Fluid-Induced Inhomogeneous Cr-spinel in Dunite and Wehrlite from the Duke Island Complex, Southeastern Alaska

Yang Luo; Ben Xun Su; Joyashish Thakurta; Yan Xiao; Yang Bai

doi:10.3390/min12060717

Fluid-Induced Inhomogeneous Cr-spinel in Dunite and Wehrlite from the Duke Island Complex, Southeastern Alaska

Yang Luo, Ben Xun Su, Joyashish Thakurta, Yan Xiao, Yang Bai

Research output: Contribution to journal › Article › peer-review

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Abstract

Cr-spinel [(Mg, Fe²⁺)(Cr, Al, Fe³⁺)2O4)] 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 + Fe³⁺) <0.37 is prominent in dunite. The inhomogeneous Cr-spinel consists of two completely different compositions: Al-rich Cr-spinel, and Fe³⁺-rich Cr-spinel with a wide range of Cr content (from 11.8 wt.% to 28.6 wt.% Cr2O3). The unmixed texture is complex, and three subtypes of inhomogeneous Cr-spinel are recognized: Type B1 Cr-spinel showing complete separation, crystallographically oriented type B2 Cr-spinel, and irregular Al-rich Cr-spinel rimmed type B3 Cr-spinel. The unmixed texture was achieved by an unmixing process at around 600 °C due to the miscibility gap of spinel between Al-rich and Fe³⁺-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.

Original language	English (US)
Article number	717
Journal	Minerals
Volume	12
Issue number	6
DOIs	https://doi.org/10.3390/min12060717
State	Published - Jun 2022
Externally published	Yes

Bibliographical note

Funding Information:
This research was funded by [the National Natural Science Foundation of China] grant number [41973012, 91755205, and 41772055] and [the Youth Innovation Promotion Association, Chinese Academy of Sciences] grant number 2016067.

Funding Information:
Funding: This research was funded by [the National Natural Science Foundation of China] grant number [41973012, 91755205, and 41772055] and [the Youth Innovation Promotion Association, Chi‐ nese Academy of Sciences] grant number 2016067.

Publisher Copyright:
© 2022 by the authors. Licensee MDPI, Basel, Switzerland.

Keywords

Alaskan-type complex
dunite
spinel
unmixing
wehrlite

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title = "Fluid-Induced Inhomogeneous Cr-spinel in Dunite and Wehrlite from the Duke Island Complex, Southeastern Alaska",

abstract = "Cr-spinel [(Mg, Fe2+)(Cr, Al, Fe3+)2O4)] 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 + Fe3+) <0.37 is prominent in dunite. The inhomogeneous Cr-spinel consists of two completely different compositions: Al-rich Cr-spinel, and Fe3+-rich Cr-spinel with a wide range of Cr content (from 11.8 wt.% to 28.6 wt.% Cr2O3). The unmixed texture is complex, and three subtypes of inhomogeneous Cr-spinel are recognized: Type B1 Cr-spinel showing complete separation, crystallographically oriented type B2 Cr-spinel, and irregular Al-rich Cr-spinel rimmed type B3 Cr-spinel. The unmixed texture was achieved by an unmixing process at around 600 °C due to the miscibility gap of spinel between Al-rich and Fe3+-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.",

keywords = "Alaskan-type complex, dunite, spinel, unmixing, wehrlite",

author = "Yang Luo and Su, {Ben Xun} and Joyashish Thakurta and Yan Xiao and Yang Bai",

note = "Funding Information: This research was funded by [the National Natural Science Foundation of China] grant number [41973012, 91755205, and 41772055] and [the Youth Innovation Promotion Association, Chinese Academy of Sciences] grant number 2016067. Funding Information: Funding: This research was funded by [the National Natural Science Foundation of China] grant number [41973012, 91755205, and 41772055] and [the Youth Innovation Promotion Association, Chi‐ nese Academy of Sciences] grant number 2016067. Publisher Copyright: {\textcopyright} 2022 by the authors. Licensee MDPI, Basel, Switzerland.",

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AU - Xiao, Yan

AU - Bai, Yang

N1 - Funding Information: This research was funded by [the National Natural Science Foundation of China] grant number [41973012, 91755205, and 41772055] and [the Youth Innovation Promotion Association, Chinese Academy of Sciences] grant number 2016067. Funding Information: Funding: This research was funded by [the National Natural Science Foundation of China] grant number [41973012, 91755205, and 41772055] and [the Youth Innovation Promotion Association, Chi‐ nese Academy of Sciences] grant number 2016067. Publisher Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

PY - 2022/6

Y1 - 2022/6

N2 - Cr-spinel [(Mg, Fe2+)(Cr, Al, Fe3+)2O4)] 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 + Fe3+) <0.37 is prominent in dunite. The inhomogeneous Cr-spinel consists of two completely different compositions: Al-rich Cr-spinel, and Fe3+-rich Cr-spinel with a wide range of Cr content (from 11.8 wt.% to 28.6 wt.% Cr2O3). The unmixed texture is complex, and three subtypes of inhomogeneous Cr-spinel are recognized: Type B1 Cr-spinel showing complete separation, crystallographically oriented type B2 Cr-spinel, and irregular Al-rich Cr-spinel rimmed type B3 Cr-spinel. The unmixed texture was achieved by an unmixing process at around 600 °C due to the miscibility gap of spinel between Al-rich and Fe3+-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.

AB - Cr-spinel [(Mg, Fe2+)(Cr, Al, Fe3+)2O4)] 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 + Fe3+) <0.37 is prominent in dunite. The inhomogeneous Cr-spinel consists of two completely different compositions: Al-rich Cr-spinel, and Fe3+-rich Cr-spinel with a wide range of Cr content (from 11.8 wt.% to 28.6 wt.% Cr2O3). The unmixed texture is complex, and three subtypes of inhomogeneous Cr-spinel are recognized: Type B1 Cr-spinel showing complete separation, crystallographically oriented type B2 Cr-spinel, and irregular Al-rich Cr-spinel rimmed type B3 Cr-spinel. The unmixed texture was achieved by an unmixing process at around 600 °C due to the miscibility gap of spinel between Al-rich and Fe3+-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.

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Fluid-Induced Inhomogeneous Cr-spinel in Dunite and Wehrlite from the Duke Island Complex, Southeastern Alaska

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