华南晚前寒武纪硅铁建造的层位、类型与形成条件

分布于华南诸省的晚前寒武纪条带状变质铁矿,1957年首先发现于江西新余地区,被命名为“新余式铁矿”,后又相继在湘中、闽北、桂北等地被发现。由于此类铁矿分布广泛,层位稳定,不仅是南方重要的铁矿资源,而且对我国南方前寒武纪地层的划分对比,澄江—加里东地槽的形成演化,以及变质铁矿的成因研究等,都有一定的理论意义,因而引起有关方面的重视。本文在系统研究江西新余式铁矿,并实地考察华南诸省铁矿的基础上,综合前     

Organische Substanzen in präkambrischen Itabiriten und deren Nebengesteinen

Marine sedimentary iron ore samples from various early and middle Precambrian ore provinces of the world (“itabirite, banded ironstones, jaspelites, Quarzbändererze”) have been investigated by means of vaporisation pyrolysis gaschromatography (VPGS) with regard of their contents of organic substances. The main results were:

1. All investigated itabirite samples show, concerning their qualitative hydrocarbon content, a typical distribution in chromatographic diagrams.
2. The amount of pristane and phytane as results of the decomposition of chlorophyll points at a reasonable photosynthetic activity of organisms during the itabirite genesis.

It appears likely that organic life has influenced and promoted the genesis of the iron ore deposits of the itabirite type.     

Variations des teneurs en éléments mineurs (Cd,In, Ge,Ga, Ag,Bi, Se,Hg, Sn) des minerais de Pb-Zn de la province polymétallique des Andes du Pérou Central

About 1,500 samples of Pb and Zn concentrates and ores from 89 ore deposits of the polymetallic province of the Andes of central Peru have been analyzed. The distributions of Cd, In, Ge, Ga, Ag, Bi, Se, Hg, and Sn in these ore deposits can be reported on the basis of

the typology of ore deposits, i.e., some types of ore deposits (syndiagenetic without associated volcanism and volcano-sedimentary of Triassic-Lias, exhalative sedimentary of Upper Jurassic) show very characteristic minor and trace element patterns;

the temperature of ore formation that controls the abundance of Bi and Hg, in general, and of Ag, Se, and Sn in the Tertiary hydrothermal deposits;

the age and nature of the country rock, e.g., an In, Ga, and Sn positive anomaly and Cd negative anomaly appears in the deposits with Paleozoic country rock;

the geographic position of ore deposits, e.g., in the northern part of the province an In, Ga, Ge, and Cd positive anomaly appears.

     

Die Banater Erzprovinz

The present work represents the first attempt to classify the entire Banatian ore deposits, from the seismo-tectono-magmatic point of view, taking into consideration the plate tectonic premises which defined this Carpathian section. The suggested classification distinguishes in the Banat area two subprovinces, which are:

1. The »Altkristallin« Banato-Carpathian province (Danubian Autochthonous a crystalline Getic Basement and Supragetic crystalline Basement) which consists of Proterozoic-Paleozoic crustal series, reactivated by the Laramidian subduction. These units contain a large number of Proterozoic and Paleozoic metamorphosed geosynclinal iron, manganese, pegmatite, gold, chromite, asbestos, and barite deposits as well as cyanite-sillimanite schists. The metallogeny of the Banatian crystalline complex represents an old crustal metallogeny.
2. The Laramidian province of the Banatites contains the classical copper, iron, lead-zinc tactite ore deposits, well known for centuries, and the recently discovered »porphyry copper« deposits. The »seismotectonomagmatic« lineaments of the province of the Banatites (Westbanatian and Eastbanatian Lineamems) are tectonically conlrolled by the marginal fault zones and the fractured proterozoic crystalline scales, as a result of the Laramidian subduction.

While the Carpathian crystalline complex represents an old crustal type of metallogeny, the Banatitic province is characterized by a typical Alpine metallogeny, including »porphyry coppers« forming part of the Tethyan panglobal copper-molybdenum belt.     

