Location of the Philippine Sea Geotraverse

Geophysical Center of the Russian Academy of Sciences, Moscow, Russia
World Data Center for Solid Earth Physics
The Geotraverse Project

The Philippine Sea Geotraverse


Table 2.
40 Ar / 39 Ar Total Fusion Ages of Mineral Separates From the Magellan Seamounts
( Smith et al., 1989 )

Sample Material J 40Ar/39Ar 37Ar/39Ar a 36Ar/39Ar 36Ar/Ca b 39ArCa b 40ArK b 40ArR b Arc c
µm   Ma ± 1 s.d.
Himu Seamount
RC26 4-1 hornblende 125-500 0.002656 30.653 5.7717 0.01718 8.87 0.39 0.02 84.9 121.0 ± 0.8
  plagioclase 125-250 0.00449 15.723 12.843 0.00483 66.76 0.86 0.24 96.7 120.2 ± 0.8
        15.639 12.797 0.00438 73.31 0.86 0.24 97.5 120.5 ± 2.6
        15.724 13.015 0.00487 67.06 0.87 0.24 96.7 120.2 ± 1.0
        15.745 14.516 0.00665 54.77 0.97 0.24 94.1 117.3 ± 1.0
        15.624 14.089 0.00472 74.86 0.95 0.24 97.5 120.5 ± 0.9
        15.964 14.273 0.00685 52.27 0.96 0.24 93.7 118.4 ± 1.3
Weighted age   119.6 ± 0.7
RC26 4-8 bornblende 250-500 0.002656 31.025 5.7963 0.01973 7.76 0.39 0.02 82.7 119.3 ± 0.8
    250-500 0.002656 30.650 5.7027 0.01823 8.26 0.38 0.02 83.9 119.6 ± 0.8
Hemler Guyot
RC26 7-5/8 nepheline 125-250 0.005137 11.020 0.02535 0.0001819 3.70 0.002 0.05 99.5 98.8 ± 0.7
        11.209 0.02454 0.0002349 2.76 0.002 0.05 99.3 100.4 ± 0.7
        11.115 0.01481 0.0000133 29.3 0.001 0.05 99.9 100.1 ± 0.8
        11.081 0.03387 0.0001626 5.50 0.002 0.05 99.5 99.4 ± 0.8
        11.004 0.00788 0.0000198 10.5 0.001 0.05 99.9 99.1 ± 0.9
        11.169 0.02065 0.0004696 1.16 0.001 0.05 99.7 99.4 ± 1.0
        11.093 0.07488 0.0001992 9.93 0.005 0.05 99.5 99.5 ± 1.3
        11.151 0.09095 0.0000370 64.5 0.006 0.05 99.9 100.4 ± 1.5
Weighted age   99.5 ± 0.6
RC26 7-15 plagioclase 125-250 0.00448 13.332 1.5626 0.002557 15.34 0.10 0.29 94.9 99.6 ± 0.9
        13.331 1.0831 0.001255 21.66 0.07 0.29 97.5 102.2 ± 1.3
        3.298 0.7551 0.001572 12.06 0.05 0.29 96.6 101.0 ± 0.9
Weighted age   100.7 ± 0.6
a - Corrected for 37 Ar decay, half-life = 35.1 days.
b - Subscripts indicate radiogenic (R), calcium-derived (Ca), and potassium-derived (K) argon, respectively.
c - Ages were calculated using L e=0.581 · 10 -10 yr -1, L b = 4.962 · 10 -10 yr -1, 40K/K-total = 1.167 · 10 -4 mol/mol; errors are estimates of the standard deviation of analytical precision with a long-term limiting precision of 0.5%. Weighted ages are weighted by the inverse of the variance.
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