Journal
JOURNAL OF STRUCTURAL GEOLOGY
Volume 29, Issue 8, Pages 1386-1399Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jsg.2007.02.016
Keywords
fracture systems; vein systems; fluid overpressure; sandstones; Tuscany
Categories
Ask authors/readers for more resources
Veins are the geologic record of fluids that filled fractures at depth in the crust. In southern Tuscany (Italy), well-exposed Oligocene-Early Miocene sandstones hosting vein systems provide insight into the role of pore fluid and the stress state at the time of vein formation. The stress ratio (Phi = (sigma(2) - sigma(3))/(sigma(1) - sigma(3))) and driving stress ratio (R' = (P-f - sigma(3))/(sigma(1) - sigma(3))) were determined by analysing the distribution, length and aperture of fractures and veins and the magnitude of fluid overpressure. The derived fluid over-pressure for the whole vein system ranges from 30 MPa to 64 MPa, with an average of 43 MPa; these values indicate that veins formed under supra-hydrostatic pressure conditions. Despite their spatial contiguity, two different vein arrays show very different stress and driving pressure ratios. One vein system is characterised by 0 = 0.62 and R' = 0.60, the other by Phi = 0.54 and R' = 0.78. The described vein systems are an example of a close spatial association of two non-hydraulically connected vein systems representing fluids focused through the upper crust. (C) 2007 Published by Elsevier Ltd.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available