Ne so silic a te s 1. Learn more about Nesosilicates, particularly - PowerPoint PPT Presentation

3/25/2015 • Learning goals Ne so silic a te s 1. Learn more about Nesosilicates, particularly (c o ntinue d ) the structures of garnet, zircon, and kyanite 2. Understand and able to explain the p differences between end members in solid solutions 3. Understand key diagnostic properties of each nesosilicate mineral W. K a nitpa nya c ha ro e n I mag e so urc e http:/ / www.thiso lde arth.ne t/ I mag e s/ silic ate _struc ture s.jpg • The Garnet group is a key mineral in Ga rne t interpreting the temperature ‐ pressure ‐ time X 3 Y 2 (SiO 4 ) 3 histories of the rocks in which they grew such as igneous and metamorphic rocks. - Mo stly fo und in me ta mo rphic ro c ks (e .g . sc hist, a mphib o lite , e c lo g ite ) a nd (e .g . sc hist, a mphib o lite , e c lo g ite ) a nd • Garnets are also relatively resistant to so me in ig ne o us ro c ks (e .g . pe g ma tite , g ra nite ) weathering and useful in defining metamorphic facies of rocks. - K e y mine ra l to inte rpre t the P-T histo ry • For instance, eclogite can be defined as a rock of basalt composition, but mainly consisting of garnet and omphacite. Pyrope ‐ rich garnet is restricted to relatively high ‐ pressure metamorphic rocks, such as those in the lower crust and in the Earth's mantle. I mag e so urc e http:/ / http:/ / www.impro ntaunika.it/ wp-c o nte nt/ uplo ads/ 2014/ 12/ L o livina-dalla-c ristallo te rapia-alla-riduzio ne -de i-g as-se rra.jpg 1

3/25/2015 Ga rne t • The general formula of garnet is X 3 Y 2 (SiO 4 ) 3 . Do d e c a he d ro n However, Ca 2+ cation is appreciably larger than X 3 Y 2 (SiO 4 ) 3 the Mg 2+ , Fe 2+ , and Mn 2+ , resulting in separate - Hig hly re sista nt to we a the ring mineralogical series of Ca ‐ rich and Ca ‐ poor g p - Symme try: Mo stly iso me tric garnets. - Cle a va g e : No ne - F ra c ture : Co nc ho ida l - Ha rdne ss: 7.5 - Ge msto ne : Ga rne t - Co lo r: Va rie s I mag e so urc e http:/ / skywalke r.c o c hise .e du/ we lle rr/ mine ral/ g arne t/ 6g arne t-almandite 172f.jpg • Ca ‐ rich garnet comprise the UGRADITE series Ga rne t The ugrandite series gets is name from the main X 3 Y 2 (SiO 4 ) 3 minerals in it: u varovite, Ca 3 Cr 2 (SiO 4 ) 3 , gr ossular, Ca 3 Al 2 (SiO 4 ) 3 , and and radite, Ca 3 Fe 3+ 2 (SiO 4 ) 3 . Site - T wo e nd-me mb e rs in so lid so lutio n: C 2+ Y Al 3+ C 3+ F 3+ Th occupancies are: X = Ca 2+ , Y = Al 3+ , Cr 3+ , Fe 3+ . The i X Ca-poor names based upon the B site occupancy. Pyra lspite : X 3 Al 2 (SiO 4 ) 3 Grossular ‐ andradite forms a complete solid solid Pyro pe -Almandine -S pe ssarite solution. X site : triva le nt c a tio n Cr 3+ , Al 3+ , F e 3+ • Ca ‐ poor garnet form the PYRALSPITE series. The Ca-r ic h Ug ra ndite : Ca 3 Y 2 (SiO 4 ) 3 g 2 ( 4 ) 3 pyralspite series name is also based upon its pyralspite series name is also based upon its 3 Uvaro vite -Gro ssular-Andradite minerals: pyr ope, Mg 3 Al 2 (SiO 4 ) 3 , al mandine, Y site : b iva le nt c a tio n Mg 2+ , F e 2+ , Mn 2+ Fe 3 Al 2 (SiO 4 ) 3 , and sp essartine, Mn 3 Al 2 (SiO 4 ) 3 . Site occupancies are: X = Mg 2+ , Fe 2+ , and Mn 2+ , Y = Al 3+ . The names based upon the A site occupancy. I mag e so urc e http:/ / uplo ad.wikime dia.o rg / wikipe dia/ c o mmo ns/ 2/ 24/ Garne t_var._S pe ssartine ,_Putian_City,_Putian_Pre fe c ture ,_F ujian_Pro vinc e ,_China.jpg 2

