Porphyry copper mineralization in panama

Recently discovered porphyry copper mineralization at Petaquilla in Panama covers an area of 8–10 sq.km (about 4 sq.km possibly economic). Some 20 ore minerals with chalcopyrite prevailing constitute the mineral association. The mineralization is related to the late Tertiary intermediate intrusives. Geochemical surveys played an important role in the determination of ore bearing areas. The possible economic importance of these deposits is being investigated.

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Zusammenfassung Die vor kurzem entdeckte Porphyrkupfer-Vererzung bei Petaquilla in Panama erstreckt sich über ein Gebiet von 8–10 qkm (davon enthalten etwa 4 qkm möglicherweise abbauwürdige Erze). Ungefähr 20 Erzmineralien mit Kupferkies als dominierender Komponente bilden die Mineralparagenese. Die Mineralisation ist an spät-tertiäre intermediäre Intrusionen gebunden. Die geochemische Exploration spielte eine wichtige Rolle bei der Bestimmung der erzführenden Zonen. Da die Erzlagerstätten vermutlich bauwürdige Zonen enthalten, rechtfertigt sich die Fortsetzung der Explorationsarbeiten.

     

Geology of the San Isidro iron ore deposit,Venezuela

The iron ore deposits of Cuadrilatero Ferrifero de San Isidro represent the largest iron ore reserves in Venezuela. The district is a part of the iron metallogenic province of northern Guayana, one of the richest iron-bearing regions of the world. All presently known iron ore deposits of Venezuela are situated within this province: Cerro Bolivar, Altamira, Rondon, San Isidro, María Luisa, El Pao and others. Their total ore reserves amount to 2,000 million tons (disregarding the unenriched or slightly enriched iron-formation). The Imataca belt to which the iron ore deposits are confined consists of metamorphosed sedimentary and igneous rocks of Early Precambrian age, the oldest rocks presently known in South America. This belt extends some 450 km from the Orinoco delta southwesterly to the Cauro River. Iron ore is formed from banded iron-formation, a member of the Imataca complex, by removal of silica. The process of supergene enrichment is controlled to a certain degree by structural elements. There are five ore bodies in the San Isidro district, extremely varied in shape and size. Single bodies extend up to 3–4 km in length, approximately parallel to the regional structure pattern, and a few hundred meters in width. The morphology of the bottom of the ore bodies is rather irregular, particularly in transversal sections. Contacts between ore and the unaltered iron-formation beneath are gradational. Maximum vertical section through ore is 260 m; the average is 60 m approximately. The stratigraphic thickness of iron formation has been magnified by structural deformations. The primary stratigraphic thickness is estimated to be some 50–150 m. The iron ore is classified into two main types: a) hard, crustal ore, b) soft, friable ore. Hematite grains which remained after the leaching of silica, and goethite (as cement) are the two main constituents of crustal ore. Hematite and magnetite and a minor amount of quartz are almost the only constituents of friable ore. The crustal ore forms a 15–60 m thick mantle covering friable ore. The overall volume ratio between the friable and the crustal ore is about 2:1. However, it varies in different zones. The mean composition of iron ore on the basis of 10,800 chemical analyses is 64.41% Fe, 2.62% SiO₂, 0.6% Al₂O₃. The ore contains a minor amount of Mn, P, Ti (no S, As, Ba). The ore reserves amount to 750 million tons; in addition, 180–300 million tons of possible ore reserves are estimated.

