Geologists and dating (India Basins Half a Billion Years Older Than Thought)

PH, I have looked at your paper "The True Age of Zircons" and would like to make the following comments.You claim to be able to make a more accurate estimation of the true age of zircons (presumably more accurate than that made by geochronologists) by determining the actual amounts of the Uranium isotopes ²³⁴U and ²³⁸U in a zircon sample. If the ratio of these two isotopes is greater than that which occurs at secular equilibrium in the ²³⁸U decay chain ie 0.00005494 then you claim the age of the zircon will be much less than that calculated by science.To prove your point you have used the results of analyses of zircons (S.Wilde et. al., NATURE 409, 175 (2001)) from the famous, Australian Jack Hills conglomerate, which contains the oldest documented zircon crystals on Earth at aprox. 4300 Myr.. By working back from the reported Pb and U isotopic data you claim that the ²³⁴U : ²³⁸U ratio is 1.301187 not the supposed 0.00005494 and that the age of the crystals must be much less than the claimed 4300 Myr.A number of questions immediately arise.1. How is it that you alone have been granted an incredible insight, which has been denied thousands of scientists over the last 70 years? Or are you suggesting a worldwide conspiracy among these scientists to hide this information from the rest of the world, or are they just incompetent?2. How has the ²³⁴U escaped detection?3. Where has this ²³⁴U come from?4. What is the true age of Wilde's zircon 74-36. He and his co-workers date it at 4383 ⁺/_- 4 Myr that's pretty accurate! But all you say is that it is "much younger than that" - hardly a "more accurate age estimation"! So what is it?5. Have you considered you might be mistaken?Let's look at your calculations.You first determine the amount of the individual Pb isotopes from the ratios wrt. ²⁰⁶Pb and the total amount of lead, Pb_Total. You state that the amount of ²⁰⁶Pb is equal to:-
Pb_Total*(1 - ²⁰⁴Pb/²⁰⁶Pb - ²⁰⁷Pb/²⁰⁶Pb - ²⁰⁸Pb/²⁰⁶Pb). Mistake no. 1 - this is wrong!Pb_Total = ²⁰⁴Pb + ²⁰⁶Pb + ²⁰⁷Pb + ²⁰⁸PbDividing by ²⁰⁶Pb gives:-Pb_Total/²⁰⁶Pb = ²⁰⁴Pb/²⁰⁶Pb + 1 + ²⁰⁷Pb/²⁰⁶Pb + ²⁰⁸Pb/²⁰⁶Pb and therefore:-²⁰⁶Pb = Pb_Total/(²⁰⁴Pb/²⁰⁶Pb + 1 + ²⁰⁷Pb/²⁰⁶Pb + ²⁰⁸Pb/²⁰⁶Pb) which is not the same as the formula that you derived.Substituting the values from Wilde - row 1 of Table 1 - which you used in your calculation gives:-²⁰⁶Pb = 355(0.00014 + 1 + 0.5432 + 0.1645) = 207.86 (not your value of 97.87)

Sorry! the second half of my post was missingThe amounts of the other isotopes are then easily calculated from their reported ratios wrt ²⁰⁶Pb
²⁰⁷Pb = 112.9 and²⁰⁸Pb = 34.2²⁰⁴Pb is negligibleYou then use the amounts of ²⁰⁶Pb and ²⁰⁷Pb to calculate the amount of ²³⁸U and ²³⁵U from the reported ²⁰⁶Pb/²³⁸U and ²⁰⁷Pb/²³⁵U ratios and obtain a value of 111.76 for ²³⁸U and 0.81 for ²³⁵U. Mistake no. 2. This is also wrong!The Pb and the Pb/U isotopic ratios are reported in atomic ratios whereas (although this is not stated in the table). The actual quantities of Pb and U are reported in weight ratios. To convert from one to another the atomic weights of each isotope must be taken into account. Thus the ratio of ²⁰⁶Pb/²³⁸U in atomic units must be multiplied by the ratio of their atomic weights ie (206/238)=0.866 to obtain the weight ratio.Similarly for ²⁰⁷Pb and ²³⁸U. The conversion factor is (207/235) = 0.884.Using the values from Wilde, row 1, Table 1.²⁰⁶Pb/²³⁸U = 0.928 in atomic units
²⁰⁶Pb/²³⁸U = 0.928 * 0.866 = 0.803 in weight units, and the value for ²⁰⁷Pb/²³⁵U becomes 69.5 * 0.884 = 61.44So ²³⁸U = ²⁰⁶Pb/0.928 = 207.86/0.928 = 258.85 and²³⁵U = ²⁰⁷Pb/61.44 = 1.84As there are only three naturally occuring isotopes of Uranium the amount of ²³⁴U can be calculated from the simple difference between U_Total less the sum (²³⁸U + ²³⁵U) i.e.258 - (258.85 + 1.84) = -2.69. The slight error is due to the errors in the absolute concentrations of U and Pb caused by uncertainties in the sample weight - something that I imagine is common to all SHRIMP analyses of zircons - and large uncertainties in the concentration of U and Pb, which can, apparently, be up to as much as 20%! As these values are not used in the calculations of age in the concordia method these errors have no bearing on the result and presumably is the reason why no errors are listed in the Table. The Pb/Pb and Pb/U ratios used for age calculation are, however, extremely accurate as Wilde's Table 1 shows.So your more accurate method is based on a simple algebraic mistake and a missing conversion factor. This hardly inspires confidence in the accuracy of your other model.Best wishesChris