Melting relations of Ca–Mg carbonates and trace element signature of carbonate melts up to 9 GPa – a proxy for melting of carbonated mantle lithologies
<p>The most profound consequences of the presence of Ca–Mg carbonates (CaCO<span class="inline-formula"><sub>3</sub></span>–MgCO<span class="inline-formula"><sub>3</sub></span>) in the Earth's upper mantle may be to lower...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2022-10-01
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| Series: | European Journal of Mineralogy |
| Online Access: | https://ejm.copernicus.org/articles/34/411/2022/ejm-34-411-2022.pdf |
| _version_ | 1811228792000086016 |
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| author | M. J. Sieber M. J. Sieber M. Wilke O. Appelt M. Oelze M. Oelze M. Koch-Müller |
| author_facet | M. J. Sieber M. J. Sieber M. Wilke O. Appelt M. Oelze M. Oelze M. Koch-Müller |
| author_sort | M. J. Sieber |
| collection | DOAJ |
| description | <p>The most profound consequences of the presence of Ca–Mg carbonates
(CaCO<span class="inline-formula"><sub>3</sub></span>–MgCO<span class="inline-formula"><sub>3</sub></span>) in the Earth's upper mantle may be to lower the
melting temperatures of the mantle and control the melt composition.
Low-degree partial melting of a carbonate-bearing mantle produces
CO<span class="inline-formula"><sub>2</sub></span>-rich, silica-poor melts compositionally imposed by the
melting relations of carbonates. Thus, understanding the melting relations
in the CaCO<span class="inline-formula"><sub>3</sub></span>–MgCO<span class="inline-formula"><sub>3</sub></span> system facilitates the interpretation of
natural carbonate-bearing silicate systems.</p>
<p>We report the melting relations of the CaCO<span class="inline-formula"><sub>3</sub></span>–MgCO<span class="inline-formula"><sub>3</sub></span> system and
the partition coefficient of trace elements between carbonates and carbonate
melt from experiments at high pressure (6 and 9 GPa) and temperature
(1300–1800 <span class="inline-formula"><sup>∘</sup></span>C) using a rocking multi-anvil press. In the
absence of water, Ca–Mg carbonates are stable along geothermal
gradients typical of subducting slabs. Ca–Mg carbonates
(<span class="inline-formula">∼</span> Mg<span class="inline-formula"><sub>0.1–0.9</sub></span>Ca<span class="inline-formula"><sub>0.9–0.1</sub></span>CO<span class="inline-formula"><sub>3</sub></span>) partially melt
beneath mid-ocean ridges and in plume settings. Ca–Mg carbonates
melt incongruently, forming periclase crystals and carbonate melt between 4
and 9 GPa. Furthermore, we show that the rare earth element (REE) signature
of Group-I kimberlites, namely strong REE fractionation and depletion of
heavy REE relative to the primitive mantle, is resembled by carbonate
melt in equilibrium with Ca-bearing magnesite and periclase at 6 and
9 GPa. This suggests that the dolomite–magnesite join of the
CaCO<span class="inline-formula"><sub>3</sub></span>–MgCO<span class="inline-formula"><sub>3</sub></span> system might be useful to approximate the REE
signature of carbonate-rich melts parental to kimberlites.</p> |
| first_indexed | 2024-04-12T10:03:35Z |
| format | Article |
| id | doaj.art-d44060524ac944679c551dff34860eae |
| institution | Directory Open Access Journal |
| issn | 0935-1221 1617-4011 |
| language | English |
| last_indexed | 2024-04-12T10:03:35Z |
| publishDate | 2022-10-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | European Journal of Mineralogy |
| spelling | doaj.art-d44060524ac944679c551dff34860eae2022-12-22T03:37:30ZengCopernicus PublicationsEuropean Journal of Mineralogy0935-12211617-40112022-10-013441142410.5194/ejm-34-411-2022Melting relations of Ca–Mg carbonates and trace element signature of carbonate melts up to 9 GPa – a proxy for melting of carbonated mantle lithologiesM. J. Sieber0M. J. Sieber1M. Wilke2O. Appelt3M. Oelze4M. Oelze5M. Koch-Müller6Section 3.6 and 3.1, GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germanypresent address: Mineralogy, Institute of Geosciences, University of Potsdam, Karl-Liebknecht-Straße 24–25, 14476 Potsdam, GermanyMineralogy, Institute