Luna 24 ferrobasalt as a low-Mg primary melt

Luna 24 very-low titanium (VLT) ferrobasalts, metabasalts, brown glasses and impact melts form a tight compositional cluster with no gradation to other groupings postulated for the Luna 24 core components. This suggests that the Luna 24 VLT ferrobasalt was extruded as a liquid of its own composition and was not derived by fractional crystallization from a more magnesian parent in a surface flow. Furthermore, the characteristics of the core lithologies are not easily visualized as components of such a differentiated flow, e.g. brown glasses. Gravitative settling models purporting to demonstrate the validity of the flow differentiation model are merely permissive.Subsurface fractionation requires that plagioclase, not olivine, be the liquidus phase.The high-Mg component in the Luna 24 core can be constrained, though not identified, chemically, and it has neither the major element, trace element, isotopic, nor mineralogical characteristics required of a possible parent to the Luna 24 VLT ferrobasalt. Thus models of fractionation lack a physical expression of the less differentiated compositions, contrary to the belief that the high-Mg component in the core is the parent material.The Luna 24 VLT ferrobasalt is probably a primary low-Mg melt from a plagioclase-bearing source region, and may have undergone little or no fractionation prior to eruption. Such a model is compatible with, and suggested by, chemical and experimental data. Caution against postulating that all Mg-poor melts are fractionated products, based on terrestrial models, is advised. The terrestrial oceanic situation of primary melts with similar Mg/Fe is probably not valid for the Moon.     

Potential health risk in areas of high natural concentrations of thallium and importance of urine screening

There is a lack of information in the literature regarding Tl exposure from naturally occurring Tl enrichment. This paper draws attention to the potential health risk posed by high concentrations of naturally occurring Tl in the environment. The inhabitants of a rural area in SW Guizhou Province, China, reside within a natural Tl accumulated environment resulting from Tl-rich sulfide mineralization, and they face ongoing severe Tl exposure. High Tl concentrations were detected in urine of the local residents. Urinary Tl concentrations are as high as 2668 μg/L, with most subjects surpassing the accepted world urinary Tl concentration at <1 μg/L for “non-exposed” humans. The urinary Tl concentrations show significant differences among three communities (n = 21, p = 0.001), but no significant difference in either sex or age groups (n = 21, p = 0.7806). However, there is a positive statistical relationship between the extent of Tl exposure from Tl concentrations in soil and crops in the immediate environment and the concentrations of Tl detected in urine. A majority of the volunteer subjects from the communities have urinary Tl concentrations above 4.5–6 μg/L, implying early adverse health effects, and some of them have over 500 μg/L urinary Tl, considered to be at/about the level of clinical intoxication. This study has been able to identify that the elevated urinary Tl concentrations are mainly attributable to Tl accumulation in locally grown vegetables, which acquire Tl from the soil. This study also shows that Tl in urine of the local population represents a steady-state condition with long-term exposure, and that urinary Tl concentrations can be taken as a bio-marker of total dose based upon total daily dietary intake. This study demonstrates that natural sources of elevated Tl pose a potential health risk to the population, and that monitoring the urinary Tl concentration is a reliable and accurate way of bio-marking Tl exposure.     

Institutional arrangements for metropolitan government and strategic planning in Auckland

Abstract:  The task of designing appropriate institutional arrangements for metropolitan government and planning has recently proved highly contestable politically. We interrogate how the role of the Auckland Regional Council (ARC) was zealously contested and hollowed-out during the 1990s. More recently, the impacts of the neo-liberal reforms in Auckland have been mediated by a further round of local government reforms inspired by a Third Way ideology and by the imperative to respond to the planning crisis resulting from infrastructure underinvestment. New regionally based governance arrangements and planning processes have been created. We argue that this new commitment to regionalism can realistically expect to be tested by deep-seated political cleavages within Auckland and by Auckland's relationship with central government.     

Evidence of diverse depletion and metasomatic events in harzburgite–lherzolite mantle xenoliths from the Iberian plate (Olot, NE Spain): Implications for lithosphere accretionary processes

Mantle xenoliths from the Olot volcanic district (NE Spain) comprise a bi-modal suite consisting of protogranular spinel lherzolites (cpx 12–14%) sometimes with pargasitic amphibole, and highly refractory spinel harzburgites (cpx ≤ 1%) with coarse-grained granular textures. The lherzolites range from slightly depleted to moderately LREE-enriched with flat HREE patterns between 1.5 and 2.7 × chondrite (Ch). In contrast, the harzburgites are extremely depleted in HREE (down to 0.2 × Ch) and strongly LREE-enriched (La_N/Yb_N = 12.3–17.2). LA-ICP-MS analyses of clinopyroxene and amphibole of the lherzolites highlight variable degrees of LREE depletion (HREE up to 13 × Ch, La_N/Yb_N down to 0.01), with the exception of a single sample in which both clinopyroxene and amphibole are LREE-enriched (La_N/Yb_N up to 19). In the harzburgites, clinopyroxenes display totally different REE distributions, characterized by extreme HREE depletion (down to 0.4 × Ch) and upward convex positively fractionated middle-light REE patterns (Nd_N/Yb_N up to 20.7 × Ch; La_N/Yb_N up to 12 × Ch). Sr–Nd–Hf isotopic data for both whole-rocks and cpx separates, coherently indicate depleted mantle (DM) compositions for the lherzolites (εSr = − 15 to − 26, εNd = + 9 to + 17, εHf = + 18 to + 68) and enriched mantle (EM) compositions for the harzburgites (εSr = − 10 to + 36, εNd = − 1 to − 6, εHf = + 3 to + 8). Modelling of the clinopyroxene REE data and isotopic systematics suggest that some lherzolites were affected by pre-Paleozoic (0.6–1 By) low-degree partial melting processes, while others probably reflect some extent of refertilization of the mantle protolith by metasomatizing melts similar to the Triassic rift-related tholeiites reported from several Pyrenean localities. The harzburgites represent extreme refractory residua, resulting from a complex depletion history due to multistage melt extraction as often observed in the cratonic mantle. The distinctive REE patterns and isotopic systematics of their clinopyroxenes suggest that the harzburgites were formed by the interaction of an ultra-depleted peridotite matrix with highly alkaline basic melts similar in composition to the Permo-Triassic alkaline lamprophyres which are widespread within the Iberian plate. Lherzolites possibly represent younger lithosphere (accreted asthenosphere?) up-lifted and juxtaposed to the older subcontinental lithospheric mantle (harzburgites) during the post-Variscan rifting of the Iberian margin. These two genetically different, but adjoining, mantle domains intimately mingled along the northern Iberian margin during the subsequent plate convergence processes, leading to the close association of harzburgites and lherzolites observed in the Olot mantle xenoliths and in some Pyrenean peridotite massifs.     

