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SiC-dominated ultra-reduced mineral assemblage in carbonatitic xenoliths from the Dalihu basalt, Inner Mongolia, China by Detao He; Yongsheng Liu; Changgui Gao; Chunfei Chen; Zhaochu Hu; Shan Gao is a Earth and Planetary Sciences article available to read on EtoBox.

What is SiC-dominated ultra-reduced mineral assemblage in carbonatitic xenoliths from the Dalihu basalt, Inner Mongolia, China about?

SiC and associated ultra-reduced minerals were reported in various geological settings, however, their genesis and preservation mechanism are poorly understood. Here, we reported a SiC-dominated ultra-reduced mineral assemblage, including SiC, TiC, native metals (Si, Fe, and Ni) and iron silicide, from carbonatitic xenoliths in Dalihu, Inner Mongolia. All minerals were identified in situ in polished/thin sections. SiC is 20-50 mm in size, blue to colorless in color, and usually identified in the micro-cavities within the carbonatitic xenolith. Four types of SiC polytypes were identified, which are dominated by b-SiC (3C polytype) and 4H polytype followed by 15R and 6H. These SiC are featured by 13 C-depleted isotopic compositions (d 13 C = -13.2 to -22.8‰, average = -17.7‰) with obvious spatial variation. We provided a numerical modeling method to prove that the C isotopic composition of the Dalihu SiC can be well-yielded by degassing. Our modeling results showed that degassing reaction between graphite and silicate can readily produce the low d 13 C value of SiC, and the spatial variations in C isotopic composition could have been formed in the progressive growth process of SiC. T

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Author

Detao He; Yongsheng Liu; Changgui Gao; Chunfei Chen; Zhaochu Hu; Shan Gao

Publisher

Mineralogical Society of America

Published

2017

Language

EN

Field

Earth and Planetary Sciences (Physical Sciences)