Granite composition

The pegmatites of the Main Double S zone are classified as Miarolitic-REE class, NYF-A type pegmatites (Cerny Ercit 2005). The granites and pegmatites have a granitic composition (72-73 wt%... 

Explosive volcanism in western North America 95 million years ago (Late Cretaceous age 42) spread volcanic ash downwind to the east of the volcanoes. Upon deposition, the volcanic ash was chemically altered (e.g., devitrification of volcanic glass) to form bentonite, in which montmorillonite is the dominant mineral. In addition, the Late Cretaceous bentonites contain low abundances of magmatic minerals (e.g., quartz, alkali-rich feldspar, zircon, biotite) that were quenched during the volcanic eruption 43, 44) and entrained in the volcanic ash. The explosive volcanic events are known to have produced ash having a granitic composition 40). 

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). 

In contrast to apatite, the solubilities of monazite and xenotime are much more limited in peraluminous melts compared with apatite solubility, with maximum solubilities of <0.05 wt % P2O5 (Wolf and London 1995). Indeed, Wolf and London (1995) report precipitation of monazite at sites of apatite dissolution in melting experiments. REE solubilities, in contrast, are higher in mafic compositions relative to granitic compositions (Ryerson and Hess 1978, 1980), and monazite solubility is greater in peralkaline melts than in meta or peraluminous melts (Montel 1986, Ellison and Hess 1988). Rapp and Watson (1986) also report a strong temperature dependence of monazite solubility. 

Hanson G.N., 1978, The application of trace elem ts to the petrogenesis of igneous rocks of granitic composition. Earth Planet, Sei. Lett., 38, 26-43. 

Plutonic rocks of granitic composition are classified on the basis of the modal abundances of quartz, alkali... 

This relationship tqypears to hold fiom 750 to 1500X and 2-6 kbar. However, Watstm and Harrison caution that the saturation equation is not a universal solution and does not describe the zircon saturation behavior observed by [76,137] in other systems. Additional zircon solubility measurements on a lunar basalt and granite compositions have been given by [27]. 

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