Ignimbritic cauldrons,alkali granites,and mineral deposits in fault-block mountains

The term fault-block mountains refers to an orogen, formed in an ensialic back arc by extension. The voluminous magmatism due to underplating of hot oceanic lithosphere, extrem thinning of the continental lithosphere and partial melting as well as mantle diapirs will be examplified by three ore provinces:

1. Southwestern North America (Middle Tertiary peralkaline ignimbrites and resurgent cauldrons)
2. Central Iran (Infracambrian ignimbrites and riebeckitegranite)
3. Arabian Shield (Infracambrian alkaligranites and rhyolites, 625-570 m.y.).

An overview of mineral deposits related to resurgent cauldrons will be given, encompassing disseminated deposits (Cu, Mo, Sn), skarns, massive magnetite ores, beryl pegmatites, sedimentary deposits (Pb-Zn; Hg, U, Li; Mn, borates, zeolites), mineralized vents (Au, U, apatite), vein type deposits (Au, Ag, Te, fluorite, U) and hydrothermal replacements (alunite). The value of several deposits exceeds 10 billion German Marks at current prices. The exploration concept based on resurgent cauldrons may also be applied successfully in other provinces.     

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.     

Aperçu sur les amas sulfurés massifs des hercynides Marocaines

Massive sulfide deposits located on Hercynian islets of northwestern Morocco exhibit four main characteristics:

They are strata-bound massive pyrrhotite deposits mined for sulfur and/or base metals occasionally occurring as sulfides of workable grade.

Volcanic rocks with which these massive sulfide orebodies are associated are scarce, although always present as acid flows of submarine emissions of either rhyolitic or more often quartz-keratophyric nature. Later on, basic plutonics intruded the pelitic country rocks.

Stockworks underlying the massive sulfide orebodies are common, but not systematic. When present, they occur in siltite ± phyllite ± carbonate rocks at the wall of massive sulfide lenses. They consist of fissural disseminations transformed by epimetamorphic recrystallization and by one schistosity generally concordant with s₀.

Associated alterites and exhalites belong to three types, i.e., sericitite (or biotite-rich rock), chloritite, and/or chert (jasper).

Generally well located in a back-arc basin environment characterized by a two-phase geological history, i.e., “extension and volcanism, compression and metamorphism”, these volcano-sedimentary deposits exhibit distal features with regard to the volcanism coeval with their sedimentation. They are mostly linked with strongly reducing environmental properties entailing pyrrhotite and/or magnetite syngenetic deposition, whatever the iron activity.     

Silikatische Kupferlagerstätten in Nordchile

The formation of isolated silicateous copper deposits is controlled by two main conditions:

1. oversaturation of groundwaters in silica
2. lateral inflow of copper bearing and slightly acid solutions originating from the oxidation of primary sulfide deposits.

The basic copper silicate chrysocolla is formed by chemisorption of copper ions by disilicic acid with a net-like structure. Under favourable conditions copper silicate deposits are formed which contain up to several million tons of copper as for example the La Exotica deposit in Northern Chile. The copper values of these deposits sometimes exceed those of the primary sulfide deposits. Thus, the oxidation of sulfide deposits, the migration of copper bearing solutions and the chemisorption of copper ions by the disilicic acid can result in workable new copper concentrations originating from sulfide protores. High concentrations of silica in groundwaters and thus the chemisorption of copper ions by the disilicic acid as an ore forming process is restricted to arid or semiarid regions. Therefore it is proposed to call such deposits arid silicateous infiltration deposits. Infiltration deposits are related to weathering processes. “They comprise products of weathering by which valuable substances were leached from the host rocks, migrated in groundwaters and were redeposited in other neighbouring rocks” (Smirnov, 1970, p. 324).     

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.

