State of Alaska Alaska | Natural Resources DNR | Geological & Geophysical Surveys DGGS | Geochemistry Geochem

Sample Detail

Sample Number MH497D

Sample Documentation

Analyses [Download All]

Reference Number MRP-13904
Reference Date 2014-11-01
Citation RDF 2015-7
Laboratory SGS Minerals Services
Laboratory Number C-386705
Description Historical sediment samples were retrieved from the National Geochemical Sample Archive (NGSA) in Denver, Colorado, by USGS staff, then weighed, ground to -200 mesh and, where sufficient material was available, split into aliquots needed for analyses. Leftover material was re-archived at the NGSA. Sample splits were submitted to the USGS contract lab (SGS Minerals Services, Lakefield, Canada) for analysis. Gold, Pt, and Pd were determined by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) after collection by fire assay. An assay ton (30 grams) was weighed into a crucible with 150 grams of flux and mixed. One mg of silver nitrate was added and covered with borax, and then placed in the furnace for 45 minutes at 1,080 degrees C. The melt was poured into a cast-iron mold, cooled, and hammered to free the lead button from the slag. The lead button was placed on a cupel and heated at 950 degrees C until all the lead was removed. The resulting dore bead was dissolved in a mixture of nitric acid and hydrochloric acid and heated in a water bath. The final solution was adjusted to 10 ml and introduced into the ICP-MS. Fifty-five major (except Si and Na), rare-earth, and trace elements were determined in geologic materials by inductively coupled plasma-atomic emission spectrometry (ICP-AES) and ICP-MS. The 0.10 g sample was decomposed using a sodium-peroxide sinter at 450 degrees C. The resultant cake was leached with water for a minimum of 4 hours, and acidified with nitric acid. After an addition of tartaric acid, aliquots of the digested sample were aspirated into the ICP-AES and the ICP-MS. The concentrations of the optimal elements from the ICP-AES and ICP-MS were determined. Tellurium content was determined by weighing 0.25 g of sample into a Teflon tube, adding a mixture of nitric, hydrofluoric, and perchloric acids and heating the sample. After the solution cooled, hydrochloric and nitric acids were added, and the sample was heated again, and then cooled. The samples were diluted and analyzed using hydride-generation atomic absorption spectrometry with an auto-analyzer and automated data collection system from Labtronics.
Sample Type glacial debris/deposit