Granite formation, Earth

The lanthanides, distributed widely in low concentrations throughout the earth s cmst (2), are found as mixtures in many massive rock formations, eg, basalts, granites, gneisses, shales, and siUcate rocks, where they are present in quantities of 10—300 ppm. Lanthanides also occur in some 160 discrete minerals, most of them rare, but in which the rare-earth (RE) content, expressed as oxide, can be as high as 60% rare-earth oxide (REO). Lanthanides do not occur in nature in the elemental state and do not occur in minerals as individual elements, but as mixtures. 

Much of the Earth s silicon is found in durable rock formations based on silica. Granite is a common example. This is consistent with a network solid. Phosphorus, in contrast. 

Petford, N., Cm den. A., McCaffrey, K., andVigneresse, J-L. Granite Magma Formation, Transport and Emplacement in the Earth s Cmst. Nature (December 2000) 669-673. 

Campbell, I. H. Hill, R. 1.1988. A two-stage model for the formation of the granite-greenstone terranes of the Kalgoorlie-Norseman area. Western Australia. Earth and Planetary Science Letters, 90, 11-25. 

The zinc concentration in the Earth s crust tends to increase on passing from the upper mantle (. x 10 - %) toward the basalt (1.3x 10 -%) and furtheron to the granite layer (6 X 10 -%). Substantial masses of zinc are found in the post-magnetic geological formations. The zinc-lead ore deposits have accumulated over 20 x 10 tons ofZn. This enormous quantity accounts for a mere 0.001% of the zinc mass occurring in a dispersed state in the uppermost granite crustal layer of 1 km depth. 

It has long been recognized that the presence of liquid water on Earth is one of the principal differences between the Earth and the other terrestrial planets. More than 20 years ago Campbell and Taylor wrote a paper entitled No water, No Granites - No Oceans, No Continents, in which they proposed that water was the vital ingredient in the formation of a felsic continental crust (Campbell Taylor, 1983). Hence, it may be no coincidence that the Earth, the only planet with abundant liquid water, is also the only planet with a substantial felsic continental crust. 

The outermost layer of our planet, the crust, contains the accessible mineral wealth of the planet. The eight most abundant elements in the crust (Table 1) make up 98.5% of the mass of the crust [10], The most common metal, silicon, is never found in its elemental form in nature. Instead, silicon is combined in silicate minerals, which make up more than 90% of the mass of the Earth s crust [11], Depending on the composition and formation conditions, silicate minerals have structures that range from individual clusters (orthosilicates) to three-dimensional networks (tecto-silicates) [11], These minerals can be contained in relatively pure single mineral deposits or, more commonly, in rocks such as granite that are made up of one or more mineral species. 

Although uncertainty remains, the environments required for the formation of Wyoming-type montmorillonites (i.e., explosive eruptions of volcanic ash granitic compositions deposition of volcanic ash into saline water shallow burial) may conceivably have been present on the prebiotic Earth. Formation of RNA oligomers would have proceeded fi-om activated monomers if the aqueous environment had a pH in the neutral to mildly basic range (40). 

The date indicates that these rocks were erupted during the Middle Cambrian Epoch. This revision of the geologic history of the Transantarctic Mountains indicates that the volcanic rocks of the Wyatt Formation were erupted at the surface of the Earth or intruded at shallow depth during the active phase of the Ross Orogeny and that the rocks probably cooled rapidly compared to the deep-seated granitic plutons of the Wisconsin... 

---