Dutrowite, Na(Fe<sup>2+</sup><sub>2.5</sub>Ti<sub>0.5</sub>)Al<sub>6</sub>(Si<sub>6</sub>O<sub>18</sub>)(BO<sub>3</sub>)<sub>3</sub>(OH)<sub>3</sub>O, a new mineral from the Apuan Alps (Tuscany, Italy): the first member of the tourmaline supergroup with Ti as a species-forming chemical constituent
<p>The new tourmaline supergroup mineral dutrowite, Na(Fe<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup>...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-02-01
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| Series: | European Journal of Mineralogy |
| Online Access: | https://ejm.copernicus.org/articles/35/81/2023/ejm-35-81-2023.pdf |
| Summary: | <p>The new tourmaline supergroup mineral dutrowite,
Na(Fe<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">2.5</mn><mrow><mn mathvariant="normal">2</mn><mo>+</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="13pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="6a8167e1d78a8502620c462a35bb5c1a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-81-2023-ie00003.svg" width="13pt" height="17pt" src="ejm-35-81-2023-ie00003.png"/></svg:svg></span></span>Ti<span class="inline-formula"><sub>0.5</sub></span>)Al<span class="inline-formula"><sub>6</sub></span>(Si<span class="inline-formula"><sub>6</sub></span>O<span class="inline-formula"><sub>18</sub></span>)(BO<span class="inline-formula"><sub>3</sub></span>)<span class="inline-formula"><sub>3</sub></span>(OH)<span class="inline-formula"><sub>3</sub></span>O,
has been discovered in an outcrop of a Permian metarhyolite near the hamlet
of Fornovolasco, Apuan Alps, Tuscany, Italy. It occurs as chemically
homogeneous domains, up to 0.5 mm, brown in colour, with a light-brown streak
and a vitreous lustre, within anhedral to subhedral prismatic crystals, up
to 1 mm in size, closely associated with Fe-rich oxy-dravite. Dutrowite is
trigonal, space group <span class="inline-formula"><i>R</i></span>3<span class="inline-formula"><i>m</i></span>, with <span class="inline-formula"><i>a</i>=15.9864(8)</span>, <span class="inline-formula"><i>c</i>=7.2187(4)</span> Å, <span class="inline-formula"><i>V</i>=1597.68(18)</span> Å<span class="inline-formula"><sup>3</sup></span>, and <span class="inline-formula"><i>Z</i>=3</span>. The crystal structure was refined to
<span class="inline-formula"><i>R</i><sub>1</sub>=0.0257</span> for 1095 unique reflections with <span class="inline-formula"><i>F</i><sub><i>o</i></sub>>4<i>σ</i></span> (<span class="inline-formula"><i>F</i><sub><i>o</i></sub></span>) and 94 refined parameters. Electron microprobe analysis,
coupled with Mössbauer spectroscopy, resulted in the empirical
structural formula <span class="inline-formula"><sup><i>X</i></sup></span>(Na<span class="inline-formula"><sub>0.81</sub></span>Ca<span class="inline-formula"><sub>0.20</sub></span>K<span class="inline-formula"><sub>0.01</sub></span>)<span class="inline-formula"><sub>Σ1.02</sub></span> <span class="inline-formula"><sup><i>Y</i></sup></span>(Fe<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M33" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">1.25</mn><mrow><mn mathvariant="normal">2</mn><mo>+</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="18pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="d74198d558a33755e55a33581ac7594b"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-81-2023-ie00004.svg" width="18pt" height="17pt" src="ejm-35-81-2023-ie00004.png"/></svg:svg></span></span>Mg<span class="inline-formula"><sub>0.76</sub></span>Ti<span class="inline-formula"><sub>0.56</sub></span>Al<span class="inline-formula"><sub>0.42</sub></span>)<span class="inline-formula"><sub>Σ3.00</sub></span> <span class="inline-formula"><sup><i>Z</i></sup></span>(Al<span class="inline-formula"><sub>4.71</sub></span>Fe<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M40" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">0.27</mn><mrow><mn mathvariant="normal">3</mn><mo>+</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="18pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="67f65a36a08ae2d68ca83715d7b23817"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-81-2023-ie00005.svg" width="18pt" height="17pt" src="ejm-35-81-2023-ie00005.png"/></svg:svg></span></span>V<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M41" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">0.02</mn><mrow><mn mathvariant="normal">3</mn><mo>+</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="18pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="6f1d79fc7ae279a8e2a716c65dac76c2"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-81-2023-ie00006.svg" width="18pt" height="17pt" src="ejm-35-81-2023-ie00006.png"/></svg:svg></span></span>Mg<span class="inline-formula"><sub>0.82</sub></span>Fe<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M43" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">0.18</mn><mrow><mn mathvariant="normal">2</mn><mo>+</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="18pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="325cb693a0f52c16c09f1cd2ccbe65c3"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-81-2023-ie00007.svg" width="18pt" height="17pt" src="ejm-35-81-2023-ie00007.png"/></svg:svg></span></span>)<span class="inline-formula"><sub>Σ6.00</sub></span> <span class="inline-formula"><sup><i>T</i></sup></span>[(Si<span class="inline-formula"><sub>5.82</sub></span>Al<span class="inline-formula"><sub>0.18</sub></span>)<span class="inline-formula"><sub>Σ6.00</sub></span>O<span class="inline-formula"><sub>18</sub></span>]
