Paläoklima und paläoozeanische Verhältnisse im SW-Pazifik während der letzten 6 Millionen Jahre (DSDP - Site 594, Chatham Rücken, östlich Neuseeland)

Detailed sedimentological investigations were performed on sediments from DSDP-Site 594 (Chatham Rise, east of New Zealand) in order to reconstruct the evolution of paleoclimate and paleoceanographic conditions in the Southwest Pacific during the last 6 million years. The results can be summarized as follows:

1. High accumulation rates of biogenic opal and carbonate and the dominance of smectites in the clay fraction suggest increased oceanic productivity and an equable dominantly humid climate during the late Miocene.
2. During Pliocene times, decreasing contents of smectites and increasing feldspar/quartz ratios point to an aridification in the source area of the terrigenous sediments, culmunating near 2.5 Ma. At that time, accumulation rates of terrigenous components distinctly increased probably caused by increased sediment supply due to intensified atmospheric and oceanic circulation, lowered sea level, and decreased vegetation cover.
3. A hiatus (1.45 to 0.73 Ma) suggests intensified intermediate-water circulation.
4. Major glacial/interglacial cycles characterize the upper 0.73 Ma. During glacial times, oceanic productivity and terrigenous sediment supply was distinctly increased because of intensified atmospheric and oceanic circulations and lowered sea level, whereas during interglacials productivity and terrigenous sediment supply were reduced.
5. An increased content of amphibols in the sediments of Site 594 indicates increased volcanic activities during the last 4.25 Ma.

     

China’s crust-and mantle-source pegmatites and their discriminating criteria

According to their material sources, China’s pegmatities can be divided into two broad types: (1) the crust-source pegmatites derived mainly from the upper continental crust, which can be subdivided into metamorphic differentiated, mixed metasomatic and anatectic magmadifferentiated pegmatites, and (2) the mantle-source pegmatites generated from the mantle, including those related to late differentiates and carbonatites. In space, carbonatites are usually accompanied with alkaii syenite. The criteria of discriminating the two-source pegmatites of China are listed as follows:

1. Rock-forming minerals (micas and feldspars);
2. REE distribution patterns;
3. Zr/Hf ratios in zircons; and
4. Species of apatite and REE contents.

     

Tonminerale in normalsedimenten,hydrothermal beeinflu\ten sedimenten und Erzschlämmen des Roten Meeres

From 14 deeps and other regions of the Red Sea totally 226 samples from 28 cores recovered during the VALDIVIA cruises (1971, 1972) were investigated according to their clay mineral content (<2μm resp. < 6.3 μm) after carbonate dissolution. Three facies groups are to distinguish:

1. normal sediments: dominance of chlorite, kaolinite, illite, small amounts of smectite and sepiolite. Two palygorskite types are present only in a few samples.
2. normal sediments with hydrothermal influence: clay mineral paragenesis similar like that of normal sediments; but increase of smectite and presence of goethite in each sample; partly small contents of talc.
3. heavy metal deposits: dominance of iron-bearing smectite, partly with amorphous components resp. pure ore mineral assemblages with authigenic silicates (talc, quartz, opal, chrysotile, sepiolite, palygorskite, chlorite).

Crystallinity of the clay and ore minerals is independent from sedimentary overburden. Sepiolite shows in small amounts a wide distribution; palygorskite₂ (d₁₁₀=11.3 Å) yields locally an increased concentration in the range of pteropod layers cemented by aragonite. The environment of ore deposits is characterized by iron-bearing smectite besides the ore minerals.     

Die Ultrabasitmassive im Präkambrium des Staates Goiäs/Brasilien

The Brazilian state of Goiás and parts of Mato Grosso represent the centre of the Brazilian shield, between the Guaporé craton in the west and the São Francisco craton in the east. In contrast to opinions before, early Precambrian gneisses and migmatites form only small parts of the shield complex whereas middle and late Precambrian sequences dominate. From tectonic position, an eugeosynclinal central zone can be distinguished accompanied by younger miogeosynclinal series to the east and west. The ultrabasic massifs of Goiás can be differentiated into following types:

1. alpinotype serpentinised dunites and peridotites,
2. gabbro-pyroxenite-peridotite associations,
3. pyroxenite-metagabbro associations,
4. dunite-pyroxenite-alkalisyenite associations,
5. lamprophyre dykes.

