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| Zwaan, P.C.; Arps, C.E.S.. |
| Three cut sphenes, originating from the Tissamaharama area in Sri Lanka, are described. Their properties are compared with those of gem quality sphenes from Capelinha, Brazil. There is hardly any difference between the chemical data of the major elements and physical properties of the specimens of these two sources. Even the inclusions are very similar. It is the first time that fine gem quality sphene has been reported from Sri Lanka. |
| Tipo: Article / Letter to the editor |
Palavras-chave: 38.30. |
| Ano: 1980 |
URL: http://www.repository.naturalis.nl/record/317475 |
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| Arps, C.E.S.; Calsteren, P.W.C. van; Hilgen, J.D.; Kuijper, R.P.; Tex, E. den. |
| In Galicia occur several polymetamorphic complexes that contain mafic and ultramafic rocks. Mafic volcanics and gabbros are situated in or near the complexes. An episode of metamorphism and granitization encompassed the generation of the volcanics and gabbros. Gravity surveys revealed the existence of deep roots below polymetamorphic complexes. Geochronological investigations yielded Palaeozoic ages from about 500 Ma for the generation of ultramafic rocks and calcalkaline granite series, till ages of around 300 Ma for postkinematic alkaline and calcalkaline granites. A model involving mantle-plume diapirism and rejuvenation of the lower crust is proposed for the Early Palaeozoic evolution of the continental lithosphere of Galicia. An excursion route is... |
| Tipo: Article / Letter to the editor |
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| Ano: 1978 |
URL: http://www.repository.naturalis.nl/record/505595 |
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| Arps, C.E.S.. |
| Within the strongly migmatized axial zone of the Hesperian massif in western Galicia a graben-like structure has been distinguished, characterized essentially by the presence of non-migmatic rocks that comprise orthogneisses with blastomylonitic textures, leucocratic gneisses, plagioclase-blastbearing paragneisses, pelitic schists, and numerous amphibolitic layers and lenses. In the southern and central part of the graben and at the borders in the north the majority of the amphibolites are metamorphosed mafic dike swarms that intruded in the Early Palaeozoic after the emplacement of biotite granites but before the intrusion of subalkaline and peralkaline granites. Few amphibolites are of sedimentary origin. The other amphibolitic rocks in the north are of... |
| Tipo: Article / Letter to the editor |
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| Ano: 1981 |
URL: http://www.repository.naturalis.nl/record/505884 |
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| Arps, C.E.S.. |
| The present area covers a part of the axial zone of the Hesperian Massif. Rocks of metamorphic and intrusive origin occur in three structural units: the central zone (which in fact forms part of what is called the “blastomylonitic graben”), the migmatic complex and the rocks in the S and SW. During the Hercynian orogeny these units were placed in juxtaposition. With respect to their age and composition the rocks can be subdivided into pre-Hercynian metasediments, metabasic rocks and orthogneisses, and Hercynian migmatites, palingenic granites and intrusive granodiorites, granites, pegmatites, aplites, quartz veins, granite porphyries, lamprophyres and olivine dolerites. Based on penological evidence, the geological history can be reconstructed as follows:... |
| Tipo: Article / Letter to the editor |
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| Ano: 1970 |
URL: http://www.repository.naturalis.nl/record/505761 |
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| Arps, C.E.S.; Kluyver, H.M.. |
| A study of the beaches on the NW shores of the Ría de Arosa was made with respect to shape and structure of the beaches, grain-size distributions, heavy mineral associations, and relations of the heavy minerals to the bedrock of the hinterland. Most of these numerous small beaches are situated in inlets determined by the occurrence of relatively weak bedrock (mostly schists). Grain-size generally fall in fractions > 50 µ, and some beaches even contain important amounts > 2000 µ. Many grain-size distributions are bimodal owing to the mixing of different beach layers by wave action or, in a few cases, to mixing with fluvial sands. The heavy mineral compositions of the fluvial and beach deposits approximately reflect the mineral compositions of the... |
| Tipo: Article / Letter to the editor |
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| Ano: 1966 |
URL: http://www.repository.naturalis.nl/record/505969 |
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| Germeraad, J.H.; Freudenthal, M.; Boogaard, M. van den; Arps, C.E.S.. |
| The new computer-based registration system, a project of the National Museum of Geology and Mineralogy in the Netherlands, will considerably increase the accessibility of the Museum collection. This greater access is realized by computerisation of the data in great detail, so that an almost unlimited number of operations to select and sort the data is possible. A flexible design of annotating information, mainly in plain words, saves considerable time. The fast mechanical data processing permits the efficient preparation of catalogues which contain selected information about the geological collection; as an additional benefit labels may be produced at low costs. The RGM system disposes of the burden of classical registration books and card-indexes, without... |
| Tipo: Article / Letter to the editor |
Palavras-chave: 38.03. |
| Ano: 1972 |
URL: http://www.repository.naturalis.nl/record/317543 |
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