Results of U-Pb dating of zircon and baddeleyite from the Noril’sk-1 ultramafic-mafic intrusion (Russia)

We present for the first time the mineralogical and isotope-geochemical particularities of zircon and baddeleyite from various rocks of the economic ore-bearing Noril’sk-1 intrusion located in the northwestern part of the Siberian platform. The ultramafic-mafic Noril’sk-1 intrusion hosts one of the world’s major economic platinum-group-element (PGE)-Cu-Ni sulphide deposits.A detailed study of crystal morphology and internal structure identify four zircon populations, characterized by different U-Pb (SHRIMP-II) ages. The U-Pb ages of baddeleyite and the defined zircon populations cover a significant time span (from 290 ± 2.8 to 226.7 ± 0.9 Ma). The established U-Pb ages imply that crystallization of baddeleyite and zircon populations corresponds to several stages of protracted evolution of the ore-forming magmatic system (290 ± 2.8, 261.3 ± 1.6, 245.7 ± 1.1, 236.5 ± 1.8, and 226.7 ± 0.9 Ma, respectively) that served as the favorable factor for accumulation of magmas and ores of unique scales and concentrations.     

Detrital and authigenic(?) baddeleyite (ZrO2) in ferromanganese nodules of Central Indian Ocean Basin

Occurrence of baddeleyite (ZrO2) which is a rare mineral has been recorded in ferromanganese nodules of Central Indian Ocean Basin (CIOB). The mineral occurs either as independent isolated sub-rounded to elliptical grains or in clusters forming fine subhedral crystals (<3 mm) within ferromanganese concretionary growth bands. The mode of occurrence, textural features and chemistry of the mineral suggest detrital and possibly an authigenic origin for baddeleyite. For authigenic origin it is proposed that zirconium might have got released either from the terrigenous sediments or the altered seafloor rocks forming halogen complexes and subsequently it has re-precipitated in the form of baddeleyite within manganese nodules under oxic to sub-oxic conditions.     

Precise U–Pb zircon–baddeleyite age of the Jinchuan sulfide ore-bearing ultramafic intrusion, western China

The Jinchuan ultramafic intrusion in western China hosts the third-largest magmatic Ni–Cu deposit in the world. The crystallization age of the intrusion has long been debated. Here, we present a U–Pb ID-TIMS zircon age of 831.8 ± 0.6 Ma obtained on thermally annealed and chemically etched zircons from a lherzolite sample. The coexisting baddeleyite in the sample is indistinguishable from the age of zircon. Our new results confirm that the emplacement of the Jinchuan ultramafic intrusion was temporally related to the breakup of the Rodinia supercontinent.     

Pb–Pb baddeleyite ages of mafic dyke swarms from the Dharwar Craton: Implications for Paleoproterozoic LIPs and diamond potential of mantle keel

The Dharwar Craton in Peninsular India was intruded by a series of mafic dykes during the Paleoproterozoic and these mafic magmatic events have important implications on continental rifting and LIPs. Here we report ten precise Pb–Pb TE-TIMS age determinations on baddeleyite grains separated from seven mafic dykes and three sills, intruding into Archean basement rocks and Proterozoic sedimentary formations of the Eastern Dharwar Craton respectively. The crystallization age of the baddeleyite shows 2366.3 ​± ​1.1 ​Ma, and 2369.2 ​± ​0.8 ​Ma for the NE–SW trending dykes, 2368.1 ​± ​0.6 ​Ma, 2366.4 ​± ​0.8 ​Ma, 2207.2 ​± ​0.7 ​Ma and 1887.3 ​± ​1.0 ​Ma for the ENE–WNW to E–W striking dykes, 1880.6 ​± ​1.0 ​Ma, 1864.3 ​± ​0.6 ​Ma and 1863.6 ​± ​0.9 ​Ma for Cuddapah sills, and 1861.8 ​± ​1.4 ​Ma for the N–S trending dyke. Our results in conjunction with those from previous studies identify eight distinct stages of widespread Paleoproterozoic magmatism in the Dharwar craton. The mantle plume centres of the four radiating dyke swarms with ages of ~2367 ​Ma, ~2210 ​Ma, ~2082 ​Ma, and ~1886 ​Ma were traced to establish their proximity to the EDC kimberlite province. Though the ~2367 ​Ma and ~1886 ​Ma plume centres are inferred to be located to the west and east of the present day Dharwar craton respectively away from the kimberlite province, location of plume heads of the other two swarms with ages of ~2207 ​Ma and ~2082 ​Ma are in close proximity. In spite of the ubiquitous occurrence of dyke intrusions of all the seven generations in the kimberlite province, only few of these kimberlites are diamondiferous. Kimberlite occurrences elsewhere in the vicinity of older Large Igneous Provinces (LIPs) like the Mackenzie, Karoo, Parana-Etendeka and Yakutsk-Vilui are also non-diamondiferous. This has been attributed to the destruction of the lithospheric mantle keel (that hosts the diamonds) by the respective mantle plumes. The diamondiferous nature of the EDC kimberlites therefore suggests that plume activity does not always result in the destruction of the mantle keel.     

