Uvarovite and grossular from the Fengtien nephrite deposits, eastern Taiwan

Abstract

Uvarovite and grossular, the former comparatively rare, occur along the serpentinite-graphite schist contact in the Fengtien area, on the eastern slope of the Central Range of Taiwan. Uvarovite occurs as small emerald-green euhedral crystals on diopside-fels with dodecahedral crystal forms and many other modifications. Its refractive index is 1.782, specific gravity 3.702, and unit cell edge 11.912 Å. Chemical and probe analyses give average Cr2O3 contents of 11.60 wt. %; spectrographic analysis shows significant enrichment in Cr, Be, Co, Y, Sb, and La over grossular. Associated minerals include nephrite, diopside, tremolite asbestos, zoisite, and clinozoisite. Grossular is reddish-brown; large crystals, dodecahedral in form often modified by trapezohedrons, are associated with diopside, idocrase, and calcite. n = 1.746, SG = 3.636, and a = 11.866 Å. Structurally and chemically it is quite near the grossular end member. Grossular is considered to be formed from pneumatolysis associated with the intrusion of ultramafic rocks, whereas uvarovite is a replacement product of relict chromite in the original ultramafic rocks where migration of elements such as silicon and calcium from wall rocks are prominent.

Petrographic and microprobe study of nephrites from Lower Silesia (SW Poland)

“…It in di cates its ge netic re la tions with rodingitization and serpentinization rather than with a host-rock man tle protolith. The cal cu lated Ca/(Ca + Mg) (close to 1) and Mg/(Mg + Fe) (0.05-0.65) ra tios cor re spond to garnets from Fengtian nephritan, Tai wan, given by Wan and Yeh (1984), with val ues close to 1 and from 0.1 to 0.5, re spec tively.…”

“…Chlorite schist, rodingite and ser pen tin ite in ter ca la tions are vis i ble by the na ked eye, al though are not al ways pres ent. Fengtian neph rite (Tai wan) af ter Wan and Yeh (1984) The neph rite is com posed of tremolite, sim i lar to Fengtian nephrite tremolite (Tai wan), with the Si con tent from 7.7 to 8.0 apfu. Other ma jor con stit u ents are di op side and chlorites.…”

“…Sig nif i cant world de pos its are re stricted to tens of lo ca tions. Ma jor neph rite de pos its are lo cated in Can ada -Brit ish Co lum bia (e.g., Simandl et al, 2000;Makepeace and Simandl, 2001), Rus sian Fed er ation -Si be ria Sorensen, 2001, 2005;£apot, 2004), China (Sax et al, 2004;Liu et al, 2011a, b), Ko rea (e.g., Yui and Kwon, 2002), Tai wan (e.g., Wan and Yeh, 1984;Hung et al, 2007), South Aus tra lia Sorensen, 2001, 2005 and ref er ences therein), New Zea land -South Is land (e.g., Root, 1994;Middle ton, 2006), and in the USA -Wy o ming, Alaska and Cal i for nia (e.g., Sinkankas, 1959;Middle ton, 2006). De spite limited num ber of de pos its, neph rite ar ti facts were found in nu merous ar chae o log i cal sites, dated back to the Neo lithic age.…”

Origin of serpentinite-related nephrite from Jordanów and adjacent areas (SW Poland) and its comparison with selected nephrite occurrences.

“…9), which im plies a pos si ble ge netic re lation ship with leucogranite rodingitisation. The Fengtien ser pentin ite-re lated neph rite (Wan and Yeh, 1984) and Crooks Mountain ser pen tin ite-re lated neph rite gar nets also plot in the crustal-de rived gar nets field (Fig. 9).…”

“…The larg est neph rite de pos its are lo cated in Brit ish Co lumbia (Can ada; Simandl et al, 2000;Makepeace and Simandl, 2001), Wy o ming, Cal i for nia, and Alaska (USA; Sinkankas, 1959;Sherer, 1972;Middle ton, 2006), Si be ria (Rus sia; Sorensen, 2001, 2005;Łapot, 2004;Kostov et al, 2012), Xinjiang, Qinghai, Liaoning, Jiangsu, Sichuan and Henan (China; Liu et al, 2010Liu et al, , 2011aSiqin et al, 2012), Chuncheon (Ko rea; Yui and Kwon, 2002), Hualien (Tai wan; Wan and Yeh, 1984;Siqin et al, 2012), South Aus tra lia and New South Wales (Aus tra lia; Aitchison et al, 1992;Sorensen, 2001, 2005), and the South Is land (New Zea land; Middle ton, 2006;Ad ams et al, 2007;Grapes and Yun, 2010). There are also neph rite de pos its in Eu rope -Sondrio (It aly; Adamo and Bocchio, 2013), Scortaseo (Swit zer land; Dietrich and de Quervain, 1968;Adamo and Bocchio, 2013;Péterdi et al, 2014), Thuringia and Ba varia (Ger many; Łobos et al, 2008;Péterdi et al, 2014), and Usinmaki and Pakila (Fin land;Gunia, 2000).…”