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Deformational, metamorphic, monazite age and fabric data from Rengali Province, eastern India converge towards a multi-scale transpressional deformational episode at ca. 498–521 Ma which is linked with the latest phase of tectonic processes operative at proto-India-Antarctica join. Detailed sector wise study on mutual overprinting relationships of macro-to microstructural elements suggest that deformation was regionally partitioned into fold-thrust dominated shortening zones alternating with zones of dominant transcurrent deformation bounded between the thrust sense Barkot Shear Zone in the north and the dextral Kerajang Fault Zone in the south. The strain partitioned zones are further restricted between two regional transverse shear zones, the sinistral Riamol Shear Zone in the west and the dextral Akul Fault Zone in the east which are interpreted as synthetic R and antithetic R' Riedel shear plane, respectively. The overall structural disposition has been interpreted as a positive flower structure bounded between the longitudinal and transverse faults with vertical extrusion and symmetric juxtaposition of mid-crustal amphibolite grade basement gneisses over low-grade upper crustal rocks emanating from the central axis of the transpressional belt. [ABSTRACT FROM AUTHOR]

Abstract: Anisotropy of magnetic susceptibility (AMS) data have been utilized to build up the multiple deformation sequences and strain variation from an apparently undeformed metabasic lava sequence of the basal part of the Paleo-Mesoarchean greenstone succession of the Iron Ore Group rocks in the western Iron Ore basin, Singhbhum craton, eastern India. The basal lava crops out bordering the regional horseshoe shaped outcrop (the horseshoe synclinorium structure) of the overlying BIF rocks. AMS data of 892 cylindrical specimens drilled from 83 samples collected from different structural domains within the synclinorium structure are presented in the analysis. AMS orientation data have been analyzed in the light of superposed fold (Type-1 interference) fabrics developed within BIF as a result of successive deformation episodes (D1 and D2). It is found that the lava samples ubiquitously present two consistent magnetic fabrics homogeneous over smaller sub-areas, which have been successfully correlated with the D1 and D2 deformation fabrics from the BIF rocks. Moreover, a regional scale variation in intensity and nature of strain is noticed from the AMS data, which have been utilized to decipher folding mechanism as well as the changing deformation pattern during successive folding events. [Copyright &y& Elsevier]

Abstract: The middle to late Archean Iron Ore Group rocks occurring along the western margin (the Western Iron Ore basin) of the Singhbhum Granite massif in the Singhbhum craton were deformed during Iron Ore orogeny and are disposed in a horseshoe-shaped synclinal structure in the eastern part of the Indian shield. The Western Iron Ore basin hosts almost all the major high-grade iron ore deposits of eastern India. Contrary to the established view, present analysis emphasizes that the horseshoe fold in reality is a synclinorium consisting of a syncline–anticline fold pair which were later cross-folded along an east–west axis. Structural analysis in the eastern anticline of the ‘horseshoe synclinorium’ suggests that the BIF hosting the high-grade iron ore bodies are disposed in three linear NNE–SSW trending belts, each showing an open synclinal geometry. Later cross folding produced development of widespread dome and basin pattern at the sub-horizontal hinge zones of these synclinal fold belts. The major iron ore deposits in the eastern anticline at the present level of erosion are preferentially localized within shallow elongated basinal structures only. The axis of the adjoining western syncline was similarly uplifted as partial culminations where cross-folded against E–W anticlinal axes. But here, the BIF-iron ore bodies are preferentially localized within elongated domal structures in contrast to the basinal sites in the adjacent eastern anticline. Such an inference based on structural analysis could probably be utilized as a potential tool for all future explorations, reserve estimation and recovery of the iron ore deposits in the terrain. [Copyright &y& Elsevier]

The Proterozoic Somanpalli Group, originally deposited in a NW–SE trending fault-controlled basin in the Pranhita–Godavari valley (PG valley), suffered contractional deformation as recorded in NW–SE trending large scale folds, imbricate thrusts, second order semibrittle shear zone, and smaller folds, faults, and cleavage. Three distinct structural stages dominated, respectively, by folding, thrusting and strike-slip faulting in that order, can be recognized from overprinting relationships, in outcrops. The local ENE–WSW fold axis azimuth and cleavage strike is related to variation in the original depositional strike controlled by E–W transfer faults rejuvenated as sinistral strike-slip zones during the main contractional deformation. A late extensional event, possibly occurring during the upper Proterozoic or Mesozoic (Gondwana), has been superimposed locally on the earlier fabric of the fold-thrust belt.The NW–SE trending folds and thrusts in the Somanpalli Group demonstrate the presence of a hitherto unrecognised compressional regime, records of which occur in a ∼200 km stretch along the eastern margin of the PG valley. The Somanpalli Group may be correlated with the Mesoproterozoic Pakhal Group (∼1350 Ma). Since the former is overlain by grossly undeformed and unmetamorphosed rocks of the Neoproterozoic Sullavai Group, a Mesoproterozoic basin inversion in this region is suggested. [Copyright &y& Elsevier]

