The Late Cretaceous Impact of the Trindade Mantle Plume: Evidence from Large-volume, Mafic, Potassic Magmatism in SE Brazil

When the subcontinental lithospheric mantle undergoes heatingand/or extension, some of the earliest mafic melts to be generatedare those rich in volatUes and potassium. In some cases, e.g.when a plume impinges on thick cratonic lithosphere or whenthe amount of extension is very small, K-rich mafic igneousrocks may be the only surface expression of mantle melting.The Alto Paranaiba Igneous Province, in SE Brazil, is one ofthe world's most voluminous mafic potassic provinces (>15000km³),which until recently was relatively unknown. The magmas wereemplaced into a narrow Proterozoic mobile belt close to thesurface margin of the Sao Francisco craton, and it is one ofseveral Cretaceous alkaline igneous provinces that are locatedaround the margin of the Parana sedimentary basin in Braziland Paraguay.Detailed geochemical analyses of samples from throughoutthe Alto Paranaiba Igneous Province show that it is composedof a relatively diverse suite of ultrapotassic-potassic, ultramaficmqfic,silica-undersaturated lavas and hypabyssal intrusions, i.e.kimberlites, madupitic olivine lamproites and kamafugitic rocks.These all have very high concentrations of incompatible traceelements and are all strongly enriched in light rare earth relativeto heavy rare earth elements (e.g. La/Yb=50-230). Wide variationsin major element ratios, which are unrelated to the effectsof crystal fractionation in these magmas (e.g. CaO/Al₂O₃), suggestthat the mafic potassic rocks were derived from a heterogeneousmantle source. They show relatively restricted ranges of initial⁸⁷Sr/⁸⁶Sr (070436-070588) and Nd₂₅ values of -4 to -8, intermediatebetween Group I and II South African kimberlites. T_DM Nd isotopemodel ages of 900 Ma suggest that the magmas were derived bythe remobilization of subcontinental lithospheric mantle thathad been enriched by small-volume K-rich melt fractions sincethe Late Proterozoic.New K/Ar ages for mica separates show thatthe kimberlites, madupitic olivine lamproites and kamafugiticrocks were emplaced together with large carbonatite-bearingplutonic complexes at 85 Ma. Reconstructions of plate motionsshow that, at this time, the location of the Alto ParanaibaIgneous Province coincided with the postulated position of thepresent-day Trindade(or Martin Vaz) plume. We propose that thewidespread Late Cretaceous alkaline magmatism in SE Brazil mayhave been caused by impingement of this plume on the base ofthe subcontinental lithosphere. Heat penetrating the lithosphere,both by conduction and advection by asthenospheric-source decompressionmelts, may have caused melting of the readily fusible partsof the lithospheric mantle and the genesis of mafic potassicand (after fractionation) carbonatite magmas. The Proterozoicmobile belt (the Brasilia Belt) appears to have acted as a Hhinspofrelative to the adjacent Sao Francisco craton, allowing greaterupwelling and melting of the asthenosphere. Subsequently, asthe craton passed over the plume, volcanism was switched off'until the Early Tertiary when the plume reemerged from beneaththe westward drifting South America continent and was the magmasource for oceanic-islands and seamounts of the Trindade-Vitriachain. Corresponding author     

Potential use of faujasite–phillipsite and phillipsite–chabazite tuff in purification of treated effluent from domestic wastewater treatment plants

Characterization of zeolitic tuff from Jabal Hannoun (HN) and Mukawir (MR) was carried out to examine the ability of using low-cost natural materials in domestic wastewater treatment. The grain size between 0.3 and 1 mm (0.3–1 mm) of the HN and MR has the highest total zeolite grade (faujasite–phillipsite and phillipsite–chabazite) and suitable cation exchange capacity. They were used as fixed-bed ion exchangers and adsorbents. The zeolitic tuff efficiently removed the organic and nitrogen compounds, Pb and Zn from the effluent. One bed volume (1 BV) of the zeolitic tuff is capable to remove up to 95 % of total organic carbon form 500 BV of the effluent. The removal percent of total nitrogen by HN and MR is close to 95 and 90 %, respectively. The zeolitic tuff has an excellent efficiency to remove Pb and Zn from the effluent. 1 BV of HN completely cleans Zn and Pb from 680 and 730 BV of the effluent, respectively, whereas 1 BV of MR is able to clean completely Zn and Pb from 500 and 685 BV of the effluent, respectively. The greater performance of the HN compared with the MR may be explained by its higher zeolites grade and presence of faujasite.     