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Zusammenfassung Die Eisenerzlagerstätten der Cuadrilatero Ferrifero de San Isidro beinhalten die größten Eisenerzreserven in Venezuela. Der Erzbezirk ist ein Teil der reichsten Eisenerzregionen der Welt. Alle bekannten Eisenerzvorkommen Venezuelas befinden sich in dieser Provinz (Cerro Bolivar, Altamira, Rondon, San Isidro, Maria Luisa, El Pao und andere). Die Gesamtvorräte werden auf etwa zwei Milliarden Tonnen geschätzt (ohne die nichtangereicherten oder nur wenig angereicherten Eisenquarzite). Die Imataca-Zone, an die die Eisenerzvorkommen angrenzen, besteht aus metamorphosierten sedimentären und magmatischen Gesteine des Archaikums, die ältesten bisher in Südamerika bekannten Gesteine. Die Imataca-Zone erstreckt sich ungefähr 450 km vom Delta des Orinoco in südwestlicher Richtung bis Rio Cauro. Die Eisenerze entstanden aus feingeschichteten (gebänderten) Eisenquarziten (Itabirite). Die Prozesse der deszendenten Anreicherung werden teilweise durch strukturelle Elemente bedingt. Fünf Erzkörper des San Isidro-Bezirks sind bekannt. Die Lagerstätten sind 3 bis 4 km lang und einige Hunderte Meter breit. Sie sind den regionalen Strukturen vorwiegend parallel gelagert. Die Morphologie der Erzkörperunterlage ist ziemlich unregelmäßig, besonders senkrecht zum Streichen. Der Kontakt zwischen dem Erz und den unterliegenden unveränderten Eisenquarziten ist stufenförmig. Das Erz ist durchschnittlich etwa 60 m mächtig, mit maximalen vertikalen Mächtigkeiten von 260 m. Die primäre stratigraphische Mächtigkeit des Eisenquarzites wurde durch strukturelle Deformationen vergrößert. Man kann die primäre Mächtigkeit auf 50–150 m schätzen. Das Eisenerz wird in zwei Typen klassifiziert: a) hartes Krustenerz, b) weiches, bröckeliges Erz. Die Hämatitkörner, die nach der Entfernung der Kieselsäure übrig blieben nebst Goethit (als Zement), sind die zwei wichtigsten Komponenten des Krustenerzes. Das weiche Erz enthält Hämatit, Magnetit und etwas Quarz. Das Krustenerz bildet eine 15–60 m mächtige Decke über dem bröckeligen, weichen Erz. Das Gesamtvolumenverhältnis zwischen dem weichen und harten Erz ist ungefähr 2:1. In anderen Zonen ist es jedoch unterschiedlich. Die durchschnittliche Zusammensetzung des Eisenerzes ist: Fe 64,41%, SiO₂ 2,62%, Al₂O₃ 0,6%; das Erz enthält auch etwas Mn, P, Ti (kein S, As, Ba). Die Eisenerzvorräte wurden auf 750 Millionen Tonnen berechnet, wozu wahrscheinlich weitere 180–300 Millionen Tonnen kommen.

     

Zur Kenntnis der Kalkinkrustation und Kalkkorrosion im Seelitoral

Ohne Zusammenfassung     

The influence of raw domestic sewage on density and distribution of meiofauna

The influence of raw domestic sewage on density and distribution of meiofauna in the sea bottom sediments in the Northern Adriatic Sea, in the area of Rovinj (Yugoslavia), was investigated, comparing meiofaunal density at the stations which are under direct influence of sewage and the stations which are far from the source of pollution. It is concluded that raw domestic sewage does not have a negative influence on the density and distribution of meiofauna, but Parker's index of pollution indicates that meiofauna at these stations were under stress.     

Croatia in the continental traffic network of Europe

Croatia is located on the southeastern edge of Central Europe (Ruppert 1995), between the navigable Danube River and the Adriatic Sea, so that participates not only in continental traffic, but in the maritime and river traffic of Europe as well.Although the transit position of Croatia is very favorable, transportation itself has unfortunately not been developed in accordance with these advantages. This is a result of the social-economic, especially political, development of the region in the course of its history. Unfortunately, politics also influences the selection of transit routes in this part of Europe today. With the break-up of socialist states, particularly the former Yugoslavia, new states have appeared which are seeking their place in the European traffic network. Because of the momentarily uncertain political circumstances, the construction of some transit routes in Croatia have not been foreseen in international developmental plans for continental transit, despite the fact that they would be logically expected given the advantages of their position.     

