A low plain between arcadia and agronomy: Ippolito Nievo and the Friulan landscape

An analysis of the historical and cultural context of a large number of literary works illuminates the concept of landscape, a recurrent theme in contemporary humanistic geography. In this context, the works of Ippolito Nievo present an opportunity to look closer at the socio-economic circumstances of his time while also offering suggestive interpretative elements about the attitudes held concerning the wetlands of the lower Friulan plain.     

Spatial variations in the progress of land reform in Romania

Romania's socialist agricultural sector has been transformed by a series of measures taken after the revolution of 1989. A new farm structure is emerging out of the restitution provided for under the Land Law of 1991. There are striking spatial variations in different aspects of the privatisation process, especially the contrasting situations between the hill country (with heavy pressure on land) and the plains (where there is much better supply in relation to demand). Very small units of land ownership are being grouped into larger functional units for management by associations which are especially prominent in the main cropping zones. Meanwhile individual smallholdings are predominant in the hill and mountain zones. Despite a desire for owner-occupation, association is often advantageous through efficient deployment of machinery and some 40 percent of land allocated to individual peasants is being worked by some 20,000 associations. However, the situation has not yet stabilised and it is emphasised that small farms should be regarded not simply as agricultural units but as the cores of diversified enterprises characterised increasingly by pluriactivity     

The private sector and local economic development in South Africa

The objective in this paper is to analyse private sector involvement in LED in South Africa. Four key spheres of private sector involvement in LED are identified and discussed: (1) as participator and occasional initiator of local development processes, (2) as major partner in the development activities of public-private sector partnerships, (3) as lead role player in certain direct initiatives for reviving South Africa's inner cities, and (4) as promoter and facilitator of local small business development. It is argued that the concept of local dependence could be usefully applied to interpret private sector involvement in LED in South Africa.     

Composition of hydrous melts in equilibrium with quartz eclogites

Summary Compositions of the hydrous melts in equilibrium with garnet, omphacitic clinopyroxene and quartz have been investigated experimentally at 28.5 and 35 kbar. They are represented by silica-rich liquids (> 70% SiO₂) with low MgO, FeO and CaO contents. The removal of ca 10–15% of the magma of this composition may be sufficient to convert quartz eclogite formed after subduction of altered MORB into a quartz-free bimineralic eclogite assemblage, which is a common type of xenoliths in kimberlites.At 28.5 kbar the solidus temperature is between 700 and 750° C in the system quartz eclogite—water, and the high pressure amphibole-out boundary lies at ca 25 kbar in accord with the previous studies.

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Die Zusammensetzung wasserhältiger Schmelzen im Gleichgewicht mit Quarz-Eklogiten

Zusammenfassung Um Prozesse zu simulieren, die bei der Subduktion von Ozeanbodenbasalten durch partielle Anatexis im Stabilitätsfeld von Eklogiten ablaufen, wurde die Zusammensetzung wasserhältiger Schmelzen in Gleichgewicht mit Granat, Omphacit und Quarz bei 28.5 und 35 Kbar experimentell untersucht. Diese Schmelzen sind reich an SiO₂ (> 70 Gew%) und arm an Mg0, Fe0 and CaO. Die Extraktion von ca. 10–15% derartiger Schmelzen würde genügen, um quarzführende Eklogite, die durch die Subduktion von alteriertem MORB Material entstanden sind, in quarzfreie bimineralische Eklogite umzuwandeln wie sie häufig als Xenolithe in Kimberliten beobachtet werden.Im System Quarz-Eklogit-Wasser liegt die Solidustemperatur bei 28.5 Kbar zwischen 700 und 750°C. Die obere Stabilitätsgrenze von Amphibol liegt in diesem Temperaturbereich bei ca. 25 Kbar.

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With 1 Figures     

The squeezing potential of rock around tunnels: Theory and prediction with examples taken from Japan

Summary Large deformations of surrounding media around tunnels are often encountered during excavations in rocks with squeezing characteristics. These deformations may sometimes continue for a long period of time. Predictions of deformations of tunnels in such grounds are urgently needed, not because of stability concerns, but also of their sevicability. In the present study, the squeezing phenomenon of rock around tunnels and its mechanism and associated factors are first clarified by carefully studying failures of tunnels, and a survey of tunnels in squeezing rocks in Japan is presented and its results are summarised. Then, a practical method is proposed to predic the squeezing potential and deformation of tunnels in squeezing rock and this method has beeen applied to actual tunnelling projects, where squeezing problems were encountered, to check its applicability and validity. Finally, an extension of this method to the time-dependent behaviour of squeezing rocks is given and an application of this method to an actual tunnel is presented.     

Mafic microgranular enclaves from the Xanthi pluton (Northern Greece): An example of mafic-felsic magma interaction

Summary Petrographic, geochemical and isotopic data are reported for the mafic microgranular enclaves occurring in a calc-alkaline Oligocene pluton outcropping near Xanthi town in northern Greece. The intrusion is composed of dominant granodiorites with minor tonalites and quartz diorites. Mafic enclaves occur in large swarms concentrated near the margins of the pluton. They have fine-grained porphyritic textures and contain the same minerals as their granodioritic and tonalitic host rocks (Pl, Qtz, Bt, Hb1, Kfs ± Ap, Zrn, Mt, Spn) but in totally different modal proportions. Chemical compositions range from mafic to intermediate and are characterized by higher abundance of Na₂O) and lower contents of CaO and Sr with respect to an average basaltic magma with a similar SiO₂ content. The initial Sr isotopic ratios, ranging from 0.7061 to 0.7063, are similar to those of the enclosing rocks (0.7062-0.7063). Field evidence, as well as petrographic and geochemical data, suggests that the analyzed enclaves derived from disruption of synplutonic intrusions of cogenetic mafic magma. The Xanthi pluton could represent ascent of a zoned magma body, with a silicic cap (granodiorite, tonalite, quartz diorite) having intruded first followed by the deeper more mafic levels as syn-intrusive dikes.

