Sulfur isotope microanalyses of pyrite and chalcopyrite from Spremberg (east Germany)

In this data publication we describe whole rock geochemistry and 34S values generated using secondary ion mass spectrometry (SIMS) from samples collected from 2 drill holes intersecting the Spremberg-Graustein deposit (eastern Germany). The samples include the uppermost Rotliegend sandstone (S1), Kupferschiefer (T1) mudstones and lowermost Zechstein Limestone (Ca1m). All analytical work was conducted at the GFZ Helmholtz Centre for Geosciences.
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A total of 17 samples were taken from two drill cores (115a/71 and 121h/72) stored in the drill core repository of the LBGR Brandenburg State Office for Mining, Geology and mineral resources in Wünsdorf, Brandenburg.

Powdered samples were prepared for whole rock analysis. Trace element concentrations were analyzed using ICP-MS as described by Romer and Hahne (2010). Briefly, around 250 mg of sample powder was weighed into 15 ml Teflon vials (Savillex®) and decomposed using HF, Aqua Regia (3:1 mixture of 37% HCl and 63% HNO3), and perchloric acid (HClO4). In a first step, 4 mL HF and 4 mL Aqua Regia were added to the samples. The tightly closed vials were placed into a heating block (160 °C) for 14 h. After cooling, 1 mL HClO4 (70%) was added to destroy the organic material and fluorides. This solution was evaporated at 180 °C to incipient dryness. The samples were re-dissolved in 1 mL 7 N HNO3 and dried. Then, the HClO4 step was repeated twice. The samples were re-dissolved in 7 N HNO3 and kept at 100 °C for 14 h. This solution was brought to a volume of 50 ml for analysis. Data were acquired in peak jumping mode using a Galileo 4870 in pulse counting mode.
To determine regions of interest for SIMS analysis, thick sections were prepared and investigated under binocular microscope. Selected areas were then extracted using a micro drill press and a total of 11 grains were prepared in a grain mount together with pyrite and chalcopyrite reference materials (Balmat, Trout Lake; δ34S = 15.1‰ and 0.3‰ respectively; Crowe and Vaughan, 1996)). The SIMS mount was polished and gold coated. The mount was imaged on the SEM in both backscattered electron (BSE) and secondary electron (SEM) model. Pyrite, chalcopyrite, and reference materials were analysed using secondary ion mass spectrometry (SIMS) following the analytical settings reported previously (Rieger et al., 2020; Magnall et al., 2020). The 133Cs+ primary ion beam with 20 KeV incident energy was focused to a beam diameter of 5 μm. Each analysis point was pre-sputtered for 100 s on a 15 μm raster to remove the potential gold coating, and data collection was then carried out for 100 s. The secondary ion signals for 34S− and 32S− were simultaneously collected using Faraday cup detectors. δ34S values are reported as per mil (‰) deviation from V-CDT (Vienna Canyon Diablo Troilite). Each analysis spot (n = 208) was imaged using SEM to identify the analyzed phases and 23 analyses were rejected due to potential mixed phases. The analytical uncertainties were monitored through the analysis of the two standards and 82 analyses were collected, yielding a standard deviation of ± 0.2‰ for Balmat pyrite (2 SD, n = 47) and ± 0.9‰ for Trout Lake chalcopyrite (2 SD, n = 35).