Nos. 1, 2 and 3 are of Precambrian age whereas 4 and 5 are surely of post-Devonian, probably of Cretaceous age and can be attributed to the phase of Paraná volcanism. The most economic types at the moment (Nos. 1 and 2) yield Ni, Cu and Co in lateritic enrichment, Cr, Pt and related elements as primary constituents. Latest, the types 4 and 5 cause special interest. From their association with carbonatites they are related to the Araxá complex of Minas Gerais and anticipate mineralizations of Nb, Ta, Ti and P.     

Altération supergène des protores à grenats manganésifères dans quelques gisements d'Afrique de l'Ouest

The wet tropical weathering of Precambrian spessartite quartzites leads to the formation of secondary oxidized ores. These ores result from different successions of superimposed elementary processes, among them:

garnet hydrolysis: Mn, Ca, and Fe are leached, and only an amorphous, silicoaluminous phase remains.

lithiophorite neoformation: Added manganese combines with alumina of the amorphous, Si-Al products.

leaching: Voids appear in the central part of the weathered garnets. They may widen, leaving only the quartz matrix with polyhedric voids.

epigenic replacement: The quartz is replaced by cryptomelane, while the garnets may remain unweathered.

The various ore types are characterized by the sequence of transformations and by the volumes that each transformation affects. These transformations are old because they are observed not only in situ ores but also in removed detrital ores. In the same way the major part of the accumulated stocks of oxidized ores must be old.     

Die Liegendschichten der devonischen Pyrit- u. Schwerspat-Lager von Eisen (Saarland), Meggen und des Rammelsberges

Detailed petrographic and geochemical investigations on the rocks underlying the Devonian stratiforme pyrite and barite deposits of Eisen (Saar district), Meggen (Westphalia), and Rammeisberg (Harz Mountains) in the Rhenish Schiefergebirge have led to the following conclusions:

1. These deposits are tied to dark shales of the pelagic basin facies. In all cases a local depression of the sea floor coincides largely with the spatial extension of the overlying pyrite and barite bodies. These depressions are marked by a large number of sand and silt intercalations, accumulations of reef debris and a significant lower carbonate content.
2. The dark shales underneath the deposits have conspicuously high, but strongly varying contents of Mn, Zn and Pb. This, corresponding with the low carbonate content, is characteristic for the presence of hydrothermal, metalliferous emissions.
3. Predepositional phases of sulfide and barite emplacement are indicated by small layers and lenses.

     

The Araguainha astrobleme/Central Brazil

The following facts have supported the origin of the Araguainha circular structure in Central Brazil by a meteoritic impact:

1. the almost circular contour
2. the impact-morphologic sequence including a central uplift, ring walls and a basin rim of escarpments
3. outcrops of suevites and mixed breccias
4. the evidence of shock metamorphism
5. the presence of shatter cones, and
6. negative anomalies of the total intensity of the magnetic field at the center of the ring structure.

     

Petrogenesis of the Elzevir batholith and related trondhjemitic intrusions in the grenville province of eastern Ontario,Canada

The Elzevir batholith belongs to a suite of trondhjemitic intrusions emplaced at ca. 1,240 Ma in the Grenville Province of eastern Ontario. New major and trace element data, including REE, combined with isotopic and petrographic data indicate that:

1. the batholith has calc-alkalic affinities;
2. the Elzevir parental magma is very similar to that of dacites in the nearby, coeval metavolcanic rocks; the magma formed by partial melting of crustal material at granulite grade;
3. chemical differences between the plutonic and volcanic rocks can be best explained by accumulation of plagioclase in the plutonic environment;
4. fractionation was dominated by plagioclase and quartz, with lesser biotite and epidote, and minor zircon and apatite.

It is suggested that melting of sialic crust took place during the ‘docking’ of a partly-evolved, originally ensimatic arc system against the main cratonic mass to the northwest.     

