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  • 館藏編號:NTUG010-T300098
  • 題名:Igneous Rocks
  • 作者:阮維周
  • 藏品形式:稿本
  • 尺寸:210X297(mm)
  • 簡述:P.96
  • 內容:

    P.96 The equivalent molecular values of SiO2, P2O5, CO2, SO3, Ti02, Cl2, F2, S, and H2O are recalculated on the basis of al + fm + c + alk = 100, that is, they must be multiplied by the same factor as was used above. The resulting terms are called si, p, co2, so3. ti. cl2, f2, s and h and are the counterparts to al, fm, c and alk. The values si, al, fm, c, alk, ti, and p usually suffice to give a general characterization of silicate rocks. However, it is desirable to indicate the ratio of the equivalent value of K20 to that of the sum of the alkalies and similarly to establish what proportion of the femic oxides is MgO. If we call these two ratio k and mg respectively, we have the following relations: k = K / (Na + K) mg = Mg / (Fe + Mn + Mg) A rock may thus be characterized by quoting these values, which in petrographical literature are known as Niggli Value. For example: Granodiorite si al fm c alk k mg ti p (Placer County): 241 36 26 19 19 0.24 0.54 1.1 0.2 - 53 -