SRMP Dynamic Earth Curriculum - American Museum of Natural ...

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Science Research Mentoring ProgramDynamic EarthSession Ten: VolcanismWORKSHEET: Volcanic Rock Identification - Page 3Identification Part BNow let’s get even more specific. You can use the Ti-Zr-Y and Zr-Nb-Y discrimination charts onpage 4 to further classify volcanic rocks. Refer to the appropriate data on Table 2. Note that thediscrimination charts may require you to multiply or divide the ppm value by a whole number.For example, on the Ti-Zr-Y chart, you multiply the ppm of Yttrium by 3, and divide the ppm ofTitanium by 100. This has been done for you in Tables 3 and 4.However, when all three elements are added up for a given rock sample, the total may not be 100.Uh-oh! That means that the data needs to be normalized; the total must be 100%, so you need toknow what percent of the total is represented by each of the three elements. These normalizedvalues appear in the tables below.Table 3: Normalizations for Ti-Zr-YRaw Data (ppm) Totals to be Normalized Normalized ValuesY Ti Zr Y*3 Ti/100 Zr Total 3*Y Ti/100 Zr Total1 9.00 2577.14 27.00 27.00 25.77 27.00 79.77 33.85 32.31 33.85 100.002 23.00 16628.78 173.00 69.00 166.29 173.00 408.29 16.90 40.73 42.37 100.003 57.00 6352.94 70.00 171.00 63.53 70.00 304.53 56.15 20.86 22.99 100.004 27.00 9289.68 139.00 81.00 92.90 139.00 312.90 25.89 29.69 44.42 100.005 49.34 11447.28 162.20 148.02 114.47 162.20 424.69 34.85 26.95 38.19 100.00Table 4: Normalization for Zr-Nb-YRaw Data (ppm) Totals to be Normalized Normalized ValuesY Nb Zr Y 2Nb Zr/4 Totals Y 2Nb Zr/4 Totals1 9.00 0.21 27.00 9.00 0.42 6.75 16.17 55.66 2.60 41.74 100.002 23.00 44.00 173.00 23.00 88.00 43.25 154.25 14.91 57.05 28.04 100.003 57.00 51.00 70.00 57.00 102.00 17.50 176.50 32.29 57.79 9.92 100.004 27.00 11.00 139.00 27.00 22.00 34.75 83.75 32.24 26.27 41.49 100.005 49.34 4.41 162.20 49.34 8.82 40.55 98.71 49.98 8.94 41.08 100.00Use the Ti-Zr-Y and Zr-Nb-Y discrimination charts on page 4, and the corresponding normalizedvalues from Tables 3 and 4 above to determine what (if any) type of volcanic rocks the samples are.4. Place the number for each rock at the appropriate place on either discrimination chart. Record theletter from the discrimination chart and the corresponding rock types below.Rock 1: Rock 4:Rock 2: Rock 5:Rock 3:© 2013 American Museum of Natural History. All Rights Reserved. 46
Science Research Mentoring ProgramDynamic EarthSession Ten: VolcanismWORKSHEET: Volcanic Rock Identification - Page 4Identification Part CNow that you know what types of rocks you have, you should be able to figure out where they werefound. Suppose you’re given the following list of locations: Saint Helena Island in the South AtlanticOcean, Mount St Helens in Washington, South Sandwich Island Arc.5. Identify the location from which specimens 1, 2 and 4 were collected, based on what you knowabout the specimens, and the types of rocks that would form at the listed locations.Rock 1: Rock 3:Rock 2: Rock 4:© 2013 American Museum of Natural History. All Rights Reserved. 47
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