Temat: platinum-group elements - Katalog OPAC zbiorów

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Tytuł:: Anomalie platynowców w historii Ziemi
PGE anomalies in Earths history
Autorzy:: Wieczorek, Anna
Brachaniec, Tomasz
Powiązania:: https://bibliotekanauki.pl/articles/1033071.pdf
Data publikacji:: 2016
Wydawca:: Polskie Towarzystwo Meteorytowe
Tematy:: PGE
anomaly
geology
impact
platinum-group elements
Opis:: The platinum-group elements comprise a very small percentage of elements in the earth’s crust. The primary sources of them are meteorite impacts and volcanism. The study of PGEs anomaly in sediment profiles as a possible indicator of impact began in 1980, when was suggested a link between high levels of iridium and the mass extinction event in Late Cretaceous.
Źródło:: Acta Societatis Metheoriticae Polonorum; 2016, 7; 177-181
2080-5497
Pojawia się w:: Acta Societatis Metheoriticae Polonorum
Dostawca treści:: Biblioteka Nauki

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Tytuł:: Podiform chromitites from the Variscan ophiolite serpentinites of Lower Silesia (SW Poland) : petrologic and tectonic setting implications
Autorzy:: Wojtulek, P. M.
Puziewicz, J.
Ntaflos, T.
Bukała, M.
Powiązania:: https://bibliotekanauki.pl/articles/2060165.pdf
Data publikacji:: 2016
Wydawca:: Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:: ophiolite
chromitite
platinum group elements
PGE
supra-subduction setting
Variscan orogeny
Opis:: The Gogołów-Jordanów Serpentinite Massif (GJSM) and the Braszowice-Brzeźnica Massif (BBM) are the largest serpentinite outcrops in the Fore-Sudetic Block (NE part of the Bohemian Massif, Central Europe). The GJSM is a peridotitic member of the Variscan Ślęża Ophiolite (SW Poland). Podiform bodies (veins and pockets) of chromitite are found on the Czernica Hill (GJSM) and on the Grochowiec Hill (BBM) within strongly serpentinized harzburgites which occur several hundred metres below Paleo-Moho. Chromitites consist of rounded chromite grains up to 3 cm across, and of chlorite filling the interstices. The veins are embedded in serpentine-olivine-chlorite aggregates. Relics of Mg-rich olivine (Fo95-96) occur in massive chromitite in the BBM. The bulk-rock total PGEs content is very low (42-166 ppm) and the PGE pattern is negatively sloped towards Pt and Pd and depleted relative to chondrite. The primary chromite I is aluminous (Cr# 0.50-0.52, Mg# 0.60-0.70). The highly aluminous and magnesian (Cr# 0.38, Mg# 0.80) chromite Ia occurs locally in the BBM. The secondary chromite II is enriched in Cr and impoverished in Al (Cr# 0.57-0.69), it replaces chromite I. Both chromite I and II contain small amounts of Ti (<0.14 wt% TiO2). Silicate inclusions in chromite are scarce. The composition and mode of occurrence of both the GJSM and the BBM chromitites are similar, thus they were formed probably under the same conditions. Textures of the chromitites suggest their magmatic origin. Their current geological position indicates their emplacement and crystallization in the uppermost mantle harzburgites occurring below the Moho Transition Zone (MTZ). The chromitites and hosting harzburgites were subjected to the greenschist-facies metamorphic overprint. The moderate Cr# and low PGEs contents suggest that the chromitites originated in the arc setting, thus their host ophiolite is of supra-subduction type.
Źródło:: Geological Quarterly; 2016, 60, 1; 56--66
1641-7291
Pojawia się w:: Geological Quarterly
Dostawca treści:: Biblioteka Nauki

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