Chrome-rich clinopyroxene in orthopyroxenite from Maowu, Dabie Mountains, central China: A second record and its implications for petrogenesis |
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| Authors: | Xiaochun Liu Huyun Zhou Zhesheng Ma & Lihua Chang |
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| Institution: | Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081,;Department of Geology, China University of Geosciences, Wuhan 430074,;Department of Geology, Changchun University of Earth Sciences, Changchun 130026, China |
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| Abstract: | A second occurrence of chrome-rich clinopyroxene has been discovered as inclusions in orthopyroxene in orthopyroxenite from Maowu, the Dabie Mountains, Central China. The average formula for chrome-rich clinopyroxene can be expressed as (Na0.39Ca0.54)0.93(Mg0.57Fe2+0.06Fe3+0.01Cr0.24Al0.15)1.03Si2.02O6, with a maximum amount of kosmochlor component of 28.52 mol%. The unit cell parameters obtained from a single-crystal are a = 9.614 Å, b = 8.800 Å, c = 5.240 Å, β = 106.59°, space group C2 / c . The indices of refraction are α = 1.697, β = 1.704, γ = 1.726. Chrome-rich clinopyroxene, which coexists with chromite, chromian rutile and chromian pyrope, crystallized at a temperature of 1025 °C and very high pressure, and therefore represents a mantle relic. Together with the appearance of low-pressure inclusion mineral assemblage and the estimation of physical–chemical conditions for matrix minerals, the Maowu eclogite–ultramafic complex is considered to be formed during ultrahigh-pressure metamorphism from the mantle-derived protolith. |
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| Keywords: | chrome-rich clinopyroxene chromian inclusion minerals eclogite–ultramafic complex petrogenesis Maowu |
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