贵州锦丰(烂泥沟)超大型金矿床构造解析及构造成矿作用

在矿区大比例尺填图的基础上,运用构造解析的理论和方法,对贵州锦丰(烂泥沟)金矿的构造特征、构造演化和构造控矿作用进行了系统的阐述。矿区构造线主要分为近NS向、NW向和NE向3组,其中NW向构造线控制了矿区的构造格架。构造变形主要经历了同生期裂陷、造山期挤压、后碰撞造山侧向挤压和岩石圈伸展等4个阶段。盆地裂陷期间(D2-T2)形成的同生断层为后续的构造活动提供了最初的构造薄弱面,并成为主要的热液通道;造山期挤压期间(T3)形成了矿区最为明显的近NS向和NW向大型倒转褶皱和逆冲断层以及配套的NE向右旋走滑断层;后碰撞造山侧向挤压期间(J1)形成走向NE的叠加褶皱,并在F2-F3"X"型断裂系上形成近EW向的拉张区,矿质沿着拉张的空间沉淀就位;燕山期(J2-K)岩石圈伸展,形成小规模的近水平逆断层。上述4个主要构造变形阶段与右江盆地的裂陷-闭合-坍塌的发展演化历史相吻合,成矿发生在由挤压向拉张过渡的构造体制转换阶段。造山期逆冲作用形成的构造闭圈和后碰撞造山期间挤压向伸展转变的过程中形成的局部张性构造环境是矿质得以大量聚集、沉淀的主要构造控制因素。构造成矿作用是锦丰(烂泥沟)金矿单一矿体垂向延深1000m以上的主要制约因素。构造成矿的观点将为在滇黔桂"金三角"卡林型金矿带的深部找矿提供重要的理论依据。     

An introduction to the South China Sea throughflow: Its dynamics, variability, and application for climate

The South China Sea throughflow (SCSTF) involves the inflow through the Luzon strait and the outflow through the Karimata, Mindoro, and Taiwan straits. Recent studies have suggested that the SCSTF act as a heat and freshwater conveyor, playing a potentially important role in regulating the sea surface temperature pattern in the South China Sea and its adjoining tropical Indian and Pacific Oceans. In this introductory paper, we attempt to convey the progress that has recently been made in understanding the SCSTF. We first provide an overview of existing observations, theories, and simulations of the SCSTF. Then, we discuss its interaction with the Pacific western boundary current and Indonesian throughflow. Finally, we summarize issues and questions that remain to be addressed, with special reference to the SCSTF's dynamics, variability, and implication for climate.     

Expansion dynamics of deciduous rubber plantations in Xishuangbanna,China during 2000–2010

Monoculture rubber plantations have been replacing tropical rain forests substantially in Southern China and Southeast Asia over the past several decades, which have affected human wellbeing and ecosystem services. However, to the best of our knowledge on the extent of rubber plantation expansion and their stand ages is limited. We tracked the spatiotemporal dynamics of deciduous rubber plantations in Xishuangbanna, the second largest natural rubber production region in China, from 2000 to 2010 using time-series data from the Phased Array type L-band Synthetic Aperture Radar (PALSAR), Landsat, and Moderate Resolution Imaging Spectroradiometer (MODIS). We found that rubber plantations have been expanding across a gradient from the low-elevation plains to the high elevation mountains. The areas of deciduous rubber plantations with stand ages ≤5, 6–10, and ≥11-year old were ~1.2 × 10⁵ ha, ~0.8 × 10⁵ ha, and ~2.9 × 10⁵ ha, respectively. Older rubber plantations were mainly located in low-elevation and species-rich regions (500–900 m) and younger rubber trees were distributed in areas of relative high-elevation with fragile ecosystems. Economic and market factors have driven the expansion of rubber plantations, which is not only a threat to biodiversity and environmental sustainability, but also a trigger for climatic disasters. This study illustrates that the integration of microwave, optical, and thermal data is an effective method for mapping deciduous rubber plantations in tropical mountainous regions and determining their stand ages. Our results demonstrate the spatiotemporal pattern of rubber expansions over the first decade of this century.     

The organisational context of retail locational planning

Retailers have a large number of techniques at their disposal to assist them in their locational planning, but the use made of them is varied, regardless of their intrinsic merits. The reasons for this lie very much in the organisational context in which the techniques are applied. This paper discusses the nature of locational planning and decision making, and puts forward a framework which links locational planning and the organisational settings in which it takes place. The preliminary results of a survey of the use of techniques by U.K. retailers are presented, which show that while most companies use more than ‘Rules of Thumb’, it is the simplest techniques which are the most widely used. The application of the more advanced knowledge based methods is still relatively uncommon. The explanation for the variations lies in the attributes of the techniques themselves, the types of locational planning undertaken, and the structural and cultural characteristics of the companies. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dynamical friction in dwarf galaxies