Precise U–Pb baddeleyite ages of mafic dykes and intrusions in southern West Greenland and implications for a possible reconstruction with the Superior craton

The Archaean block of southern Greenland constitutes the core of the North Atlantic craton (NAC) and is host to a large number of Precambrian mafic intrusions and dyke swarms, many of which are regionally extensive but poorly dated. For southern West Greenland, we present a U–Pb zircon age of 2990 ± 13 Ma for the Amikoq mafic–ultramafic layered intrusion (Fiskefjord area) and four baddeleyite U–Pb ages of Precambrian dolerite dykes. Specifically, a dyke located SE of Ameralik Fjord is dated at 2499 ± 2 Ma, similar to a previously reported ⁴⁰Ar/³⁹Ar age of a dyke in the Kangâmiut area. For these and related intrusions of ca. 2.5 Ga age in southern West Greenland, we propose the name Kilaarsarfik dykes. Three WNW-trending dykes of the MD3 swarm yield ages of 2050 ± 2 Ma, 2041 ± 3 Ma and 2029 ± 3 Ma. A similar U–Pb baddeleyite age of 2045 ± 2 Ma is also presented for a SE-trending dolerite (Iglusuataliksuak dyke) in the Nain Province, the rifted western block of the NAC in Labrador. We speculate that the MD3 dykes and age-equivalent NNE-trending Kangâmiut dykes of southern West Greenland, together with the Iglusuataliksuak dyke (after closure of the Labrador Sea) represent components of a single, areally extensive, radiating swarm that signaled the arrival of a mantle plume centred on what is presently the western margin of the North Atlantic craton. Comparison of the magmatic ‘barcodes’ from the Nain and Greenland portions of the North Atlantic craton with the established record from the north-eastern Superior craton shows matches at 2500 Ma, 2214 Ma, 2050–2030 Ma and 1960–1950 Ma. We use these new age constraints, together with orientations of the dyke swarms, to offer a preliminary reconstruction of the North Atlantic craton near the north-eastern margin of the Superior craton during the latest Archaean and early Palaeoproterozoic, possibly with the Core Zone craton of eastern Canada intervening.     

Precise conventional and SHRIMP baddeleyite U‐Pb age for the Binneringie Dyke,near Narrogin,Western Australia

A precise baddeleyite U‐Pb age of 2418 ± 3 Ma is reported for the westerly extension of the Binneringie Dyke in the south‐western Yilgarn Craton of Western Australia. The Binneringie Dyke is a member of the large and extensive Widgiemooltha dyke swarm that trends east‐west across the craton. This age is similar to ages of major dyke swarms In other Archaean Cratons and supports the hypothesis that dykes of the Widgiemooltha swarm are part of a worldwide Palaeoproterozoic mafic magmatic event at ca 2420 Ma.     

The Paleoproterozoic Fedorov–Pana Layered PGE complex of the northeastern Baltic Shield,Arctic Region: New U–Pb (baddeleyite) and Sm–Nd (sulfide) data

For the first time zircons have been extracted from gabbro–norite of a lower layered horizon of the West Pana Massif in the Pt–Pd Kievei deposit of the Fedorov–Pana Layered Complex. Those zircons have been used for U–Pb dating along with Sm–Nd age determination on sulfide minerals. The obtained new isotopic data are a U–Pb zircon age of 2500 ± 4 Ma, while the Sm–Nd (mineral and whole-rock) isochron yielded 2483 ± 86 Ma. These results correspond to the first phase of the Pt–Pd reef complex formation in the Layered Complex. The Pt–Pd reef formation has been dated by U–Pb baddeleyite and zircon analyses in the East Pana Massif to 2464 ± 12 Ma. The 2485–2464 Ma time span corresponds to the second phase of the Pt–Pd reef formation in the Fedorov–Pana ore cluster.     

