In 14 12 § • |l;imi«HL' ■ » ■ * i i id»r I j BasaJdc | ■ Bisjli , indt&iic r AnrJeske ' Dkjuc T-H-1-1_I_■__J_^_ % HIiynlilL- V \ -I-1. 41 45 49 5.1 57 61 SiO? St) 73 \ 1 77 3-1* Iold atkaJ Jes-silka diapram yli winK fcjd* and examples of sunlitsjjnv linJ alkaline ™k nnlH» Imtfutar "did Iine wparatrt i k lidd oJ iicphdinc normative rocks from rooks having no normative iwphdinc in the 11,J64-siinip[c database of Le Cr d 11992J I ijthr Jfd7 ,Kt IUGS W1™" Kick-type classification from Fi«ure2.J5. N„e ,bat single lyp,. such * basalt can be ttberdtaUta hV-normiHivc) or snK.lkaJine (Hy-norm.idve). Tbr alMine volcanic stiite of basanitc, ptwm«cPhrite. rephriphonotitc «nd ivhondilc UiJJ«l ordcsl is Iron. [>i*uri ttu Cunha, a wloinic crank island near the intersection of »k Mid-Atlantic and Waki* Ruljws ■n ih* South Atlantic tWi (U Kocx cl al.. 1990). TT* subaltaW volcanic suite from rbe oceanic ^IsikI arc of fen* irilk-d ttian,l«l w rw*(k b,u .Itx andwite, undent*. ,ind daeile KkiJc, Subdkalinesuite rocks from Vokafl IX*L:ilw,idu Grande and ferm \kljJ m the Jouirwm volume tunc of the Andes io central Chile billed squaw) are mostly b*.ftic ar.desire. irachvandcsrte, trachydadie and rhyohif iHildrtih and hrWrbuth. l9K8i. Toial Fe as FeO 2.17 Subalkalinc rocks can be subdivided teto thoteiittc and ealc-alkaline rock suites. AFM diagram in terms of alkalies (Na20 + K2Q\ ratal Fe as FeO, and MgO. Solid iine separates fields of tholeiitic rocks, exemplified by volcanic rocks from the Tonga island arc in the Pacific Ocean (Figure 2,16), from calc-alkaline, rocks, exemplified by most of the volcanic rocks from, the Norxh Island of New Zealand. Approximate range of rhyolire, dacue, andesite, and basalt rock types in New Zealand is indicated, Dam from Cole (1982), i-r--r-f-1-t-1-1-1-f-1-1-r Ta b Je 7-5 Comparisons of a basa/tic magma, postulated to be the parental magma for Krlauea Volcano, and a garnet Iherzohte thai could be a possible source rock for such a basalt. AJso given is the calculated com- position of the residue left on extraciion of the liquid Basalt Peridotiie Residue Maj or Elements—Wt % so, 46.70 44.50 44.44 J.85 1.30 1.29 ÁJA 9.17 2.80 2.64 ■ ; 90 10.30 10.26 %0 20.00 37.90 37.90 CdO 7.86 3.30 3.18 \a-0 1.54 0.40 0.37 K;Ô 0,40 0.01 0 (10 Trace Elements— ppm Kl 855 2300 2337 Cr 14 O 3000 3041 Ba 195 5 <0.01 L -1 7 0.02 <0.01 Hi 0.3 0.08 <0,01 Normative and Modal Minerals Olivine 5.1 50.6 54.0 "Ojw 31.9 20.5 1S.0 Cpx .12.4 14.3 20.2 Garnet 25.6 14.4 6.5 PhlogopiEti 3.2 0.2 0.0 RuiÜe LS 0.0 1.3 Density 2.SI 3.47 3.46 Temperature. "C- %OCP iZCO 1400 P-lagi-oclose Lhcrzol»t« <3 a Spin«r LhcrzoSite 40L Garrvct _«crZDSite Figure 7*14 MeJrjng at a cusp in the mantle solrdus. Mote that the change of slope resulting from a transition from one alumfnous phase to another causes the soJidus to be convex toward the thermal gradient. The levels at which mis occurs would be favored places for melting, either by rising temperature, falling pressure, or Jowering of the solidus, (Adapted from E. Takahashf and 1. Kushiro. \983rAmer Mtn. 68:859-879J 'Z2 ef 30% Ce Nd Sfl-'EuGd Dv Er Yfe r. r ■■ loop- Welting -of C-arriGt Lherzol itc □ -J Figure 7-27 Catenated REE distribution patterns for meJts derived by oatch melting erf two Jherzolites. one |a) without garnet arnd anoiner |bj with 5 percent garnet. Note rhe sronger depletion of heavy REE jh small fcae? aons of meJt from the garneifferous IherzoAte and the srmilanty of melts evolved beyond 5 percent meHmg Patterns tn natural basarts [cj from some intra-pfate volcanoes are strongly depleted ?n heavy REE as one rrughr expect from small amounts or meeting or a garnet-beanng source ronk. whereas most basalts from mid-ocean ridges (N-MOR8J have flatter slopes that could resur? from meeting at shal-taw levers where garnet rs not stable or, after natively by advanced degrees of meiting. An enriched type of mrct-ocean ridge basalt \E-MOttflj has a steeper pattern, suggesting a deeper ongjn where garnet is stabFe Aoun-sances of SEE ^n all three diagrams are plotted on logarithmic scales; those of fa] and |o] are normalized to the abundances ^n the originär pendotite. wh;le those in fcf are normalized to the abundances m chondntfc meteorites. The differences between abundances in chondrfuc meteorrtes and sheared mantle pendotrtes are not large, faj and fb| after G. N. Hanson. 1978. Ann Rev. Eann Planet Sei. 8.371-406 Figure 7-28 [$] Calculated concen[rations of La in liquids produced by progressive batch melting of spinel iherzohre and placjioclase Jher-zotte of the same hulk chemical cornposjftans. jbj Ltf-Sm ratio few the same melts as En jaj Laf jhe lightest of Lbe REE. >s not shown in the diagrams of Figure 7-27 but would fall ro the left | Ce on the horizontal scale fAfter J. F Allan. | Bato, and P Lonsdale. [937. Seamoums. &jrtfs. jnd Arofte Geoph Mono. 43. Amer Geooh Un. 235-282} 13.2 Primitive-mamle-nonnaliaed trace element patterns oi oceanic thoieituc basalts. Decreasing element jncomiwubiliiy in nufic from left to right. MORB data and normalizing values from Sun and McDonough i 1989). Hawaiian tholeiire from Table 13.5. MiK3di proportions Compositions, of MORE ;irtcl abyssal |>cridocitc reflect varying decrees of partial nit-Inn^ ot the mantle source. Ul tiWwl MOHIJ Uinv position. Variable 00 tilt X Axis- it the concentration of Na al & wt.% MpO on a Na-M^O varialton diitp/aiii drawn tor K-4 sites hi spread ing ridpes umund the world (775 samples in ;itt). The Ci»0/AijC\ ratio is taken Irom 3 CaO/AljO,-MfcO variation diagram tor samples ■I each intnsite variation in (be rutin b negligible. I Redrawn from Klein and Lur^niuir, 1987.) samples from J6 dredge haul site* itlong tift* in the Atlantic Ocean. Indian Occam, iind < jinhbcan Sea. The classifies! ton diagram is for ultumafic nocks Ipigtne 2,10h>. The nwjt cxierwwiy melted |*erkhnite. that h. lis jiiiKt sd-rtU.-. hits least (!px ant! Op-x and |jivaicsi I'o content of olivine i compare l;t(jijjx; I ] .*)).