (BNSZ). The BNSZ is geologically manifested by the Mugagangri Group (MG) accretionary complexes developed during northward Meso-Tethyan subduction, whose timing and processes are, however, contentious. Herein, we conducted provenance analysis on the MG trench deposits, via petrography, whole-rock geochemistry and detrital-zircon geochronology. The results reveal a complete picture of provenance evolution during passive- to active-margin transition (from subduction initiation through fringing oceanic-arc, to continental-arc developments) at the SQT margin. In particular, the earliest trench deposits (subunit Tr ma ; ~222 Ma), which contain olistostromes with blocks of oolitic limestone shed from the destructing SQT passive margin, mark the subduction initiation. A second subunit (Tr mb ; ~210 Ma) has periodically elevated volcanogenic components. Conglomerates of subunit Tr mb have abundant basaltic clasts of intra-oceanic arc geochemical affinities, which were likely derived from an intra-oceanic arc fringing the SQT. The youngest subunit (J md ; ~190 Ma) exhibits enriched ferromagnesian elements and a major youngest detrital-zircon age peak, indicating a continental-arc provenance. Moreover, detrital-zircon age spectra suggest that, at ~210 Ma, the central Qiangtang metamorphic belt became an important source area, and the North Qiangtang terrane (NQT) replaced SQT as the main provenance. This is best explained by that the SQT underthrusted beneath the NQT and was downwarped to form a foreland basin. Our findings confirm that the initial subduction of Meso-Tethys beneath SQT was coeval to other Cimmerian terranes, likely a uniform response to the Paleo-Tethys closure and collision between Eurasia (NQT) and Cimmeria (SQT). [ABSTRACT FROM AUTHOR]

When the Cimmerian Continent separated from Gondwana and drifted northward to equatorial latitudes, sedimentary rocks on the continent underwent intense weathering, resulting in the formation of bauxite deposits. Gheshlagh is one such bauxite deposit, located in the Alborz Mountains in northern Iran. The bauxite deposit at Gheshlagh, 12–18 m in thickness with a strike length > 4 km, is hosted by Permian strata and unconformably overlain by Early Triassic limestone. Detrital zircon grains in the bauxite deposit yielded U-Pb ages ranging from 2.5 Ga to 0.5 Ga, with most ages between ca. 0.9 Ga and 0.5 Ga. The detrital zircon grains with age populations between ca. 0.9 Ga and 0.6 Ga are tabular and rounded with sharp oscillatory zoning, and most likely derived from igneous rocks in the northern part of the Arabian-Nubian Shield. The detrital zircon grains with ages of ~1 Ga are long and rounded in shape with slightly obscure growth zoning and probably originated from metamorphic rocks of the Sinai basement in the northernmost part of the shield. Detrital zircon with ages between 1.8 and 2.5 Ga are smoothly rounded in shape with faint internal zoning, suggesting long transport from a metamorphosed source(s), possibly including the Saharan Metacraton, and/or the Kabul Block. The Gheshlagh deposit contains minor needle-like to prismatic-shaped zircon grains, with U-Pb ages ranging from ca. 571 to 521 Ma, corresponding to the timing of the Cadomian magmatic event in northern Gondwana. The occurrence of such proximal sourced zircons at Gheshlagh supports the notion that northern Gondwana was an active margin in response to southward subduction of Prototethys during late Neoproterozoic to Early Cambrian. Our data also suggest that the Cimmerian Continent was still located on the northern margin of Gondwana during deposition of the bauxite protolith in the Permian. [Display omitted] • U-Pb ages of detrital zircon from the Gheshlagh bauxite range from 2.5 to 0.5 Ga • Main provenances of bauxite protolith are Arabian-Nubian Shield. • The Cimmerian Continent rifted from Gondwana in terminal Permian time. [ABSTRACT FROM AUTHOR]

The Cimmerian continent is the north piece of the Gondwana super-continent collaged to the south edge of the Laurasia super-continent during the closure of the Paleo-Tehyan Ocean. Researchers recently have identified the Rushan-Pshart-Longmu Co-Shuanghu-Bitu-Changning-Menglian-Inthanon suture zone as the northern boundary of the eastern Cimmerian continent. However, a detailed correlation of this complicated tectonic zone from Pamir to Sumatra remains unclear. For example, while a back-arc suture is developed in southeast Tibet and Southeast Asia, no evidence of the same suture has been reported in eastern and central Tibet. In this study, we investigate an ophiolite mélange suite exposed in the Deqin back-arc suture of this tectonic zone in eastern Tibet, and interpret it as the northward extension of the Jinghong-Nan River back-arc suture. The mélange includes serpentinites, gabbros, basalts, and minor abysmal radiolarian-bearing cherts, and these rocks appear as isolated blocks in fault contact with Permian strata. Geochemical data of the serpentinites from the Deqin suture and Bitu suture indicate that they are MOR-type and SSZ-type sutures, respectively. Zircon U Pb dating of the gabbro and diorite from the Deqin suture yields crystallization ages ranging from ca. 246 Ma to ca. 276 Ma, and a zircon U Pb age of ca. 285 Ma is obtained from the Bitu suture. Geochemical analysis shows that the rocks from the Deqin suture have OIB or MORB characteristics, suggesting southwest subduction of the oceanic lithosphere beneath the North Lancangjiang tectonic belt since the Middle Permian. Two Meso-Tethyan magmatic rock samples from the Bitu and the Deqin sutures crystalized at 114 Ma and 111 Ma, respectively, and their geochemical data indicate OIB-type signature. We conclude that the Bangong Co-Nujiang Ocean lithosphere subducted northeastward beneath the Qamdo terrane at a low angle. Based on the correlation between the Rushan-Pshart suture and the Longmu Co-Shuanghu suture, our pre-Cenozoic plate reconstruction suggests that the Karakorum fault right-laterally offset the northern boundary of the Cimmerian continent by 140 ± 10 km. The offset further implies that the Cenozoic deformation of the Tibetan plateau is accommodated mainly by distributed structures rather than by several discrete fault systems. • Deqin ophiolitic mélange is discovered at west margin of the Qamdo terrane. • Mafic- and ultramafic rocks in the Deqin suture are MORB-type rocks. • The Deqin suture connects the Jinghong-Nan back-arc suture in eastern Tibet. [ABSTRACT FROM AUTHOR]