Automatic time recording in determination of astronomical latitude and longitude using an astrolabe and an HP41CX

The paper presents the automatic time recording of transits of the image of a star across the hairs in the visual field of a telescope and the automatic reception of radio time signals for the determination of astronomical latitude and longitude of a station using an astrolabe. The automatization was achieved by an electronic calculator Hewlett Packard HP41CX and an especially constructed relay. The method proved very practical in the course of making the network of geoidal points more dense for the needs of geodesy.     

The two polymorphs of TlPbSbS3 and the structural relations of phases in the system TlSbS2-PbS

Summary The synthetic TlPbSbS₃ represents a rare example of a sulphosalt with statistical distribution of Tl, Pb and Sb in the structure. Within the TlSbS₂-PbS system, TlPbSbS₃ is the end member of the solid solution series with TlSbS₂, but no solubility with PbS is detected. The high temperature-TlPbSbS₃ is orthorhombic and inverts at about 620 K to the low-temperature phase. The low-temperature modification of TlPbSbS₃ was structurally investigated by X-ray powder diffraction and by the Rietveld analysis of the data. The structure is monoclinic, with a = 4.1707(4) Å, b = 4.2856(4) Å, c = 12.157(1) Å, = 105.49(1)°, space group P2₁/c. Like in the high-temperature form, there is a cation disorder over the equivalent positions in the structure. The interatomic distances of (Tl, Ph, Sb) to S are 2.71, 2.72, 2.88, 3.15, 3.29, 3.51 (Å). There is a close similarity between the TlPbSbS₃ polymorphs and the and forms of SnS, as regards the atomic coordinations and the general structure types and the same type of phase transformation is supposed for both cases. The small differences in the structure type and symmetry, between the low temperature forms of SnS and TlPbSbS₃, result probably from stronger metal-metal interactions in the latter. A substitution-derivative relation to SnS type is established owing to the strong structural effect of the lone electron pairs of Tl and Sb. The substitution of Ag for Tl and Bi for Sb in ABCS₃ type compounds diminishes this effect and PbS type structures are produced.

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Die zwei Polymorphen von TlPbSbS₃ und die Strukturellen Beziehungen von Phasen in System TlSbS₂-PbS

Zusammenfassung Die synthetische Phase TlPbSbS₃ ist ein seltenes Beispiel von einem Sulfosalz mit der statistischen Verteilung von TI, Pb und Sb in der Struktur. In der TlSbS2-PbS Phasensystem, ist TlPbSbS₃ das Endmitglied der Mischkristallreihe, die sich im Richtung TlSbS₂ ausstreckt. Weitere Ausdehnung der Mischkristallreihe in der Richtung SbS konnte nicht bewiesen werden. Die Hochtemperatur-TlPbSbS₃ ist rhombisch und wird beim 620 K in die Tieftemperatur Modifikation umgewandelt. Die Tieftemperaturphase ist mit der Röntgenpulverdiffraktion und Rietveld Methode strukturell untersucht worden. Die ist monoklin, mit den Gitterkonstanten: a = 4.1707(4) Å, b = 4.2856(4) Å, c = 12.157(1) Å, = 105.49(1)°, Raumgruppe P2₁/c. Die statistische Verteilung von Kationen ist auch hier vorhanden. Die zwischenatomare Abstande (Tl, Pb, Sb)-S sind: 2.71, 2.72, 2.88, 3.14, 3.28, 3.51 (Å). Es besteht eine enge Verwandschaft zwischen den polymorphen Modifikationen von TlPbSbS₃ und den und Polymorphen von SnS, was die atomare Koordinationen und den generellen Strukturtypus betrifft, wobei ein ähnlicher Mechanismus der Phasenumwandlung für die beiden Fälle vermutet werden könnte. Die Differenzen in der Struktur und Symmetrie zwischen der Tieftemperaturmodifikationen von SnS und TlPbSbS₃ sind wahrscheinlich durch die bedeutende Metall-Metall Wirkungen in der zweiten verursacht. Die Phase TlPbSbS₃ ist ein substitution-derivative von der SnS Struktur, was durch die starke lone-electron-pair Aktivität von Kationen zu erklären ist. Die Ersetzung von Tl durch Ag und Sb durch Bi vermindert diese Aktivität und die entstandenen Strukturen sind in dem Fall dem PbS-Typus verwandt.

