JonF
Posts: 634
Joined: Feb. 2005
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That article's a rehash of his 1998-ish work in The Cause of Anomalous Potassium-Argon "Ages" for Recent Andesite Flows at Mt. Ngauruhoe, New Zealand, and the Implications for Potassium-Argon "Dating". Large swathes of the "new" article are word-for-word cut-and-pasted from the old article.
Ngauruhoe lava is chock-full of xenoliths; it's a mixture of old and new material. Any dating of Ngauruhoe lava is invalid unless the method for separating the xenoliths is specified. I quote Snelling:
| Quote | All samples were sent first for sectioning—one thin section from each sample. These were subsequently all carefully examined under a petrographic microscope and their mineralogy and textures recorded. A set of representative pieces from each sample (approximately 100 g) was then dispatched to the AMDEL Laboratory in Adelaide, South Australia, for whole-rock major, trace and rare earth element analyses. A representative set (50–100 g from each sample) was also sent to Geochron Laboratories in Cambridge (Boston), Massachusetts, for whole-rock potassium-argon (K-Ar) dating.81 A third representative set (50–100 g from ten of the samples—two samples from each flow) was sent to the PRISE Laboratory in the Research School of Earth Sciences at the Australian National University in Canberra, Australia, for Rb-Sr, Sm-Nd, and Pb-Pb isotopic determinations.
At the AMDEL Laboratory each sample was crushed and pulverized. Whole-rock analyses were undertaken by total fusion of each powdered sample and then digesting them before ICP-OES (inductively coupled plasma—optical emission spectrometry) for major and minor elements, and ICP-MS (inductively coupled plasma—mass spectrometry) for trace and rare earth elements. Fe was analyzed for amongst the major elements by ICP-OES as Fe2O3 and reported accordingly. Additionally, separate analyses for Fe as FeO were undertaken via wet chemistry methods, which were also used to measure the loss on ignition (primarily H2O content). The detection limit for all major element oxides was 0.01%. For minor and trace elements the detection limits varied between 0.5 and 20 ppm, and for rare earth elements between 0.5 and 1 ppm.
The Rb-Sr, Sm-Nd, and Pb-Pb isotopic analyses were undertaken at the PRISE Laboratory under the direction of Dr. Richard Armstrong. No specific sample location or expected age information was supplied to the laboratory, although samples were described as young andesites so that the laboratory staff would optimize the sample preparation procedure in order to obtain the best analytical results. At the laboratory the sample pieces were crushed and pulverized, and then dissolved in concentrated hydrofluoric acid, followed by the standard chemical separation procedures for each of these isotopic systems. Once separated, the elements in each isotopic system were loaded by standard procedures onto metal filaments to be used in the solid source thermal ionization mass spectrometer (TIMS), the state-of-the-art technology in use in this laboratory. Sr isotopes were measured using the mass fractionation correction 86Sr/88Sr = 0.1194. The 87Sr/86Sr ratios reported were normalized to the NBS standard SRM 987 value of 0.710207. Nd isotopes were corrected for mass fractionation using 146Nd/144Nd = 0.7219, and were normalized to the present-day 143Nd/144Nd value of 0.51268 for BCR-1. Pb isotope ratios were normalized to NBS standard SRM 981 for mass fractionation.
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Steiner111 stressed that xenoliths are a common constituent of the 1954 Ngauruhoe lavas, but also noted that Battey112 reported the 1949 Ngauruhoe lava was rich in xenoliths. All samples in this study contained xenoliths, including those from the 1975 avalanche material. |
{emphasis added}
"Whole-rock" means what it says; the entire sample is crushed and analyzed without any attempt to separate any constituents. Nobody separated the xenoliths.
It's pure garbage, and even recycled garbage.
{ABE: Geochron hasn't done K-Ar analyses for several years. It's declined in popularity, and their main K-Ar guy quit, so they just shut sown the division}.
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