The records of extreme biotic and environmental crises have been well documented worldwide from Permian-Triassic successions. However, the Cimmerian continent, a Gondwana-derived continental terrane/block strip, has received insufficient attention in terms of its eastern part including the Baoshan block. Here, we report an integrated conodont biostratigraphic zonation and carbon isotope profile from the Permian-Triassic boundary (PTB) beds and Lower Triassic succession of the Baoshan block. The conodont faunas obtained from the dolomitized Hewanjie Formation at the Dajianshan section are dominated by Hindeodus and Isarcicella species. Representatives of Eurygnathodus and the Ellisoniidae are also present. Five conodont zones are recognized in ascending order: the Hindeodus parvus Zone, the Isarcicella staeschei Zone, the Isarcicella isarcica Zone, the Hindeodus postparvus Zone, and the Eurygnathodus costatus Zone. The carbon isotope curve exhibits two pulses of negative excursion around the PTB. In general, both the conodont zones and the carbon isotope profile correlate well with those from other well-documented sections in the world. The Permian-Triassic boundary, extinction horizons and Induan-Olenekian boundary are calibrated in terms of conodont and carbon isotopic data. In addition, conodont biofacies analyses show that the depositional water-depth was shallow in general, as indicated by the lack of gondolellids and neospathodids and the presence of ellisonids and Eurygnathodus. • Five Lower Triassic conodont zones are recognized from the Baoshan block. • The conodont zones overall correlate well with those recognized worldwide. • The PTB and IOB are recognized based on conodonts and δ13C excursions. • Conodont biofacies show very shallow depositional water-depth in the section. [ABSTRACT FROM AUTHOR]

Permian fusulinoidean faunas occur in mainly four stratigraphic levels in the Baoshan Block of West Yunnan and the Sibumasu Block of Southeast Asia, which constituted part of the eastern Cimmerian Continent. The oldest fauna, from the upper part of the Dingjiazhai Formation in the Baoshan Block, consists of Pseudofusulina, Eoparafusulina, and a new boultoniid genus, and is assignable to the Yakhtashian (=Artinskian). The second one, which occurs in the basal part of the Ratburi Limestone and its equivalent strata in the Sibumasu Block, is represented by Monodiexodina, and is probably referable to the Bolorian (=Kungurian). The third fauna, composed of Eopolydiexodina, Rugososchwagerina, Yangchienia, Chusenella, Jinzhangia, and several other genera, is dated to the Murgabian (=Wordian), and occurs in the lower part of the Shazipo and Daaozi formations in the Baoshan Block and the main part of the Ratburi Limestone in the Sibumasu Block. The youngest fauna of probably Dzhulfian (=Wuchiapingian) age is found in the upper part of the Ratburi Limestone, and contains Nanlingella, Reichelina, Codonofusiella?, and a few staffellid genera. A smaller foraminiferal genus, Shanita, found from the upper part of the Ratburi Limestone and the upper part of the Shazipo Formation is also an important element of the foraminiferal assemblage near the Midian–Dzhulfian (=Capitanian–Wuchiapingian) boundary in the Baoshan and Sibumasu blocks.In the eastern Cimmerian Continent, low generic diversity throughout the Permian and the paucity of Tethys-characterizing neoschwagerinid and verbeekinid genera during Middle Permian time are two remarkable features of the Permian fusulinoidean faunas. In the Cimmerian Continent, the generic diversity of Permian fusulinoidean faunas in space and time gradually increases from the Early Permian to late Middle Permian as well as from the eastern Cimmerian areas to western ones. The temporal increase of the generic diversity can be explained by the northward drift of the Cimmerian Continent during Permian time. In contrast, the lower generic diversity of the eastern Cimmerian Permian fusulinoidean faunas against western ones is possibly due to an oblique arrangement of the continent to paleolatitude. Thus, the western Cimmerian Continent was more proximal to the tropical Tethyan domain than its eastern part. In addition, the Middle Permian Cimmerian paleobiogeographic region is likely to be subdivided into two subregions, the western Tethyan Cimmerian and the eastern Gondwanan Cimmerian, based on the distribution pattern of verbeekinid and neoschwagerinid fusulinoideans and overall generic diversity. The scarce occurrence or total absence of these essentially Tethys-indicating fusulinoideans in the Baoshan and Sibumasu blocks suggests that the eastern Cimmerian Continent was still far from the equatoro–tropical Cathaysian domain and was probably in a warm temperate or subtropical zone until the end of the Permian. The eastern Cimmerian areas finally migrated into a tropical zone by the Late Triassic judging from well-developed Carnian sponge–coral buildups in the Chaiburi Formation in the Sibumasu Block. [Copyright &y& Elsevier]