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With 3 Figures     

Jankovićite,Tl5Sb9(As,Sb)4S22, a new TI-sulfosalt from Allchar,Macedonia

Summary A hitherto unknown TI-sulfosalt, containing antimony and arsenic, was discovered by ore microscopy (including quantitative reflectance measurements) and electron microprobe analysis in samples from the Allchar TI-Sb-As sulfide ore deposit (Macedonia). The chemical formula is TI₅Sb₉(As,Sb)₄S₂₂, X-ray single crystal and powder diffration data gave the lattice parameters _o = 7.393(4) Å, b₀ = 8.707(2) Å, c_o = 17.584(3) Å, = 103.81(1)°, = 91.79(1)°, = 109.50(1)°; space group , Z = 1. The new mineral and the new mineral naine jankoviéite have been approved by the IMA/CNMMN.

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Jankoviit, Tl₅Sb₉(As,Sb)₄S₂₂, ein neues TI-Sulfosalz aus Allehar, Macedonien

Zusammenfassung Ein bislang unbekanntes Thallium-Antimon-Arsen-Sulfosalz wurde mittels Erzmikroskopie (inklusive quantitativer Reflexionsmessungen) und Elektronenstrahl-Mikrosonde in Proben aus der TI-Sb-As-Sulfid-Lagerstätte Allchar in Macedonien entdeckt. Die chemische Formel lautet Tl₅Sb₉(As,Sb)₄S₂₂, aus Röntgen-Einkristallaufnahmen und Pulverdiffraktogrammen konnten folgende Gitterkonstanten bestimmt werden: a_o = 7.393(4) Å, b_o = 8.707(2) _Å, c_o = 17.584(3) Å, a = 103.81(1)°, = 91.79(1)°, = 109.50(1)°; Raumgruppe , Z = 1. Das neue Mineral, sowie der neue Mineralname Jankoviit wurden durch die IMA/CNMMN anerkannt.

     

Surfactant production by marine phytoplankton

Electrochemical methods based on adsorption of organic molecules at the mercury electrode-solution interface were used to investigate surfactant production by marine phytoplankton. Six species of marine phytoplankton, representing the classes of Bacillariophyceae, Haeptophyceae, Chlorophyceae and Cryptophyceae, were studied in batch cultures.Our experimental results showed that surfactants were produced in culture media by healthy exponential growing cells. The measured response was found to depend on the particular species and the age of the culture.Total surfactant content in culture media generally increased with cell density, while surfactants per cell showed an inverse relation to cell density. However, we found that in Cryptomonas culture medium, during the exponential growth, excretion of the insoluble surfactant material per cell was independent of cell concentration.In addition to culture experiments, surfactant activity at several northern Adriatic stations was measured during various stages of phytoplankton bloom. It was concluded that a significant part of surfactant activity in a seawater column is due to phytoplankton production.     

DNA damage and apoptosis in the mussel Mytilus galloprovincialis

The effects of known genotoxic substances (4-nitroquinoline-N-oxide, benzo[a]pyrene, teniposide, etoposide, cycloheximide, tributyltin) on human cells (FLC, HL-60) and on mussels were investigated. The correlations between formation of DNA strand breaks and DNA fragmentation characteristic for the process of apoptosis were estimated. Strand breaks induced by 4-nitroquinoline-N-oxide and benzo[a]pyrene did not correlate with DNA fragmentation detected in the process of apoptosis. Induction of internucleosomal DNA fragmentation in HL-60 cells was initiated by teniposide, etoposide and tributyltin, while in the gills of mussels this was detected only with tributyltin. Levels of DNA strand breaks in natural mussel populations, living at locations under the influence of urban and industrial wastes, do not mirror the apoptotic processes.