Ar–Ar age determinations of eclogitic clinopyroxene and garnet inclusions in diamonds from the Venetia and Orapa kimberlites

Ar–Ar age measurements are reported for selected eclogitic clinopyroxene and garnet inclusions in Orapa diamonds and clinopyroxene inclusions in Venetia diamonds. Laser drilling of encapsulated clinopyroxene inclusions within Venetia diamonds released a maximum of 3% of the total ⁴⁰Ar, indicating little diffusive transfer and storage of radiogenic ⁴⁰Ar at the diamond–inclusion boundary. Apparent ages obtained during stepped heating of three diamonds are consistent with diamond crystallisation occurring just prior to the kimberlite eruption 520 Ma ago. Stepped heating of three clinopyroxene-bearing Orapa diamonds gave ages of 906–1032 Ma, significantly above the eruption age, but consistent with previously determined isotopic ages. A few higher apparent ages hint at the presence an older generation of Orapa diamonds that formed >2500 Ma ago. Orapa garnets also contain measurable K contents, and record a range of ages between 1000 and 2500 Ma. The old apparent ages and lack of significant interface ⁴⁰Ar released by the laser probe, suggests that pre-eruption radiogenic ⁴⁰Ar and mantle-derived ⁴⁰Ar components are trapped in microinclusions within the pyroxene and garnet inclusions.     

Investigation of ammonia removal from polluted waters by Clinoptilolite zeolite

Ammonia nitrogen compounds in the wastewaters and effluents have harmful effects on water resources. Ion exchange with zeolites is a separation process for ammonia removal from effluents. The objective of this research was to study the efficiency of an ammonia removal and the factor affecting to this process. The Clinoptilolite was obtained from Semnan mines at the north part of Iran. The samples were grounded and sieved based on the U.S. standard mesh number 20, 30, 40 and conditioned by ammonia sulfate and sodium chloride solutions. The characteristics of samples for ammonia removal and the selectivity sequence for adsorbing interfering cations were then determined. Results shown that the average ion exchange capacity of zeolite in batch and continuous systems were 6.65–16 and 16.31–19.5 mg NH₄ ⁺ /g zeolite weight, respectively. In study on the zeolite for selective cations showed the ranking of K⁺, NH₄ ⁺, Na⁺, Ca²⁺ and Mg²⁺ respectively. Results indicated that high level of regeneration (95–98%) might be achieved with NaCl solution. Based on the results, Clinoptilolite may be effective applied in wastewater treatment, both from technical and economical aspects.     

Mineral inclusions in diamonds from the Sputnik kimberlite pipe, Yakutia

The Sputnik kimberlite pipe is a small “satellite” of the larger Mir pipe in central Yakutia (Sakha), Russia. Study of 38 large diamonds (0.7-4.9 carats) showed that nine contain inclusions of the eclogitic paragenesis, while the remainder contain inclusions of the peridotitic paragenesis, or of uncertain paragenesis. The peridotitic inclusion suite comprises olivine, enstatite, Cr-diopside, chromite, Cr-pyrope garnet (both lherzolitic and harzburgitic), ilmenite, Ni-rich sulfide and a Ti-Cr-Fe-Mg-Sr-K phase of the lindsleyite-mathiasite (LIMA) series. The eclogitic inclusion suite comprises omphacite, garnet, Ni-poor sulfide, phlogopite and rutile. Peridotitic ilmenite inclusions have high Mg, Cr and Ni contents and high Nb/Zr ratios; they may be related to metasomatic ilmenites known from peridotite xenoliths in kimberlite. Eclogitic phlogopite is intergrown with omphacite, coexists with garnet, and has an unusually high TiO₂ content. Comparison with inclusions in diamonds from Mir shows general similarities, but differences in details of trace-element patterns. Large compositional variations among inclusions of one phase (olivine, garnet, chromite) within single diamonds indicate that the chemical environment of diamond crystallisation changed rapidly relative to diamond growth rates in many cases. P-T conditions of formation were calculated from multiphase inclusions and from trace element geothermobarometry of single inclusions. The geotherm at the time of diamond formation was near a 35 mW/m² conductive model; that is indistinguishable from the Paleozoic geotherm derived by studies of xenoliths and concentrate minerals from Mir. A range of Ni temperatures between garnet inclusions in single diamonds from both Mir and Sputnik suggests that many of the diamonds grew during thermal events affecting a relatively narrow depth range of the lithosphere, within the diamond stability field. The minor differences between inclusions in Mir and Sputnik may reflect lateral heterogeneity in the upper mantle.     

