Case histories of some Transylvanian glauconies
Several Romanian glaucony-bearing units (Cretaceous, Eocene, Oligocene and Miocene) from the Transylvanian Depression and, for comparision, one Cretaceous outcrop from the post-tectonic cover of the Southern Carpathians were studied from mineralogical, lithological and sedimentological point of view...
Elmentve itt :
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| Dokumentumtípus: | Cikk |
| Megjelent: |
University of Szeged, Department of Mineralogy, Geochemistry and Petrology
Szeged
1996
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| Sorozat: | Acta mineralogica-petrographica
37 |
| Kulcsszavak: | Kőzettan, Ásványtan, Földtan |
| Tárgyszavak: | |
| Online Access: | http://acta.bibl.u-szeged.hu/24830 |
| Tartalmi kivonat: | Several Romanian glaucony-bearing units (Cretaceous, Eocene, Oligocene and Miocene) from the Transylvanian Depression and, for comparision, one Cretaceous outcrop from the post-tectonic cover of the Southern Carpathians were studied from mineralogical, lithological and sedimentological point of view. The study focused on the morphological (as noticed under binocular, polarizing microscope, SEM and TEM-replica method) and the X-ray powder diffraction characteristics of the glauconitic grains. The general lithological and sedimentological context, as well as data supplied by the mineralogical study of glauconies made possible a preliminary genetical characterization of the green grains (sensu AMOROSI 1993a). Both Eocene occurrences, Luna de Sus and Ortelec (e.g. samples GE 2, GE 3 resp. GE 5) contain the most evolved glauconies understudy: they consist of highly evolved, ordered glauconites (1M). They are considered authigenic, possibly perigenic glauconies. The Miocene samples (e.g. GM 2, GM 7) from Tihau display a mineralogical variability: GM 2 represents transition from the ordered to the moderately disordered species (lMd) and GM 7 shows the features of moderately disordered glauconite (lMd). Both samples reflect the evolved stage of glauconitization. They are assumed to be perigenic glauconies. The Cretaceous glauconies from Sebe$el are moderately disordered glauconites (lMd), with a maturity degree between slightly evolved to evolved glauconies (e.g. GC 28). The genetic type is either authigenic or perigenic. The other Cretaceous glauconies from Rajnov (e.g. GC 3) have a more opened and disordered structure: they contain extremely disordered glauconites (lMd) and represent the less evolved glauconies under study (slightly evolved stage). We assume a perigenic origin of these glauconies. The Oligocene sample (GO 1) from Var displays XRD features which characterize also the extremely disordered glauconites (lMd), but the green grains show an intermediate glauconitization stage, between slightly evolved and evolved. They are transported (detrital/perigenic) glauconies. |
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| Terjedelem/Fizikai jellemzők: | 5-33 |
| ISSN: | 0365-8066 |