Epidote zoisite

Melting of subducted crust can occur under fluid-saturated or huid-absent conditions. The principal hydrous phases involved are phengite, biotite, epidote/zoisite, and amphibole. If melting of the oceanic crust occurs at pressures below 2.5 GPa, the oceanic crust will go through a greenschist and epidote-amphibolite facies stage at low pressures (both stages not discussed above). 

Graham, C.M., Sheppard, S.M.F. and Healton, T.H.E. (1980) Experimental hydrogen isotope studies, I. Systematics of hydrogen isotope fractionation in the system epidote-H20, zoisite-H20 and AIO(OH)-H2O. Geochim. Cosmochim. Acta, 44, 353-364. 

Epidote-clinozoisite Ca2(Al, Fe )3(Si04)3(0H) Piedmontite Ca2(Al,Mn+ Fe+= )3(Si04)3(0H) Zoisite Ca2Al3(Si04)3(0H) dimorph clinozoisite Humite (morphotrophic series with olivine)... 

Cr3+ uvarovite (garnet), kammererite (chlorite), tawmawite (epidote) Mn3+ piemontite (epidote), thulite (zoisite), viridine (andalusite), blan-fordite (pyroxene), juddite and winchite (amphiboles)... 

Graham CM, Sheppard SMF, Heaton THE (1980) Experimental hydrogen isotope studies hydrogen isotope fractionation in the systems epidote-H20, zoisite- H2O and A10(0H)-H20. Geochim Cosmochim Acta 44 353-364... 

Direct exchange of epidote with H2 gas. 71-91% exchange. P = 0.3-2 bars. At 300°C, epidote-H20 fractionations derived from these results are approximately 35%o more negative than those reported in the direct epidote-H20 exchange experiments of Graham et al. (1980) and Chacko et al. (1980). Epidote composition is pistacite (Fe/Fe+Al) = 0.30. Direct exchange. 35-100% exchange. P= 4 kbar. Zoisite composition is pistacite (Fe/Fe+Al) = 0.03. 

The mineral composition (mode) of the Wyatt Formation in the Scott-Glacier area was determined by Minshew (1967) and is listed in Appendix 6.7.3.1 followed by chemical analyses in Appendix 6.7.3.2. The rocks of the Wyatt Formation in the La Gorce Mountains were altered either by the original magmatic fluid or during later metamorphism. In extreme cases, plagioclase was completely altered to sericite or saussurite (Stump et al. 1986). Saussurite is a mineral aggregate composed of albite and zoisite or epidote with variable amounts of calcite, sericite, and prehnite (Jackson 1997). 

CaBj(SijO )j, Epidote Ca2(Al,Fe)3Si30jj(OH), Enstatite Mg Si O, Hemimorphite Zn SijO,(OH)jHjO, Fibrolite/Sillimanite Al SiO (after the name of Benjamin Silliman, professor of Chemistry at Yale University in 1824), Olivine, sulfur crystds, Topaz Al3SiO (F,OH)j, Zoisite CUjAlj (Si30jj)(0H) (after the name of the Australian mineralogist Von Zois). 

Sm and possibly V emission centers (Fig. 4.138). Excitation of zoisite and epidote by CW laser with 532 and 785 nm revealed luminescence IR luminescence lines evidently belonging to Nd ", red lines belonging to Cr " and broad red bands of unknown origin (Fig. 4.139). 

Fig. 4.139 (a-d) Laser-induced cw luminescence spectra of zoisite and epidote under 532 and 785 nm excitations (http //rruff.info)... 

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