Three-dimensional geometry, ore distribution and time-integrated mass transfer through the quartz–tourmaline–gold vein network of the Sigma deposit (Abitibi belt, Canada)

We present a reconstruction of the three‐dimensional (3D) geometry and gold grade distribution of shear zone‐hosted, Au‐mineralized, quartz–tourmaline veins of the Sigma deposit (Abitibi belt). Host shears and veins form a network of anastomosing, steeply dipping structures associated with smaller subhorizontal extensional veins. Our reconstruction has been carried out using the exceptionally large geological database of the mine. From this database, we extracted the geometric position, thickness and gold grades of geometrically best‐defined steep veins contained in a representative subvolume of the deposit. These data allowed the 3D representation of 53 veins, which have been constructed by fitting surfaces through the geometrical data and by contouring thickness and gold grade. The geometry of the network is mainly characterized by: (i) a few large segmented veins, with sinuous and helicoidal shape, and typical vertical dimension of >100 m; (ii) a large number of smaller vertical veins, some of which splay off the steep veins with high dip angles; (iii) subhorizontal extension veins (joints) located at, or close to, the tips of steep veins. The absolute thickness of the vertically short veins is the same as that of the large veins, suggesting that they formed simultaneously, but only a few of them interconnect to form vertically continuous bodies. Patchy, vertically elongated zones of high dilation are present in the large veins, and are poorly correlated with Au‐rich zones. They presumably represent former high‐permeability zones of the network. The highest gold grades occur at the interconnections between the large veins and small splays or subhorizontal joints. This indicates the important role of vein interconnection for fluid flow and gold precipitation within the network. Combining the calculation of the volume of the network with the estimation of tourmaline abundance in the veins, we calculate that 2.1 × 10⁶ m³ of tourmaline and 3.2 × 10⁶ m³ of quartz precipitated during Au deposition.     

The origins of salinity in metamorphic fluids

Evaluation of data on formation waters and metamorphic fluids sampled by drilling or preserved in fluid inclusions reveals little correlation between fluid salinity and metamorphic grade, but a strong link to original sedimentary setting. Sediments and metasediments deposited originally in shallow marine environments can contain fluids with a very wide range of salinities, but they are commonly near twice seawater salinity or higher. With increasing metamorphic grade, a very wide range of salinities may develop, with the highest levels tracking halite saturation. Oceanic and accretionary prism sequences yield low‐salinity fluids, close to seawater values, almost irrespective of metamorphic grade until extreme conditions are reached where removal of water may increase fluid salinity. The salinities of metamorphic fluids exert a fundamental control on both fluid phase equilibria and metal‐transporting capability, and appear, to a large degree, to reflect the original presence or absence of highly saline formation waters and/or evaporites in the initial sedimentary sequence.     

The Performance of Policy Networks: The Relation between Network Structure and Network Performance

The importance of policy networks has long been emphasized within the field of policy analysis. However, few attempts have been made to investigate the explanatory power of policy networks using the tools and theoretical concepts provided by social network analysis (SNA). This paper aims to address this need by determining if a relationship exists between the structural features of policy networks, their organizing capacities, and their performance. A comparative case study of four networks within the higher education policy sector confirms the assumption related to the existence of such a relation. It is proposed that an efficient and innovative policy network consists of a heterogeneous set of actors that are centrally and densely integrated. Furthermore, while the level of network heterogeneity is positively related to the function of resource mobilization in the process of policymaking, the level of centralized integration promotes the function of prioritizing. These findings are believed to contribute to our understanding of policymaking in contemporary society. The current paper indicates that a significant explanatory power exists in the concept of policy networks and that SNA is one way of advancing its possibilities.     

中日全面战争后的在日华侨、印侨网络

以近代日本在成为亚洲主权国家过程中经济方面的经历为线索,将居住在神户的华侨和印侨作为研究对象,探讨了华侨通商网络在20世纪30年代得以扩展、1940年后衰退的原因;简述了30年代起印侨通商网络的显著发展;揭示了欧洲近代帝国主义的本质与亚洲华侨、印侨通商网络的形成与扩展间的密切关系。     

Gender differences in children's pathways to independent mobility

This paper presents some empirical findings relating to the independent mobility of children in two parts of south-east England – one a south London borough, the other a suburban county north of London. In both locations boys appear to enjoy greater mobility than girls, and become independent much earlier. But closer analysis suggests that girls manage to attain similar levels of independence from adults by travelling more in groups. This collective independence achieved through peers is often overlooked, and may compensate modern children to some extent for their loss of individual freedom.     

