Original paper
Tectonic brines and their effect on geological processes
Behr, H.-J.; Hein, F.; Schmidt-Mumm, A.
Neues Jahrbuch für Mineralogie - Abhandlungen Band 165 Heft 1 (1992), p. 101 - 102
13 references
published: Dec 3, 1992
DOI: 10.1127/njma/165/1992/101
ArtNo. ESP154016501010, Price: 29.00 €
Abstract
External zones, and in particular orogenic fronts, represent geodynamic situations with an exceptionally enhanced fluid activity ("tectonic brines") in which a variety of fluid producing and fluid mobilizing processes take place (Behr 1989). All fluid systems which have been expelled from the allochthonous complex through decollements, ramps, thrusts and faults are included in the term "tectonic brines". The most important fluid pulses are - connate pore waters and sedimentary brines in the foreland and the orogenic front, which have been expelled through thrust tectonic mobilization from non- to poorly metamorphosed complexes - metamorphic waters, which have been liberated by dehydration processes - magmatic waters, which have been released from high-grade internal zones and have passed through the thrust system - volcanic waters, which have been generated during volcanic activity along the orogenic front and - sedimentary brines ascending through the thrust system, which have been released from the overridden autochthon through increasing compaction and temperature gradients. Additionally, large volumes of CO2, CH4 and N2 are released from organic components during increasing metamorphism. Tectonic brines are therefore characterized by high gas contents. Within the external zone, tectonic brines are active during the thrust tectonic crustal stacking and may contribute to ore deposition along shear zones (Behr & Schmidt-Mumm 1987, Cox et al. 1987, Behr & Hein 1991, Hein & Behr 1991 b). Phenomena associated with the orogenic front are - Leaching of evaporites and resulting collapse breccias. Newly developed fluid pathways permit mineralization. - Fluid mixing and unmixing ( e.g. CO2) (Oliver 1986, Hein & Behr 1991 a). - Fluidization of evaporite collapse breccias, which infiltrate shear zones and thrust surfaces, and which could influence the tectonic style of the external zone (Behr & Schmidt-Mumm 1987). - Development of large scale silicification fronts and carbonate and sulphide mineralization (Duane & de Wit 1988, Romer 1990, Schmidt-Mumm 1989, Schmidt-Mumm & Behr 1987). The orogenic uplift of external zones results in large scale fluid migration in the platform sediments of the foreland, which may influence coalification, diagenesis, hydrocarbon generation and the formation of MVT mineralization (Bethke & Marshak 1990, Oliver 1990).
Keywords
Tectonic brines • external zones • metamorphism • fluid • coalification