Grains scaling

Micro-scale characterization (p-XRF, p-XANES, p-XRD, petrography, and EPMA) was able to confirm As forms identified by bulk XRD and in all cases identify additional As forms. Grain-scale mineralogical analysis unambiguously identified a minimum of two and typically four or more As-bearing phases in each tailings sample (Fig. 2, Table 2). 

Walker, S.R., Jamieson, H.E., Lanzirotti, A., Andrade, C.F., Hall, G.E.M. 2005. The speciation of arsenic in iron oxides in mine wastes from the Giant gold mine, N.W.T. Application of synchrotron micro-XRD and micro-XANES at the grain scale. Canadian Mineralogist, 43, 1205-1224. 

Valley JW (2003) Oxygen isotopes in zircon. Rev Miner Geochem 53 343-385 Valley JW, Graham C (1993) Cryptic grain-scale heterogeneity of oxygen isotope ratios in metamorphic magnetite. Science 259 1729-1733... 

Cunningham, J. A., Werth, C. J., Reinhard, M., and Roberts, P. V. (1997). Effects of grain-scale mass transfer on the transport of volatile organics through sediments. Water Resour. Res., 33(12), 2713-2726. 

Figure 2 Schematic representation of metamorphic porphyrohlasts and matrix, illustrating the concept of pervasive, grain-scale flow. Flow paths around grains denoted by black arrows.

Lewis S., Holness M., and Graham C. (1998) Ion microprobe study of marble from Naxos Greece grain-scale fluid pathways and stable isotope equilibration during metamorphism. Geology 26, 935-938. 

A fundamental observation of melt transport at mid-ocean ridges is that in both major and trace elements, MORBs are out of chemical equilibrium with the shallow upper mantle (e.g., see Kelemen et al, 1997, for review). One mechanism that has been suggested is that melt migration is localized into some form of channel network fed by porous flow at the grain scale. This basic idea has been incorporated into several different two-porosity models to try to reconcile U-series observations with those of stable trace elements. 

Local isotherms are defined here as sorption relationships resulting from particular classes or types of sorption reactions. For soil and sediment systems involving heterogeneous mixtures of sorbent surfaces and phases, such local isotherms may be expressed at some level of physical division, such as the grain scale. Alternatively, they may be expressed per unit of some quantifiable component of the solid phase that can be characterized by either mineralogical or elemental analysis, such as organic carbon. 

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