PoerPoint Presentation Chapter 9a Trace ELementsPowerPoint演示文稿第9A微量元素

1、figure 8-2. harker variation diagram for 310 analyzed volcanic rocks from crater lake (mt. mazama), oregon cascades. data compiled by rick conrey (personal communication). fig. 6-10. isobaric t-x phase diagram at atmospheric pressure after bowen and shairer (1932), amer. j. sci. 5th ser., 24, 177-21

2、3. relative ionic radii for common valencesand coordination numbersplot of ionic radius vs. ionic charge for trace elements of geological interest. ionic radii are quoted for eight-fold coordination to allow for comparison between elements. from rollinson(1993).3. if two ions have a similar radius,

3、but different valence: the ion with the higher charge is preferentially incorporated into the solid over the liquidltrace element concentrations are in the henrys law region of concentration, so their activity varies in direct relation to their concentration in the system, where a = (c)lthus if xni

4、in the system doubles the xni in all phases will doublelincompatible elements are concentrated in the melt (kd or d) 1lcompatible elements are concentrated in the solid kd or d 1lfor dilute solutions can substitute d for kd:d =where cs = the concentration of some element in the solid phaselincompati

5、ble elements commonly two subgroupstable 9-1. partition coefficients (cs/cl) for some commonly used trace elements in basaltic and andesitic rocksolivineopxcpxgarnetplagamphmagnetiterb0.0100.0220.0310.0420.0710.29 sr0.0140.0400.0600.0121.8300.46 ba0.0100.0130.0260.0230.230.42 ni14570.9550.016.829cr0

6、.7010341.3450.012.007.4la0.0070.030.0560.0010.1480.5442ce0.0060.020.0920.0070.0820.8432nd0.0060.030.2300.0260.0551.3402sm0.0070.050.4450.1020.0391.8041eu0.0070.050.4740.243 0.1/1.5*1.5571dy0.0130.150.5821.9400.0232.0241er0.0260.230.5834.7000.0201.7401.5yb0.0490.340.5426.1670.0231.6421.4lu0.0450.420.

7、5066.9500.0191.563data from rollinson (1993).* eu3+/eu2+italics are estimatedrare earth elementslfor a rock, determine the bulk distribution coefficient d for an element by calculating the contribution for each mineraltable 9-1. partition coefficients (cs/cl) for some commonly used trace elements in

8、 basaltic and andesitic rocksolivineopxcpxgarnetplagamphmagnetiterb0.0100.0220.0310.0420.0710.29 sr0.0140.0400.0600.0121.8300.46 ba0.0100.0130.0260.0230.230.42 ni14570.9550.016.829cr0.7010341.3450.012.007.4la0.0070.030.0560.0010.1480.5442ce0.0060.020.0920.0070.0820.8432nd0.0060.030.2300.0260.0551.34

9、02sm0.0070.050.4450.1020.0391.8041eu0.0070.050.4740.243 0.1/1.5*1.5571dy0.0130.150.5821.9400.0232.0241er0.0260.230.5834.7000.0201.7401.5yb0.0490.340.5426.1670.0231.6421.4lu0.0450.420.5066.9500.0191.563data from rollinson (1993).* eu3+/eu2+italics are estimatedrare earth elementsltrace elements stron

10、gly partitioned into a single minerallni - olivine = 14trace element concentrations are in the henrys law region of concentration, so their activity varies in direct relation to their concentration in the systemthus if xni in the system doubles the xni in all phases will doubletrace element concentr

11、ations are in the henrys law region of concentration, so their activity varies in direct relation to their concentration in the systemthus if xni in the system doubles the xni in all phases will doublebecause of this, the of trace elements are often superior to the concentration of a single element

12、in identifying the role of a specific minerallk/rb often used the importance of amphibole in a source rocktable 9-1. partition coefficients (cs/cl) for some commonly used trace elements in basaltic and andesitic rocksolivineopxcpxgarnetplagamphmagnetiterb0.0100.0220.0310.0420.0710.29 sr0.0140.0400.0

