Metamorphic minerals

MetamorphicDeposits. Uranium deposits belonging to the metamorphic class occur in metasediments or metavolcanics generally, without direct evidence of post-metamorphic mineralization. Examples include the deposits at Eorstau, Austria (16). 

Mueller R. F. (1961). Analysis of relations among Mg, Fe and Mn in certain metamorphic minerals. Geochim. Cosmochim. Acta, 25 267-296. 

Ganguly J., Dsasgupta S., Cheng W., and Neogi S. (2000) Exhumation history of a section of the Sikkim Himalayas, India records in the metamorphic mineral equilibria and compositional zoning of garnet. Earth Planet. Sd. Lett. 183, 471-486. 

ANAMORPHISM. A term proposed by Van Hise in 1904 to designate the deep-seated constructive processes of metamorphism by which new complex (metamorphic) minerals are formed from the preexisting simpler minerals, as contrasted with the surface alteration of rocks due to weathering and cementation, termed katamorphism. 

Biotite is occasionally found in large sheets, especially in pegmatite veins. It also occurs as a contact metamorphic mineral or the product of the alteration of hornblende, augite, wernerite, and similar minerals. 

Spinel is found as a metamorphic mineral, and also as a primary mineral in basic rocks, because in such magmas the absence of alkalies prevents the. formation of feldspars, and any alnininnin oxide present will form corundum or combine with magnesia to form spinel. This fact accounts for the finding of both ruby and spinel togedier. 111 addmon to the localities mentioned above, which yield beautiful specimens, spinel is found in Italy and Sweden and in Madagascar, Also in the United States in Orange County, New York, and ill Sussex County. New Jersey, are many well-known spinel localities. Spinel is found also in Macon County, North Carolina, and in Canada in Quebec and Ontario. 

The mineral beryls, cordierite, and tourmaline, collectively designated as cyclosilicates, have large open channels in their crystal structures. These channels are large enough to accommodate atoms and molecules extraneous to the structure, and these minerals are well known as hosts of such extraneous elements as noble gases. Beryl and tourmaline are characteristic minerals of pegmatites, and cordierite is a common metamorphic mineral. 

Schwartz, H. P. (1967) The effect of crystal field stabilization on the distribution of transition metals between metamorphic minerals. Geochim. Cosmochim. Acta, 31,503-17. 

Asbestos— A general term applied to certain polysilicate fibrous minerals displa5dng similar physical characteristics although differing in composition. The most common asbestos mineral (over 95% of U.S. production) is chrysotile, a variety of serpentine, a metamorphic mineral. 

The body of evidence for deep crustal fluids has grown substantially in the last several decades, and includes the following, (i) High-density fluid inclusions that were trapped in metamorphic minerals that grew under deep crustal conditions. 

There have been several previous reviews of chemical zoning in metamorphic minerals (e.g., Tracy, 1982 Loomis, 1983 Chakraborty and Ganguly, 1991 Spear, 1993). This review differs from them in three ways. 

---