3/25/2015 Pyr a lspite g ro up • Ca ‐ poor garnet form the PYRALSPITE series. The pyralspite series name is also based upon Pyr o pe its minerals: Mg 3 Al 2 (SiO 4 ) 3 • pyr ope Mg Al (SiO ) pyr ope, Mg 3 Al 2 (SiO 4 ) 3 , - Co lo r: re d , purple , b la c k • al mandine, Fe 3 Al 2 (SiO 4 ) 3 , and - F o und in ultra ma fic ig ne o us ro c ks, e c lo g ite , pe rido tite , • sp essartine, Mn 3 Al 2 (SiO 4 ) 3 . se rpe ntinite I mag e so urc e http:/ / myzo ne -inte rnatio nalg e m1.ne tdna-ssl.c o m/ wp-c o nte nt/ uplo ads/ 2014/ 10/ pyro pe -g arne t.jpg pyr AL spite g ro up • Ca ‐ poor garnet form the PYRALSPITE series. The pyralspite series name is also based upon ma ndine AL its minerals: F e 3 Al 2 (SiO 4 ) 3 • pyr ope Mg Al (SiO ) pyr ope, Mg 3 Al 2 (SiO 4 ) 3 , - Co lo r: re d , b ro wn, b la c k • al mandine, Fe 3 Al 2 (SiO 4 ) 3 , and - F o und in me ta mo rphic ro c ks: sc hist • sp essartine, Mn 3 Al 2 (SiO 4 ) 3 . I mag e so urc e http:/ / uplo ad.wikime dia.o rg / wikipe dia/ c o mmo ns/ c / c 9/ Almandin.jpg 3

3/25/2015 pyra l SP ite g ro up • Ca ‐ poor garnet form the PYRALSPITE series. The pyralspite series name is also based upon SP e ssa rite its minerals: Mn 3 Al 2 (SiO 4 ) 3 • pyr ope Mg Al (SiO ) pyr ope, Mg 3 Al 2 (SiO 4 ) 3 , - Co lo r: re d , o ra ng e , b ro wn • al mandine, Fe 3 Al 2 (SiO 4 ) 3 , and - F o und in me ta mo rphic ro c ks, pe g ma tite s • sp essartine, Mn 3 Al 2 (SiO 4 ) 3 . I mag e http:/ / 40.me dia.tumblr.c o m/ 5f683f6f91b c b 9ffa7b 8052227f3fb 0e / tumblr_ndo 4wkwjc e 1tfq o l2o 1_500.png U g ra ndite g ro up • Ca ‐ rich garnet comprise the UGRADITE series The ugrandite series gets is name from the U va ro vite main minerals in it: Ca 3 Cr 2 (SiO 4 ) 3 • u varovite, Ca 3 Cr 2 (SiO 4 ) 3 , • u varovite Ca Cr (SiO ) - Co lo r: b rig ht g re e n • gr ossular, Ca 3 Al 2 (SiO 4 ) 3 , and - Ra re g a rne t - F o und a s sma ll c rysta ls • and radite, Ca 3 Fe 3+ 2 (SiO 4 ) 3 . a sso c ia te d with pe rido tite , c hro mite , se rpe ntinite , kimb e rlite I mag e so urc e http:/ / http:/ / www.mindat.o rg / pho to s/ 0307363001306726370.jpg 4

3/25/2015 u GR a ndite g ro up • Ca ‐ rich garnet comprise the UGRADITE series The ugrandite series gets is name from the Gr o ssula r main minerals in it: Ca 3 Al 2 (SiO 4 ) 3 • u varovite, Ca 3 Cr 2 (SiO 4 ) 3 , • u varovite Ca Cr (SiO ) - Co lo r: c inna mo n b ro wn, g re e n • gr ossular, Ca 3 Al 2 (SiO 4 ) 3 , and - F o und in c o nta c t me ta - mo rpho se d lime sto ne s with • and radite, Ca 3 Fe 3+ 2 (SiO 4 ) 3 . d io psid e , wo lla sto nite I mag e so urc e http:/ / http:/ / www.dako tamatrix.c o m/ imag e s/ pro duc ts/ g ro ssular34047e .jpg ug r AND ite g ro up • Ca ‐ rich garnet comprise the UGRADITE series The ugrandite series gets is name from the AND ra dite main minerals in it: Ca 3 F e 2 (SiO 4 ) 3 • u varovite, Ca 3 Cr 2 (SiO 4 ) 3 , • u varovite Ca Cr (SiO ) - Co lo r: ye llo w, g re e n, b la c k • gr ossular, Ca 3 Al 2 (SiO 4 ) 3 , and - F o und in de e p-se a te d ig ne o us ro c ks, se rpe ntine s, sc hist • and radite, Ca 3 Fe 3+ 2 (SiO 4 ) 3 . I mag e so urc e http:/ / www.dako tamatrix.c o m/ imag e s/ pro duc ts/ andradite 34231b .jpg 5

3/25/2015 4- te tra he dro n • Garnet is one of the most common SiO 4 T riva le nt: F e 3+ , Al 3+ , Cr 3+ nesosilicates but it has a complex structure. Oc ta he dro n e 2+ , Mg 2+ , Mn 2+ Biva le nt: F • Bivalent cations and SiO4 forms tetrahedral sites (yellow orange) while trivalent cations sites (yellow, orange) while trivalent cations and oxygenn forms octrahedral sites (blue). Mo difie d fro m http:/ / www.uwg b .e du/ dutc hs/ pe tro lo g y/ Garne t%20S truc ture .HT M Mg 3 Al 2 (SiO 4 ) 3 Pyr o pe • Pyrope ‐ almandine and almandine ‐ spessartine form complete solid solutions. Co mple te so lid so lutio n se rie s F e 3 Al 2 (SiO 4 ) 3 Mn 3 Al 2 (SiO 4 ) 3 v v v v v v v v v Al ma ndine Sp e ssa rite 0 10 20 30 40 50 60 70 80 90 100 Co mpo sitio n (Mo le c ula r %) Mo difie d fro m https:/ / www4.nau.e du/ me te o rite / Me te o rite / Bo o k-Glo ssaryG.html 6