Decision-support systems for groundwater protection: innovative tools for resource management

Governmental authorities are forced by law to make decisions within the framework of European, national and regional directives in the fields of spatial planning, groundwater and environmental protection. These tasks can be supported by a decision-support system, which integrates data from various sources and helps to make decision processes more effective and transparent. Basic work for such a decision support system has been done in a transnational and interdisciplinary project (Interreg II C: KATER), including metadata definition, metadata system, cartographic tools and GIS tools. The direct integration of these tools and information in the decision process will be implemented in the next few years (project KATER II).     

Luminescence from glacimarine sediment-trap samples at the Antarctic Peninsula

Radiocarbon (¹⁴C) dating yields variable and high reservoir and core-top ages for glacimarine sediments around Antarctica. To test the suitability of luminescence as an alternate dating method we investigated the effectiveness of clock zeroing (by daylight) within fine-silt-size siliciclastic sediments from year-long vertical-array sediment traps in Andvord Bay and Brialmont Cove at the Antarctic Peninsula. Both long-bleach and short-bleach multi-aliquot IR-PSL (infrared photon stimulated luminescence) and single-aliquot, post-IR blue-PSL dating tests were conducted. As well, dual-bandwidth-bleaching thermoluminescence (TL) tests were performed on samples from Brialmont Cove. These TL bleaching tests indicate that silt from the middle and bottom traps at this site has had little or no exposure to daylight, but that silt from the top trap has had some exposure. All 24 samples (representing different seasons and different trap depths) exhibit anomalously old apparent ages (12 ka–60 ka) across annual seasons and depths of deposition when either long-bleach multi-aliquot or late-background-subtraction single-aliquot PSL procedures were employed. Thus regional bottom silts would be unsuited for dating by these two luminescence dating approaches. However, a short-bleach multi-aliquot IR-PSL procedure yields the expected zero ages for several samples, a promising result that requires further exploration.     

Distribution of trace elements in the coastal sea sediments of Maslinica Bay, Croatia

Spatial distributions of trace elements in the coastal sea sediments and water of Maslinica Bay (Southern Adriatic), Croatia and possible changes in marine flora and foraminifera communities due to pollution were investigated. Macro, micro and trace elements’ distributions in five granulometric fractions were determined for each sediment sample. Bulk sediment samples were also subjected to leaching tests. Elemental concentrations in sediments, sediment extracts and seawater were measured by source excited energy dispersive X-ray fluorescence (EDXRF). Concentrations of the elements Cr, Cu, Zn, and Pb in bulk sediment samples taken in the Maslinica Bay were from 2.1 to over six times enriched when compared with the background level determined for coarse grained carbonate sediments. A low degree of trace elements leaching determined for bulk sediments pointed to strong bonding of trace elements to sediment mineral phases. The analyses of marine flora pointed to higher eutrophication, which disturbs the balance between communities and natural habitats.     

How fast does tufa grow? Very high-resolution measurement of the tufa growth rate on artificial substrates by the development of a contactless image-based modelling device

Accurate determination of the tufa growth rate (TGR) is required to answer the fundamental geomorphological question of tufa evolution. The TGR has been measured by various direct and indirect methods. One of the most popular direct methods uses modified micro-erosion meter (MEM), which has several drawbacks. Here, we present for the first time a coordinate measuring macro-photogrammetry device (CMD) for monitoring the TGR in a contactless manner. The CMD was applied on 28 limestone plates at 14 locations within the Skradinski buk area, Croatia, and measurements were performed in the laboratory. The TGR was derived from digital tufa high-resolution models (DTHRMs). The accuracy of the device was evaluated using state-of-the-art three-dimensional (3D) scanners and error calculation at checkpoints. Moreover, the precision was evaluated with the split test (n = 5). A total of 74 DTHRMs with a spatial resolution of 0.0236 mm were created. The TGR ranged from 0.327 to 19.302 mm a⁻¹, with an average of 5.771 mm a⁻¹. A higher TGR was observed on the limestone plates near mosses, located in fast and turbulent water rather than in stagnant water. We found that specific micro-environmental factors (e.g. proximity to moss) positively affected tufa growth. Erosion events were observed, as well as the presence of aquatic insect larvae (Simuliidae and Chironomidae), which positively affected tufa growth. The CMD is a precise and accurate device that does not suffer from the drawbacks of the MEM method and has many other advantages. It has a high capability of tufa erosion detection, enables the identification of macroinvertebrates, and multispectral or hyperspectral cameras can be mounted on the device for spectral reflectance analysis of the tufa surface. The CMD can be applied in any study requiring a sub-millimetre data quality and involving the comparison of consecutive 3D models and derivation of various parameters of smaller objects. © 2020 John Wiley & Sons, Ltd.     

Metallogenic provinces and epochs in southern Central America

The southern part of Central America is characterized by common geological features. The ophiolitic belt running alongside the Pacific is related to the late Mesozoic eugeosynclinal trough. No significant mineralization is known in this rock complex. Copper ore occurrences in the Azuero peninsula are associated with the late Cretaceous diorite pluton. During Tertiary time, radial tectonic deformation and basaltandesite-dacite volcanism took place. Gold-silver quartz veins and Cu-, Pb-, Zn- (Ag)-sulfidic ore formation associated with this magmatic and tectonic activity form the largest metallogenic provinces. Porphyry copper mineralization in northern Panama is confined to the late Tertiary intermediate hypabyssal intrusives. Laterite, and gold placers are the only exogenic deposits. The relative abundance of copper ores in southern Central America indicates a geochemical specialization of magma in copper and the possible continuation of the circum-Pacific copper belt across Central America.

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Zusammenfassung Der südliche Teil von Zentralamerika zeichnet sich durch regionale Merkmale der geologischen Beschaffenheit aus: Die ophiolitische Zone längs der Pazifikküste ist mit der spät-mesozoischen Eugeosynklinale verbunden. Keine bedeutende Mineralisation ist in diesem Komplex bekannt. Die Kupfererzvorkommen auf der Azuero-Halbinsel sind mit spät-kretazischen Dioritintrusionen verbunden. Während des Tertiärs entstanden radialtektonische Störungen und Basalt-Andesit-Dazit Vulkanismus. Die Gold-Silber Quarzgänge und die sulfidische Cu-Pb-Zn-(Ag-) Erzformation, die mit dieser magmatischen und tektonischen Aktivität verbunden ist, bildet die grössten metallogenetischen Provinzen. Die porphyrische Kupfermineralisation in Nord-Panama ist mit den spät-tertiären intermediären hypoabyssischen Intrusionen assoziiert. Laterit und Seifen sind die einzigen exogenen Lagerstätten. Die relative Häufigkeit der Kupferlagerstätten im südlichen Teil Zentralamerikas weisen auf eine mögliche geochemische Spezialisation der Magmen in Kupfer und Fortsetzung der zirkumpazifischen Kupferzone quer durch Zentralamerika hin.

     

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.