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TIMS Pb-Pb geochronological data allow determination of the timing and genesis of the Fazenda Coqueiro volcanic‑hosted massive sulfide (VHMS) Zn-Pb deposit hosted in the Neoarchean Mundo Novo greenstone belt (MNGB), NE São Francisco Craton. The deposit is inserted in the Rhyacian-Orosirian Contendas-Jacobina lineament between Archean cratonic blocks. The basement of the deposit is composed of Paleoarchean metagranite and metarhyolite nuclei tectonically emplaced within the supracrustal rocks. The volcanic-sedimentary rocks comprise the ocean floor western metabasalt, calcsilicate rock, aluminous schist, metachert, banded iron formation, and tremolitite of the middle sequence and metasedimentary siliciclastic rocks of the uppermost sequence of the MNGB. The western metabasalt is hydrothermally altered, which resulted in the formation of two alteration zones. They consist of carbonate zone, proximal, hosting massive sulfides composed mainly of sphalerite and galena with minor chalcopyrite; and sericite-chlorite zone, distal, hosting mainly disseminated chalcopyrite. Pb-Pb galena, chalcopyrite and sphalerite data from the massive and disseminated zones in the Fazenda Coqueiro deposit yielded model ages of 2,804 ± 11.15, 2,794 ± 11.2, and 2,767 ± 11.1 Ma, respectively, with the Pb sourced from the upper crust, based on the uranogenic and thorogenic diagrams. The Pb-Pb isochron mineralization age of 2,747 ± 16 Ma obtained from chalcopyrite and sphalerite samples from the massive and disseminated zones suggests that the sulfides were coeval and do not record later metamorphic-hydrothermal events. Therefore, the Fazenda Coqueiro deposit would have formed from Neoarchean ocean floor volcanic-exhalative processes. The Rhyacian-Orosirian tectonic event compressed the deposit between Archean blocks along the Contendas-Jacobina lineament, preserving the sulfides from remobilization processes.

Trace element characteristics of rubies from the Aappaluttoq deposit, SW Greenland, were measured using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), laser ablation - inductively coupled plasma-time of flight-mass spectrometry (LA-ICP-TOF-MS) and offline laser ablation followed by solution ICP-MS. LA-ICP-TOF-MS - applied to rubies for the first time - effectively maps trace element spatial variation in these gems. With the exception of a small number of elements that can substitute for Al3+ in the crystal structure (e.g., Ti, Fe, V, Cr, Mg), trace element mapping clearly demonstrates that most elements such as Th, U, Sr and Rb are hosted in mineral and fluid inclusions or are present along fractures. Primitive mantle normalized trace element patterns show characteristics that are broadly correlative to mineral inclusions within the analysed rubies. These minerals include rutile (enrichment of HFSE over LREE, high Ta/Nb and Hf/Zr ratios and low Th/U ratios), phlogopite (enrichment in Rb and Ba and positive Sr anomalies), and zircon (extreme enrichment in Zr–Hf, U and Th, HREE enrichment over LREE and positive Ce anomalies). The sample suite analysed here is derived from a bulk sample of ore composed of three different rock types (sapphirine-gedrite, leucogabbro and phlogopitite). Two different populations of ruby were identified at Aappaluttoq; these can be defined on the basis of their different V content within the corundum lattice. Therefore, V content may be able to geochemically define rubies from different host rocks within the same deposit. Using offline laser ablation followed by thermal ionization mass spectrometry (TIMS) we measured the radiogenic isotope compositions in ruby for the first time. A Pb–Pb isochron age of 2686 +300/−74 Ma, was defined for gem formation at Aappaluttoq. We believe that this is the first ever direct age determined on a ruby suite, independent of associated minerals, derived by bulk sampling sub-micron to micron sized inclusions in the corundum lattice. This age likely reflects the re-crystallization and re-setting of the ruby (and its U–Pb system) during the Neoarchean in SW Greenland, due to regional granulite to upper-amphibolite facies metamorphism. [ABSTRACT FROM AUTHOR]

The C and Sr isotopic signatures and the Pb–Pb age of carbonate sedimentary rocks of the Vorogovka Group in the reference section in the Vorogovka River valley, northwestern Yenisei Range, were obtained. The deposits of the group ascribed to the Severnaya Rechka, Mutnina, and Sukhaya Rechka Formations fill a large trough, and lithological and textural features indicate a high sedimentation rate. Most of the carbonate rocks are represented by limestones with low Fe/Sr and Mn/Sr ratios and average δ18O value (–6.0 ± 1.6‰ V-PDB), indicating the well-preserved isotope systems of the rocks. The 87Sr/86Sr ratios and δ13С values vary within narrow limits of 0.70816–0.70826 and –1.4 to +0.8‰ for Upper Severnaya Rechka limestones and 0.70818–0.70829 and +1.0 to +2.0‰ for Sukhaya Rechka limestones, respectively. The Pb–Pb isochrone ages of carbonate rocks of the Severnaya Rechka and Sukhaya Rechka formations are 580 ± 40 Ma (MSWD = 1.4) and 565 ± 90 Ma (MSWD = 1.1), respectively. According to chemostratigraphic and isotope-geochronological data, the accumulation of limestones of the Vorogovka Group could have occurred at 580–550 Ma, that corresponds to the Late Vendian or Late Ediacaran. It is evident that the duration of accumulation of Vorogovka Group did not exceed 10–15 m.y. The Vorogovka Trough is different from in the sedimentation pattern from other Late Vendian marginal troughs at the southwestern part of the Siberian Platform and formed independently. [ABSTRACT FROM AUTHOR]