(BO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M50" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi/><mn mathvariant="normal">3</mn></msub><msubsup><mo>)</mo><mn mathvariant="normal">3</mn><mrow><mi mathvariant="normal">O</mi><mo>(</mo><mn mathvariant="normal">3</mn><mo>)</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="27pt" height="18pt" class="svg-formula" dspmath="mathimg" md5hash="e57b9d6e546a8e37da530423cc2f1384"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-81-2023-ie00008.svg" width="27pt" height="18pt" src="ejm-35-81-2023-ie00008.png"/></svg:svg></span></span>(OH)<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M51" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mrow><mi mathvariant="normal">O</mi><mo>(</mo><mn mathvariant="normal">1</mn><mo>)</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="18pt" height="18pt" class="svg-formula" dspmath="mathimg" md5hash="1fddf79d9ea518687ce38e53f8cffa37"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-81-2023-ie00009.svg" width="18pt" height="18pt" src="ejm-35-81-2023-ie00009.png"/></svg:svg></span></span>[O<span class="inline-formula"><sub>0.59</sub></span>(OH)<span class="inline-formula"><sub>0.41</sub></span>]<span class="inline-formula"><sub>Σ1.00</sub></span>, which was recast in the
empirical ordered formula, required for classification purposes:
<span class="inline-formula"><sup><i>X</i></sup></span>(Na<span class="inline-formula"><sub>0.81</sub></span>Ca<span class="inline-formula"><sub>0.20</sub></span>K<span class="inline-formula"><sub>0.01</sub></span>)<span class="inline-formula"><sub>Σ1.02</sub></span> <span class="inline-formula"><sup><i>Y</i></sup></span>(Fe<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M61" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">1.43</mn><mrow><mn mathvariant="normal">2</mn><mo>+</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="18pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="69ab4f63245877ed82f4a1cd76757ae3"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-81-2023-ie00010.svg" width="18pt" height="17pt" src="ejm-35-81-2023-ie00010.png"/></svg:svg></span></span>Mg<span class="inline-formula"><sub>1.00</sub></span>Ti<span class="inline-formula"><sub>0.56</sub></span>)<span class="inline-formula"><sub>Σ3.00</sub></span> <span class="inline-formula"><sup><i>Z</i></sup></span>(Al<span class="inline-formula"><sub>5.13</sub></span>Fe<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M67" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">0.27</mn><mrow><mn mathvariant="normal">3</mn><mo>+</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="18pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="b40639bc955e6d5f1ec9652615c8f64c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-81-2023-ie00011.svg" width="18pt" height="17pt" src="ejm-35-81-2023-ie00011.png"/></svg:svg></span></span>V<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M68" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">0.02</mn><mrow><mn mathvariant="normal">3</mn><mo>+</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="18pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="0799fff967e588b08f97a81a63f9d74b"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-81-2023-ie00012.svg" width="18pt" height="17pt" src="ejm-35-81-2023-ie00012.png"/></svg:svg></span></span>Mg<span class="inline-formula"><sub>0.58</sub></span>)<span class="inline-formula"><sub>Σ6.00</sub></span> <span class="inline-formula"><sup><i>T</i></sup></span>[(Si<span class="inline-formula"><sub>5.82</sub></span>Al<span class="inline-formula"><sub>0.18</sub></span>)<span class="inline-formula"><sub>Σ6.00</sub></span>O<span class="inline-formula"><sub>18</sub></span>]
(BO<span class="inline-formula"><sub>3</sub></span>)<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M77" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mi>V</mi></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="7pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="f05be9fd583d3c630b40f0b404220928"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-81-2023-ie00013.svg" width="7pt" height="17pt" src="ejm-35-81-2023-ie00013.png"/></svg:svg></span></span>(OH)<span class="inline-formula"><sub>3</sub></span> <span class="inline-formula"><sup><i>W</i></sup></span>[O<span class="inline-formula"><sub>0.59</sub></span>(OH)<span class="inline-formula"><sub>0.41</sub></span>]<span class="inline-formula"><sub>Σ1.00</sub></span>. Dutrowite is an
oxy-species belonging to the alkali group of the tourmaline supergroup.
Titanium is hosted in octahedral coordination, and its incorporation is
probably due to the substitution 2Al<span class="inline-formula"><sup>3+</sup></span> <span class="inline-formula">=</span> Ti<span class="inline-formula"><sup>4+</sup></span> <span class="inline-formula">+</span> (Fe,Mg)<span class="inline-formula"><sup>2+</sup></span>. Its occurrence seems to be related to late-stage
high-T/low-P replacement of “biotite” during the
late-magmatic/hydrothermal evolution of the Permian metarhyolite.</p> |
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| ISSN: | 0935-1221 1617-4011 |