--> ABSTRACT: Large-Scale Brine Migrations Related to the Geodynamic Evolution of the Eastern Alps (Austria, Germany), by Uwe Walter, Stefan Zeeh, Thilo Bechstadt; #91020 (1995).

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Large-Scale Brine Migrations Related to the Geodynamic Evolution of the Eastern Alps (Austria, Germany)

Uwe Walter, Stefan Zeeh, Thilo Bechstadt

Deep burial carbonate cements occurring within Permian to Tertiary sediments from different parts of the Eastern Alps have been investigated to reconstruct the pore fluid flow in space and time. Cathodoluminescence petrography, microthermometry, isotope and trace element analysis allow to distinguish two generations of saddle dolomites and three generations of blocky calcites. The stratigraphic range of each cement generation offers a fairly precise dating of precipitation.

The first generation of saddle dolomite, which is regionally associated with MVT-mineralizations, disappears in rocks younger than Norian. This implies a connection with the onset of Tethys rifting at the Triassic/Jurassic boundary within the Austroalpine realm. The brines may have derived from the northwestern hinterland (Vindelician-Bohemian Massif). Due to gravitation they might have travelled southward, rising up in the rifted area, which is characterized by a well established thermal anomaly.

During Jurassic and Early to Middle Cretaceous time late diagenetic cements apparently did not have precipitated. Progressive rifting and spreading (opening of the Penninic ocean) divided the Austroalpine domain into more or less isolated blocks and separated it from the increasingly flooded former recharge area so that far-reaching fluid migrations could obviously not take place.

Instead, all succeeding deep burial cements seem to have been formed in the relatively short time span between Latest Cretaceous and Neogene, probably controlled by uplift and metamorphism of the Central Eastern Alps. Gravity- and pressure-driven flow towards the southern and northern foreland might have produced the overall similar cement succession we observed.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995