新疆伊犁吐拉苏地区的线性构造及控矿特征

采用多种数值图像进行线性构造解译，其中DEM和NOAA主要用于区域尺度，TM用于勘探区尺度，地面磁法数据用于靶区范围的解译分析。研究认为该区线性构造与金矿床的空间分布关系密切，表现为：（1）区域尺度的一级控矿构造为NEE、NE和NW向构造的交汇部位；吐拉苏地区的一级控矿构造为WNW和NNW及NE方向构造的交汇部位；（2）吐拉苏地区的次级控矿构造为NNE和环形构造的交汇部位；（3）靶区的一级控矿构造为NE、SN和环形构造。线性构造异常分析结果显示，当线性构造的优益度大于40时，有较大的成矿可能性。     

Latest Pleistocene paleoecology of Jefferson's ground sloth (Megalonyx jeffersonii) and elk-moose (Cervalces scotti) in northern Illinois

New records of Jefferson's ground sloth (Megalonyx jeffersonii) and elk-moose (Cervalces scotti) from Lang Farm provide the first precise temporal correlation of these taxa with the specific environments inhabited by them near the time of their extinction. Six AMS ¹⁴C measurements establish an age of 11,405 ± 50 ¹⁴C yr B.P. for Lang Farm Cervalces and an age of 11,430 ± 60 or 11,485 ± 40 ¹⁴C yr B.P. for the Megalonyx. These measurements represent the youngest ¹⁴C dates for these two genera based on direct dating. Comparison of the dates with pollen data from northern Illinois indicates that these species inhabited a nonanalog environment that was transitional from mid-latitude tundra to mixed conifer and deciduous woodland. Although spruce (Picea sp.) was dominant, it was less abundant than prior to 12,500 ¹⁴C yr B.P. The presence of black ash (Fraxinus nigra) and fir (Abies sp.) indicates a wet climate and heavy winter precipitation. This may have been the preferred habitat for Cervalces because of its narrow geographic range. However, this habitat type was only one of many occupied by Megalonyx as indicated by its broad geographic distribution.     

Intercomparison of Boron Isotope and Concentration Measurements. Part II: Evaluation of Results

The Istituto di Geoscienze e Georisorse (IGG), on behalf and with the support of the International Atomic Energy Agency (IAEA), prepared eight geological materials (three natural waters and five rocks and minerals), intended for a blind interlaboratory comparison of measurements of boron isotopic composition and concentration. The materials were distributed to twenty seven laboratories - virtually all those performing geochemical boron isotope analyses in the world -which agreed to participate in the intercomparison exercise. Only fifteen laboratories, however, ultimately submitted the isotopic and/or concentration results they obtained on the intercomparison materials. The results demonstrate that interlaboratory reproducibility is not well reflected by the precision values reported by the individual laboratories and this observation holds true for both boron concentration and isotopic composition. The reasons for the discrepancies include fractionations due to the chemical matrix of materials, relative shift of the zero position on the δ¹¹B scale and a lack of well characterized materials for calibrating absolute boron content measurements. The intercomparison materials are now available at the IAEA (solid materials) and IGG (waters) for future distribution.     

The abundance of volatiles in Hawaiian tholeiitic submarine basalts

High-temperature mass spectrometric studies have been made to determine the distribution of volatiles within glassy rims of submarine pillow basalts dredged from the east rift zone of Kilauea volcano, Hawaii. The CO₂/H₂O mole ratio for glass-vapor inclusions within olivine phenocrysts in the glassy rims is greater than 30 : 1 compared to 0.06 for matrix glasses. Enclosing matrix glasses contain 0.53–0.74 wt.% H₂O, 0.02–0.04 wt.% carbon, 0.08–0.12 wt.% sulfur, 0.012–0.028 wt.% chlorine and 0.012–0.077 wt.% fluorine.     

The actinolite-hornblende series in metabasites and the so-called miscibility gap: A review

Variation of calcic amphibole chemistry with increasing grade of metamorphism in different metamorphic facies series is reviewed, and the nature of reactions generating hornblende in natural assemblages is discussed. Recent publications on the variation of calcic amphibole composition with metamorphic grade have provided a variety of conflicting evidence regarding the reality or otherwise of a miscibility gap within the calcic amphibole series. It is here concluded that, in most cases, composition gaps may be better ascribed to disequilibrium and kinetic factors, and to abrupt or discontinuous changes in the compositions of, or in the appearance or disappearance of, other phases involved in proposed reactions occurring at the actinolite-hornblende transition. The weight of current evidence does not support the existence of a miscibility gap.