We present the structural history of a suite of high-grade rocks of the Phulbani area of the Eastern Ghats Belt, India, based on structural study at meso- and micro-scales combined with published metamorphic and the geochronological data. Structural data suggest multiple generations of fabric (S 1 –S 5) development during a punctuated deformational history (D 1 −D 5). The S 1 fabric is present only in grain-scale and developed during the prograde metamorphic stage (M 1). The regionally recognizable composite S 2 /S 3 gneissic fabric developed in the realm of ultra-high temperature metamorphism (D 2 /D 3 , M 2) during ca. 987–970 Ma as a result of the contraction and closure of the continental back-arc basin. The D 4 deformation folded the earlier formed composite S 2 /S 3 gneissic fabric and developed a shear-related mylonitic foliation (S 4), possibly after ca. 970 Ma. Deformation in the Phulbani area culminated through the formation of the S 5 mylonitic fabric (D 5 , M 3) along the Ranipathar Shear Zone, possibly at ca. 500 Ma, which exposed the anomalously hot deep continental crustal rocks to shallower crustal level. Development of the Ranipathar Shear Zone is interpreted to be kinematically linked with several other such crustal-scale shear zones in the area which together played a pivotal role in the final tectonic evolution of the northern Eastern Ghats Belt. Image 1 • Structural mapping is integrated with metamorphic and microstructural studies to constrain the structural evolution of the northern Eastern Ghats Belt (EGB). • Ultra-high temperature (UHT) rocks documenting signature of lower crustal deformation before exhumation. • The deformation phases are linked with the timing of metamorphism. • Deformation at Ranipathar Shear Zone and other E−W trending shear zones marks the final tectonic episode of the northern EGB. [ABSTRACT FROM AUTHOR]

High-strength low-carbon ferritic steels attaining a maximum yield strength of 1600MPa by combined Cu and NiAl precipitation-strengthening were developed. The yield strength of the alloys increases monotonically with the total concentration of the principal alloying elements i.e. Mn, Cu, Ni and Al. At 12.40at.%, a 1600MPa yield strength is achieved after solution treatment at 950°C followed by aging at 550°C for 2h. For all three alloys investigated, the hardness reached a maximum after 1–2h aging at 500–550°C. At peak hardness, the combined precipitation of the body-centered cubic (bcc) Cu-alloy and B2-ordered NiAl-type intermetallic precipitates is observed by atom probe tomography (APT). The morphology, composition and structure of the Cu-alloy and NiAl-type precipitates were characterized using APT and transmission electron microscopy, as a function of aging time at 550°C. In peak hardness conditions, the equiaxed bcc Cu-alloyed precipitates contain substantial amounts of Fe and are enriched in Ni, Al and Mn. Ni and Mn segregate at the Cu-alloy precipitate/ferrite matrix interface. In addition to the segregation, B2 NiAl-type precipitates nucleate at the Cu-alloy precipitates. After aging for 2h, most Cu-alloy precipitates have a NiAl-type precipitate attached to their side. On subsequent further aging, the Cu-alloyed precipitates enrich progressively with Cu and elongate, indicating a transformation to the 9R or face centered cubic structure. The Cu-alloyed precipitates coarsen slower than the NiAl-type precipitates due to interfacial energy differences between the two types of precipitates, slower diffusion kinetics of Cu through the NiAl precipitates, different matrix equilibrium solubility and solute transfer from Cu-alloyed precipitates to NiAl-type precipitates. The relatively slow growth and coarsening of Cu-alloyed precipitates are consistent with the observation of an only modest decrease of hardness with extended aging. [ABSTRACT FROM AUTHOR]

The impurity diffusivities (D) of the 5d transition metal solutes, Ta–Au, in α-Fe have been computed within a framework combining density-functional-theory calculations, harmonic transition-state theory, the Le Claire nine-frequency model and semi-empirical corrections for magnetic disorder. The calculated diffusion constants show a trend vs. atomic number featuring minimum values corresponding to Re and Os, at the center of the transition metal series. The results for D are correlated with minima and maxima in the magnitudes of the solute–vacancy binding energy and migration energy, respectively. [ABSTRACT FROM AUTHOR]