Thermodynamics of arsenates, selenites, and sulfates in the oxidation zone of sulfide ores: VI. Solubility of synthetic analogs of ahlfeldite and cobaltomenite at 25°C

The understanding of the mechanisms of the selenium behavior under near-surface conditions is an urgent problem of modern mineralogy and geochemistry, and is very important for solving environmental problems. The objective of this study is to synthesize analogs of ahlfeldite and cobaltomenite and to estimate their solubility in water. These analogs have been synthesized by mixing aqueous solutions of cobalt and nickel nitrates, respectively, and sodium selenite acidified with a solution of nitric acid. The obtained samples have been identified by X-ray diffraction and IR spectroscopy. The solubility has been determined by the isothermal saturation method in ampoules at 25°C, while the solubility products have been calculated using the Geochemist’s Workbench (GMB 7.0) software package. The solubility products of ahlfeldite and cobaltomenite are 10^?9.20 and 10^?9.44, respectively. The Eh-pH diagrams were calculated and plotted with the GMB 7.0 software package. The Eh-pH diagrams of the Ni-Se-H₂O and Co-Se-H₂O systems have been calculated for the average contents of these elements in underground water and their contents in acidic water of the oxidation zone of sulfide deposits. The formation of ahlfeldite and cobaltomenite under near-surface conditions is discussed.     

Continuous process study on simultaneous nitrification–denitrification of high ammoniacal nitrogen load wastewater in aerobic–anoxic sequencing bioreactors

The study focused on the feasibility of high NH₄ ⁺–N (400–600 mg/L) and COD load at two different hydraulic retention times (HRTs = 36 and 24 h) in two identical aerobic–anoxic sequencing bioreactors which were constructed in series in a single system using a specifically designed single biomass containing autotrophic nitrifying and heterotrophic denitrifying bacteria. Internal recirculation of synthetic wastewater from one tank to other was not carried out like the conventional aerobic–anoxic processes. Cycles of 15 days under sequences of aerated and non-aerated periods of three hour each were repeated during each continuous flow experiment conducted. Sodium bicarbonate and sodium acetate were selected as the appropriate inorganic and organic carbon sources. The results showed that the HRT may not affect the simultaneous nitrification and denitrification processes. Average nitrification ratio was obtained to be above 20 mg/L NH₄ ⁺–N/h daily. Results of 90 days’ operation also showed high removal efficiencies of ammoniacal nitrogen of about 83% daily. The main advantage of this process includes efficient ammoniacal nitrogen removal without separated aerobic and anoxic tanks, decrease operating costs due to the lesser oxygen concentration requirement in the bioreactors.     

Was Himalayan normal faulting triggered by initiation of the Ramgarh–Munsiari thrust and development of the Lesser Himalayan duplex?

The Ramgarh–Munsiari thrust is a major orogen-scale fault that extends for more than 1,500 km along strike in the Himalayan fold-thrust belt. The fault can be traced along the Himalayan arc from Himachal Pradesh, India, in the west to eastern Bhutan. The fault is located within the Lesser Himalayan tectonostratigraphic zone, and it translated Paleoproterozoic Lesser Himalayan rocks more than 100 km toward the foreland. The Ramgarh–Munsiari thrust is always located in the proximal footwall of the Main Central thrust. Northern exposures (toward the hinterland) of the thrust sheet occur in the footwall of the Main Central thrust at the base of the high Himalaya, and southern exposures (toward the foreland) occur between the Main Boundary thrust and Greater Himalayan klippen. Although the metamorphic grade of rocks within the Ramgarh–Munsiari thrust sheet is not significantly different from that of Greater Himalayan rock in the hanging wall of the overlying Main Central thrust sheet, the tectonostratigraphic origin of the two different thrust sheets is markedly different. The Ramgarh–Munsiari thrust became active in early Miocene time and acted as the roof thrust for a duplex system within Lesser Himalayan rocks. The process of slip transfer from the Main Central thrust to the Ramgarh–Munsiari thrust in early Miocene time and subsequent development of the Lesser Himalayan duplex may have played a role in triggering normal faulting along the South Tibetan Detachment system.     

Composition of sand storm particles in the Southern Far East

Lithostructural composition of the dust storm material (DMS) sampled in the southern Far East in the spring of 2002–2004 has been analyzed. Samples were taken near Vladivostok, where the eolian dust precipitation varied from 0.1 to 6.5 g/m² at that time. Pelitic and fine-silt particles predominate in eolian dust. Grain size, mineral, and chemical compositions of the DSM are compared to data on the DSM in adjacent territories of China, Korea, and Japan, as well as to background data on aerosol precipitation in southern Primorye. Possible mechanisms of the eolian dust transport from inner parts of Asia at different climatic variations in the Pleistocene-Holocene are discussed.     

