Nickel peridotites

Mysen B. O. (1977a). Partitioning of nickel between liquid, pargasite and garnet peridotite minerals and concentration limit of behavior according to Henry s law at high pressure and temperature. Amer. Jour. ScL, 278 217-243. 

GARNIERITE. This mineral occurs as amorphous masses, presumably as a product of secondary alteration of nickel-bearing peridotites. It is a... 

Rocks consisting essentially of olivine alone are known as dunites, the name coming from the occurrence of this rock in the Dun mountains of New Zealand. In the United States, this mineral is found in North Carolina, South Carolina, and Georgia, where corundum is associated wtith the dunite in commercial quantities. The olivine of peridotites alters readily to the mineral serpentine, often to such an extent that the rock itself is called a serpentine. As mentioned above, the pendotites may contain chromite or other valuable minerals, often to such an extent that they may be commercially exploited, for nickel, platinum, and precious garneL... 

Figure 7 Plots of Ti02 (anhydrous wt.%), nickel, and chromium (anhydrous ppm) versus AI2O3 (anhydrous wt.%) in whole-rock orogenic, ophiolitic, and abyssal peridotites. The symbols and the data sources are the same as in...

Figure 14 Covariation of V with AI2O3 in (a) abyssal peridotites, orogenic massifs, off-craton xenoliths, arc xenoliths, and (b) cratonic xenoliths (data sources in Table 6). Shown for illustrative purposes are residue trends for partial melting at 1.5 GPa as a functions of/o (expressed relative to the nickel-nickel oxide (NNO) buffer) calculated using methods described in Canil (2002).

Nickel K. G. and Green D. H. (1985) Empirical geothermo-barometry for garnet peridotites and implications for the nature of the lithosphere, kimberlites and diamonds. Earth Planet. Sci. Lett. I i, 158-170. 

Figure 6 Effect of silicate melt composition on metal/silicate partition coefficients for cobalt ( ), gallium (+), tungsten (o), and phosphorus ( ) (Jaeger and Drake, 2000 Pak and Fruehan, 1986). NBO/t is calculated according to Mysen (1991) and corresponds to basalt values of 1, komatiite —1.7, and peridotite —2.8. In general, high-valence elements such as tungsten and phosphorus are affected more strongly than lower valence elements such as cobalt (or nickel).

Figure 16 Comparison of observed (open) and calculated (solid) depletions of phosphorus, tungsten, cobalt, nickel, molybdenum, and rhenium (circles) together with those for gallium, tin, and copper (inverted triangles) (sources Righter and Drake, 1997, 1999, 2000). The calculated depletions utilize the partitioning expressions of Righter and Drake (1999) for conditions of 2,250 ( 300) K (1,973 °C), 27 ( 6) GPa, AIW = — 0.4 ( 0.3) between a hydrous peridotite (NBO/t = 2.65) magma ocean and metallic liquid. The observed depletions are those of McDonough and Sun (1995), but volatility corrected as described by Newsom and Sims (1991), where the correction is made based on comparisons to trends of lithophile volatile element depletions.

Lateritic weathering, promoted by warm-humid environments and low rates of erosion, can enhance some geochemical anomalies to the point where they may be mined at a profit. For example, lateritic weathering of dunites and peridotites or their serpentinized equivalents can produce ores of nickel with 1 -2% nickel. Nickel is commonly hosted by either iron oxides or silicates (garnierite). The deposits may be cmdely vertically zoned with pisolitic iron-oxide and nickel-bearing zones above richer saprolitic silicate ore. 

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