     

The “South-Italian City” — a cultural-genetic type of city

The “South-Italian city” is characterized at four different levels as an independent cultural-genetic city-type:

1. The characteristics arrangement of the functional areas and the residential areas of different social groups is represented in a model.
2. From the model, developments and changes in the arrangement of the functional areas can be identified which clearly deviate from those which are derived from the universal city model.
3. Some of the structural individuality can be directly explained by the peculiar features of the respective social and economic history.
4. Some of the special features must, however, be traced back to a wider historico-cultural background. Through this run processes which flow through the universal city development in similar forms, to the deviating structure of the “South-Italian city”.

     

Granites and migmatites of the Damara belt,South West Africa. Petrography and melting experiments

In the central area of the early paleozoic Damara belt migmatites and some types of granites (sensu lato) crop out. Conventional petrographic data were collected and melting experiments were carried out with 63 samples of such rocks. Based on these data, migmatite genesis can be classified as follows:

1. Formation by partial melting and separation of more liquid and more crystalline fractions, the melting behaviour of these fractions has to be principally similar then.
2. Formation by injection of “geologically liquid” crystal-melt mixes into rocks of (incidentally) similar or (more frequently) dissimilar melting behaviour.
3. Formation by partial melting of metasediments of originally different composition. The method is applied and demonstrated for outcrops with complicated interrelations and it is shown that temperature estimates are possible thereby (670° to 710° at 4–5 kb H₂O pressure in the central Damara belt).

     

Ore mineralization related to geological evolution of the Karkonosze–Izera Massif (the Sudetes,Poland) — Towards a model

The Karkonosze–Izera Massif is a large tectonic unit located in the northern periphery of the Bohemian Massif. It includes the Variscan Karkonosze Granite (about 328–304 Ma) surrounded by the following four older units:

• -Izera–Kowary (the Early Paleozoic continental crust of the Saxothuringian Basin),
• -Ještĕd (the Middle Devonian to Lower Viséan sedimentary succession deposited on the NE passive margin of the Saxothuringian Terrane), out of the present study area,
• -Southern Karkonosze (metamorphosed sediments and volcanics filling the Saxothuringian Basin), out of the present study area,
• -Leszczyniec (Early Ordovician, obducted fragment of Saxothuringian Basin sea floor).

The authors present a genetic model of ore mineralization in the Karkonosze–Izera Massif, in which ore deposits and ore minerals occurrences are related to the successive episodes of the geological history of the Karkonosze–Izera Massif:

• -formation of the Saxothuringian Basin and its passive continental margin (about 500–490 Ma)
• -Variscan thermal events:
  • -regional metamorphism (360–340 Ma)
  • -Karkonosze Granite intrusion (328–304 Ma)
• -Late Cretaceous and Neogene-to-Recent hypergenic processes.

The oldest ore deposits and ore minerals occurrences of the Karkonosze–Izera Massif are represented by pyrite and magnetite deposits hosted in the Leszczyniec Unit as well as by magnetite deposit and, presumably, by a small part of tin mineralization hosted in the Izera–Kowary Unit. All these deposits and occurrences were subjected to the pre-Variscan regional metamorphism.Most of the Karkonosze–Izera Massif ore deposits and occurrences are related to the Karkonosze Granite intrusion. This group includes a spatially diversified assemblage of small ore deposits and ore mineral occurrences of: Fe, Cu, Sn, As, U, Co, Au, Ag, Pb, Ni, Bi, Zn, Sb, Se, S, Th, REE, Mo, W and Hg located within the granite and in granite-related pegmatites, in the close contact aureole of the granite and within the metamorphic envelope, at various distances from the granite. Assuming world standards, all these deposits are now uneconomic. Various age determinations indicated that ore formation connected with the Karkonosze Granite might have taken place mostly between about 326 and 270 Ma.The last ore-forming episode in the Karkonosze–Izera Massif is related to hypergenic processes, particularly important in the northern part of the massif, in the Izera–Kowary Unit where some uranium deposits and occurrences resulted from the infiltration of ore solutions that originated from the weathering of pre-existing accumulations of uranium minerals. A separate problem is the presence of oxidation zones of ore deposits and occurrences, both the fossil and the recent.A full list of ore minerals identified in described deposits and occurrences of the Karkonosze–Izera Massif together with relevant, key references is presented in the form of an appendix.     

