Skip to Main Content
Book Chapter

Modelling of structural and lithological controls on mobility of fluids and gold in orogenic belts, New Zealand

By
Phaedra Upton
Phaedra Upton
1
GNS Science, PO Box 30-368, Lower Hutt, 5040 New Zealand
2
Geology Department, University of Otago, PO Box 56, Dunedin 9054 New Zealand
Search for other works by this author on:
Dave Craw
Dave Craw
2
Geology Department, University of Otago, PO Box 56, Dunedin 9054 New Zealand
Search for other works by this author on:
Published:
January 01, 2014

Abstract

Numerical models have been run to evaluate the key parameters that affect fluid flow and gold mineralization at a range of scales, from the full thickness of the crust to the mineral grain scale. These models are constrained with real examples of orogenic gold in southern New Zealand. Large scale modelling shows that differences in crustal strength and thickness affect the locus, scale, and rate of crustal fluid flow and hence influence gold deposition. The most vigorous hydrothermal activity and gold mineralization occurs in narrow zones with maximum uplift close to a major crustal boundary. Relatively strong middle crust develops deformation-driven permeability and fluid flow in a broad diffuse zone. Deformation of randomly inhomogeneous rocks under mid-crustal conditions results in horizontal fabric and horizontal shear zones, and these can control fluid flow locally. The addition of graphite to flat shear zones causes an increase in deformation-induced permeability, and this can encourage further graphite deposition in a feedback effect. Fluid flow in these flat shears is very slow (mm/year) compared to fluid flow in fracture-controlled permeability at shallow crustal levels. Rock strength inhomogeneities in mid-crustal shear zones can result in localized decrease in differential stress, facilitating the switching of orientations of principal stress axes and the formation of steeply-dipping quartz veins.

You do not currently have access to this article.

Figures & Tables

Contents

Geological Society, London, Special Publications

Gold-Transporting Hydrothermal Fluids in the Earth’s Crust

P. S. Garofalo
P. S. Garofalo
University of Bologna, Italy
Search for other works by this author on:
J. R. Ridley
J. R. Ridley
Colorado State University, USA
Search for other works by this author on:
Geological Society of London
Volume
402
ISBN electronic:
9781862396784
Publication date:
January 01, 2014

GeoRef

References

Related

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal