Selected Whole-Rock and Sediment Geochemistry Reanalysis Data Additions to the Alaska Geochemical DataBase (AGDB) from Archived Samples, Alaska

This data release contains elemental concentration data from the reanalysis of 13,930 archived stream-sediment sample and associated stream sediment reference material and 968 archived rock samples and associated rock reference material. All archived material was from samples that were collected in Alaska. Samples were retrieved from the USGS Mineral Program's sample archive in Denver, CO. Sample processing consisted of splitting the appropriate aliquot for the requested analyses. Sample splitting was performed in the USGS Mineral Program's sample prep facilities. 13,800 samples were analyzed using a multi-element analytical method involving decomposition of the sample by sodium peroxide and elemental analysis by inductively coupled plasma-optical emission spectroscopy (ICP-AES) or inductively coupled plasma-mass spectroscopy (ICP-MS) depending on the element. A suffix AES_ST or MS_ST is used in column headers to indicate analysis by this method. Additionally, some samples were also analyzed by one of two other multi-element methods. 4864 samples were analyzed by a multi-element method in which a mixture of nitric acid (HNO3) and hydrochloric acid (HCl) was used to decompose the sample. This digestion method it commonly referred to as an Aqua Regia (AR) digestion and is considered a less aggressive digestion than a sinter digestion. Elemental analyzed was by ICP-MS. A suffix MS_AR_P column headers indicates analysis by this method. 118 samples were analyzed by a multi-element method using a mixture of hydrochloric, nitric, perchloric, and hydrofluoric acids to decompose the sample. Elemental analysis was done by ICP-AES or ICP-MS depending on the element. The suffix AES_HF or MS_HF indicates analysis by this mix-acid method. 130 stream sediment samples were analyzed only for the mercury. For these samples mercury concentrations were determined by cold-vapor atomic absorption spectrometry following sample digestion by a mixture of sulfuric and nitric acids, and dilute potassium permanganate and potassium persulfate. The suffix AA_CV indicates analysis by this method. All rock samples (968) were analyzed by the method using the sodium peroxide sample digestion described above. As with the stream sediment samples a suffix AES_ST or MS_ST is used in column headers in the rock sample dataset to indicate analysis by this method. 490 rock samples were also analyzed by the aqua-regia method. A suffix MS_AR_P column headers indicates analysis by this method. 478 samples were analyzed by a multi-element method in which the sample is decomposed using a lithium metaborate fusion and analysis by ICP-AES. A suffix AES_Fuse indicates analysis by this method. All analyses were performed between 2019 to 2023 by AGAT laboratories. AGAT was the USGS contract laboratory during the period of analysis.