GEMOC ARC National Key Centre
Parameters used in correction of common lead, and shorthand notation used in equations |
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Parameter |
Standard notation |
Shorthand |
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Radiogenic 206Pb/238U ratio |
206Pbr/238U |
yr |
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Radiogenic 207Pb/235U ratio |
207Pbr/235U |
xr |
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Radiogenic 208Pb/232Th ratio |
208Pbr/232Th |
zr |
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Concordant isotopic ratios at t1 |
206Pbt1/238U, 207Pbt1/235U, 208Pbt1/232Th |
yt1, xt1, zt1 |
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Concordant ratios at t2 |
206Pbt2/238U etc |
yt2, xt2, zt2 |
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207Pb/206Pb of common lead |
207PbC/206PbC |
c7 |
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208Pb/206Pb of common lead |
208PbC/206PbC |
c8 |
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Isotope ratio in present-day uranium (137.88) |
238U/235U |
k |
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Ratio in sample |
238U/232Th |
u |
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Observed, uncorrected ratios |
206Pb/238U, 207Pb/235U, 208Pb/232Th |
y, x, z |
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Fraction of common 206Pb |
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fc |
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Fraction of lead lost at t2 |
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fl |
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Discordance (in percent) |
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D=(1-fl)*100 |
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Real age of zircon (upper intercept age) |
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t1 |
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Age of lead loss (known or assumed) |
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t2 |
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206Pb/207Pb of corrected composition |
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t76r |
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206Pb/238U of corrected composition |
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t6r |
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207Pb/235U of corrected composition |
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t7r |
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208Pb/232Th of corrected composition |
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t8r |
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Error (standard deviation) in parameter a |
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σa
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Correlation coefficient of errors in measured 206Pb/238U, 207Pb/235U |
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ρ
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Correlation coefficient of errors in corrected 206Pb/238U, 207Pb/235U |
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ρr
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symbol |