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Mafische mikrogranulare Enklaven aus dem Xanthi Pluton, Nord-Griechenland: Ein Beispiel von mafisch-felsischer Magma-Wechselwirkung

Zusammenfassung Petrographische, geochemische und Isotopen-Daten für mafische mikrogranulare Enklaven in einem kalk-alkalischen oligozänen Pluton, der in der Nähe der Stadt Xanthi in Nord-Griechenland aufgeschlossen ist, werden präsentiert. Die Intrusion besteht hauptsächlich aus Granodioriten mit untergeordneten Tonaliten und QuarzDioriten. Mafische Enklaven kommen in großen Schwärmen, besonders an den Rändern des Plutons vor. Sie zeigen feinkörnige prophyritische Texturen und enthalten diesselben Minerale wie ihre granodioritischen und tonalitischen Wirtsgesteine (P1, Qtz, Bt, Hb1, Kfs ± Zrn, Mt, Spn), aber in vollkommen verschiedenen modalen Verhältnissen. Chemische Zusammensetzungen schwanken von mafisch bis intermediär und werden durch höhere Gehalte an Na₂O und niedriger Gehalte von CaO und Sr, verglichen mit durchschnittlichem Basaltmagma mit ähnlichem SiO₂-Gehalt, gekennzeichnet. Die Strontium-Initiale schwanken von 0,7061 bis 0,7063, und sind denen der umgebenden Gesteine (0,7062-0,7063) ähnlich. Geländebefunde, wie auch petrographische und chemische Daten, zeigen, daß die analysierten Enklaven auf das Aufbrechen von synplutonischen Intrusionen cogenetischen mafischen Magmas zurückgehen. Der XanthiPluton könnte dem Aufstieg eines zonierten Magmenkörpers zuzuordnen sein, mit einem Si-reichen Dach (Granodiorite, Tonalite, Quarzdiorite), das zuerst intrudiert ist, gefolgt von den tiefer angesiedelten, mehr mafischen Gesteinen als syn-intrusive G:ange.

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With 7 Figures     

中国南方海相含油气保存单元的层次划分与综合评价

以最近十年中国南方的海相新区油气勘探评价成果为依托 ,以油气成藏和整体封闭保存体系评价为核心 ,在渝东—湘鄂西、中下扬子和滇黔桂三大区域划分出 9个有利区块 5 1个含油气保存单元 ,并将其归纳为四个层次。综合评价认为 ,方西和石柱保存单元具有较好的整体封存体系 ,属持续性含油气保存单元 ,为首选勘探目标 ;江汉盆地南部、句容—海安区块、南鄱阳坳陷、楚雄盆地东北部具备或基本具备整体封存条件 ,属于沉积重建型含油气保存单元 ,通过精细勘探可望获得商业性油气流 ;楚雄盆地西北部、南盘江坳陷、十万大山盆地和渝东—湘鄂西地区利川复向斜由于晚期强烈构造改造而仅存在部分封存体系 ,需要攻关探索 ;思茅、渝东—湘鄂西地区的花果坪和桑植—石门地区已失去整体封闭保存条件 ,仅局部存在封存体系 ,地质条件高度复杂 ,勘探风险甚高。     

岩层离距图法研究沉积岩断裂发育史——以松辽盆地敖古拉断裂为例

利用断裂活动过程中留下的各种地质标记研究断裂发育史是比较困难的 ,已有的研究方法主要可归纳出七种 ,都存在局限性。岩层离距图法是以地震剖面为基础 ,将穿过断裂的各剖面上的标志层投影到沿断裂走向的铅垂面上 ,得到多组标志层的垂向断距数据 ,然后用下部各标志层的断距减去最上部标志层的断距 ,并作多轮次计算 ,直到最后的断距差近似为零或仅剩一个非零标志层。每一轮次计算代表一个活动期次 ,如果出现负值 ,则表示有构造反转。对松辽盆地敖古拉断裂作了实例计算 ,结果为该断裂发育经历了三个正断活动期和一个逆断活动期 ,与盆地区域性活动有些差别。岩层离距图法比起其他已有方法 ,可靠程度大大提高     

The solar wind and the Sun–Earth link

Plasma streams out from the Sun in the form of the solar wind. Shadia Rifai Habbal and Richard Woo examine the workings of this enigmatic link between the Earth and the Sun.     

The organisation of fish assemblages in the regulated Lima basin, Northern Portugal

In order to understand the structure of fish assemblages in the modified Lima basin (Northern Portugal), two distinct datasets concerning the presence and abundance of fish species were subjected to multivariate analysis. On the River Lima two types of flow modification are present within kilometres of one another: (a) a reduced and constant flow due to hypolimnetic release; and (b) an intense and irregular flow. A comparison of their influence on fish assemblages revealed a gradient of assemblage types from tributaries to main river sites. The latter were characterised by a strong dominance of cyprinids, particularly Iberian barbel (Barbus bocagei). The former harboured two kinds of fish assemblages: those closer to the river mouth were dominated by the cyprinids Iberian chub (Squalius carolitertii) and Iberian nase (Chondrostoma polylepis), which were also frequently present in the main river; while in those further upstream the predominant species was the brown trout (Salmo trutta). Although explanatory variables such as distance from source, altitude, substrate coarseness and width were the primary correlates of fish assemblage composition, dam construction and flow regulation also had a significant effect upon assemblage structure, particularly by: i) reducing the importance of migratory species; ii) constraining the presence of trout in the regulated segments; and iii) simplifying the community, especially in the case of the constant and reduced flow regime.