Ranking desertification indicators using TOPSIS algorithm

Desertification is the result of natural and anthropogenic processes, leading to degradation or loss of the land’s productivity and complexity. To assess the desertification status, integrated set of indicators must be identified. Indicators must provide synthetic information on threshold levels, status and evolution of relevant physical, chemical, biological and anthropogenic processes. Multi-criteria decision-making (MCDM) is a collection of methodologies to compare, select, or rank multiple alternatives that involve incommensurate attributes. Technique for order preference by similarity to ideal solution (TOPSIS) method is a multiple criteria method to identify solutions from a finite set. TOPSIS is an algorithm for determining the most preferable choices among the possible indicators that can be developed. The aim of this paper is to introduce TOPSIS as a decision-making method for the selection and integration of desertification indicators. The simulation case study presented here is related to the selection of the best set of indicators to monitor land degradation by remote sensing in three different countries (Brazil, Mozambique and Portugal), within the framework defined by the DesertWatch Extension project.     

Se and Te mineralization in albitites and prospects of the metasomatites for Au,Salla-Kuolajarvi belt,Northern Karelia

On the basis of the complex of geological features, the eastern flank of the Salla-Pana-Kuolajarvi belt is a prospect structure for gold mineralization in the U-bearing albitites and related acid and mafic metasomatites. Visible tellurides and selenides, which are typical of gold deposits of the Fe-Co-Au-U group in the adjacent territory of Finland within the Salla-Pana-Kuolajarvi belt, were found in the Ozerny occurrence as a result of studies. Native gold is found in association with tellurides. Molybdenite from the occurrence has a high Re content up to 0.3%.     

Little Ice Age advance and retreat sediment budgets for an outlet glacier in western Norway

Burki, V., Hansen, L., Fredin, O., Andersen, T. A., Beylich, A. A., Jaboyedoff, M., Larsen, E. & Tønnesen, J.‐ F. 2009: Little Ice Age advance and retreat sediment budgets for an outlet glacier in western Norway. Boreas, Vol. 39, pp. 551–566. 10.1111/j.1502‐3885.2009.00133.x. ISSN 0300‐9483 Bødalsbreen is an outlet glacier of the Jostedalsbreen Ice Field in western Norway. Nine moraine ridges formed during and after the maximum extent of the Little Ice Age (LIA). The stratigraphy of proglacial sediments in the Bødalen basin inside the LIA moraines is examined, and corresponding sediment volumes are calculated based on georadar surveys and seismic profiling. The total erosion rates (e_tot) by the glacier are determined for the periods AD 1650–1930 and AD 1930–2005 as 0.8 ± 0.4 mm/yr and 0.7 ± 0.3 mm/yr, respectively. These rates are based on the total amount of sediment delivered to the glacier margin. The values are almost one order of magnitude higher than total erosion rates previously calculated for Norwegian glaciers. This is explained by the large amount of pre‐existing sediment that was recycled by Bødalsbreen. Thus, the total erosion rate must be considered as a composite of eroded bedrock and of removed pre‐existing sediments. The total erosion rate is likely to vary with time owing to a decreasing volume of easily erodible, unconsolidated sediment and till under the glacier. A slight increase in the subglacial bedrock erosion is expected owing to the gradually increasing bedrock surface area exposed to subglacial erosion.     

