Geochemical data from a weathered profile of Castlemaine Group sediments at Lockington, central Victoria, southeastern Australia.
Description
The mineralogy and geochemistry of a fresh to weathered profile of Ordovician Castlemaine Group turbiditic sediments from the Lockington East prospect, in central Victorian, southeastern Australia, is investigated to determine weathering conditions leading to the dissolution of apatite. A single drillhole, 07LODH030 from Lockington East, was used in this study based on the preservation of a large interval of fresh through to weathered basement. A combination of portable X-ray fluorescence (pXRF), whole rock geochemistry and apatite geochemistry has been utilised to characterise the mineral and chemical changes throughout the weathered profile.
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A single drillhole 07LODH030 from Lockington East was chosen in this study. The hole contains HQ diamond core from 66-134.2 m and NQ2 diamond core 134.2-307.6 m. Nine samples of sandstone and one sample of shale were taken through the cored section of drill hole 07LODH030 and selected to ensure a spread of fresh through to weathered rock. Handheld portable X-Ray Fluorescence measurements were taken every metre downhole, from the start of diamond coring at 66 m to the end of hole (308 m depth). The location for the analysis was chosen near the metre mark. The lithology was noted at each 1m interval to produce a complimentary geological log. QAQC included a quartz blank, standards (OREAS powders 602 and 621) and duplicates for every 20th sample in a standard bracketing array. Whole rock geochemistry of all ten samples was conducted at Bureau Veritas Mineral Testing and Laboratory Services at Wingfield, South Australia. Samples were initially coarse crushed and then pulverised to 75 μm. A lithium metaborate fusion was conducted prior to digest in nitric acid, in preparation for detection by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Fire assay was conducted on 40 g samples and Au detected by Atomic Absorption Spectrometry (AAS). Au internal standards were verified and are within 10 % error of determined concentrations. Apatite geochemistry was collected using an Agilent Triple Quadropole 8900X Inductively-Coupled Plasma-Mass Spectrometry coupled to a RESOlution 193 nm laser (LA-ICP-MS) at Adelaide Microscopy, University of Adelaide, South Australia. A series of standards were routinely measured throughout the analytical session in a standard bracketing procedure. Iolite (v. 4.0) was used to reduce raw data including corrections for baseline, instrumental drift and down-hole fractionation (Paton et al. 2011). Apatite geochemical data was calibrated and instrumental drift was corrected using the NIST 610 glass primary standard (Chew, Petrus & Kamber 2014). Secondary standard reference material, NIST 612, was analysed and compared to a known value of each element.
Institutions
- University of South Australia
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Funders
- Mineral Exploration Cooperative Research Centre