Kyanite eclogites

Prior experimental work has shown that in the laboratory the mineralogy of eclogites is sensitive to the ratio of CaO ∶ MgO ∶ FeO and that the reaction pyroxene + kyanite?garnet + quartz proceeds to the right at high pressures in rocks rich in magnesium and to the left in rocks rich in calcium and iron. Typical basalts crystallized at high pressure never contain kyanite. The chemistry and mineralogy of a large number of naturally occurring eclogites show they belong to three classes.

1. Kyanite-free magmatic eclogites, rich in magnesium, from:
2. kimberlites
3. dunites and serpentinites.
4. Kyanite-bearing eclogites and grosspydites rich in CaO and low in FeO with intermediate MgO from:
5. kimberlites
6. gneisses.
7. Kyanite-free eclogites of metamorphic origin rich in iron with low magnesium and intermediate amounts of calcium from:
8. glaucophane schists
9. gneisses.

     

Origin and composition of the ferruginous oolites and laterites of North-Western Nigeria

The ferruginous deposits of north-western Nigeria occur extensively capping sediments which outcrop over thousands of square kilometers. These deposits could be subdivided into 3 major groups:

1. Ferruginous oolites;
2. Crusty/Concretionary laterites;
3. Ferruginous sandstones.

The iron-rich oolites are primary deposits and deposition of ferruginous materials occurred during the late Paleocene. All gradations can be traced between a pure oolitic ironstone and concretionary laterite with scattered oolitic grains of limonite. The crusty laterites and Ferruginous sandstone were formed during the late Tertiary or early Quaternary. They are definitely post Miocene in age and consists of abundant angular quartz grains embedded in a matrix of gothite, haematite, limonite and clay. The laterites and oolites posses different element concentrations which indicate formation under different environmental conditions ranging from deep Marine through shallow near shore marine to continental (fluviatile and lacustrine). The crusty laterites and ferruginous sandstones in northwestern Nigeria attain a thickness of approximately 4 meters or more forming the crust of flat-topped hills or mesas. They are almost certainly equivalent to the laterites covering much of the Northern plains and the Fluvio-volcanic series of the Jos Plateau. In northwestern Nigeria the laterites are restricted to outcrops of sediments of appropriate composition and drainage properties. These ferruginous deposits are usually massive with almost horizontal bedding planes marked by abrupt or gradual changes in morphology and lithology. Cross bedding and ripple-marks can be observed at Gundumi and Imasa as well as in Birnin Kebbi and large scale stratification of the laterites occur at Kalambaina. Laminations are generally localised.     

Preliminary study of REE iron formations in China

Geological and geochemical characteristics of REE iron formation (REEIF), a term proposed by Prof. Tu Kuang-chih to specify a special type of Precambrian iron formations rich in REE, are discussed in this paper with special reference to its REE contents, REE distribution patterns, the formation mechanism, the relationship between its development and the multi-stage evolution of the continental crust in China, and the implications of REE as an indicator of oxidation state for ancient atmosphere. Major conclusions are outlined as follows:

1. REEIFs are characterized by high REE concentrations against the very low REE levels in normal Precambrian iron formations.
2. REEIFs are formed by marine sedimentary-diagenetic processes in miogeosynclines or transition zones during Proterozoic times To some extent, volcanic activity may play an important role in the deposition of ore-forming materials. In a broader sense, REEIFs belong to Fe-bearing dolomite formations. Most REEIFs in China may be superimposed by late geological processes such as hydrothermal-metasomatism, migmatization and metamorphism. Generally, REEIFs have much in common with stratabound ore deposits in respect to their characteristic features.
3. Similar to Precambrian iron formations, REE are enriched in LREE. But, the degree of LREE enrichment is noticed to increase of total REE content. Most REEIFs are characterized by high ratios of σ Ce/σY, (Mg+Fe)/Ca, Na/K, Nb/Ta, Zr/Hf, Th/U, Ba/Sr, etc.
4. The extensive occurrence of REEIFs indicates higher REE abundance in the continental crust of China, thus lending further support to the multi-stage theory regarding the evolution of chemical elements and the differentiation in the continental crust of China.
5. Preliminary data seem to support the time-dependence of REE distribution patterns and relative Eu contents of REEIFs in China.

