Problems with the U-Pb Radioisotope Dating Methods—1. Common Pb

U-Pb radioisotope dating is now the absolute dating method of first choice among geochronologists, especially using the mineral zircon. A variety of analytical instruments have also now been developed using different micro-sampling techniques coupled with mass spectrometers, thus enabling wide usage of U-Pb radioisotope dating. However, problems remain in the interpretation of the measured Pb isotopic ratios to transform them into ages. Among them is the presence of non-radiogenic Pb of unknown composition, often referred to as common or initial Pb. There is also primordial Pb that the earth acquired when it formed, its isotopic composition determined as that of troilite in the Canyon Diablo iron meteorite. Subsequently new crustal rocks formed via partial melts from the mantle. U decay in those rocks added daughter Pb isotopes to the common or initial Pb isotopes in them, inherited from the rock’s sources. So the Pb isotope ratios measured in these rocks today must be interpreted before their U-Pb ages can be calculated. Various methods have been devised to determine this initial or common Pb, but all involve making unprovable assumptions. Zircon does incorporate initial Pb when it crystallizes. The amount of 204Pb cannot be measured independently and accurately. It cannot be demonstrated that the initial Pb only consisted of 204Pb atoms. It cannot be proven that the Pb in apparently cogenetic Uor Th-free minerals is only initial Pb, and that it is identical to the initial Pb in the mineral being dated. Nor can the measured 206Pb, 207Pb, and 208Pb isotope ratios be used to somehow decide what proportions of them are the initial Pb without recourse to unprovable assumptions about the mineral or rock’s history or their interpreted U-Th-Pb ages within an assumed deep time history. Nevertheless, the ultimate foundation of this U-Pb dating methodology is the assumption that the earth formed from the solar nebula. However, from a biblical perspective the earth was created by God on Day 1 of the Creation Week before the sun and the rest of the solar system were created on Day 4, all only about 6000 or so years ago. Yet the earth would still have had an initial (created) Pb isotopic endowment. Once radioactive decay of U and Th started after creation, daughter Pb isotopes were added inside the earth. Then catastrophic plate tectonics during the Flood stirred the mantle and via partial melting added new rocks to the crust. These new rocks rapidly accumulated more Pb isotopes due to the concurrent accelerated radioactive decay of U and Th in them during the Flood. Thus, without being able to unequivocally distinguish the daughter Pb atoms produced by in situ U and Th decay from the initial Pb atoms in a mineral or rock, it is impossible to determine their absolute U-Pb ages. All the unprovable assumptions ultimately depend on an assumed deep time history. Its rejection is recognized as fatal to the earth’s claimed age of billions of years. There is thus no impediment to accepting and using the Bible’s account of Creation and the Flood as a reliable framework for unravelling the history of the earth and the Pb isotopes found in its minerals and rocks.