13、600.0121.8300.46 ba0.0100.0130.0260.0230.230.42 ni14570.9550.016.829cr0.7010341.3450.012.007.4la0.0070.030.0560.0010.1480.5442ce0.0060.020.0920.0070.0820.8432nd0.0060.030.2300.0260.0551.3402sm0.0070.050.4450.1020.0391.8041eu0.0070.050.4740.243 0.1/1.5*1.5571dy0.0130.150.5821.9400.0232.0241er0.0260.2

14、30.5834.7000.0201.7401.5yb0.0490.340.5426.1670.0231.6421.4lu0.0450.420.5066.9500.0191.563data from rollinson (1993).* eu3+/eu2+italics are estimatedrare earth elementslsr and ba (also incompatible elements)table 9-1. partition coefficients (cs/cl) for some commonly used trace elements in basaltic an

15、d andesitic rocksolivineopxcpxgarnetplagamphmagnetiterb0.0100.0220.0310.0420.0710.29 sr0.0140.0400.0600.0121.8300.46 ba0.0100.0130.0260.0230.230.42 ni14570.9550.016.829cr0.7010341.3450.012.007.4la0.0070.030.0560.0010.1480.5442ce0.0060.020.0920.0070.0820.8432nd0.0060.030.2300.0260.0551.3402sm0.0070.0

16、50.4450.1020.0391.8041eu0.0070.050.4740.243 0.1/1.5*1.5571dy0.0130.150.5821.9400.0232.0241er0.0260.230.5834.7000.0201.7401.5yb0.0490.340.5426.1670.0231.6421.4lu0.0450.420.5066.9500.0191.563data from rollinson (1993).* eu3+/eu2+italics are estimatedrare earth elementscompatible example: lni strongly

17、fractionated olivine pyroxenelcr and sc pyroxenes olivine lni/cr or ni/sc can distinguish the effects of olivine and augite in a partial melt or a suite of rocks produced by fractional crystallizationtable 9-1. partition coefficients (cs/cl) for some commonly used trace elements in basaltic and ande

18、sitic rocksolivineopxcpxgarnetplagamphmagnetiterb0.0100.0220.0310.0420.0710.29 sr0.0140.0400.0600.0121.8300.46 ba0.0100.0130.0260.0230.230.42 ni14570.9550.016.829cr0.7010341.3450.012.007.4la0.0070.030.0560.0010.1480.5442ce0.0060.020.0920.0070.0820.8432nd0.0060.030.2300.0260.0551.3402sm0.0070.050.445

19、0.1020.0391.8041eu0.0070.050.4740.243 0.1/1.5*1.5571dy0.0130.150.5821.9400.0232.0241er0.0260.230.5834.7000.0201.7401.5yb0.0490.340.5426.1670.0231.6421.4lu0.0450.420.5066.9500.0191.563data from rollinson (1993).* eu3+/eu2+italics are estimatedrare earth elementsmodels of magma evolutionlbatch melting

20、 batch melting a plot of cl/co vs. f for various values of di using the previous equationfdi = 1.0di 1.0 (compatible element)fvery low concentration in meltfespecially for low % melting (low f)highly incompatible elements las f 1 the concentration of every trace element in the liquid = the source ro

21、ck (cl/co 1)cc1di(1f) flo=-+as f 0 cl/co 1/diif we know cl of a magma derived by a small degree of batch melting, and we know di we can estimate the concentration of that element in the source region (co)cc1di(1f) flo=-+cc1flo=cc1di(1f) flo=-+table 9-2. conversion from mode toweight percentmineral m

22、odedensity wt prop wt%ol153.6540.18cpx333.4112.20.37plag512.7137.70.45 sum303.91.00table 9-2. conversion from mode toweight percentmineral modedensity wt prop wt%ol153.6540.18cpx333.4112.20.37plag512.7137.70.45 sum303.91.00table 9-3 . batch fractionation model for rb and srcl/co = 1/(d(1-f)+f)drbdsr