     

Geochemistry of uranium in sediments of the Bohai Gulf,China

The following conclusions can be drawn from the work reported in this paper:

1. Sixteen samples were determined for uranium by spectrophotometric method. The uranium content in the sea floor sediments of the Bohai Gulf ranges from 1.6 to 6.3 ppm, with an average of 4.3 ppm.
2. Statistical data show close relationship between U concentration and grain size. Relatively larger amount of uranium was found accumulated in mud than in sand. The bulk of uranium is assumed to be derived from terrestrial detrital minerals.
3. A positive correlation between U and Fe is recognized. Similar relation also can be seen between U and Al. The plot of U concentration vs. Fe is linear, and can be expressed by the linear regression equation:Y=?0.37+1.35X. The plot of U against Al gives an equation ofY=?2.48+1.01X.
4. The average U/C_org. ratio for these sediments is 7×10^?4, and the average ratios of U/P, U/Mn, and U/CaCO₃ are 100×10^?4, 50×10^?4 and 2×10^?4, respectively.
5. Compared with the abundances of other shelf sediments, the average concentration of U in the area under consideration is close to that of sediments on the selves of Japan and the Gulf of Mexico, and the Black Sea. Uranium concentration in the Bohai Gulf sediments is comparable to that of the continental crust, but differs from that of deep-sea clay.

     

Les granites du Massif Central Français: étude comparée des leucogranites et granodiorites

Chemical and mineralogical compositions of granitic rocks of the French Massif Central enable us to classify them into two distinct groups: (i) leucogranites, (ii) granodiorites or quartz-monzonites, separated by a natural gap. The differences between these two groups are not only chemical and mineralogical, but are also reflected by:

conditions of crystallization as deduced from compositions and from thermal metamorphism of xenoliths.

nature of inclusions and, especially, the occurrence of basic fine-grained igneous xenoliths restricted to the granodiorite — quartz-monzonite group

relations between intrusive and autochtonous migmatitic masses;

levels of formation and of intrusion; the granodioritic and quartz-monzonitic magmas have originated at deeper horizons of the earth's crust than the leucogranitic one, but have risen higher.

In our opinion these differences are linked, and the specific characteristics of the granodiorites and quartz-monzonites are related to the presence of basic igneous inclusions. These inclusions are relics of deep basic intrusions in the earth's crust, which have overheated the surrounding acid rocks beyond the minimum temperature of melting. Thus granodioritic or quartz-monzonitic melts were produced and were able to rise to superficial levels. These inclusions are missing in leucogranites. The compositions of the latter and their poor mobility suggest a wet anatectic origin in minimal PT conditions.     

Groundwater development,Kharga Oases,Western Desert of Egypt: A long-term environmental concern

The groundwater reserves in Kharga Oases have been studied for the long-term socioeconomic development in the area. The Nubian Sandstone, which consists of a thick sequence of coarse clastic sediments of sandstone, sandy clay interbedded with shale, and clay beds, forms a complex aquifer system. The Nubian Aquifer has been providing water to artesian wells and springs in the Kharga Oases for several thousand years. Groundwater in the Kharga Oases is withdrawn from springs and shallow and deep artesian wells Nearly all the wells originally flowed, but with the exploitation of ground-water from deep wells for irrigation beginning about 1959. the natural flows declined as more and more closely spaced deep wells were drilled By 1975 many deep wells had ceased to flow The water demand in the area has been met by pumping both shallow and deep wells The total annual extraction from deep wells has fluctuated over the year, however, the annual withdrawal from deep wells has exceeded extraction from shallow wells About 17 billion m³ of water was withdrawn from the combination of shallow and deep wells during the period 1960–1980 The Nubian complex aquifer in the Kharga Oases has a very large groundwater potential that could be exploited and beneficially used for a long-term agricultural development in the area, provided proper well spacing and management are implemented Other major environmental considerations for which precise hydrogeologic data are needed include

1. Determination of the long-term yield available from properly constructed and producing artesian wells that will support a planned migration of population from the overcrowded Nile delta and flood plain areas
2. Development of an effective management program and adequate staff to maintain groundwater production over an extended period of years
3. The impact on climate caused by extensive irrigation in the oases of the Western Desert of Egypt
4. Protection against water logging of soils from irrigation practices
5. Protection against salinization of soils from irrigation practices
6. Development of effective surface and subsurface drainage practices
7. The impact of farming and pest control practices on the shallow groundwater of the oases
8. Determination of the long-term development of the artesian water on the quality of the water from the aquiter systems in the Western Desert

This paper addresses items 1, 2 and 8.     

