Structurally controlled fluid flow: High-grade silver ore-shoots at Martha epithermal mine, Deseado Massif, Argentina

• Published in: Journal of structural geology 2011-05, Vol.33 (5), p.985-999
• Main Authors: Páez, G.N., Ruiz, R., Guido, D.M., Jovic, S.M., Schalamuk, I.B.
• Format: Article
• Language: English
• Subjects: Concentrates (ores); Deposits; Epithermal veins; Fluid dynamics; Fluid flow; Fluids; Hydrothermal flow; Jurassic; Mines; Normal faults; Ore-shoots; Patagonia; Silver; Veins
• ISSN: 0191-8141; 1873-1201
• DOI: 10.1016/j.jsg.2011.02.007

The role of structurally controlled fluid flow during epithermal ore-shoot formation is addressed through a structural study of the high grade Martha Mine epithermal deposit (Deseado Massif, Patagonia, Argentina). Martha is a silver-rich deposit, characterised by a complex mineralogy dominated by Ag–As–Sb sulphosalts and Cu–Pb–Zn sulphides. Mineralised veins can be subdivided into two groups: master structures that trend approximately NW–SE, and second-order structures that trend E–W and coalesce into the master structures. The Martha vein system is interpreted as a hard-linked step-over zone between two NW–SE trending fault segments. Furthermore, the geometry of ore-shoots at Martha Mine suggests a first-order structural control on their location and orientation. At the deposit scale, mineralisation is concentrated in the step-over zone. Mineralisation, and presumably hydrothermal fluid flow, was concentrated at the intersection between the two main vein groups. Finally, at the scale of single veins, jogs and subordinate step-overs were important channels for hydrothermal fluids and the formation of high-grade ore-shoots. ► Structure of high-grade silver ore-shoots at Martha Mine is described. ► The geometry of ore-shoots at Martha Mine suggests a first-order structural control on their location and orientation.► Controls on permeability and fluid flow during epithermal vein formation are analysed. ► Mineralisation, and presumably hydrothermal fluid flow, was concentrated on a step-over zone developed between two NW trending structures. ► Hydrothermal ascending fluids took advantage of vein intersections and were also channelized along preferred opening areas within individual veins.