A flow-foliated ignimbrite related to the Åland rapakivi granite in SW Finland

A flow-foliated felsic ignimbrite constitutes the uppermost lithological unit of the 1.58 Gyr anorogenic magmatic rocks in SW Finland. The ignimbrite is derived from an explosive eruption of hot (≅ 950 °C) phenocryst-bearing A-type (rapakivi-type granite magma.
The ignimbrite is close in composition to subvolcanic rapakivi granites that occur in the margins of the kand rapakivi batholith. The subvolcanic granites crystallized under a pressure of ≅ 1 kbar and at temperatures of about 650–700 °C. However, both major and rare earth elements show that the ignimbrite- forming magma was more fractionated than the magma forming the subvolcanic varieties.
Supported by evidence of mafic-felsic magma mingling, it is suggested that injection of hot mafic magma into a shallow magma chamber produced the high temperature of the ignimbrite-forming magma. This injection increased the magmatic and the volatile pressure that caused the eruption of the dry felsic magma.     

我国主要硫矿床类型及成矿若干规律

我国硫矿资源丰富多采,有自然硫、硫化氢、硫铁矿、石膏、明矾石等。对于这些矿产中的主要矿床类型地质特征总结归纳,显然将有助于提高地质理论水平和扩大找矿远景。成矿规律是成矿地质条件的全面反映,矿质来源则为成矿地质的前提和物质基础。本文拟从物质来源探索出发,提出以下硫矿床的分类方案。     

Geology of Ladakh,Lahaul and spiti regions of Himalaya with special reference to the stratigraphic position of flysch deposits

An attempt has been made to produce the geological map of Ladakh, Lahaul and Spiti regions of Himalaya on the basis of the field work done by the authors and the observations made by earlier workers. The stratigraphy of this region has been discussed in the light of new fossil finds from different stratigraphical horizons. Stratigraphical columns have been prepared and the formations of this region have been correlated with those exposed in other parts of the Himalaya. The age of the flysch deposits (Indus Flysch of Ladakh and Chikkim Shales of Spiti) has been defined on the basis of the microfauna.

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Zusammenfassung Aus Feldarbeiten und bereits vorliegenden Fakten resultierte eine neue geologische Karte des Gebietes von Ladakh, Lahaul und Spiti im Himalaya. Die Stratigraphie wird mit Hilfe neuer Fossilfunde geändert und mit anderen Teilgebieten des Himalayas verglichen. Das Alter der Flyschserien (Indus-Flysch von Ladakh und Chikkim-Shales von Spiti) wurde mit Hilfe von Mikrofaunen bestimmt.

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Résumé Les levés de terrain des auteurs, combinés avec des travaux antérieurs, ont permis de dresser une nouvelle carte géologique du Ladakh, Lahaul et Spiti dans l'Himalaya. La stratigraphie a été modifiée grâce à de nouvelles découvertes de fossiles et comparée avec celle d'autres régions de l'Himalaya. L'âge de la série du flysch (Flysch de l'indus de Ladakh et schistes de Chikkim de Spiti) a été déterminé à l'aide de microfaunes.

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Conditions of ore mineral formation in certain Zambian Copperbelt deposits with special reference to the role of cobalt

Studies of the compositions of coexisting sulphide assemblages from certain Zambian Copperbelt deposits and of their textural relations and host rock environments have been undertaken by routine microscopy and using electron microprobe analysis. Special attention has been paid to sulphide assemblages containing cobalt. Using experimental data on the systems Cu-Co-S, Cu-Fe-Co-S and on sulphidation equilibria, together with the available information on equilibria involving gangue minerals and some new calculations, an attempt has been made to define the chemical conditions of ore formation and/or re-equilibration in several deposits (Baluba, Chibuluma West and Chibuluma, Chambeshi S.E.). If a re-equilibration temperature of 300°C is assumed the range of aS₂ prevailing during final formation of the assemblages was of the order 10^–7 – 10^–9 atm, more rarely dropping to 10^–11 – 10^–12 atm. If magnetite is present, and this is considered very unlikely in most cases, aO₂ may have reached as high as 10^–35 atm but it is generally likely to have been around 10^–50 atm or even lower. Values of aCO₂ are assumed to have been of the order of 10^–0.5 atm. Detailed studies of drill hole samples from the Chambeshi S.E. deposit suggest an important link between the petrology of the host rocks and the sulphide mineral chemistry. In particular, the control exerted on sulphide composition by aS₂ may have been related to the availability of sulphate in the form of diagenetic anhydrite or in sulphate-rich interstitial waters. The distinctive distribution of cobalt in the ores appears related to the distribution of amphibolite bodies and in turn to rift fault systems in the Basement which allowed upward movement of fluids enriched in magmatically derived cobalt.     

扬子地台西南缘传统型铂族矿产地质特征

传统型铂族矿产,系指与镁铁质岩浆成矿作用有关的铂族矿产资源。华力西运动时期,扬子地台西南缘沿超壳深断裂带发生的大陆裂谷作用,为来自上地幔的镁铁质(拉斑玄武岩质)岩浆的上涌和侵位提供了极为有利的前提条件。含铂基性超基性岩的时空分布,受到大陆裂谷作用的主要发生发展时期和裂谷活动带的控制。通过对典型矿床特征及其成矿作用的探讨,论述了扬子地台西南缘主要的铂族矿床类型;并从四维成矿的角度,阐述了对区域成矿规律的一些基本认识。     

Remarkably uniform oxygen isotope systematics for co-existing pairs of gem-spinel and calcite in marble,with special reference to Vietnamese deposits

Oxygen isotope systematics for co-existing pairs of gem-spinel and calcite in marble from Vietnam and other worldwide deposits have been determined in order to characterize the O-isotope fractionation between calcite and spinel. In Vietnam, the Δ¹⁸O_cc–sp (= 3.7 ± 0.1‰ for six samples from the An Phu and Cong Troi deposits) is remarkably constant. The combination of these data with those obtained on calcite–spinel pairs of Paigutan (Nepal, n = 2), Ipanko (Tanzania, n = 1), and Mogok (Myanmar, = 2) are also consistent with an overall Δ¹⁸O_cc–sp of 3.6 ± 0.3‰ for all the spinel samples (n = 11). The straight line correlation δ¹⁸O_cc = 0.96 δ¹⁸O_sp + 4.4 is excellent despite their worldwide geographic spread. The increment method of calculating oxygen isotope fractionation gave a geologically unreasonable temperature of formation for both minerals at 1374 °C when compared to temperatures obtained by mineral assemblage equilibrium of these marble type deposits, between 610 and 750 °C. The constant Δ¹⁸O_cc–sp reflects a constant temperature for this amphibolite facies assemblage, whose current best estimate is calculated at 620 ± 40 °C, but unquantified uncertainties remain.     

Formation of the Micro-Disseminated Strata-bound Gold Deposits,With Special Reference to Structural Evolution,Miliang Area,Zhen‘an County,Shaanxi Province,China

Based on detailed geologic study,the important role of structuring in the formation of gold deposits in the area is discussed with special reference to structural evolution,Syngenetic faulting contemporaneous with tectonic-volcanic events is thought to be responsible for providing the ore-forming material at depth.The lithofacies formed by highly alternating deposition of terrestrial and carbonate detritus is chemically characterized by the assemblage of Au-Sb-As,constituteing a favorable source bed for the activation and enrichment of gold.This gold source bed has undergone four major stages of structural deformation,accompanied by multi-staged alteration and mineralization.     

Fisheries in upwelling regions — with special reference to peruvian waters

The anchovy population that is the basis of the Peru fishery, the world's largest, is a phytoplankton feeding species, supported by an upwelling based ecosystem. The fish is very short-lived and grows rapidly — both criteria for high turnover rate — high yield fisheries. The maximum sustainable yield is around 10 million metric tons. Analysis of the dynamics of the fishery suggests that the fleet is overbuilt, applying too much fishing effort, and slightly overfishing the population. In consequence, the population may be approaching a size and stress level at which it will be unstable.     

A possible origin of uranium deposits in granites in special reference to the formation of SL deposit

The tectonic destruction and hydrothermal alteration of the H granite massif resulted in the formation of the green alteration zone. During this process, infiltrating hydrothermal solutions would resorb uraninite in the rocks, leading to the mobilization and thus migration of uranium into fissures and grain interstices, or being adsorbed on clay minerals. As a result, the medium and space were provided for later mineralization. In the Cretaceous period, the upper part of the green alteration zone underwent strong oxidation, followed by the resorption and then the transformation of metallicsulfides into limonite and hydrogeothite. And uranium present both in uraninite and in fissures was further mobilized and concentrated to form uranium ore deposits of economic importance in the redox boundary between the green zone and the purple zone.     

