Microseismic and Groundwater Geochemistry data at Grimsel Test Site

Microseismic data: This data set includes the microseismic recordings used for the paper by Stillings et al. The data were acquired at Grimsel Test Site using two microseismic arrays. All data sets provides come from the North microseismic array. For the dates 14th and 20th March 2016, the data provided also include the recordings from the South array.
Groundwater Geochemistry data: Table of physiochemical and dissolved ion chemical results for groundwater sampled from 13 different borehole intervals at the Grimsel Test Site (Switzerland), collected from Nov-2014 to Apr-2016. This data table accompanies a publication where the necessary methodology and sampling procedures have been recorded. Detection limits are recorded in the table.
Physiochemical data (electrical conductivity, pH and redox potential) were recorded using a YSI ProPlus multi meter attached to borehole flow lined via a flow through cell. The multi meter was calibrated daily using a one-point calibration for electrical conductivity and redox potential and a three-point calibration for pH. Eh measured using ORP probe was calibrated with a one-point calibration using Reagecon 250mV (± 5mV) Redox Oxidation/Reduction (ORP) standard (measurement accuracy ± 20mV). 3-point pH calibration was carried out using Reagecon buffer solutions pH 4.00 (± 0.01), pH 7 (± 0.01), pH 10 (± 0.01) (measurement accuracy ± 0.2). Electrical conductivity one-point calibration using Reagecon 84 μS/cm (± 1%) (measurement accuracy ± 1%). Water samples, Flow rate and physiochemistry data were collected every 30 seconds during and after the borehole interval was flushed. Flushing involved flowing through three times the interval volume prior to collecting a water sample to ensure formation water was being sampled and not residual water in the flow lines or borehole. Flow rate was measured using a measuring cylinder and stopwatch. Water samples were taken for analysis of dissolved ions, and alkalinity. Samples were collected in duplicate for Cation and Anion analysis, filtered through a 0.45 μm cellulose acetate filter, sealed in HDPE centrifuge tubes, and stored at 4°C. Cations were acidified to pH 2 using analytical grade HNO3 prior to storage. Unfiltered samples were collected for alkalinity titration using a Hach digital field titrator the same day, titrations were completed within six hours of sample collection. Alkalinity titrations are time sensitive as CO2 in-gassing and degassing causes a change in the carbonate/bicarbonate/carbon dioxide equilibrium, which could potentially lead to anomalous alkalinity results.

Major and minor ions (University of Strathclyde, Glasgow), analysis was performed under laboratory conditions, on collected and preserved samples. Anion analysis (Br-, Cl-, F-, NO2-, NO3-, PO43-, SO42-) was carried out using Ion Chromatography (Metrohm 850 Professional IC). Calibration was performed using a 7-point calibration, standards were prepared from stock 10000 mg/l solutions of certified reference material (CRM) TraceCERT® diluted by 18.2 MΩ-cm ultrapure water. Quantification limits for each analyte are as follows: Cl-/F-/SO42- – 0.1 mg/l, Br-/NO2-/NO3-/PO43- – 0.01 mg/l. Cation (Al3+, Ba2+, Ca2+, Fetot, K+, Li+, Mg2+, Mn2+, Na+, Sr+, Si dissolved) analysis, and Inductively Coupled Plasma Optical Emission Spectra (ICP-OES) iCAP 6000 Series (ThermoFisher). Calibration was performed using 3-point calibration. Calibration standards were prepared from a stock solution 10000 mg/l solution in HNO3 2-3% (CRM) Centipur® diluted by 18.2 MΩ-cm ultrapure water. The matrix matched to the acidified sample. Quantification limits for each analyte are as follows: Al3+/Ba2+/Fetot /Mg2+/Mn2+/Li+/Sr+ -- 0.001 mg/l, K+ -- 0.09 mg/l, Na+ -- 0.052 mg/l, Si dissolved – 0.003 mg/l, Ca2+ -- 0.52 mg/l.