河道水体中氢氧稳定同位素组成的微分方程模型

介绍了前人提出并被广泛应用的瑞利分馏模型,指出了其优缺点。针对其不足,在作了一定的假定和简化的前提下,基于瑞利分馏原理和水力学基本定律分别推导了:①静止水体的氢氧稳定同位素组成随时间变化的微分方程模型,揭示了静止水体的同位素组成与时间、分馏系数和蒸发率之间的关系;②河道中运动水体的同位素组成随时间和空间变化的微分方程模型,导出了河道运动水体中稳定同位素组成与分馏系数、流速、流量、蒸发率之间的定量关系。最后通过数学推导论述了上述各模型之间的内在联系。上述模型的建立为定量计算和精确模拟运动水体中氢氧稳定同位素组成的变化提供了确定性的数学基础,也为更客观、更充分的解译水的稳定同位素数据提供了帮助。     

Asteroid impact in the Black Sea. Death by drowning or asphyxiation?

Normally the consequences of an impact of an asteroid in a water body are discussed in terms of the beach run up of impact-generated waves. If even a small asteroid would hit the Black Sea, however, the potential emissions of toxic and flammable gases could be more disastrous to the region (comprised of Romania, Ukraine, Russia, Georgia, Turkey and Bulgaria) than the tsunami caused by the impact.     

Occurrence of hydrogen sulfide in the ground water of Kuwait

Hydrogen sulfide occurs in high concentration (10–200 mg/l) in different parts of Kuwait City and its suburbs at relatively shallow depths (15–40 m from the surface). This was revealed by drilling through the aquifer system underlying the city and sampling and analyzing the ground water at the drilled locations. The near-absence of coliform bacteria in the sulfide-rich zones, the presence of sulfur-reducing bacteria in the deep (>80 m) Dammam Formation aquifer and a linear positive relation between the concentration of hydrogen sulfide and the total dissolved solids content suggested non-anthropogenic origin of the sulfide in the ground water of Kuwait. The upward movement of sulfide-rich water from depth and its differential flushing by surface recharge through outcrops of the aquifers appear to have given rise to the present distribution of hydrogen sulfide in the aquifers underlying the Kuwait City.     

Geological and geochemical characteristics of the Baimazhai Ni-Cu-（PGE） sulphide deposit in Yunnan, China

The sulphide ores of the Baimazhai deposit, although typically orthomagmatic, locally exhibit peculiar textural features and are intimately associated with hydrothermal minerals, such as biotite, amphibole and chlorite. This association suggests that the magmatic sulphide ores were subjected to hydrothermal alteration and subsequent redistribution, resulting in the observed textural features. Geochemically, the Baimazhai sulphide ores are enriched in Cu, Pd and Au, which,according to previous studies, reflects the action of hydrothermal fluids. Interestingly, Ar-Ar dating yielded the plateau ages of about 160–170 Ma, which are at odds with the established Permian age of the Emeishan large igneous province. We interpreted these younger ages as due to thermal resetting during post-Permian tectonothermal events. We have proposed a model in which tectonic movements and hydrothermal fluids related to these events modified the pre-existing magmatic sulphides. Given the degree of overprint, we suggested two possible scenarios: 1) the sulphide disseminations that surround the massive magmatic ores are the result of deformation and hydrothermal alteration; and 2) there were both magmatic massive and disseminated sulphides, in which case the scale and relocation of remobilization would have been smaller, but still detectable.     

Diffuse Emission of Hydrogen from Poás Volcano,Costa Rica,America Central

We report the results of four soil H₂ surveys carried out in 2000–2003 at Poás volcano, Costa Rica, to investigate the soil H₂ distribution and evaluate the diffuse H₂ emission as a potential surveillance tool for Poás volcano. Soil gas H₂ contents showed a wide range of concentration from 0.2 to 7,059 ppmV during the four surveys. Maps of soil gas H₂ based on Sequential Gaussian Simulation showed low H₂ concentration values in the soil atmosphere (<0.7 ppmV) for most of the study area, whereas high soil gas H₂ values were observed inside the active crater of Poás. A significant increase in soil gas H₂ concentration was observed inside the active crater during 2001 and 2002 with respect to year 2000, followed by a decrease in 2003. The observed spatial and temporal variations of soil H₂ concentration have been well correlated with seismicity, microgravimetry and fumarolic chemistry changes which occurred during this study. These observations evidence changes in the shallow magmatic-hydrothermal system of Poás, and it might be related to a potential magmatic intrusion during the period 1998–2004. Therefore, monitoring diffuse H₂ emission of Poás has become an important geochemical tool for the monitoring of its volcanic activity.     