An alternative Weichselian glaciation model, with special reference to the glacial history of Skåne, South Sweden

A revised lithostratigraphy of Skåne, South Sweden, constitutes the basis of an alternative Weichselian glaciation model for southern Scandinavia, progressively anchored to the stratigraphy. Skåne was not glaciated during the Weichselian until 21,000 B.P. The concepts, outlet surge and marginal dome (the main tools of the model) are defined. The palaeogeography of the Baltic and Kattegatt basins during the Mid-Weichselian are reconstructed. Shorelines, during the advance stage, are calculated from an inferred proglacial depression. Outlet surges, which occurred in three basins of the Baltic, guided the ice sheet during its growth. The growth of marginal domes on the outlet surge lobes resulted in changes in the configuration of the ice sheet and in the lowering of its surface profile. The South Scandinavian ice divide became located over a former outlet surge lobe NNE-NE of the island of Gotland in the northern Baltic. This gave the main ice in South Sweden and Denmark a NE ice movement during the whole glaciation until the deglaciation of SE Sweden. The Kattegatt Ice Lake was formed due to damming in the Skagerack area. Surging ice tilled in the basin resulting in the formation of vast areas of stagnant ice in front of the advancing NE-ice. Marginal domes were formed on these giving rise to the early glacial episodes in the southwest of Sweden and Denmark. During the deglactanon, tnree pnases of marginal dome formation are recorded in the soutnern Baltic area and the growth of these domes resulted in the East Jylland advance, the Bælthav readvance and the Simrishamn readvance. The marginal domes were formed on vast fields of stagnant ice left behind by the receding main ice. Baltic erratics, englacially present in the main ice as well as in the stagnant ice in front of it, were transported (stepwise) towards the west and northwest, partly by the advancing marginal domes and partly by ice streams formed between the marginal domes and the main (NE-) ice. It is argued that the classical, so-called Low Baltic ice stream in the sense of a readvancing glacier lobe never existed. The first two marginal domes collapsed due to starvation and the ice movement returned gradually to the independent NE ice movement of the main ice. The third marginal dome collapsed due to a downdraw caused by a large transgression recorded in the Kattegatt and the Öresund regions. The transgression took place roughly around 13,300 B.P. and was possibly caused by damming of the Kattegatt basin in the north in connection with a marine downdraw. The collapse of the third marginal dome and the subsequent ‘ice lake downdraw’ of the dome centre NNE-NE of Gotland took place during a cold period of the deglaciation. This resulted in an extremely high recessional rate on the Swedish cast coast compared with the west coast and a contemporaneous westwards displacement of the South Scandinavian ice divide. After the downdraw, the recession rate on the east coast slowed down markedly and became more or less equal to that of the west coast. Pure dynamic causes for the extremely high recession rate in SE Sweden are expected because the decrease in this rate coincides with the onset of a recorded, marked climatic amelioration at around 12,600 B.P. Formation of the marginal domes during the deglaciation indicates periods of increased cyclon activity at the southwest margin of the Weichsclian Scandinavian ice sheet alternating with periods of ice sheet starvation. Detailed modelling of the marginal domes is therefore expected to have significant palaeoclimatic implications. The marginal dome concept is believed to he useful also in the reconstruction of earlier glaciations.     

Storegga tsunami deposits in a coastal lake on Suouroy, the Faroe Islands

Presumed deposits of the Storegga tsunami have been recognized in a coastal lake situated 4 m a.s.l. on the island of Suðuroy, the Faroe Islands. The stratigraphy in the lake reveals a major erosion and redepositional event. The deposited material ranges from sand and sandy gyttja, with marine shell fragments and foraminifera, to gyttja with rip-up clasts, wood fragments and thin sand layers. Diatom analysis indicates that the deposit contains 5-8% polyhalobous (full marine) species, decreasing to 1-2% in the undisturbed lacustrine gyttja above. The tsunami event was dated to some time between 7300 and 6400 14 C yr BP. Lithostratigraphic profiles in the lake suggest that at least two large waves inundated the basin. The first and largest wave eroded most or all of the sediments previously deposited in the basin. The next wave caused minor erosion of the redeposited material. The waves deposited two generations of sand overlain by organic conglomerates, after which followed a unit of suspension material and normal lacustrine gyttja.     

Urbanization and desertification in the Sudan with special reference to Khartoum

Urbanization-desertification interactions in the arid zones of the Sudan represent a challenge for future management planners. Desertification leads to a considerable movement into the towns, thereby encouraging the urbanization process. However, due to the large pull effect of large urban centres which are limited in number and unevenly distributed over the area, most of the migration is oriented towards them. This tendency is strengthened, furthermore, by the present planning trends of growth pole centres. The result is overcrowding, negative over-urbanization diseconomies and more pressure on the natural resources in the immediate hinterland, thus further accelerating the desertification process. Some examples are given in the paper to show how the rapid increase of urban population and the rapid growth of urban centres have reflected themselves in difficulties in procuring wood fuel or naturally grown raw materials for traditional and small urban industries. The specific example of Khartoum, the largest urban centre in the Sudan with the highest rate of growth is treated in detail to show how rapid urbanization processes would result in intensified desert conditions and how ecological interactions and effects would be faster and more serious in a more vulnerable ecological location.     

