Modal mineralogy

The ultimate objective of remote reflectance spectral measurements is to obtain quantitative estimates of the modal mineralogy of unexplored surfaces of the Moon and, indeed, other terrestrial planets. This necessitates difficult and elaborate spectrum-curve fitting procedures, which has been the focus of detailed research (e.g., Roush and Singer, 1986 Clouds et al., 1986 Mustard... 

Chapter 10 describes how spectral measurements of sunlight reflected from surfaces of planets, when correlated with experimental visible to near-infrared spectra of rock-forming minerals, have been used to detect transition metal ions, to identify constituent minerals, and to determine modal mineralogies of regoliths on terrestrial planets. 

Bland P. A., Cressey G., Alard O., Rogers N. W., Forder S. D., and Gounelle M. (2002) Modal mineralogy of carbonaceous chondrites and chemical variation in chondrite matrix. In Lunar Planet. Sci. XXXIII, 1754. The Lunar and Planetary Institute, Houston (CD-ROM). 

Table 3 Mean and median modal mineralogy of xenoliths.

Some insight into this issue may be obtained by combining the experimentally determined phase equilibria with internally consistent thermodynamic databases, which allow interpolation and extrapolation of the extant data. In a series of papers, Kerrick and Connolly (1998, 2001a,b) calculated phase equihbria and modal mineralogies... 

A third approach that is commonly used to constrain chemical fluxes compares differently altered materials, such as altered pillow margins and less altered pillow interiors, or samples with or without alteration haloes around veins (e.g., Alt et al., 1986), mineralized and unmineralized zones or differently altered gabbros (e.g., Bach et al., 2001) in order to constrain chemical changes associated with alteration. However, least altered samples only rarely reflect the original composition reliably. A second problem in this approach is the relatively small sample sizes typically analyzed from ocean drilling materials. Typical sample sizes are about 15 cm, which is small when compared with local variability in modal mineralogy. Indeed, individual phenocryst phases can be several millimeters in size. Local variability in modal mineralogy is particularly common in pillow lavas where phenocryst abundances can vary as a function of radial distance from the center or vertically within the center... 

Fig. 10. The filled circles show estimates of the density, V, and Vp expressions and models of nodule compositions and modal mineralogy from Tainton McKenzie (1994) for PKP nodules (92 km), depleted and GPP nodules (112 and 142 km), and fertile nodules (172 and 202 km).

Table III. Modal Mineralogic Composition of Devonian Oil Shales.

Table 5. Modal mineralogy of a sandstone after 500 pore volumes of fluid flow...

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