Stratigraphy,type and formation conditions of the late precambrian banded iron ores in south China

Based on research on the “Xinyu-type” Sinian iron deposits in Jiangxi Province and metamorphosed iron deposits in Jiangkou and Qidong of Hunan, Sanjiang and Yingyangguan of Guangxi, Longchuan of Guangdong and some other areas in Fujian, the authors have come to the following conclusions:

1. The metamorphosed late Precambrian iron ores widespread in south China may be roughly assigned to two ore belts, namely the Yiyang-Xinyu (Jiangxi)-Jiangkou(Hunan)-Sanjiang (Guangxi) ore belt or simply the north ore belt, and the Songzheng(Fujian)-Shicheng (Jiangxi)-Bailing (Longchuan of Guangdong)-Yingyangguan (Guangxi) ore belt or the south ore belt. Tectonically, the former lies along the southern margin of the “Jangnan Old Land”, while the latter along the northwestern border of the “Cathaysian Old Land”.
2. Iron deposits of this type occur exclusively in the same interglacial horizon of the Sinian Glaciation in south China. Above and below the ore bed there lie the glacial till-bearing volcanic-sedimentary layers.
3. Based on sedimentary features, the iron formations can be divided into four types: silica-iron-basalt formation, silica-iron-clastic rock formation, silica-iron-tuff formation and silica-iron-carbonate rock formation, which progressively grade into each other.
4. Iron ores were formed at the late stage of late Proterozoic rifting in neritic environments, with their distribution governed by the rift valleys on the margins of the “Jiangnan Old Land” and “Cathaysian Old Land”. Consequently, intense mafic volcanism as well as weathering and denudation of palaeocontinent during rifting provided material sources for the formation of iron deposits. Meanwhile, warm and humid stationary neritic environment during the south China great glacial period constitutes favorable palaeoclimatologic and palaeogeographic conditions for the deposition of iron ores.
5. The iron formations have undergone regional metamorphism of greenschist-amphibolite facies.

To sum up, the late Precambrian banded iron ores should be of metamorphosed volcano-sedimentary type.     

Hydrological and hydrochemical studies in the permafrost drainage basin of Oobloyah Valley,N-Ellesmere Island,NWT, Canada

During the “Heidelberg-Ellesmere-Island-Expedition” to Oobloyah Valley, N-Ellesmere Island, NWT, Canada in 1978 the summerly water balance of this high arctic catchment area with continuous permafrost was investigated. The following results will be presented:

1. Three hydrogeological areas with different physical parameters, thawing depths and drainage are distinguished and studied on slope I, II and slope III.
2. The climatic situation of summer 1978 was mainly influenced by the change of radiating and cloudy periods. Due to air temperatures (2 m above ground), which never went below 0°C, these periods regulated the thawing of the glaciers and the respective run-off.
3. Most of the winterly snow cover melted before July, thereafter soil thawing and its drainage began. In none of the sediments the latter reached field capacity.
4. Considering the course of daily discharge and soil water balance the three studied streams were characterized by the “Dry-Weather-Discharge-Line”, DWL, of Peri-Creek the “Radiation-Weather-Discharge-Line”, RWL, and the “Cloudy-Weather-Discharge-Line”, CWL, of Nukapingwa River and Heidelberg River.
5. The periglacial streams never had a measurable sediment load not even during snow melt, whereas the glacial and mixed glacial-periglacial streams as Nukapingwa River and Heidelberg River showed a sediment drift depending on their run-off. Only in Peri-Creek the ion concentrations were correlated to discharge.
6. Precipitation (snow plus rain) add up to 51% of the summerly water balance. The glaciers contributed up to 48%, and the actual evapotranspiration is only 1%.

     

The sedimentation of copper-bearing shales (Kupferschiefer) in the sudetic foreland

The profile of the copper-bearing shales (Kupferschiefer) displays 3 types of lithological developments of the Sudetic Foreland:

in reduction facies: with the notably diminishing of participation of clay minerals and organic substance from bottom to top.

