Rates of retrograde metamorphism and their implications for crustal rheology

The rate of reaction of a natural hornblende garnet granulite with water under a range of mid- to lower crustal conditions has been investigated experimentally. In runs of between 7 and 84 days small but measurable amounts of water were consumed, and sheet silicates (300°C, 300 MPa and 400°C, 400 MPa) and/or secondary actinolite (400°C, 400 MPa and 500°C, 500 MPa) were observed to have grown. When normalized to the surface area of the starting materials, hydration rates were in the range of 2–5 × 10⁻⁸ g m⁻² sec⁻¹. These reaction rates imply that a film of water that infiltrated a planar crack with a half width of 100 μm would be completely consumed within c. 100 years. These results imply that where water infiltrates the crust along faults or underlying shear zones in response to a deformation, it will remain as a free phase for only a finite period of time, which in some cases will be less than the repeat time for major earthquakes in the fault system. Thus, the rheology of fault zones and shear zones is likely to be cyclical, with the zone becoming stronger with time as water is consumed, and then weakened by infiltration of water after each rupture.     

Geomorphic reconstruction of formation and recession processes of waterfalls of the Kaminokawa river basin on Osumi Peninsula,southern Kyushu,Japan

To assess the geomorphological importance of waterfall recession in volcanic bedrock, we examined recession rates of six waterfalls in the lower reaches of Kaminokawa river basin on the Osumi Peninsula in southern Kyushu. The examination was performed with an empirical equation that uses a dimensionless parameter obtained by dimensional analysis of relevant measured factors, including erosive force, size of waterfall, and bedrock resistance. Welded Ata ignimbrite, formed at approximately 110 ka, may have played an initiating role to maintain such waterfalls because it resists weathering more than other local rocks. Estimated recession rates for the six waterfalls range from 0.2 to 3.0 cm/y, which compare with estimated rates for waterfalls in another region characterised by welded ignimbrite. Comparison of equation‐derived recession rates of waterfalls with actual recession distances from confluences supports the idea that an original waterfall will subsequently split into two distinct waterfalls when it recesses past an upstream junction of two channels. Our findings revealed that all six waterfalls likely would have been at almost the same point lower in the watershed in the past, marking the general site of the original waterfall. Moreover, the ancestral original waterfall is highly likely to have started from a point between the caldera rim and present river mouth. There, a knickpoint was likely caused by the river dropping into an inner part of the caldera, possibly just after the eruption of the Ata ignimbrite. The waterfall erodes upstream away from the caldera basin, and this happens to be to the east.     

汉长安城遗址出土骨签名物和用法再议

汉长安城遗址出土的骨签是研究汉代工官制度的重要资料,关于其性质,学界还有不同的争论。本文主要探讨了骨签的性质,认为骨签的正式名称应该为“揭”,并对骨签的用法进行了阐述。     

Searching for Ancient Shipwrecks in the Aegean Sea: the Discovery of Chios and Kythnos Hellenistic Wrecks with the Use of Marine Geological-Geophysical Methods

This paper presents the results of two deep-water archaeological surveys recently conducted in the Aegean Sea, and the advantages of using conventional marine geological techniques in deep-water archaeology. Two Hellenistic wrecks were discovered: one in the Chios-Oinousses strait at 70 m, was a concentration of over 400 amphoras in a 1.5-m-high, high-backscattering, morphological high; the second, west of Kythnos island, at 495 m, consisted of a few amphoras scattered in a 20 × 20-m-wide area. Side-scan sonar was integrated with high-resolution sub-bottom profiling, and the integration of the two data-sets proved to contribute significantly to realistic interpretation of the sonar targets.
© 2007 The Authors     

Mineral precipitation associated with vertical fault zones: the interaction of solute advection,diffusion and chemical kinetics