We present a simplified analytic approach to the problem of the spiralling of a massive body orbiting within the dark halo of a dwarf galaxy. This dark halo is treated as the core region of a King distribution of dark matter particles, in consistency with the observational result of dwarf galaxies having solid-body rotation curves. Thus we derive a simple formula which provides a reliable and general first-order solution to the problem, totally analogous to the one corresponding to the dynamical friction problem in an isothermal halo. This analytic approach allows a clear handling and a transparent understanding of the physics and the scaling of the problem. A comparison with the isothermal case shows that in the core regions of a King sphere, dynamical friction proceeds at a different rate, and is sensitive to the total core radius. Thus, in principle, observable consequences may result. In order to illustrate the possible effects, we apply this formula to the spiralling of globular cluster orbits in dwarf galaxies, and show how present-day globular cluster systems could, in principle, be used to derive better limits on the structure of dark haloes around dwarf galaxies, when the observational situation improves. As a second application, we study the way a massive black hole population forming a fraction of these dark haloes would gradually concentrate towards the centre, with a consequent deformation of an originally solid-body rotation curve. This effect allows us to set limits on the fraction/mass of any massive black hole minority component of the dark haloes of dwarf galaxies. In essence, we take advantage of the way the global matter distribution fixes the local distribution function for the dark matter particles, which in turn determines the dynamical friction problem.     

Petrology and genesis of natrocarbonatite

Microprobe analyses of phenocrysts and groundmass, and crystal-size distributions of phenocrysts of pahoehoe natrocarbonatite lavas of the 1963 eruption of Oldoinyo Lengai have been determined. Nyerereite phenocrysts are homogeneous, with average composition Nc₄₁Kc₉Cc₅₀ (neglecting F, Cl, P₂O₅, and SO₃) where Nc=Na₂CO₃, Kc=K₂CO₃, and Cc= (Ca,Sr)CO₃. Gregoryite phenocrysts have turbid, pale brown, oscillatorily zoned cores (average composition Nc₇₇Kc₅Cc₁₈) with 0–30% oriented inclusions of exsolved nyerereite. Overgrowths on gregoryites (30 m wide) are relatively sodic (Nc₈₁Kc₄Cc₁₅) and are free of inclusions. Cores and rims are rich in SO₃ (4%) and P₂O₅ (2%). Blebs of pyrite-alabandite mixtures (100 m) occur in the groundmass. The groundmass has the simplified composition Nc₆₅Kc₁₅Cc₂₀, less calcic than the composition of the 1-kbar nyerereite+gregoryite +liquid cotectic in the ternary system Nc-Kc-Cc. Groundmass quench growth of alkali halides + carbonate was followed by slower growth of coarse-grained and irregular gregoryite +KCl+BaCO₃. Crystal size distributions of gregoryite and nyerereite in one sample are linear, implying little loss or gain of phenocrysts by crystal settling. AverageG is 0.15 mm, compared toG=0.03 mm for combeite phenocrysts from consanguineous nephelinite. Assuming an equal residence time () for both lavas, the apparent crystal growth rate (G) in carbonate melt is 5 times greater than in peralkaline undersaturated silicate melt. Data from experiments with natrocarbonatite and related synthetic systems indicate that Na–K–Ca carbonatite magmas which crystallize calcite cannot fractionate to nyerereite+gregoryite +liquid assemblages. Natrocarbonatites plot in the liquidus field of nyerereite, and minor fractionation of nyerereite to produce the erupted lavas is indicated. The term natrocarbonatite has been inappropriately applied to other eruptive rocks with calcite phenocrysts, and the only known occurrence of gregoryite-bearing natrocarbonatite is Oldoinyo Lengai. Natrocarbonatite probably originates by liquid immiscibility from strongly peralkaline nephelinites, which have also been erupted at Oldoinyo Lengai.     

The Asian Tsunami disaster,December 2004

The tragic scenes of human suffering in the wake of the Asian tsunami in late December 2004 have thrown into sharp relief the Earth's destructive power (Fig. 1 ). Caused by a tectonic event off the coast of Sumatra, it could be described as a very large earthquake, an unusual tsunami and a massive disaster. Or, with a longer view, it could be considered a normal feature of a convergent plate boundary. Both views are correct.

Figure 1 Open in figure viewer PowerPoint Mass destruction after the tsunami hit the village on the sand bar at Phi Phi Island, Thailand, with unscathed limestone hills behind (Rex Features).     

Role of lipid/water partitioning and membrane composition in the uptake of organochlorine pesticides into a freshwater mussel

The aim of this investigation is to understand the factors influencing uptake of persistent organochlorine pesticides into a freshwater mussel (Sphaerium corneum). Previous work has shown that although a substantial proportion of dieldrin is bound to particulates in the river system, uptake is from the dieldrin in solution. This suggests partitioning of the hydrophobic xenobiotics into membranes as the major route of entry. Membrane composition was established using lipid fractionation into neutral lipids and phospholipids followed by derivatisation to fatty acid methyl esters and estimation using GC/FID. Membrane composition varied with acclimation temperature over the range 5–20°C. Dieldrin concentrations in the mussel at equilibrium with 2000 ng dieldrin/litre water burden were studied at one temperature under laboratory conditions using animals acclimated to different temperatures. Any differences may be explicable in terms of effects of membrane composition on partitioning or other physiological adaptations. To establish which of these factors is most significant a membrane fragment partition system has been analysed in vitro. Preliminary results indicate that although water/lipid partitioning may be important in entry (and exit) of non-polar xenobiotics, significant differences could not be found using current methods. The role of membrane composition and therefore temperature history of the organism may still be significant. The implications of this for attempted correlations between bioaccumulation factors and simple octanol/water partition coefficients are discussed.