Results of a high throughput, robust and sensitive method for the precise analysis of 87Sr/86Sr by Multi-Collector-Inductively Coupled Plasma-Mass Spectrometer (MC-ICP-MS), Thermo Scientific Neptune PlusTM are reported. The data were obtained after accurate procedures of chemical separation and purification of Sr from geological matrices such as silicates, sulfides, carbonates and waters, using Eichrom Sr-spec resins as well as the routine for Sr isotope measurement. Mass discrimination and instrument drift were corrected by using natural constant 86Sr/88Sr ratios as an internal standard. Data on set of international certified standard materials (SRM NIST 987 and AGV-1) as well as intra-lab reference samples (water sample KGV-9) measured with MC-ICP-MS Neptune Plus, focusing on the accuracy and reproducibility of the analyses performed in the Neptune-TIMS Laboratory are here reported.
Trace metal and isotopic ratios, including some rare earth elements, Mg/Ca, manganese and strontium concentrations, δ¹⁸O, δ¹³C, and ⁸⁷Sr/⁸⁶Sr, were analyzed in the carbonate cements from 17 Phanerozoic carbonate hardgrounds. The sensitivity of the geochemical signal to alteration depends on the geochemical analysis in question and the environmental water-rock ratio. Of these samples, only our modern sample has measurements consistent with primary precipitation from seawater; all other samples precipitated from chemically evolved seawater or were influenced by meteoric water, even if only minimally changed. The more recent samples from the Cenozoic had seawater ⁸⁷Sr/⁸⁶Sr. The Mesozoic samples, in contrast, did not preserve seawater ⁸⁷Sr/⁸⁶Sr, even though the Mg/Ca, δ¹⁸O, and δ¹³C values were consistent with precipitation from seawater. Finally, the Paleozoic samples preserved expected seawater ⁸⁷Sr/⁸⁶Sr, though REE and δ¹⁸O suggest primary precipitation was from evolved seawater. Additionally, we place our results in the context of open vs. closed system precipitation using transects of the Mg/Ca ratios across individual cements. Overall, we stress that one geochemical measurement provides only a partial record of fluid composition, but multiple measurements allow a potential understanding of the seawater geochemical signal.