Ore textures: problems and opportunities

Abstract

Over the past several decades, thinking about chemical processes in rocks had been dominated by experimental and theoretical treatments of mineral equilibrium, which is the state from which the time variable has been excluded. But, to an extent exceeding that of any of our sister sciences, we in geology are concerned with the behaviour of things as a function of time; thus equilibrium is but one of several interesting boundary conditions. Textures, (defined as the spatial relations within and among minerals and fluids, regardless of scale or origin) provide a means to sort out and identify successive states. In fact, it is the pattern of evolution of those states that enables us to deduce the processes. We may well draw the analogy with thermodynamics and kinetics, respectively: equilibrium textures and phase assemblages, via thermodynamic analysis ~ definition of conditions of equilibration, whereas kinetics, as displayed in disequilibrium textures --~ sequence of events and processes of mineralization.

Sulfur isotopic study of ore minerals and altered host rocks of Neogene-Quaternary overprinting hydrothermal systems in the Toyoha-Muine area, southwest Hokkaido, Japan

“…Dissolution of earlier minerals (hydrothermal leaching in Fig. 3f) and mineral replacement (Table 1) is common in the hydrothermal depositional history in response to the levels of saturation of ore fluids (e.g., Barnes, 1979;Barton, 1991;Craig and Vaughan, 1994). The uniform sulfur isotopic values of sulfides between temporally distinct mineralizations of the massive sulfide deposits are also evidence of remobilization of the pre-existing ore (Tornos and Arias, 1993;Wagner et al, 2004).…”

Mechanisms of fluid flow and fluid–rock interaction in fossil metamorphic hydrothermal systems inferred from vein–wallrock patterns, geometry and microstructure

“…We restrict ourselves here to those broad textural classes commonly used in the tectonic interpretation of veins and refrain from discussing the large variety of textures used for ore‐related veins (e.g. Barton 1991; Dong et al . 1995).…”

Orogenic Gold Mineralization in the Qolqoleh Deposit, Northwestern Iran

“…The spatial relationships, at the microscopic scale, between mylonite fabric and disseminated sulfide demonstrate a microtextural evidence to support a syn‐ and late‐tectonic emplacement of the sulfides and, by association, the gold (Barton, 1991). In texturally well‐documented cases of some gold mineralization being induced by ductile deformation, there is abundant evidence for the ore minerals being affected by crystal–plastic deformation (e.g.…”