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| Wegen, G. van der. |
| The present study deals with polyphase deformed and metamorphosed basic rocks from the Blastomylonitic Graben. The Blastomylonitic Graben is one of a number of meso- to catazonal complexes of probably Precambrian age in north-western Spain and northern Portugal. The results of the present study are obtained by application of the following methods: optical-mineralogical research, electronprobe microanalysis, X-ray powder diffraction and chemical whole-rock analysis. It is stated that the metabasites are originally of one, mainly bi-mineralic, rock type, altered by polymetamorphism. The successive phases of metamorphosis and deformation are differently developed locally and belong to two orogenies. The protolith was a rock, in which granoblastic... |
| Tipo: Article / Letter to the editor |
Palavras-chave: 38.30. |
| Ano: 1978 |
URL: http://www.repository.naturalis.nl/record/317533 |
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| Wegen, G. van der. |
| Low-grade metamorphics of West Irian occur to the east of Geelvink Bay associated with two narrow belts of basic and ultrabasic igneous rocks which represent ophiolitic suites of an eugeosynclinical development beginning in Early Mesozoic time. In both of these belts there are indications of regional metamorphism under high pressure and low temperature conditions. Within the miogeosynclinal, Australian-sided part of the Papuan Geosyncline, on the other hand, metamorphic rocks seem to be associated with intrusives of medium to acidic composition. |
| Tipo: Article / Letter to the editor |
Palavras-chave: 38.27. |
| Ano: 1971 |
URL: http://www.repository.naturalis.nl/record/317506 |
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| Wegen, G. van der. |
| Au S-W de Tinerhir, dans le Maroc occidental, on trouve des verres volcaniques pris dans des dépôts de tufs. Quelques échantillons de ces verres contiennent du cuivre natif sous forme finement répartie. Les verres sont dus à une activité volcanique d’âge pliocène. Ils sont accompagnés par des laves dont la composition varie entre celle d’une phonolite et celle d’une ankaratrite. Il est probable que le cuivre natif se soit formé lors d’une éruption, laquelle aurait entrainé un fragment de la roche encaissante riche en sulfures de Cu. Sous l’action des gaz ascendants, ces sulfures auraient été réduits en libérant ainsi le Cu-natif. |
| Tipo: Article / Letter to the editor |
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| Ano: 1955 |
URL: http://www.repository.naturalis.nl/record/505949 |
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