Identification and investigation of sulphur plumes along the Namibian coast using the MERIS sensor

In the upwelling area along the Namibian coast of SW-Africa sulphur discolorations were investigated to study the impact of hydrogen sulphide on the ecosystem using satellite imagery. The formation of colloidal sulphur in the upper water layer results from the oxidation of hydrogen sulphide. The occurrence of sulphur plumes as well as their temporal and spatial development was investigated in relation to the driving meteorological and oceanographic conditions. Because of the sporadic occurrence of sulphur events and the limited number of ship-borne investigations in that area remote sensing of ocean colour is the only method to follow these phenomena continuously and synoptically. In the past the sulphur plumes were studied by true colour images derived from ocean colour satellite data like sea-viewing wide field of view sensor or moderate resolution imaging spectroradiometer and identified by their typical milky turquoise discoloration.     

Interactive effects of the type of milling media and copper sulphate addition on the flotation performance of sulphide minerals from Merensky ore Part I: Pulp chemistry

It is well known that the chemical environment determines the success of the flotation process, however its characterisation and control is difficult to achieve. This paper, as two parts, Part I and Part II, evaluates the use of various measurements and their interpretation to gain an understanding of the influence of varying parameters such as the type of milling media and copper sulphate addition on the flotation performance of sulphide minerals from a platinum group mineral (PGM) bearing Merensky ore. It shows the complexity of interpretation and the importance of analysing flotation performance holistically. Part I focuses on the pulp chemistry and mineral potential measurements have been used to show the differences in the response of the various mineral electrodes to different conditions. The final flotation recoveries of the sulphide minerals in the ore followed the same trend as the decrease in mineral potential due to collector addition viz. chalcopyrite > pentlandite > pyrrhotite. Type of milling media and copper sulphate addition slightly affected the mineral electrode potential and flotation recovery of chalcopyrite. Addition of copper sulphate increased the recovery of pentlandite and particularly pyrrhotite due to activation by copper (II) ions. The copper activation mechanism was likely to be in the form of initial adsorption of copper hydroxide followed by reduction to Cu⁺ at the surface. However, the changes in flotation performance of the different minerals in the ore could not be completely described by the electrochemical changes, demonstrating the limitations of these measurements. Part II addresses the effect of froth stability as demonstrated by the variations in the mass and water recovery data resulting from the different milling conditions and addition of copper sulphate which emphasised the importance of considering the froth phase in the evaluation of flotation data.     

Overview of In-Situ Biodegradation and Enhancement

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Lewis Ponds, a hybrid carbonate and volcanic-hosted polymetallic massive sulphide deposit, New South Wales, Australia

