Anorthosite

However, separation between resistance levels of 1000 to 300 kH may be marginal. A typical application of conductivity sorting is the separation of massive ilmenite from anorthosite. Both are compact rocks, but ilmenite is a good electrical conductor, whereas anorthosite is an insulator. The dimensions and operating information for the Sor-tex CS-03 conductivity sorter, which is capable of processing up to about 25,000 kg/h (27.5 tons/h) of 0.05-to 0.15-in mesh size (2 to 6 in), are given in Table 19-4. 

Boslough, M.B., and Ahrens, T.J. (1984), Particle Velocity Experiments in Anorthosite and Gabbro, in Shock Waves in Condensed Matter—1983, (edited by Asay J.R. et al.), Elsevier Science, New York, pp. 525-528. 

Anortal [Anorthosite aluminium] A process for extracting alumina from anorthosite ore (a calcium aluminosilicate) by leaching with hydrochloric acid, precipitating aluminum trichloride hexahydrate, and calcining this. Developed and piloted by I/S Anortal in Norway in the late 1970s but not commercialized. 

Anorthositic deposits - nearly all of the known commercially important rock deposits of titanium minerals are associated with anorthositic or gabbroic rocks. There are three main types (a) ilmenite-magnetite (titanoferous magnetite), (b) ilmenite-haematite, and (c) ilmenite-rutile. 

M. D. Schmitz, S. A. Bowring, and T. R. Ireland. Evaluation of Duluth Complex Anorthositic Series (AS3) Zircon as a U-Pb Geochronological Standard New High-Precision Isotope Dilution Thermal Ionization Mass Spectrometry Results, Geochim. Cosmochim. Acta, 67(2003) 3665-3672. 

Table 5.28. Ar outgassing data for lunar anorthosite 15415 (Turner, 1972).

Figure 5.15 Distribution of spallogenic 38Ar in plagioclase crystals from the lunar anorthosite 15415 analyzed by Turner (1972). A population of spherical grains with uniform grain size is assumed. The t( values were deduced from the diffusion of 37Ar (Albarede, 1978).

Table 8.3. Experimental results on 15415 lunar anorthosite, ( Turner, 1972). Cumulated fraction 1 — Fk of37Ar outgassed at each temperature step, k =0 refers to the undegassed state.

Figure 8.21 Arrhenius plot of the 37Ar outgassed from the lunar anorthosite 15415 (Turner, 1972). Only steps 1-5 are taken into account in calculating the least-square straight-line...

Turner, G. (1972). 40Ar-39Ar age and cosmic ray irradiation history of the Apollo 15 anorthosite 15415. Earth Planet. Sci. Letters, 14, 169-75. 

Sr and Ba, with application to anorthosite and basalt genesis. Geochim. Cosmochim. Acta, 34 307-322. 

Example 5.7. The oldest lunar rock known to date is a lunar highland anorthosite 60025. The data for different minerals in a single rock are shown in the table below (Carlson and Lugmair, 1988). Find the age. 

Carlson R.W. and Lugmair G.W. (1988) The age of ferroan anorthosite 60025 oldest crust on a young Moon Earth Planet. Sci. Eett. 90, 119-130. 

Morgan Z., Liang Y., and Hess P.C. (2006) An experimental study of anorthosite dissolution in lunar picritic magmas implications for crustal assimilation processes. Geochim. Cosmochim. Acta 70, 3477-3491. 

The formation of the Moon s crust, composed primarily of feldspar (the rock is called anorthosite) illustrates how physical fractionation can occur during differentiation. Early in its history, a significant portion of the Moon was melted to form a magma ocean. The first minerals to crystallize, olivine and pyroxene, sank because of their high densities and formed an ultramafic mantle. Once feldspar began to crystallize, it floated and accumulated near the surface to produce the crust. 

Lunar surface materials (Apollo and Luna returned samples and lunar meteorites) are classified into three geochemical end members - anorthosite, mare basalt, and KREEP. These components are clearly associated with the various geochemically mapped terrains of different age on the lunar surface. The composition of the lunar interior is inferred from the geochemical characteristics of basalts that formed by mantle melting, and geochemistry provides constraints on the Moon s impact origin and differentiation via a magma ocean. 

Samples returned by the Apollo and Luna missions can be readily distinguished based on their contents of FeO and thorium. This may seem like an unlikely choice of chemical components for classification, but they nicely discriminate rock types and are easily measured by remote sensing. The FeO and thorium contents of ferroan anorthosites, mare basalts, impact melt breccias, and lunar meteorites are shown by various symbols in Figure 13.4. 

Lunar rocks Ferroan anorthosite Lunar meteorite... 

Analyses of thorium and FeO in lunar rocks and lunar meteorites can be described by three compositional end members - ferroan anorthosite, KREEP, and mare basalt. The various lunar terranes defined by orbital measurements of Th and FeO, illustrated by shaded and hatched fields, can also be explained by mixtures of these components. Terrane abbreviations are PKT (Procellarum KREEP Terrane) FHT (Feldspathic Highlands Terrane) SPA (South Pole-Aiken Terrane). Modified from Jolliff etal. (2000). 

Anorthosites and basalts form two end members distinguished by FeO contents, and the impact melt breccias extend upward towards a KREEP end member with high thorium and intermediate FeO contents. Besides thorium, the KREEP end member is obviously enriched in the other incompatible elements that define its name. The impact melt breccias contain small clasts of KREEP basalt, which has not been sampled as large rocks. 

The same ferroan anorthosite-mare basalt-KREEP components also define the compositions of lunar soils. The soils from each site contain different proportions of these end members. For example, Apollo 12 soils are mixtures of mare basalt and KREEP, whereas Apollo 15 soils contain all three components. 

As noted earlier, lunar meteorites are mostly breccias of ferroan anorthosite and related early crustal rocks, although a few mare basalt meteorites are known. The lunar meteorites likely sample the whole Moon. The absence of KREEP-rich breccias so common among Apollo samples collected from the nearside in the lunar meteorite collection implies that KREEP-rich rocks cover only a small area on the Moon. In fact, the lunar highlands meteorites appear to provide a closer match to the average lunar crust than do the Apollo highlands samples (Fig. 13.5), as measured by geochemical mapping (see below). 

The Feldspathic Highlands Terrane (FHT) is characterized by its relatively low FeO and Th contents (Fig. 13.4), which are consistent with ferroan anorthosite. The FHT is the most extensive terrane and is concentrated on the lunar farside (Fig. 13.7). The Procellarum KREEP Terrane (PKT) occupies a large oval-shaped portion (Oceanus Procellarum) of the nearside (Fig. 13.7). The PKT has both light and dark areas, corresponding to highlands (non-mare) rocks and mare basalts. All of these materials... 

Ryder, G. (1991) Lunar ferroan anorthosites and mare basalt sources the mixed connection. Journal of Geophysical Research, 118, 2065-2068. 

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