The structure of the Lower Palaeozoic rocks of Anglesey,with special reference to faulting

The principal structures of the Lower Palaeozoic rocks of Angelsey are described. Tight folding, with variably developed slaty cleavage and a first phase of reverse faulting, took place probably in late Silurian times, along axes which are parallel to pre-Cambrian foliation trends. A second phase of reverse faulting followed basic dyke intrusion and was succeeded by normal faulting and mineralization. Joint production was a comparatively late feature. A technique for analysing fault data, in terms of stress axes, is outlined and applied to faulting within the Lower Palaeozoic rocks.     

A new Geologic Time Scale, with special reference to Precambrian and Neogene

A Geologic Time Scale (GTS2004) is presented that integrates currently available stratigraphic and geochronologic information. Key features of the new scale are outlined, how it was constructed, and how it can be further improved. The accompanying International Stratigraphic Chart, issued under auspices of the International Commission on Stratigraphy (ICS), shows the current chronostratigraphic scale and ages with estimates of uncertainty for all stage boundaries. Special reference is made to the Precambrian part of the time scale, which is coming of age in terms of detail, and to the Neogene portion, which has attained an ultra-high-precision absolute-age calibration.     

Faunal dating of the late Cenozoic of southern Africa,with special reference to the Carnivora

Since chronometric data comparable to that available from the late Cenozoic succession of East Africa have not, and probably cannot be obtained in southern Africa, faunal dating methods retain their traditional significance in the latter area. Five successive late Cenozoic mammal ages, the Namibian, Langebaanian, Makapanian, Cornelian, and Florisian have been proposed as a framework for discussions relating to the chronology of southern African mammalian faunas. The Namibian fauna is poorly known, but is evidently of Miocene age. It is not discussed in this paper. The Langebaanian fauna is well known only from the prolific occurrence at the type site of Langebaanweg and is Pliocene in age. Makapanian faunas are best represented at the Transvaal Australopithecine sites and probably overlap the Plio-Pleistocene boundary. The Cornelian fauna is not as well known as others, the largest assemblage having been recorded from Elandsfontein, although this assemblage is one which is unfortunately temporally heterogeneous. Florisian faunas have been recovered from a relatively large number of localities, including several for which there are radiometric dates. The recorded southern African fossil Carnivora are listed and the local evolution of this group is discussed in terms of the mammal age chronology. It is concluded that secure faunal dating of individual fossil occurrences is enhanced by an appreciation of the nature of changes undergone in evolutionary lineages, while an uncritical knowledge of recoreded taxa is less useful.     

Aspects of the mineralogy and hydrometallurgy of chrysocolla,with special reference to the Cuajone,Peru, ores

Chrysocolla in the Cuajone ores appears to be microcrystalline and to exhibit a fibrous structure.Sulphuric acid leaching of the chrysocolla is facilitated by a microcracked surface structure. A marked surface structural change is evidenced as hydrogen ions replace the copper. The end result is a noncontinuous surface layer of silica from which the copper has been essentially completely removed.The results of this study provide confirmatory evidence for the structure and hydrometallurgy of chrysocolla.     

Middle to Late Weichselian Norwegian Channel Ice Stream deposits and morphology on Jæren, southwestern Norway and the eastern North Sea area

Glacial lineations on a bank area and a coastal lowland, both bordering the Norwegian Channel, are studied with regard to morphology and distribution by means of side-scan sonar data, detailed digital maps and fieldwork. Their genesis and age are further elucidated through stratigraphic and sedimentologic information from excavations in one typical coast-parallel drumlin. Four excavated sections revealed four lithologic units: Prodeltaic glaciomarine sand, glaciofluvial gravel, glaciomarine diamicton and deformation till. After Middle Weichselian delta progradation, glaciomarine diamicton was deposited and later subglacially reworked by a northwards flowing glacier. The two upper diamictons form the main volume of the ridge, which is interpreted as a drumlin, and imply a reinterpretation of the Jæren part of the so-called Lista moraine. Preconsolidation of glaciomarine diamicton suggests a maximum ice thickness of 500 m during drumlin formation, indicating an ice surface slope of 1 m/km. The occurrence of sediments that provided low basal shear stresses, and the orientation of drumlins and megaflutes indicating ice confluence both point to high glacier flow velocities and suggest that an ice stream, rather than a slower moving part of the ice sheet, occupied the Norwegian Channel during the Late Weichselian maximum. Deformation till overlying, more or less, undeformed glaciomarine diamicton suggests that high glacier velocities during periods of low driving stresses were possible due to a subglacial deformable layer.