Using mg isotopes to estimate natural calcite compositions and precipitation rates during the 2010 eyjafjallajökull eruption
Chemical weathering of silicate rocks is a key control on the long-term climate, via drawdown of atmospheric CO 2 . Magnesium isotopes are increasingly being used to trace weathering, but are often complicated by several coincident fractionating processes. Here we examine Mg isotope ratios of waters...
| Published in: | Frontiers in Earth Science |
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| Main Authors: | , , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
2019
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| Subjects: | |
| Online Access: | https://hdl.handle.net/1983/4439aa25-9551-4753-8d30-f580cf7f6df8 https://research-information.bris.ac.uk/en/publications/4439aa25-9551-4753-8d30-f580cf7f6df8 https://doi.org/10.3389/feart.2019.00006 https://research-information.bris.ac.uk/ws/files/201205855/Full_text_PDF_final_published_version_.pdf http://www.scopus.com/inward/record.url?scp=85062193401&partnerID=8YFLogxK |
| Summary: | Chemical weathering of silicate rocks is a key control on the long-term climate, via drawdown of atmospheric CO 2 . Magnesium isotopes are increasingly being used to trace weathering, but are often complicated by several coincident fractionating processes. Here we examine Mg isotope ratios of waters stemming from beneath lava flows from the 2010 Eyjafjallajökull eruption. Travertine calcite was observed directly precipitating from these high-TDS (total dissolved solids) waters, and were also sampled. This system therefore provides the opportunity to study natural Mg isotope fractionation by calcite. Riverine δ 26 Mg increase from −2.37 to +0.43% with flow distance, as isotopically light travertine precipitates (δ 26 Mg = −3.38 to −3.94%). The solution Mg isotope ratios also co-vary with pH, calcite saturation indices and Sr/Ca ratios, strongly indicating that they are dominantly controlled by carbonate precipitation. Using experimental isotopic fractionation factors and the measured δ 26 Mg values, we can predict the compositions of the precipitated travertines that are within uncertainty of the directly measured travertines. Hence, in some systems, Mg isotopes can be used to quantify carbonate precipitation. |
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