Genesis of carbonates from the Parnok ferromanganese deposit,Polar Urals

The Parnok deposit is made up of stratiform lodes of iron (magnetite) and manganese (oxide-carbonate, carbonate, and carbonate-silicate) ores localized among terrigenous-carbonate sediments (black shales) on the western slope of the Polar Urals. The lithological study showed that ore-bearing sediments were accumulated in a calm hydrodynamic setting within a relatively closed seafloor area (trap depressions). Periodic development of anaerobic conditions in the near-bottom seawater was favorable for the accumulation of dispersed organic matter in the terrigenous-carbonate sediments. Carbon required to form calcium carbonates in the ore-bearing sediments was derived from carbon dioxide dissolved in seawater. In the organic-rich sediments, carbonates were formed with the participation of carbon dioxide released by the destruction of organic matter. However, δ¹³C values (from 0.5 to ?4.4‰ PDB) suggest a relatively low fraction of the isotopically light biogenic carbon in the host calcite. The most probable sources of Fe and Mn were hydrothermal seepages at the seafloor. The Eh-pH conditions during stagnation were favorable for the precipitation of Fe and accumulation of Mn in a dissolved state. Transition from the stagnation regime to the concentration of oxygen in near-bottom waters was accompanied by oxidation of the dissolved Mn and its precipitation. Thus, fluctuations in Eh-pH parameters of water led to the differentiation of Fe and Mn. Initially, these elements were likely precipitated as oxides and hydroxides. During the subsequent lithification, Fe and Mn were reduced to form magnetite and rhodochrosite. The texture and structure of rhodochrosite aggregates indicate that manganese carbonates already began to form at the diagenetic stage and were recrystallized during the subsequent lithogenetic stages. Isotope data (δ¹³C from ?8.9 to ?17.1‰ PDB) definitely indicate that the oxidized organic matter of sediment served as the main source of carbon dioxide required to form manganese carbonates. Carbonates from host rocks and manganese ores have principally different carbon isotopic compositions. Unlike carbonates of host rocks, manganese carbonates were formed with an active participation of biogeochemical processes. Further processes of metagenesis (T ≈ 250–300°C, P ≈ 2 kbar) resulted in the transformation of textures, structures, and mineral composition of all rocks of the deposit. In particular, increase in temperature and pressure provided the formation of numerous silicates in manganese ores.     

Hydrothermally altered hyaloclastites at the Earth’s surface in the rift zone of Iceland: Problem of the biochemogenic accumulation of trace elements

Results of the mineral and chemical study of surface-altered hyaloclastites from the Theistareykir and Nämafjall geothermal zones, the North Iceland rift, are considered. The paper scrutinizes the composition of hydrothermally altered rocks mainly consisting of clay minerals related to the transformation of bedrock hyaloclastites. The clay minerals also make up slope talus or proluvial deltas around highlands. The major clay minerals in areas of the present-day fumarole activity are kaolinite and smectite, while the redeposited talus-proluvial sediments are mainly composed of smectites. The studied rocks contain framboids, globules, rods, and other structures with morphology and size similar to those of mineralized bacteria. The local concentration of Ag in proluvial deposits is attributed to the intense bacterial activity. It is supposed that elevated contents of some trace elements could be related to an intense microbiotic influence.     

Evolution of pyroxene in peralkaline magmatic system: An example of an agpaitic syenite dyke complex and the Niva intrusion,Kola Peninsula

The paper presents pioneering data on the composition of pyroxenes and the distribution of trace elements in this mineral in small geological bodies that were formed by single magma injections and their subsequent rapid crystallization: the Niva intrusion and an agpaitic syenite dyke. The pyroxene is highly alkaline and shows continuous compositional trends with an increase in the aegirine concentration. The Ti concentrations of the pyroxene are much higher than in pyroxenes in agpaitic syenites in other alkaline complexes. In spite of the fact that the pyroxene is hosted in small bodies, the evolution of these pyroxenes was similar to that of pyroxenes in the Lovozero and Khibina alkaline massifs.     

Observation of abnormal thermal and infrasound signals prior to the earthquakes: a study on Bonin Island earthquake M7.8 (May 30, 2015)

Scientists from all over the world try to incorporate multi-disciplinary precursors to forecast the earthquake on a short-term basis. The authors here have analyzed outgoing longwave radiations acquired from polar-orbiting National Oceanic and Atmospheric Adminstration (NOAA) satellites and long-period infrasound waves recorded by the ground observatories in China prior to the recent Bonin Islands, Japan region earthquake which occurred on May 30, 2015 with the magnitude of 7.8. The anomalous outgoing longwave radiation (OLR) was observed on May 15, 2015, and was recorded by “NOAA 18” satellite during its “night pass.” Similarly, an abnormal infrasound spike was recorded at the Beijing station on May 17, 2015. The delay in observing anomalous infrasound waves compared to the OLR anomaly is due to these low-frequency waves traveling at low speed with the velocity range of 10–15 m/s. From the analysis of the results, it can be inferred that there is a substantial relation between parameters like OLR and infrasound waves; hence, the authors conclude that it is possible to forecast the earthquake on a short-term basis with reasonable accuracy.