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U-Th-Pb (LA-ICP-MS) geochronological studies of detrital zircon from the Quaternary deposits of the western part of the Ufaley block (Middle Urals) were performed. The studied area was a tectonic fragment composed of an amphibolite-gneiss complex containing bodies of Precambrian clinopyroxenites. The pronounced age maximum corresponds to the age interval of 2100-2000 Ma, and several small peaks correspond to the interval of 3200-2500 Ma. All this gives us a good reason to believe that Early Precambrian rocks, which have not been identified before, are present within the Ufaley block.

The Singhbhum craton is one of five Archean cratons constituting the Indian subcontinent. It consists of four major lithotectonic units with broadly defined ages from Eoarchean to Neoarchean: the Older Metamorphic Group (3.7-3.2 Ga), Older Metamorphic Tonalite Gneisses (3.8-3.1 Ga), Singhbhum Granite (3.5-3.0 Ga), and Iron Ore Group (3.51-2.55 Ga). In this study, 270 zircons were separated from modern sediment of the Baitarani River, which is wholly contained within the craton. Zircons were analyzed with laser ablation ICP-MS for their U-Pb systematics, >50% were less than 5% discordant. Three primary age groupings account for ∼98% of analyses: 3.62-3.55 Ga (5%), 3.50-3.22 Ga (87%), and 3.10-3.06 Ga (6%). The preponderance of 3.50-3.22 Ga zircons is consistent with the local basement that includes a 3.47 Ga tonalite gneiss enclave within a 3.35-3.30 Ga outcrop of the Singhbhum Granite near Keonjhar. Lu-Hf systematics of zircons yielded 67% with positive initial εHf, scattered above and below the mantle growth curve and 33% with negative initial εHf, indicating contributions from both depleted mantle and older crustal sources. Single-stage model ages range from 4.29 to 3.10 Ga. Of note is a single zircon with a 207Pb/206Pb age of 4015±9 Ma (1.3% discordant), which is the first Hadean zircon documented from any of the Indian cratons. This grain yielded an initial εHf of -5.30, which indicates an episode of Hadean felsic crust formation in the Singhbhum craton comparable to that proposed for the Jack Hills of the Yilgarn craton (Australia).

Microstructural deformation and the age of monazite (Ce) from diatectite granite of the presumably impact Jarva-Varaka structure in the Kola Region (northeastern Fennoscandian Shield) are presented. Biotite diatectite granite forms lenses in the aluminous gneisses of the Kola group hosting the 2.5-Ga-layered Jarva-Varaka Massif (JVM). A sample of biotite granite was collected northeast of the Jarva-Varaka Massif near the earlier described pseudotachylitic breccias. BSE images revealed primary domains in monazite grains with rhythmic euhedral zoning and secondary altered domains. Backscattered electron diffraction maps of monazite grains document the development of deformation twins along 100 and 001 and plastically deformed domains with a maximum misorientation of up to 10°. Newly formed areas of recrystallization (neoblasts) cut the twins and plastically deformed domains. Monazite yielded a U-Pb age of 2706 ± 10 Ma (ID-TIMS method), which defines the crystallization age of the host diatectite granite coeval to the 2.76–2.70 Ga metamorphism of the Kola gneisses. A similar age of 2734 ± 139 Ma (ThO2*–PbO isochron) was obtained for primary monazite domains by the chemical U-Th-total Pb isochron method (CHIME). Domains altered under late hydrothermal processes yield CHIME ages of 1796–1723 Ma. Monazite neoblastic domains are close to primary domains in chemical composition and yielded CHIME ages of 2550–2519 Ma, reflecting probably an influence of the JVM formation. The data obtained are insufficient to confirm the impact origin of the Jarva-Varaka structure, which requires further investigation.

This paper focuses on one orogenic belt that formed during the Rinconada phase on the final stage of the Famatinian orogeny, between 445 and 410 Ma, which is well exposed at Sierra de Ramaditas and neighbouring ranges in western Argentina. The Ramaditas Complex is formed by metasedimentary and meta-ultrabasic rocks and amphibolites. This complex forms the upper nappe of a thrust stack resulting from westward thrusting. Deformation consists of an early high-temperature S1 foliation (stromatic migmatites), coeval with thrusting and metamorphism. Metamorphism attained peak P-T conditions of 6.0-6.9 kbar and 795-810 °C, at c. 440 Ma, i.e. coincident with the Rinconada orogenic phase. The lower unit and intermediate nappes crop out in the nearby sierras of Maz and Espinal and underwent low- to medium-grade Silurian metamorphism, respectively, together with the upper nappe, defining an inverted Barrovian-type metamorphism with T decreasing and P increasing downwards across the thrust stack (i.e. westward). We argue that the Rinconada orogenic phase developed near the continental margin of SW Gondwana, during a magmatic lull following accretion of the Precordillera terrane to the continental margin at c. 470 Ma. The active margin jumped to the west after accretion, and flat-slab subduction resumed in the early Silurian, provoking thrusting and imbrication of nappe stack under the still hot root (800-900 °C) of the older Famatinian magmatic arc. This 'hot-iron' process explains both the inverted Barrovian-type metamorphism and the missing overburden of 21 to 24 km implied by the P estimate.

A comprehensive study based on U–Pb and Hf isotope analyses of zircons from gneisses has been conducted along the western part (Babina area) of the E–W-trending Bundelkhand Tectonic Zone in the central part of the Archaean Bundelkhand Craton. 207Pb–206Pb zircon ages and Hf isotopic data indicate the existence of a felsic crust at ~ 3.59 Ga, followed by a second tectonothermal event at ~ 3.44 Ga, leading to calc-alkaline magmatism and subsequent crustal growth. The study hence suggests that crust formation in the Bundelkhand Craton occurred in a similar time-frame to that recorded from the Singhbhum and Bastar cratons of the North Indian Shield.