Many horizons of concentration of copper, lead and zinc are present.

in oxidation facies: where marley shales are forming, the metals decrease to trace contents.

in intermediate zones, from reduction facies to oxidation facies shales, the lithological formation is changing and the greatest variability is encountered in the intensity of metal contents.

The concentrations of copper sulphides occur in lagoonal areas in which an oxigen deficiency was associated with a great amount of organic matter. The beds formed in the oxidation facies represent the coastal zones of an open sea basin where the influence of inflow and outflow were considerable.     

Geologische und geochemische Untersuchungen im Zentralgneis und in der Greiner Schiefer Serie (Zillertaler Alpen,Tirol)

Geologic, petrological and geochemical investigations have been carried out in the western part of the “Zillertaler Alpen”. Important results are:

1. The premetamorphic material of the Greiner series consists of conglomerates, breccias, arcosic-sandstones or greywackes, bituminous shales, volcanic lavas and tuffs.
2. The southern part of the “Zentralgneis” shows a differentiation trend from alkaline granite to quarzdiorite with predomination of granodiorite.
3. Chemical relationships of granodiorite to its restitic inclusions allow the supposition of a palingenetic origin of the granitic rocks.
4. At least two stages of metamorphism can be differentiated.
5. Parts of the Greiner series, covered by triassic metasediments, are supposed to be of Permian age. A lower age boundary can not yet be given.
6. Some vertical, northeast striking faults with throws of more than 1 or 2 kilometers produced southward verging drag folds.
7. Geodynamic aspects, revealed from regional metamorphism and tectonics, are discussed.

     

Zur Petrographie der Bauxitlagerstätten auf der „Charnockite-suite“ im Salemdistrikt und in den Nilgiri-Hills,Südindien

Three profils of fossil Bauxites probably of Early Tertiary age in the Shevaroy Hills and in the Nilgiri Hills, South India, are examined. They are formed by isovolumetric transformation of charnockites under conservation of relict structures. The chemical and mineralogical composition of the bauxites depends on the petrology of the source rock. Na, K, Ca, Mg and the main quantity of silica are extracted, Al and Fe have been enriched relatively and in certain places even absolutely. The mineral transformation in the beginning of the weathering developped in two phases:

1. Leaching and precipitation within the cleavage pattern of the minerals,
2. Leaching and precipitation in the places of the former mineral relicts.

Different later phases of weathering produced Fe- and Al-rich solutions, which are precipitated in the intervals of porous rocks.     

Charriage crustal,anatexie et decrochements ductiles dans les Maures orientales (Var,France) au cours de l'orogenese varisque

The kinematics of the deformational events recorded in the catazonal gneisses within the eastern part of the Maures massif (Variscan basement of Provence, southeastern France) has been established. These events can be correlated with both the metamorphic and the magmatic evolution, and the orogenic history of the eastern Maures then consists of the following stages:

1. -HP-metamorphism preserved only in relict eclogites and quartzites rich in calc-silicates,
2. -Catazonal metamorphism involving anatectic melting, broadly contemporaneous with large-scale horizontal transport towards the NNE. During this event, the lithologic units were disrupted and intensively mylonitized.
3. -Intrusion of a first generation of anatectic granitoids.
4. -A second tectonic event under epi-to mesozonal metamorphism conditions is responsible for the northward displacement of the eastern Maures relative to the western part along a sinistral strike-slip fault 4 km wide (Ramatuelle — Plan de la Tour fault) in which the early anatectic granitoids have been mylonitized. Outside the fault zone, this event is marked by upright to W-vergent open folds trending N-S, i.e. parallel to the transport direction.
5. -A moderate cataclastic reactivation of the Ramatuelle — Plan de la Tour fault with a dextral sense of shear, locally accompanied in the eastern part of the area by minor lowtemperature thrusting towards the south.
6. -Intrusion of a second generation of anatectic granites about 320 Ma ago.

The metamorphic, magmatic and tectonic evolution of the eastern Maures suggests a continuous orogenic history in an area of rapid crustal thickening by large-scale thrusting within the continental crust. This evolution may be related to the development of continental subduction during the continent/continent collision responsible for the Variscan orogeny in southern Europe.