Petrogenesis of Plio-Pleistocene volcanic rocks from the chagai arc ...

Table 1. ContinuedElements Dam Koh Volcanics Koh-e-Dalil Volcanics& Ratios Dk-1 Dk-2 Dk-3 Dk-4 Dk-5 Kd-1 Kd-2 Kd-3 Kd-4SiO 2 60.15 61.55 60.98 63.16 63.76 57.98 58.12 59.87 59.37TiO 2 0.51 0.52 0.54 0.48 0.49 0.7 0.71 0.61 0.61Al 2 O 3 17.4 17.97 17.83 17.22 17.01 17.76 17.93 17.6 17.41Fe 2 O 3 5.45 5.47 5.58 4.88 4.65 6.47 6.49 5.72 5.74MnO 0.1 0.12 0.11 0.1 0.1 0.11 0.11 0.1 0.1MgO 3.24 2.43 2.89 2.57 2.6 4.11 3.99 3.51 3.59CaO 7.96 6.37 6.36 5.95 5.65 7.76 7.6 7.2 8.16Na 2 O 4.25 4.43 4.36 4.21 4.24 3.78 3.72 3.87 3.78K 2 O 0.78 0.94 1.11 1.26 1.33 1.12 1.14 1.18 1.09P 2 O 5 0.17 0.2 0.24 0.17 0.18 0.2 0.19 0.26 0.16FeOt/MgO 1.50 2.00 1.72 1.69 1.59 1.42 1.46 1.48 1.44Na 2 O/K 2 O 5.45 4.71 3.93 3.34 3.19 3.38 3.26 3.28 3.47K 2 O/Na 2 O 0.18 0.21 0.25 0.30 0.31 0.30 0.31 0.30 0.29Mg # 54 47 51 51 53 Ti 3055 3115 3235 2875 2935 4193 4253 3654 3654K 6474 7802 9213 10458 11039 9296 9462 9794 9047P 741 872 1046 741 785 872 828 1134 698Rb 16 21 31 31 30 16 16 18 17Sr 590 523 545 619 591 917 890 857 855Ba 369 375 423 661 608 410 398 425 423V 112 105 105 84 96 201 195 183 170Cr 74 54 115 43 56 32 33 33 35Co 19 16 18 13 14 21 19 12 20Ni 21 7 18 13 14 14 13 12 12Zr 92 128 124 96 98 113 113 112 109Y 12 15 15 12 12 13 14 13 12Nb 4 5 7 6 7 4 4 4 4Sc 17 12 15 14 16 28 26 22 23Rb/Y 1.33 1.40 2.07 2.58 2.50 1.23 1.14 1.38 1.42Ba/Y 30.75 25.00 28.20 55.08 50.67 31.54 28.43 32.69 35.25Ba/Zr 4.01 2.93 3.41 6.89 6.20 3.63 3.52 3.79 3.88Zr/Y 7.67 8.53 8.27 8.00 8.17 8.69 8.07 8.62 9.08Zr/Nb 23.00 25.60 17.71 16.00 14.00 28.25 28.25 28 27.25Ti/Zr 33.21 24.33 26.09 29.95 29.95 37.11 37.64 32.63 33.52Ti/V 27.28 29.66 30.81 34.23 30.57 20.86 21.81 19.97 21.49K/Rb 405 372 297 337 368 581 591 544 532K/Ba 17.54 20.81 21.78 15.82 18.16 22.67 23.77 23.04 21.39Rb/Sr 0.027 0.040 0.057 0.050 0.051 0.017 0.018 0.021 0.020Sr/Rb 37 25 18 20 20 57.31 55.63 47.61 50.29Nb/Y 0.33 0.33 0.47 0.50 0.58 0.31 0.29 0.31 0.33Sc/Ni 0.81 1.71 0.83 1.08 1.14 2.00 2.00 1.83 1.92FeOt = Total iron as FeOt, Mg # =100xMg /Mg+Fe +2 , SiO 2 -P 2 O 5 are in %, Rb-Yb are in ppmAll the rock samples collected from Plio-Pleistocene volcanics are classified according tothe TAS (total alkali silica) classification of IUGSand are plotted in SiO 2 versus alkali (wt. %)diagrams (Fig. 5) of Le Bas et al. (1986). In thisdiagram, 22 samples plot in andesite fields,whereas five from Koh-e-Sultan area and twofrom Dam Koh area plot in dacite field or just onboundary between andesite and dacite fields. Allthe samples from Plio-Pleistocene volcanics arealso plotted in K 2 O versus SiO 2 diagrams (afterGill, 1981). In this diagram samples plot inmidium to low-K.andesite and dacite fields (Fig.6).12