The Pb–Pb isotope age and the Sr isotope signature of the Upper Riphean sedimentary limestones from the south of the Yenisei Range on the western margin of the Siberian Craton were obtained. The Pb–Pb age of carbonate deposits of the Dadykta Formation of the Tungusik Group in the Kamenka facial zone in the east of the Yenisei Range is 1020 ± 20 Ma. The Pb–Pb age of limestone of the Gorevka Formation of the Shirokaya Group in the Glushikha facies zone in the western part of the region is estimated at 1020 ± 70 Ma. The 87Sr/86Sr ratio in limestones of the Dadykta Formation lies within 0.70536–0.70590 and that of the Gorevka Formation lies within 0.70552–0.70578. This coincides with a decrease in the 87Sr/86Sr ratio in a paleo-ocean immediately after the culmination of the Grenville orogeny. The correlation of the Shirokaya Group with the Oslyanka Group of the Kamenka Zone in combination with other data has shown that the accumulation of the Tungusik, Shirokaya, and Oslyanka groups occurred within an interval of 1030–950 Ma. The isotope age of the Middle and Upper Riphean boundary at the base of the Tungusik Group of the Yenisei Range is estimated at 1030 Ma, which is consistent with the age of this boundary in the sections of the Turukhansk Uplift and the Uchur-Maya Region of Siberia. It was revealed that the greater part of the Upper Riphean (Neoproterozoic) in the sedimentary record of the Yenisei Range is missing. The observed facial zoning of the Riphean deposits of the Yenisei Range represents the configuration of the ancient sedimentary basin that existed at the western margin of the Siberian Craton long before the collisional events accompanied by granite intrusions and superimposed metamorphism in the Neoproterozoic. [ABSTRACT FROM AUTHOR]

We report eight new Pb-Pb baddeleyite ages and paleomagnetic results on a series of hitherto unknown Neoarchean NNE-SSW trending mafic dyke swarms intruding the Paleoarchean basement rocks in the Singhbhum craton, eastern India. Being the most dominant dyke swarms in the region, they occur over the entire Singhbhum craton with an areal distribution extending to about 30,000 km 2 . Of the eight dyke samples analysed across the entire dyke swarm, six were emplaced at 2762.4 ± 2.0 Ma (weighted mean of 6 dyke ages), two with similar strike directions, yielded older and younger ages of 2800.2 ± 0.7 Ma and 2752.0 ± 0.9 Ma respectively. The older 2800.2 ± 0.7 Ma dyke event appears to be coeval with several other magmatic events reported earlier from the Singhbhum craton. Emplacement of dacite tuffs within the Malaigiri basin, on the southern margin of the craton, the Budhapal and Rengali granite from the south-western and southern parts of the craton, along with the Temperkola granite activity and associated acid volcanics in the western part of the craton, and perhaps the Mayurbhanj granite (fine-grained phase) are also contemporaneous, suggesting a fairly wide spread thermal event in the region at this time. Well defined craton-wide magmatic events contemporaneous to the 2762.4 ± 2.0 Ma Singhbhum dyke activity have been reported from the Pilbara. The younger 2752.0 ± 0.9 Ma age dyke event occurring in the Singhbhum is also know from the eastern Pilbara. An older event at 2783 ± 1.2 Ma (Gaborone-Kanye-Plantation Porphyry-Derdepoort-Modipe episode) was identified in the Kaapvaal craton. Comparison of paleomagnetic data obtained on the Singhbhum Neoarchean dyke swarms with the Pilbara and Kaapvaal data, show all these continents were located at steep latitudes and could have been proximal to each other during this time. If Pilbara and Kaapvaal formed supercraton Vaalbara during the Neoarchean time, we propose Singhbhum with similar Archean geology could also have had its ancestry in the same supercraton. [ABSTRACT FROM AUTHOR]