Abstract Five successive deformation phases have been identified from structural analysis of granitoid and gneissic rocks of the study area. The magnetic foliation data of the studied granitoids show two distinct NW and NE trending sets. The NW trending magnetic foliation is found to be essentially parallel to the mesoscale planar structures of regional D1-D2 deformations and is thus correlated with the D1-D2 phases. On the contrary, the NE trending magnetic foliation appears to be kinematically compatible with the NW-SE compression direction deciphered from conjugate ductile shear zone patterns of the D3 event. Combining AMS, field and microstructural data, the granitoid outcrop have been separated into older D1-D2 and younger D3 domains. The published geochronological data from the area when compared with the established D1-D2 and D3 domains, shows a good correlation pointing tentatively the timing of the D1-D2 deformation phase to be ∼2550 Ma while the D3 phase to be ∼2524 Ma. Hence the study highlights the importance of combining AMS data with field and microstructural studies to constraint the timing of regional successive deformation imprints. It also helps to identify the chronologically separated emplacement phases of the granitoid massif in question, which would not have been possible otherwise. Highlights • The deformed Neoarchaean granitoids of the study area in the EDC, south India show evidences of five successive deformation imprints (D1-D5). • The D1-D3 phases represent early ductile episodes which are well documented from the EDC. • The hitherto undetected D4-D5 phases represent essentially brittle shallow crustal events of which the overlying Mesoproterozoic Srisailam Formation manifests the D5 phase only. • The observed magnetic fabrics from granitoids depict NW-SE and NE-SW trends which are correlated with D1-D2 and D3 deformation phases respectively. • AMS data along with field, microstructural and published geochronological data help to constraint the chronology of successive deformation imprints and identify the separate emplacement phases in the granitoid massif. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Emplacement of granite at ca. 1173 Ma formed part of the basement of Eastern Ghats Province. • UHT metamorphism occurred at ca. 1026–987 Ma followed by charnockite magmatism at ca. 985–970 Ma. • The lower crust was thermally perturbed and subsequently cooled near-isobarically. • Phulbani and the adjacent Visakhapatnam domains have similar evolutionary history within the broad framework of Rodinia. • Crustal-scale shearing occurred at ca. 781 Ma. Abstract We present zircon U-Pb (SHRIMP) and monazite U-Th-total Pb (EPMA) ages from a suite of high-grade rocks of the Phulbani domain of the Eastern Ghats Belt, India. These ages are integrated with the metamorphic and magmatic histories of the Phulbani domain to put precise time constraints on the tectonothermal evolution of the northern part of the Eastern Ghats Belt. Zircon from the coarse-grained charnockite rock shows crystallization age of ca. 970 Ma. Aluminous granulite contains spinel and quartz-bearing mineral assemblage indicating ultrahigh temperature metamorphism (>900 °C at 8–10 kbar) which possibly occurred during ca. 987 Ma as revealed from monazite included in porphyroblastic garnet. Monazite in the aluminous granulite and the migmatitic felsic gneiss grew dominantly at 966 ± 4 Ma and 968 ± 4 Ma ages respectively, which are interpreted as the cooling ages subsequent to peak metamorphism. Oscillatory-zoned zircon grains of the felsic augen gneiss yield ca. 1173 Ma age which is interpreted as the crystallization age of the granitic protolith. This ca. 1173 Ma age granite possibly composed a part of the Proterozoic basement of the Eastern Ghats Province. A monazite age of 781 ± 15 Ma from the aluminous granulite may indicate the timing of a localized shear-induced thermal process in the Phulbani domain. The presently studied rock suite thus recorded three distinct events (ca. 1173 Ma, ca. 1000–900 Ma and ca. 781 Ma) of magmatism, metamorphism and deformation of Eastern Ghats Belt. Metamorphic and magmatic histories of the Phulbani domain are similar to those of the adjacent Visakhapatnam domain and the Rayner Province of East Antarctica during the time frame ca. 1000–900 Ma. [ABSTRACT FROM AUTHOR]

The microstructures of the heterogeneously deformed limestones of the Kolhan Group, Singhbhum Craton (SC), eastern India are investigated to study deformation mechanism, grain size and shape preferred orientation (SPO) development. The texture of the deformed rocks is analyzed by Electron Back-Scattered Diffraction (EBSD) in order to determine crystallographic preferred orientation (CPO) development in calcite grains. The c-axis pattern in protomylonite and mylonite define girdle patterns developed perpendicular to local shear planes showing monoclinic symmetry. The latter is interpreted in terms of a top-to-south shear, which is consistent with the observed microstructural and fabric data from the deformed rocks. The Anisotropy of Magnetic Susceptibility (AMS) studies are performed on 22 heterogeneously strained limestone specimens to document strain variation within the Kolhan rocks. The field fabric, SPO data measured from calcite and mica grains (κ cal and κ mi ) and calcite CPO data are compared with observed variation in AMS fabric intensity (P j) across the Kolhan basin. Integration of these data sets help to establish presence of large internal thrust planes within the Kolhan basin, which form a part of the regional foreland vergent thrust system developed along the northern margin of the SC. [ABSTRACT FROM AUTHOR]