23、f0.0450.848rb/sr0.059.351.148.190.16.491.135.730.154.981.124.430.24.031.123.610.32.921.102.660.42.291.082.110.51.891.071.760.61.601.051.520.71.391.041.340.81.231.031.200.91.101.011.09incremental batch meltinglcalculate batch melting for successive batches (same equation)lmust recalculate di as solid

24、s change as minerals are selectively melted (computer)lrayleigh fractionation the rare earth elements (ree)contrasts and similarities in the d values:all are incompatibletable 9-1 . partition coefficients for some commonly used trace elements in basaltic and andesitic rocksbulk d calculationolivineo

25、pxcpxgarnetplagamphrb0.0060.020.040.0010.10.3sr0.010.010.140.0011.80.57ba0.0060.120.070.0020.230.31ni1452.60.40.013cr2.1108.40.17101.6la0.0070.020.080.050.140.27ce0.0090.020.340.050.140.34nd0.0090.050.60.070.080.19sm0.0090.050.90.060.080.91eu0.0080.050.90.9 0.1/1.5*1.01tb0.010.0515.60.031.4er0.0130.

26、311180.080.48yb0.0140.340.2300.070.97lu0.0160.110.82350.080.89data from henderson (1982)* eu3+/eu2+italics are estimatedrare earth elementsree diagramsplots of concentration as the ordinate (y-axis) against increasing atomic number-3-2-1012345678910110102030405060708090100atomic number (z)log (abund

27、ance in ci chondritic meteorite)hhelibebcnofscfeninemgsiscaartipbptsnbavknaalpclthufeliminate oddo-harkins effect and make y-scale more functional by normalizing to a standard0.002.004.006.008.0010.00565860626466687072sample/chondritel la ce nd sm eu tb er yb lu?0.002.004.006.008.0010.00565860626466

28、687072sample/chondritel la ce nd sm eu tb er yb luleuropium anomaly when plagioclase isfig. 9-6. spider diagram for an alkaline basalt from gough island, southern atlantic. after sun and macdonough (1989). in a. d. saunders and m. j. norry (eds.), magmatism in the ocean basins. geol. soc. london spe

29、c. publ., 42. pp. 313-345. application of trace elements to igneous systemstable 9-1 . partition coefficients for some commonly used trace elements in basaltic and andesitic rocksbulk d calculationolivineopxcpxgarnetplagamphrb0.0060.020.040.0010.10.3sr0.010.010.140.0011.80.57ba0.0060.120.070.0020.23

30、0.31ni1452.60.40.013cr2.1108.40.17101.6la0.0070.020.080.050.140.27ce0.0090.020.340.050.140.34nd0.0090.050.60.070.080.19sm0.0090.050.90.060.080.91eu0.0080.050.90.9 0.1/1.5*1.01tb0.010.0515.60.031.4er0.0130.311180.080.48yb0.0140.340.2300.070.97lu0.0160.110.82350.080.89data from henderson (1982)* eu3+/

31、eu2+italics are estimatedrare earth elements0.002.004.006.008.0010.00565860626466687072sample/chondrite la ce nd sm eu tb er yb lu67% ol 17% opx 17% cpx0.002.004.006.008.0010.00565860626466687072sample/chondrite la ce nd sm eu tb er yb lu57% ol 14% opx 14% cpx 14% grtgarnet and plagioclase effect on

32、 hree0.002.004.006.008.0010.00sample/chondrite60% ol 15% opx 15% cpx 10%plag la ce nd sm eu tb er yb lutable 9-6 a brief summary of some particularly useful trace elements in igneous petrologyelementuse as a petrogenetic indicatorni, co, cr highly compatible elements. ni (and co) are concentrated in

33、 olivine, and cr in spinel andclinopyroxene. high concentrations indicate a mantle source.v, tiboth show strong fractionation into fe-ti oxides (ilmenite or titanomagnetite). if they behavedifferently, ti probably fractionates into an accessory phase, such as sphene or rutile.zr, hfvery incompatible elements that do not substitute into major silicate phases (although they mayreplace ti in sphene or rutile).ba, rbincompatible element that substitutes for k in k-feldspar, micas, or horn