A Clockwise P-T Path from the Variscan Basement of the Tisza Unit, Pannonian Basin, Hungary

Geologia Croatica

Peter Arkai¹  Geza Nagy¹  Peter Horvath¹ 

[1] Laboratory for Geochemical Research, Hungarian Academy of Sciences;

关键词: Gneiss;    Amphibolite;    Geothermobarometry;    Variscan regional metamorphism;    Tisza Unit;    Pannonian Basin;    Hungary;   

DOI  :  10.4154/GC.1999.09

来源: DOAJ

【 摘 要 】

The polymetamorphic basement of the Tisza Unit forms a detached

fragment of the Variscan European foreland of the Neotethyan

realm. A clockwise evolution path of a gneiss-amphibolite complex

of the Tisza Unit was reconstructed, investigating the polymetamorphic

rocks of the borehole Baksa-2, SE Transdanubia, Hungary.

The results obtained by microstructural and mineral paragenetic

observations, mineral chemical analyses, and thermobarometric calculations define a P-T loop which suggests a complex Variscan

polyphase model rather than a pre-Variscan - Variscan polycyclic

one. The early part of the prograde path with kyanite is characterized

by T-P conditions of 480±50¡C and 470±70 MPa, respectively. The

metamorphism reached its peak at 660±25 ¡C and 750±50 MPa,

when both kyanite and staurolite were stable. This metamorphic climax

was followed by a nearly isothermal decompression to 440±2 0

MPa at 650±40¡C. This event is marked by the presence of sillimanite

and a second generation of garnet, and is closely related to the collisional Variscan granitoid magmatism observed in considerable parts

of the Tisza Unit. In amphibolites intercalated with gneisses, only this

last event was preserved, providing T-P estimates of ca. 650-690¡C /

400-500 MPa. The present paper provides the first demonstration of a

continuous, clockwise P-T path from the metamorphic basement of

the Hungarian part of the Tisza Unit.

【 授权许可】

Unknown