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%.

     

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.

     

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.

     

Geochemical model for the genesis of Gongchangling rich magnetite deposit in China

Based upon geological and geochemical data on the genesis of Gongchangling rich magnetite deposit, it is suggested that the deposit is of multi-genesis, and a three-stage geochemical model for the genesis of the deposit is proposed:

1. Sedimentary stage: the deposition of BIF (magnetite-quartzite) was accompanied by high-grade magnetite (hematite)-siderite ores which are intercalated with magnetite-quartzites as lenses or stratoid shoots.
2. Metamorphic stage: in response to metamorphism, siderite, was decomposed into magnetite and graphite with decreasing f_{O 2} and increasingP _{CO 2}. In the marginal parts of magnetite-siderite ores or within the thin-layered interbeds where f_{O 2} was high relative toP _{CO 2} were formed graphite-free rich magnetite ores.
3. Hydrothermal stage: as a result of later hydrothermal process diffusive metasomatism between the rich ores and the host rocks and silica leaching took place, thus giving rise to the rich magnetite ore of metasomatic type and altered rocks.

     

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.     

The Bushveld granites around Rooiberg,Transvaal, South Africa

The detailed investigation of the Bushveld granites, around the Rooiberg area, has revealed the existence, in the field, of at least three main types:

1. Granophyric rocks, which form a belt (transition-zone) between the country rocks (sediments and felsite) and the Main granite.
2. Main granite, which is the most common type of granite.
3. Younger granites, which are responsible for the tin mineralization.

All evidence points to a metasomatic origin for the granophyric rocks. For the Main granite, a probable anatectic origin is proposed, which is borne out by the presence of ghost-stratigraphy patterns, detected by trend surface analysis. The younger granites are undoubtely magmatic. On account of parallelism between the structural lines of the granitic rocks and the country rocks, an hypothesis based on deformation contemporaneous with the emplacement of the granites is advanced to explain the structure of the Rooiberg Area. In view of this hypothesis, the “Rooiberg roof-pendant” is considered to be probably a portion of the roof in its normale position.     

Forest condition and forest damages — contribution of remote sensing to different inventory approaches

The development of inventory activities in the field of forest damage assessment and monitoring during the last decade in Germany and the present state are recorded as far as remote sensing has been involved. Any forest inventory is influenced by external factors, and the resulting difficulties for an introduction of new technologies are described. The following tasks and/or methods are discussed:

-global approaches to deforestation monitoring

-working experience from local and regional case studies

-vegetation and vegetation-damage monitoring in ”urban forestry”

-sampling approaches for large areas

-the contribution of spectral signatures and satellite remote sensing to damage assessment

     

Über die Vergleichbarkeit von Lösungsformen auf Chlorid-, Sulfat- und Karbonatgestein — Überlegungen zu Fragen der Nomenklatur und Methodik der Karstmorphologie

The study deals with the comparison of corrosion forms in differently soluble rocks from different climatic regions, namely forms of the naked karst (lapies), depressions, and corrosive plains. The far-reaching morphographic conformity of corresponding forms permits some general conclusions:

1. The forms in question have the same genesis, there is no casual convergence of forms. It would be convenient to term them as forms of the salt-, gypsum-, and carbonate karst. There is no justification for a fundamental distinction between the “karstification” of limestone and the “leaching” of gypsum and salt.
2. The different liability to karstification (Karstgunst) of rocks can be compensated by a different liability to karstification due to climatic factors.
3. Similarly the other factors of karstification vary gradually; they add up or compensate each other. A classification of climatic-morphological karst provinces seems to be possible only by means of analysis and balance of the single factors and their effects.