Using consistent paleomagnetic data together with precise Pb–Pb baddeleyite ages, on a series of mafic dykes occurring over an area of at least 70,000 km 2 , a 2081.8 ± 1.1 Ma (weighted mean of 4 dykes) dyke swarm was identified intruding the Archean basement rocks in the Eastern Dharwar Craton skirting the Cuddapah basin on its north, northwest and western flanks. The geometry of these dykes collectively, due to their progressive variation in trend from N134° W to N28° E, defines a fan angle of about 162° and forms a spectacular radiating swarm converging toward a focal point beneath the Cuddapah basin. Anisotropy of magnetic susceptibility (AMS) investigations on these dykes, based on the orientation of principal eigenvectors indicate magma flow was vertically upward in them, suggesting the magma source of these dykes to be proximal to the sampling sites. These features together with reported geophysical evidence for high density material below the Cuddapah basin suggest that this mafic volcanic province probably formed due to the impact of an asthenospheric mantle upwelling perhaps triggered by a plume head or other causal mechanisms like global warming of mantle or small-scale instability like edge-driven convection. This may have resulted in the domal uplift of the continental lithosphere, large-scale crustal extension and thinning followed by thermal relaxation and subsidence that may have been responsible for the formation of the intra-cratonic Cuddapah basin, shortly after 2082 Ma. Dyke swarms of this age (Fort Frances dykes; 2076 + 5/−4 Ma) or of slightly younger (Lac Esprit dykes; 2069 ± 1 Ma) and older (Cauchon lake dykes; 2091.1 + 1.8/−2.1 Ma) ages are fairly wide spread in the Superior province. However, a reconstruction of the paleopositions of Dharwar (Cuddapah dykes: 38° N; 180° E, A 95 = 4°) and Superior at ∼2080 Ma using paleomagnetic data (Fort Frances dykes: λp: 43° N; Lp: 184° E) does not suggest a close proximity for these provinces at that time. Their disparate locations could therefore suggest these were two distinct nodes of wide spread magmatism between 2080 Ma and 2065 Ma. [ABSTRACT FROM AUTHOR]

Highlights: [•] Uranium-bearing hematite is confirmed in Cu-ores from Olympic Dam, South Australia. [•] U, Mo and W occur within grains displaying oscillatory zonation and porous structures. [•] The suitability of U-bearing hematite for Pb–Pb geochronology was tested. [•] 207Pb–206Pb ages of 1590±8Ma and 1577±5Ma are reported. [ABSTRACT FROM AUTHOR]

Abstract: Provenance studies carried out on the soft and flint facies of the Capim River kaolin (northern Brazil) trace the possible sources of sediments that host the ore. Pb–Pb evaporation geochronology was applied to four predominant morphologic classes of detrital zircons, and the ages obtained were compared to the main age intervals of the rocks surrounding the Capim kaolin district (CKD). Four major plateau ages (2.15, 2.02, 1.87, and 1.51Ga) were defined for both soft and flint facies, indicating a common source for the kaolin and provenance from NE and SW. The 2.15 and 2.02Ga ages correlate with the granitic bodies of the Gurupi region, located NE of the study area. The 1.87 and 1.51Ga ages show provenance from the Amazon Craton, the former from the southern portion, in the Carajás region, and the latter from the southwestern portion. Although less abundant, Archean (3.18, 2.79, and 2.55Ga) and Neoproterozoic ages (0.8 and 0.51Ga) also correlate with the SW and NE provenances, respectively. The first corresponds to the oldest rocks of the Carajás region and the second to the rocks of the Gurupi region, corresponding to the Brasiliano orogeny. [Copyright &y& Elsevier]

Abstract: The Puttetti alkali syenite pluton in southern India belongs to the suite of felsic magmatic intrusives emplaced during the Late Neoprotrozoic-Cambrian time during the final phase of amalgamation of the Gondwana supercontinent. In this study, we evaluate the cooling history of this pluton based on various isotopic systems. We present whole-rock Pb-Pb data on the syenite which yields an isochron age of 508±25Ma. Three phlogopite separates from the syenite pluton give K-Ar ages of 454.0±9.0, 448.5±8.9 and 445.6±8.8 Ma indicating cooling age at temperatures of ?415°C. U-Pb analyses of zircons from this syenite yielded an age of 572±2 Ma in a previous study. With U-Pb closure temperatures >800 o C, this age probably indicates the timing of emplacement of the Puttetti pluton. Collectively, we estimate from the isotopic age data and respective closure temperatures that the syenite body cooled at about 3.2 o C/Ma from about 800 o C to about 415 o C. The markedly low cooling rate of the syenite pluton, absence of chilled margin effects, and common occurrence of pyroxene, feldspar, phlogopite and zircons megacrysts in the rock indicate that the host granulites were at high temperatures during the emplacement of the syenite magma. The cooling history of Puttetti syenite estimated in this study is closely comparable with the 3–4 o C/Ma cooling rate estimated for a granite pluton in a previous study from Madagascar. Our study suggests protracted cooling rates for the late Pan-African intrusives emplaced within the Gondwana crust, with a long residence history in a hot crust bore they were exhumed to shallower levels. [Copyright &y& Elsevier]