U–Pb baddeleyite ages and Hf,Nd isotope chemistry constraining repeated mafic magmatism in the Fennoscandian Shield from 1.6 to 0.9 Ga

The Palaeoproterozoic (1.90–1.60 Ga) crust of central Fennoscandia was intruded repeatedly by dolerite dikes and sills during the Neo- and Mesoproterozoic eons. We report 17 new baddeleyite U–Pb dates comprising six generations of dolerites (in Ma):

Blekinge-Dalarna dolerites	946–978
Protogine Zone dolerites	1,215–1,221
Central Scandinavian Dolerite Group	1,264–1,271
Tuna dikes and age equivalents in Dalarna	1,461–1,462
Värmland dolerites	～1,568
Breven-Hällefors dolerites	～1,595

The favoured tectonic model implies that the majority of these suites were related to active margin processes somewhere west (and possibly south) of the Fennoscandian Shield. Dolerite intrusions are interpreted to reflect discrete events of back-arc extension as the arc retreated oceanward. Initial Hf and Nd isotope compositions of the dolerite swarms fall between CHUR and normal-depleted mantle, and suggest a variably depleted and re-enriched mantle as the source for the here investigated 1.6 to 0.95 Ga old mafic rocks. Repeated recycling of older crustal components, mainly sediments (dominated by material with short residence ages) in earlier subduction systems may have been very efficient at producing geochemically and isotopically variably enriched lithospheric mantle sections beneath the Fennoscandian Shield.

     

The Central Scandinavian Dolerite Group—Protracted hotspot activity or back-arc magmatism?: Constraints from U–Pb baddeleyite geochronology and Hf isotopic data

The Central Scandinavian Dolerite Group (CSDG) occurs in five separate complexes in central Sweden and SW Finland. U–Pb baddeleyite ages of dolerite dikes and sills fall into three age intervals: 1264–1271 (the Dalarna complex), 1256–1259 (the Västerbotten-Ulvö-Satakunta complexes) and 1247 Ma (the Jämtland complex). Timing and spatial distribution of CSDG are unlike expressions of the voluminous and short-lived magmatism which characterises plume-associated large igneous provinces (LIPs). Protracted mafic magmatism in association with mantle plume tail (hotspot) activity beneath the Fennoscandian lithosphere or discrete events of extension behind an active margin (subduction) are considered more plausible tectonic settings. Both settings are consistent with timing, relative magma volumes between complexes and vertical ascent of individual magma pulses through the crust, as inferred from seismic sections [Korja, A., Heikkinen, P., Aaro, S., 2001. Crustal structure of the northern Baltic Sea palaeorift. Teconophysics 331, 341–358]. In the hotspot model, the lack of a linear track of intrusions can be explained by an almost stationary position of Fennoscandia relative to the hotspot, in agreement with palaeomagnetic data [Elming, S.-Å., Mattsson, H., 2001. Post Jotnian basic intrusion in the Fennoscandian Shield, and the break up of Baltica from Laurentia: a palaeomagnetic and AMS study. Precambrian Res. 108, 215–236]). Together with geological evidence, dolerite sill complexes and dike swarms in Labrador (Canada), S Greenland and central Scandinavia in the range 1234–1284 Ma are best explained by long-lived subduction along a continuous Laurentia-Baltica margin preceding Rodinia formation. There is no support for the hypothesis that CSDG was fed by magma derived from a distal mantle plume located between Baltica and Greenland and, hence, for rifting between the cratons at 1.26 Ga.The epsilon-Hf in various members of the CSDG varies between 4.7 and 10.3, which are overall higher than both older and younger Mesoproterozoic mafic intrusions in central Fennoscandia. Magma generated from a hotspot mantle source that was mixed to highly variable degrees with an enriched subcontinental lithospheric mantle could account for the wide range in Hf isotope composition. In the course of Hf isotope development work during this project we have analysed four fragments of the Geostandard 91500 reference zircon and after evaluating the existing ICPMS and TIMS data we calculate a mean ¹⁷⁶Hf/¹⁷⁷Hf value of 0.282303 ± 0.000003 (2σ).     

U–Pb baddeleyite ages linking major Archean dyke swarms to volcanic-rift forming events in the Kaapvaal craton (South Africa), and a precise age for the Bushveld Complex

The Archean basement in the northeastern part of the Kaapvaal craton is intruded by a large number of mafic dykes, defining three major dyke swarms, which collectively appear to fan out from the Bushveld Complex. Herein we present U–Pb baddeleyite ages for two of these dyke swarms, the northwest trending Badplaas Dyke Swarm and the east-west trending Rykoppies Dyke Swarm, and infer their correlation with tectonic events in the Kaapvaal craton. We also present a U–Pb baddeleyite age for a noritic phase of the Marginal Zone of the Rustenburg Layered Suite (Bushveld Complex).     

