Fluid-Induced Inhomogeneous Cr-spinel in Dunite and Wehrlite from the Duke Island Complex, Southeastern Alaska
Cr-spinel [(Mg, Fe<sup>2+</sup>)(Cr, Al, Fe<sup>3+</sup>)<sub>2</sub>O<sub>4</sub>)] is a common mineral in the ultramafic core of the Duke Island complex in southeastern Alaska, US. Cr-spinel grains with an unmixed texture have been observed in dunite...
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MDPI AG
2022-06-01
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| Series: | Minerals |
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| Online Access: | https://www.mdpi.com/2075-163X/12/6/717 |
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| author | Yang Luo Ben-Xun Su Joyashish Thakurta Yan Xiao Yang Bai |
| author_facet | Yang Luo Ben-Xun Su Joyashish Thakurta Yan Xiao Yang Bai |
| author_sort | Yang Luo |
| collection | DOAJ |
| description | Cr-spinel [(Mg, Fe<sup>2+</sup>)(Cr, Al, Fe<sup>3+</sup>)<sub>2</sub>O<sub>4</sub>)] is a common mineral in the ultramafic core of the Duke Island complex in southeastern Alaska, US. Cr-spinel grains with an unmixed texture have been observed in dunite and wehrlite of the complex. Inhomogeneous Cr-spinel with a ratio of Cr/(Al + Cr + Fe<sup>3+</sup>) <0.37 is prominent in dunite. The inhomogeneous Cr-spinel consists of two completely different compositions: Al-rich Cr-spinel, and Fe<sup>3+</sup>-rich Cr-spinel with a wide range of Cr content (from 11.8 wt.% to 28.6 wt.% Cr<sub>2</sub>O<sub>3</sub>). The unmixed texture is complex, and three subtypes of inhomogeneous Cr-spinel are recognized: <i>Type</i><i>B<sub>1</sub> Cr-spinel</i> showing complete separation, crystallographically oriented <i>type B<sub>2</sub> Cr-spinel</i>, and irregular Al-rich Cr-spinel rimmed <i>type B<sub>3</sub> Cr-spinel</i>. The unmixed texture was achieved by an unmixing process at around 600 °C due to the miscibility gap of spinel between Al-rich and Fe<sup>3+</sup>-rich phases. The unmixed patterns of inhomogeneous Cr-spinel are controlled by the initial chemical composition, grain size of the initial spinel, and the cooling process. We propose that the initial composition of inhomogeneous Cr-spinel was formed by the interaction of high-temperature fluid and olivine; Cr-spinel that experienced unmixing may be a useful proxy to unveil the activity of high-temperature fluid in the formation of Alaskan-type complexes. |
| first_indexed | 2024-03-09T22:57:53Z |
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| language | English |
| last_indexed | 2024-03-09T22:57:53Z |
| publishDate | 2022-06-01 |
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| record_format | Article |
| series | Minerals |
| spelling | doaj.art-2cfe057d10f04f54be399ef985ac8baf2023-11-23T18:06:39ZengMDPI AGMinerals2075-163X2022-06-0112671710.3390/min12060717Fluid-Induced Inhomogeneous Cr-spinel in Dunite and Wehrlite from the Duke Island Complex, Southeastern AlaskaYang Luo0Ben-Xun Su1Joyashish Thakurta2Yan Xiao3Yang Bai4State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, ChinaInnovation Academy for Earth Science, Chinese Academy of Sciences, Beijing 100029, ChinaDepartment of Earth and Environmental Sciences, University of Minnesota Duluth, 1119 Kirly Drive, Duluth, MN 55812, USAState Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, ChinaCollege of Mining Engineering, Taiyuan University of Technology, Taiyuan 030024, ChinaCr-spinel [(Mg, Fe<sup>2+</sup>)(Cr, Al, Fe<sup>3+</sup>)<sub>2</sub>O<sub>4</sub>)] is a common mineral in the ultramafic core of the Duke Island complex in southeastern Alaska, US. Cr-spinel grains with an unmixed texture have been observed in dunite and wehrlite of the complex. Inhomogeneous Cr-spinel with a ratio of Cr/(Al + Cr + Fe<sup>3+</sup>) <0.37 is prominent in dunite. The inhomogeneous Cr-spinel consists of two completely different compositions: Al-rich Cr-spinel, and Fe<sup>3+</sup>-rich Cr-spinel with a wide range of Cr content (from 11.8 wt.% to 28.6 wt.% Cr<sub>2</sub>O<sub>3</sub>). The unmixed texture is complex, and three subtypes of inhomogeneous Cr-spinel are recognized: <i>Type</i><i>B<sub>1</sub> Cr-spinel</i> showing complete separation, crystallographically oriented <i>type B<sub>2</sub> Cr-spinel</i>, and irregular Al-rich Cr-spinel rimmed <i>type B<sub>3</sub> Cr-spinel</i>. The unmixed texture was achieved by an unmixing process at around 600 °C due to the miscibility gap of spinel between Al-rich and Fe<sup>3+</sup>-rich phases. The unmixed patterns of inhomogeneous Cr-spinel are controlled by the initial chemical composition, grain size of the initial spinel, and the cooling process. We propose that the initial composition of inhomogeneous Cr-spinel was formed by the interaction of high-temperature fluid and olivine; Cr-spinel that experienced unmixing may be a useful proxy to unveil the activity of high-temperature fluid in the formation of Alaskan-type complexes.https://www.mdpi.com/2075-163X/12/6/717spinelunmixingwehrliteduniteAlaskan-type complex |
| spellingShingle | Yang Luo Ben-Xun Su Joyashish Thakurta Yan Xiao Yang Bai Fluid-Induced Inhomogeneous Cr-spinel in Dunite and Wehrlite from the Duke Island Complex, Southeastern Alaska Minerals spinel unmixing wehrlite dunite Alaskan-type complex |
| title | Fluid-Induced Inhomogeneous Cr-spinel in Dunite and Wehrlite from the Duke Island Complex, Southeastern Alaska |
| title_full | Fluid-Induced Inhomogeneous Cr-spinel in Dunite and Wehrlite from the Duke Island Complex, Southeastern Alaska |
| title_fullStr | Fluid-Induced Inhomogeneous Cr-spinel in Dunite and Wehrlite from the Duke Island Complex, Southeastern Alaska |
| title_full_unstemmed | Fluid-Induced Inhomogeneous Cr-spinel in Dunite and Wehrlite from the Duke Island Complex, Southeastern Alaska |
| title_short | Fluid-Induced Inhomogeneous Cr-spinel in Dunite and Wehrlite from the Duke Island Complex, Southeastern Alaska |
| title_sort | fluid induced inhomogeneous cr spinel in dunite and wehrlite from the duke island complex southeastern alaska |
| topic | spinel unmixing wehrlite dunite Alaskan-type complex |
| url | https://www.mdpi.com/2075-163X/12/6/717 |
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