The Lewis Ponds Zn–Pb–Cu–Ag–Au deposit, located in the eastern Lachlan Fold Belt, central western New South Wales, exhibits the characteristics of both volcanic-hosted massive sulphide and carbonate-hosted replacement deposits. Two stratabound massive to disseminated sulphide zones, Main and Toms, occur in a tightly folded Upper Silurian sequence of marine felsic volcanic and sedimentary rocks. They have a combined indicated resource of 5.7 Mt grading 3.5% Zn, 2.0% Pb, 0.19% Cu, 97 g/t Ag and 1.9 g/t Au. Main Zone is hosted by a thick unit of poorly sorted mixed provenance breccia, limestone-clast breccia and quartz crystal-rich sandstone, whereas Toms Zone occurs in the overlying siltstone. Pretectonic carbonate–chalcopyrite–pyrite and quartz–pyrite stringer veins occur in the footwall porphyritic dacite, south of Toms Zone. Strongly sheared dolomite–chalcopyrite–pyrrhotite veins directly underlie the Toms massive sulphide lens. The mineralized zones consist predominantly of pyrite, sphalerite and galena. Paragenetically early framboidal, dendritic and botryoidal pyrite aggregates and tabular pyrrhotite pseudomorphs of sulphate occur throughout the breccia and sandstone beds that host Main Zone, but are rarely preserved in the annealed massive sulphide in Toms Zone. Main and Toms zones are associated with a semi-conformable hydrothermal alteration envelope, characterized by texturally destructive chlorite-, dolomite- and quartz-rich assemblages. Dolomite, chlorite, quartz, calcite and sulphides have selectively replaced breccia and sandstone beds in the Main Zone host sequence, whereas the underlying porphyritic dacite is weakly sericite altered. Vuggy and botryoidal textures resulted from partial dissolution of the dolomite-altered sedimentary rocks and unimpeded growth of base metal sulphides, carbonate and quartz into open cavities. The intense chlorite-rich alteration assemblage, underlying Toms Zone, grades outward into a weak pervasive sericite–quartz assemblage with distance from the massive sulphide lens. Limestone clasts and hydrothermal dolomite at Lewis Ponds are enriched in light carbon and oxygen isotopes. The dolomite yielded ¹³C_VPDB values of –11 to +1 and ¹⁸O_VSMOW values of 6 to 16. Liquid–vapour fluid inclusions in the dolomite have low salinities (1.4–7.7 equiv. wt% NaCl) and homogenization temperatures (166–232°C for 1,000 m water depth). Dolomitization probably involved fluid mixing or fluid–rock interactions between evolved heated seawater and the limestone-bearing facies, prior to and during mineralization. ³⁴S_VCDT values range from 2.0 to 5.0 in the massive sulphide and 3.9 to 7.4 in the footwall carbonate–chalcopyrite–pyrite stringer veins, indicating that the hydrothermal fluid may have contained mamgatic sulphur and a component of partially reduced seawater. The sulphide mineral assemblages at Lewis Ponds are consistent with moderate to strongly reduced conditions during diagenesis and mineralization. Low temperature dolomitization of limestone-bearing facies in the Main Zone host sequence created secondary porosity and provided a reactive host for fluid-rock interactions. Main Zone formed by lateral fluid flow and sub-seafloor replacement of the poorly sorted breccia and sandstone beds. Base metal sulphide deposition probably resulted from dissolution of dolomite, fluid mixing and increased fluid pH. Pyrite, sphalerite and galena precipitated from a relatively low temperature, 150–250°C hydrothermal fluid. In contrast, Toms Zone was emplaced into fine-grained sediment at or near the seafloor, above a zone of focused up-flowing hydrothermal fluids. Copper-rich assemblages were deposited in the Toms Zone footwall and massive sulphide lenses in Main and Toms zones as the hydrothermal system intensified. During the D₁ deformation, fracture-controlled fluids within the Lewis Ponds fault zone and adjacent footwall volcanic succession remobilized sulphides into syntectonic quartz veins. Lewis Ponds is a rare example of a synvolcanic sub-seafloor hydrothermal system developed within fossiliferous limestone-bearing facies. The close spatial association between limestone, hydrothermal dolomite, massive sulphide and dacite provides a basis for new exploration targets elsewhere in New South Wales.Editorial handling: D. Lentz     

水对Wadsleyite和Ringwoodite电导率的影响及地球动力学意义

在Kawai-1000型多顶砧压机上，利用橄榄石相变人工合成地幔转换带矿物wadsleyite和ringwoodite，其含水量从0．03wt％到2．0wt％变化不等。在压力14～16GPa，温度873K-1273K，通过Mo：MoO2固体反应控制氧逸度的条件下，利用阻抗谱分析方法，测量获得了这些样品的电导率。实验结果显示：wadsleyite的电导率与GH^0.66呈正比，ringwoodite的电导率与GH^0.69呈正比，水极大地增强了样品的电导率；在我们的实验条件下，含水wadsleyite和ringwoodite样品的主要电荷栽体是自由质子。另外，结合大地电磁反演获得的电导率结果和我们的实验数据，我们推断中国东北地区地幔转换带中的水含量约为0．1～0．3wt％，远远高于上地幔中的水含量，这或许表明在410km处可能发生了部分熔融。