An 40Ar/39Ar study of a polymetamorphic complex in the Arunta Block,Central Australia

A polymetamorphic complex in the Arunta Block, Central Australia, which has undergone metasomatism involving introduction of Rb and loss of Sr has been investigated by ⁴⁰Ar/ ³⁹Ar step and total-degassing techniques in an attempt to date five metamorphic events (M1–M5) identified microstructurally. The complex isotopic data and apparent age spectra obtained have been interpreted in the light of constraints provided by an associated tectonometamorphic study, together with independent geochronological controls from the immediate study area and elsewhere in the Arunta Block. This has led to the delineation of ages of 1,780–1,820 M.y. for M1, 1,690–1,720 M.y. for M2, 1,450–1,500 M.y. for M3, 1,030–1,060 M.y. for M4 and 370–510 for M5. The polyphase M5 event is correlated with the Alice Springs Orogeny, previously accorded younger age limits of 330–370 M.y. The latter are interpreted to reflect closure of mica K/Ar systems as uplift continued subsequent to the close of the event, possibly culminating in minor high-level brittle deformation and the development of pseudotachylytes in the study area.Apparent age spectra recorded in this study do not all conform with generally accepted patterns of behaviour of mineral systems which have undergone polythermal histories. Two hornblendes have survived subsequent high temperature metasomatic reheating without loss of argon or resetting of their ages. Their resistance to argon loss may be attributable to low water contents, due to their growth under anhydrous granulite facies conditions, and may reflect a relationship between argon loss from hornblende and the water content of hornblende, which decreases with increasing metamorphic grade (Kostyuk and Sobolev 1969). Other samples display false plateaux in their apparent age spectra and in three cases the spectra are indistinguishable from those of undisturbed spectra.The age data recorded in this study suggest that during basement reactivation loss of argon is mainly confined to the vicinity of shear zones, implying that diffusion of argon from minerals in the deep crust may be dependent more on deformation than on reheating. However, thermal activity may also be associated with active shear zones, through the medium of superheated fluids streaming up the shear zones from below. The wide spread of K/Ar and ⁴⁰Ar/³⁹Ar ages (330–510 M.y.), recorded for the Alice Springs Orogeny in the Arunta basement, may reflect such controls.     

A preliminary case study of potential ceramic raw materials in the Aileu area of Timor Leste

The newly independent country of Timor Leste is located in the eastern half of Timor Island (Indonesian archipelago). Geological studies of the country’s mineral resources and extractive activities are practically non-existent. There is evidence of the exploitation of ceramic raw materials at outcrop level and two small brick kilns, nowadays inactive, in the Dili and Aileu areas. Near Aileu, there are light-coloured silt-rich deposits, interpreted as overbank deposits, interbedded with ancient river terraces (post-Pliocene) overlying metamorphic bedrock. These sediments are the subject of this study, which encompassed geological mapping and preliminary characterisation. Tectonically, the area is a graben, preserving alluvium and colluvium deposits. Five channel samples representative of the silt-rich deposits were collected. Semi-quantitative mineralogical analysis shows that the samples are made of illite, quartz and kaolinite clays, with accessory illite/vermiculite interstratified minerals and K-feldspar. The chemical data show agreement with the estimated mineralogical composition. The grain size distribution points to a silt-dominated assemblage. Most samples have a satisfactory extrudability but deficient moulding properties. After firing, the sampled raw materials form a final product with possible ceramic capability for whiteware production.     

澳大利亚的第三纪及第三纪—第四纪过渡期(英文)

第三纪的板块运动驱动着澳大利亚的气候和植被进行演化。广布的湿润森林区是澳大利亚老第三纪的特征。一直到始新世 ,生物多样性都在不断地提高。毫无疑问 ,这是澳大利亚由高南纬区向北部中纬区运移的结果。从始新世到上新世 ,澳大利亚的气候总体上要比现在湿润 ,但降水量季节性变化的增强推动了中新世以后硬叶植物和旱生植物的发展。上新世晚期似乎与第四纪一样 ,都出现过周期性干旱。这种干旱与冰期条件有关 ,至少由南澳大利亚晚第四纪的记录可以认识到这一点 ,澳大利亚的这段历史与东亚的气候变迁是同步发生的。在东亚 ,印—澳板块的运动致使青藏高原抬升 ,从而引发了区内乃至全球气候的巨变。穿越赤道区的季风和信风的环流格局 ,致使新第三纪和第四纪中国与澳大利亚的气候系统的相关性更强。