A comparative petrologic study of Sarmatian pyroxene-andesites near Telkibánya-Pányok (Tokaj-Mts, NE-Hungary)
As a result of the author's investigations, it has been stated, that the acidic pyroxene-andesite of the belt between Szurokhegy in Kéked and Magostér in Telkibánya (both in NE-Hungary) belongs to the leucogabbroidic type of igneous rocks defined by NIGGLI. (The foliated rocks of the Hosszúkő i...
Elmentve itt :
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| Dokumentumtípus: | Cikk |
| Megjelent: |
University of Szeged, Department of Mineralogy, Geochemistry and Petrology
Szeged
1975
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| Sorozat: | Acta mineralogica-petrographica
22 No. 1 |
| Kulcsszavak: | Kőzettan, Ásványtan, Földtan |
| Tárgyszavak: | |
| Online Access: | http://acta.bibl.u-szeged.hu/24590 |
| Tartalmi kivonat: | As a result of the author's investigations, it has been stated, that the acidic pyroxene-andesite of the belt between Szurokhegy in Kéked and Magostér in Telkibánya (both in NE-Hungary) belongs to the leucogabbroidic type of igneous rocks defined by NIGGLI. (The foliated rocks of the Hosszúkő in Telkibánya characterized by parallel lamellae belong to this group, too.) This fact refers to the basic character of the original magma corroborated also by the presence of hypersthene and bronzite as well as that of diopside and endiopside from among the monoclinic pyroxenes. The latter minerals are missing in the foliated andesite of Hosszúkő. This can be explained by a relatively rapid ascendence of the rock as compared to that of the acidic pyroxene-andesite. In this case there was not time for a fractional crystallization. The path of the acidic pyroxene-andesite interrupted by "stopovers" (i.e. by magma-chambers) could be traced easily by minerals which crystallized from it. From the clinopyroxene lamellae of the hypersthene appearing first and containing 51—52mol% of MgSi03, Ca2 + and Fe 2+ ions have been removed in a temperature range of 800—1000 °C. This phenomenon — together with an intake of O H - ions — have resulted in uralitization consisting of structural realignment and starting along transversal clefts. (The clinohypersthene lamellae are lamellae parallel to the (100) plane of the orthopyroxene with higher Ca2 + and Fe 2+ content as compared to their environment.) Assuming that more significant Si addition from the surroundings necessary for pyroxene amphibole transformation is impossible, Mg2+ and Fe 2 + are released by this transformation process. The release of Mg2+ has lead to formation of MgSi03-rich orthopyroxene types (i.e. bronzite), while the released Fe2+ content which attained a higher oxydation-reduction potential in an OH "-rich environment, could not be fixed in the orthopyroxene, but have been separated as hematite. Thus the bronzite-formation is promoted by the amphibolization in a double way. In this environment characterized by relative low Fe 2 + content, diopside and endiopside are formed instead of augite. Lacking this quiet, fractional crystallization clinohypersthene and augite have formed in the foliated andesite. Under thicker cover and in presence of higher volatile concentration even the chloritization of the uralite has started (Hasdát-völgy), and the released Ca content has been fixed in apatite crystals. This phenomenon is the sign of a commencing propylitization, though in that case higher temperature (epidote) and H2S addition (pyrite) should also be reckoned with. |
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| Terjedelem/Fizikai jellemzők: | 97-112 |
| ISSN: | 0365-8066 |