This article is concerned with chemical reactions that occur between two interacting parallel fluid flows using mixing in vertical faults as an example. Mineral precipitation associated with fluid flow in permeable fault zones results in mineralization and chemical reaction (alteration) patterns, which in turn are strongly dependent on interactions between solute advection (controlled by fluid flow rates), solute diffusion/dispersion and chemical kinetics. These interactions can be understood by simultaneously considering two dimensionless numbers, the Damköhler number and the Z‐number. The Damköhler number expresses the interaction between solute advection (flow rate) and chemical kinetics, while the Z‐number expresses the interaction between solute diffusion/dispersion and chemical kinetics. Based on the Damköhler and Z‐numbers, two chemical equilibrium length‐scales are defined, dominated by either solute advection or by solute diffusion/dispersion. For a permeable vertical fault zone and for a given solute diffusion/dispersion coefficient, there exist three possible types of chemical reaction patterns, depending on both the flow rate and the chemical reaction rate. These three types are: (i) those dominated by solute diffusion and dispersion resulting in precipitation at the lower tip of a vertical fault and as a thin sliver within the fault, (ii) those dominated by solute advection resulting in precipitation at or above the upper tip of the fault, and (iii) those in which advection and diffusion/dispersion play similar roles resulting in wide mineralization within the fault. Theoretical analysis indicates that there exists both an optimal flow rate and an optimal chemical reaction rate, such that chemical equilibrium following focusing and mixing of two fluids may be attained within the fault zone (i.e. type 3). However, for rapid and parallel flows, such as those resulting from a lithostatic pressure gradient, it is difficult for a chemical reaction to reach equilibrium within the fault zone, if the two fluids are not well mixed before entering the fault zone. Numerical examples are given to illustrate the three possible types of chemical reaction patterns.     

Forging Environmentalism: Justice,Livelihood and Contested Environments. Joanne Bauer,ed.

A senior Japanese authority on the Russian economy and its energy sector addresses the country's exposure to the so-called Dutch disease, suggesting that Russia did suffer from the potentially ruinous overdependence on oil and gas exports. The author argues, however, that the symptoms of the disease were actually not severe, attributing his interpretation to: (1) drastic decline of noncompetitive domestic manufacturing industries in the 1990s, which prompted a huge inflow of imports in the 2000s, but left competitive manufacturing enterprises in a position to survive; (2) extraordinary oil price increases in the 2000s, which significantly raised household and business incomes, creating augmented demand for products of domestic origin; (3) large differences between Russian and world prices of oil and gas, which functioned as subsidies for domestic manufacturing; and (4) massive intervention in foreign exchange markets by the Central Bank of Russia, which restricted the growth of imports and thus strengthened the surviving domestic manufacturing enterprises.     

Exchange Rate Policy and the Central and East European Financial Crisis

A prominent specialist on economic developments in the former Soviet Union and Central and Eastern European (CEE) countries examines the ways in which the global financial crisis of 2008-2010 has impacted the economies of the 10 new eastern member states of the European Union (CEE-10). The author assesses the multiple preconditions of the crisis (e.g., excessive current account deficits, large foreign debt, inadequate currency reserves, immense credit expansion, rising inflation and real estate prices) as well as the rapid financial adjustments that had to be undertaken to overcome it (e.g., current account rebalancing, reducing budget deficits, pension and fiscal reform). He devotes considerable attention to the key issue of how the differences in exchange rate policies in these countries affected their abilities to respond to the crisis and outlines measures that should be implemented to enhance the crisis management capability of non-eurozone states relying on currency boards or floating exchange rates.     

Exchange Rate Policy and Economic Growth after the Financial Crisis in Central and Eastern Europe

In a paper on the effects of the global financial crisis in Central and Eastern Europe (CEE), a European Union economist reacts to a companion paper (Åslund, 2001) published in the same issue of Eurasian Geography and Economics on the influence of exchange rate policies on the region's recovery. The author argues that post-crisis corrections in current account deficits in CEE countries do not in themselves signal a return to steady economic growth. Disagreeing with Åslund over the role of loose monetary policy in fostering the region's economic problems, he outlines a number of competitiveness problems that remain to be addressed in the 10 new EU member states of CEE, along with improvements in framework conditions supporting future macroeconomic growth.     

上海市就业市场状况与城市犯罪的空间计量分析

基于2008年上海市经济普查数据和城市犯罪数据,改变以往学者以失业率描述就业市场状况的做法,构建就业市场状况指数,并将其扩展到所有行业;同时,构建空间计量模型,研究上海市就业市场状况与刑事犯罪率之间关系,结果表明:1)就业市场状况对刑事犯罪率影响显著,不同行业的影响并不相同;其中,批发零售业、租赁和商业服务业、居民服务和其他服务业、公共管理和社会组织业就业的集中会引发犯罪活动的发生。2)空间计量模型在解释就业市场状况与刑事犯罪率之间关系时,计量效果良好。3)"空间效应"是影响刑事犯罪率的重要因素,其影响来自"空间邻近效应"和"空间误差效应"。     

次贷危机中的日本金融经济动向

本文通过分析日本金融市场短期利率、长期利率、股票指数、日元汇率指标的变动,来评估次贷危机对日本金融市场和金融体系产生的影响。文章认为次贷危机使日本丧失了一个难得的金融政策正常化以及走向长期经济增长的机会,日本金融指标变动与美欧的同步化使得日本难以独善其身,而高企的日元汇率随时有反转的可能。