This study focuses on the evolution of the Central Gneissic Belt of the Archean Rengali Province which evolved as a craton-margin orogenic belt. The Central Gneissic Belt is constituted of charnockite gneiss, migmatitic hornblende gneiss and granite gneiss often showing gradational contacts. While mafic granulite occurs as enclave within the charnockite gneiss, amphibolite and calc-silicate granofels enclaves are present within the granite gneiss. Mafic granulite shows peak metamorphic assemblage of garnet + clinopyroxene + plagioclase + quartz ± orthopyroxene which was stabilized at 10.6 ± 0.5 kbar and 860 ± 20 °C. Charnockite gneiss with the peak assemblage of orthopyroxene + quartz + plagioclase + K-feldspar was metamorphosed at 792 ± 48 °C and 7.6 ± 0.4 kbar. Amphibolite and migmatitic hornblende gneiss contain hornblende along with plagioclase and garnet and these rocks were metamorphosed at 800 ± 20 °C, 8.5 ± 0.2 kbar and 695 °C, 8 kbar respectively. Later meta-dolerite dikes exhibit relic igneous textures which are slightly modified by greenschist-facies metamorphism. Charnockite gneiss, migmatitic hornblende gneiss and granite gneiss show similar trace and REE characteristics (moderate fractionation in terms of La and Yb, LREE enrichment and flat HREE pattern) implying the same protolith composition for these rock groups. Based on the field, petrographic and geochemical data, we propose that the protoliths for the charnockite gneiss, the migmatitic hornblende gneiss and the granite gneiss crystallized as fractionated magma in within-plate syncollisional setting during the ca. 2860–2780 Ma orogeny at the Rengali Province. [ABSTRACT FROM AUTHOR]

The quartz-pebble conglomerate (QPC)-hosted detrital uranium mineralization is unique in character in terms of their restricted distribution before 2.2 Ga atmosphere during pre-Great Oxidation Event (pre-GOE). Such QPC paleoplacer deposits over the world are good targets for moderate to high tonnage and low grade uranium deposits and more importantly for their gold content. The Mahagiri Quartzite, dated c. 3.02 Ga for their youngest detrital zircon population, is developed unconformably over the Mesoarchean Singhbhum Granite (3.44 Ga to 3.1 Ga). The Mahagiri Quartzite includes a conglomerate-pebbly sandstone dominated subaerial alluvial fan to coastal braided plain sequence in the lower parts and shallow marine mature quartz arenite in the upper parts. The alluvial fan-braided plain deposits in the lower parts host a number of pyritiferous and uraniferous conglomerate and pebbly sandstone beds. The uraninite grains are rounded to subrounded in outline suggesting mechanical transport and detrital origin. Together with detrital pyrite and uraninite constitute the example of > 3.0 Ga paleoplacer closely comparable to the Witwatersrand Au–U deposits. EPMA and SEM-EDS studies suggest that the uraninite grains are rich in Th (> 4 wt.%), S and REE-Y. Chemical formula calculations from EPMA analyses suggest uraninite grains belong to two populations with different oxidation states as revealed from Y/REE and cation U 4 + : U 6 + [apfu] ratios. The U contents of the detrital uraninite grains from Mahagiri are significantly lower than that of the ideal stoichiometric composition of UO 2 . This is mainly due to higher amount of heterovalent cationic substitution by Th, REE, Y, Pb, and Ca in Mahagiri QPC uraninite structures, and partial alteration and metamictization of uraninites. Alteration due to metamictization resulted in elevated concentration of Si, Al, P, and Ca in more altered and metamict uraninite grains. The REE pattern is typically flat with comparable LREE–HREE concentration. The high Th content flat REE-pattern suggests that the uraninitere presents high temperature phases (> 350 °C) and are magmatic in origin. The Mahagiri detrital uraninite grains suggest existence of highly felsic and K-rich (richer than TTG) granodiorite–granite–monzogranite suites (GGM) of rocks older than 3.1 Ga in the Singhbhum craton. [ABSTRACT FROM AUTHOR]

Abstract: Self- and impurity diffusivities in body-centered-cubic (bcc) iron have been calculated within the formalisms of harmonic transition-state theory and the Le Claire nine-frequency model for vacancy-mediated diffusion. The approach combines first-principles calculations of vacancy formation, migration, and solute-binding enthalpies and entropies in the ferromagnetic phase, with an empirical relationship for the effect of magnetic disorder on diffusion activation energies. Calculated Fe self-diffusion and Mo and W impurity-diffusion coefficients are shown to agree within a factor of five with the most recent experimental measurements in both the ferromagnetic and paramagnetic phases. Calculated diffusion coefficients for Mo and W impurities are comparable to or larger than that for Fe self-diffusion at all temperatures below the α–γ phase transition. Calculated activation energies for Ta and Hf impurities suggest that these solutes should also display impurity-diffusion coefficients larger than that for self-diffusion in body-centered cubic Fe. [Copyright &y& Elsevier]