of Geosciences, University of Potsdam, Karl-Liebknecht-Straße 24–25, 14476 Potsdam, GermanySection 3.6 and 3.1, GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, GermanySection 3.6 and 3.1, GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germanypresent address: Bundesanstalt für Materialforschung und -prüfung (BAM), Richard-Willstätter-Straße 11, 12489 Berlin, GermanySection 3.6 and 3.1, GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany<p>The most profound consequences of the presence of Ca–Mg carbonates (CaCO<span class="inline-formula"><sub>3</sub></span>–MgCO<span class="inline-formula"><sub>3</sub></span>) in the Earth's upper mantle may be to lower the melting temperatures of the mantle and control the melt composition. Low-degree partial melting of a carbonate-bearing mantle produces CO<span class="inline-formula"><sub>2</sub></span>-rich, silica-poor melts compositionally imposed by the melting relations of carbonates. Thus, understanding the melting relations in the CaCO<span class="inline-formula"><sub>3</sub></span>–MgCO<span class="inline-formula"><sub>3</sub></span> system facilitates the interpretation of natural carbonate-bearing silicate systems.</p> <p>We report the melting relations of the CaCO<span class="inline-formula"><sub>3</sub></span>–MgCO<span class="inline-formula"><sub>3</sub></span> system and the partition coefficient of trace elements between carbonates and carbonate melt from experiments at high pressure (6 and 9 GPa) and temperature (1300–1800 <span class="inline-formula"><sup>∘</sup></span>C) using a rocking multi-anvil press. In the absence of water, Ca–Mg carbonates are stable along geothermal gradients typical of subducting slabs. Ca–Mg carbonates (<span class="inline-formula">∼</span> Mg<span class="inline-formula"><sub>0.1–0.9</sub></span>Ca<span class="inline-formula"><sub>0.9–0.1</sub></span>CO<span class="inline-formula"><sub>3</sub></span>) partially melt beneath mid-ocean ridges and in plume settings. Ca–Mg carbonates melt incongruently, forming periclase crystals and carbonate melt between 4 and 9 GPa. Furthermore, we show that the rare earth element (REE) signature of Group-I kimberlites, namely strong REE fractionation and depletion of heavy REE relative to the primitive mantle, is resembled by carbonate melt in equilibrium with Ca-bearing magnesite and periclase at 6 and 9 GPa. This suggests that the dolomite–magnesite join of the CaCO<span class="inline-formula"><sub>3</sub></span>–MgCO<span class="inline-formula"><sub>3</sub></span> system might be useful to approximate the REE signature of carbonate-rich melts parental to kimberlites.</p>https://ejm.copernicus.org/articles/34/411/2022/ejm-34-411-2022.pdf |
| spellingShingle | M. J. Sieber M. J. Sieber M. Wilke O. Appelt M. Oelze M. Oelze M. Koch-Müller Melting relations of Ca–Mg carbonates and trace element signature of carbonate melts up to 9 GPa – a proxy for melting of carbonated mantle lithologies European Journal of Mineralogy |
| title | Melting relations of Ca–Mg carbonates and trace element signature of carbonate melts up to 9 GPa – a proxy for melting of carbonated mantle lithologies |
| title_full | Melting relations of Ca–Mg carbonates and trace element signature of carbonate melts up to 9 GPa – a proxy for melting of carbonated mantle lithologies |
| title_fullStr | Melting relations of Ca–Mg carbonates and trace element signature of carbonate melts up to 9 GPa – a proxy for melting of carbonated mantle lithologies |
| title_full_unstemmed | Melting relations of Ca–Mg carbonates and trace element signature of carbonate melts up to 9 GPa – a proxy for melting of carbonated mantle lithologies |
| title_short | Melting relations of Ca–Mg carbonates and trace element signature of carbonate melts up to 9 GPa – a proxy for melting of carbonated mantle lithologies |
| title_sort | melting relations of ca mg carbonates and trace element signature of carbonate melts up to 9 thinsp gpa a proxy for melting of carbonated mantle lithologies |
| url | https://ejm.copernicus.org/articles/34/411/2022/ejm-34-411-2022.pdf |
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