论上海旅游集散中心的形成与发展

上海旅游集散中心开创了散客旅游的一种组织模式。是散客旅游需求的扩张为散客接待服务的专业化提供了必要条件,专业化程度的提高又导致企业与企业纵向一体化的发展。     

国外社会升级研究进展及对中国的启示

社会升级研究的兴起源于经济全球化带来的经济升级不能产生相应的社会升级,是对联合国2030可持续发展目标(SDG)之"体面劳动与经济增长"目标的响应.为弥补国内地理学偏重经济升级而忽视社会升级的研究不足,本文系统梳理了国际上社会升级研究的主要进展,对其概念、理论基础和主要研究议题开展了分析.认为当前社会升级研究方兴未艾,...     

Social capital determinants and labor market networks

We explore the links between determinants of social capital and labor market networks at the neighborhood level. We harness rich data taken from multiple sources, including matched employer–employee data with which we measure the strength of labor market networks, data on neighborhood homogeneity that has previously been tied to social capital, and new data—not previously used in the study of social capital—on the number and location of nonprofit sector establishments at the neighborhood level. We use a machine learning algorithm to identify the potential determinants of social capital that best predict neighborhood‐level variation in labor market networks. We find evidence suggesting that smaller and less centralized schools, and schools with fewer poor students, foster social capital that builds local labor market networks, as does a larger Republican vote share. The presence of establishments in a number of nonprofit‐oriented industries are identified as predictive of strong labor market networks, likely because they either provide public goods or facilitate social contacts. These industries include, for example, churches and other religious institutions, fire and rescue services including volunteer fire departments, country clubs and golf courses, labor unions, chamber music groups, hobby clubs, and schools.     

A consideration on the interest of a pottery typology adapted to the late Sasanian and early Islamic monastery at al-Qusur (Kuwait)

Since 2011, the French–Kuwaiti Archaeological Mission in Failaka has aimed at defining the function and the chronology of al-Qusur, located in the middle of Failaka Island (Kuwait). The central part of the site appeared to be a monastery, mainly occupied in early Islamic times. The creation of a site-specific pottery typology adapted to this settlement was one of the main objectives of the team. This typology is still in progress and the present paper will highlight the variety of questions that it can address. Certain pottery types provide new information about the monastery’s foundation, probably at the end of the Sasanian period, and abandonment, maybe during the ninth century AD. Pottery studies are also crucial for a better understanding of the monastery’s economic life and the eating practices of the monks. The question of the local or regional provenance of the pottery provides an insight into the inclusion of Failaka in exchange networks.     

Geometry‐coupled reactive fluid transport at the fracture scale: application to CO2 geologic storage

Water acidification follows CO₂ injection and leads to reactive fluid transport through pores and rock fractures, with potential implications to reservoirs and wells in CO₂ geologic storage and enhanced oil recovery. Kinetic rate laws for dissolution reactions in calcite and anorthite are combined with the Navier‐Stokes law and advection–diffusion transport to perform geometry‐coupled numerical simulations in order to study the evolution of chemical reactions, species concentration, and fracture morphology. Results are summarized as a function of two dimensionless parameters: the Damköhler number Da which is the ratio between advection and reaction times, and the transverse Peclet number Pe defined as the ratio between the time for diffusion across the fracture and the time for advection along the fracture. Reactant species are readily consumed near the inlet in a carbonate reservoir when the flow velocity is low (low transverse Peclet number and Da > 10^?1). At high flow velocities, diffusion fails to homogenize the concentration field across the fracture (high transverse Peclet number Pe > 10^?1). When the reaction rate is low as in anorthite reservoirs (Da < 10^?1), reactant species are more readily transported toward the outlet. At a given Peclet number, a lower Damköhler number causes the flow channel to experience a more uniform aperture enlargement along the length of the fracture. When the length‐to‐aperture ratio is sufficiently large, say l/d > 30, the system response resembles the solution for 1D reactive fluid transport. A decreased length‐to‐aperture ratio slows the diffusive transport of reactant species to the mineral fracture surface, and analyses of fracture networks must take into consideration both the length and slenderness of individual fractures in addition to Pe and Da numbers.