Comparison of Different Estimates of the Accuracy of Forecasts of the Earth’s Rotation Parameters

Astronomy Reports - Improvement of the prediction accuracy of the Earth’s rotation parameters (ERP) is one of the main problems of applied astrometry. In order to solve this problem, various...     

Increasing of efficiency of desulphurisation processes of coals during thermal destruction

As is well known, a high content of sulphur in coals is an effect of the post-depositional history of coal seams and one of the most important criteria of its use as a fuel. Sulphur in coals can cause a serious environmental and technological problem during their utilization. This problem is very actual for the Donetsk Basin because 734 mined seams out of the total of 1009 （73%） are comprised of coals with sulphur content -2%. The chemical pre-treatment as a first stage in their processing is widely used in order to effectively obtain the thermal destruction products of coals （such as semi-coke, coke, adsorbents, etc.） and to simultaneously utilize coal wastes. Development in pre-treatment methods for high-sulphur, low-rank coals is especially desirable for reducing the sulphur contents of the solid products. The aim of the present work is to investigate the influence of coal pre-treatment on the yield and composition of thermal destruction products, and the sulphur distribution among different components of the coals of different genetic types by reductivity （low-reduced LRC and reduced RC coals）. The thermal behavior of the coals was studied by means of the Fisher method （heated to 520℃, at a rate of 7℃/min）. The composition of the semi-coking gas was investigated by means of a VTI gas analyzer. The coal samples were chemically treated directly before thermal destruction by the introduction of 1-% solutions of radical polymerization initiator AAD （acrylic acid dinitrile C8H12N4） and products of coal-tar distillation （absorber oil）. Coal pre-treatment increases the semi-coke yield and its coking ability, and changes the liquid/gaseous product ratio.     

Possibility of degradation of phenylarsonic acid in the presence of ferrihydrite

Although inorganic species are predominant in natural systems, but there are many kinds of organoarsenic species such as methylated and phenylated arsenic compounds. Phenylarsonic acid （PA） is a degradation product of organoarsenics used for chemical warfare agents, which has been detected in well water at the disposal site of the agents in Japan. There are few reports studying behavior of PA in soil. In this study, PA was adsorbed onto ferrihydrite and its chemical forms were determined using high performance liquid chromatography connected to inductivity-coupled plasma mass spectrometry （HPLC-ICP-MS）. 100 mg/kg of PA was mixed with 0.03 g of 2-line ferrihydrite. For each suspension, pH was adjusted by HNO3 or NaOH. Each sample was incubated for more than 19 hours and the final pH was measured. After filtration, the chemical form of arsenic in the filtrate was measured using HPLC-ICP-MS. In addition, ferrihydrite separated by filtration was dissolved by 3 ml of 0.5 M HCI and the arsenic species in the solution was detected by HPLC-ICP-MS （column： Tosoh TSKgel SuperlC-AP, eluent： 0.01 M HNO3）. It was verified that PA is not degraded by heating in 0.5 M HCl solution. At pH 3.1, any arsenic compounds were not detected from the solution, because almost all arsenic species were adsorbed onto ferrihydrite at lower pH. At pH= 12, however, 7%-10% of inorganic arsenic was detected in the solution. In solid phase, there are some problems to determine the precise ratio of inorganic and organic species. When the solution includes Fe ion at 0.01 M level, the retention time of arsenic species drifted compared to those in standard solution, which makes it difficult to determine precisely the arsenic species adsorbed on ferrihydrite. Therefore, more study is needed to determine the ratio of inorganic and organic species in the system.     

An Interpretation of the Origin of Distribution Anomalier of △C

Zonal distribution of seepage hydrocarbon-induced altereb carbonates over oil/gas reservoirs is a common phenomenon observed in the field.The authors considered that the continuous production of CO2 within the “alteration chimney ”gives rise to a significant difference in physical and chemical properties between its interior and the surrounding country rocks.And it is this difference that has promoted the erosion and precipitation of carbonates,thus leading to the zonal distribution of seepage hydrocarbon-induced altered carbonates over oil/gas reservoirs.This may be a reasonable interpretation of the phenomenon described above.