期刊
JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
卷 126, 期 9, 页码 -出版社
AMER GEOPHYSICAL UNION
DOI: 10.1029/2021JE006847
关键词
classification; highly siderophile elements; Huoyanshan iron; IAB iron meteorite; IAB-sLH subgroup; thermal history
资金
- Strategic Priority Research Program on Space Science, Chinese Academy of Sciences [XDA15020300, XDB41020305]
- Key Research Program of Frontier Sciences, CAS [QYZDJ-SSW-DQC001]
- Pre-research project on Civil Aerospace Technologies by CNSA [D020201, D020203]
- key research program of the Institute of Geology and Geophysics, CAS [IGGCAS-201904]
- Natural Science Foundation of China [41521062, 41973062, 42073061]
The Huoyanshan iron meteorite in the Gobi Desert has high Ni content, low precious metal content, and belongs to the IAB-sLH subgroup. Its structure indicates a formation process and a cooling rate of 3-50 degrees C/Myr, consistent with other sLH irons, suggesting re-accretion with a thick brecciated layer in the parent body.
The Huoyanshan iron meteorite shower, recently found in the Gobi Desert of Hami, Xinjiang, China, has very high Ni (21.1 wt%) content and low Au (2.0 ppm), Ir (0.02 ppm), Ge (1.7 ppm), and Ga (1.1 ppm) contents, and was classified into IAB-sLH subgroup. The iron has a finest octahedrite structure of Widmanstatten pattern (the intergrowth of kamacite [alpha] and taenite [gamma]) with plessite matrix, and euhedral schreibersite (Sch) crystals exclusively enclosed in kamacite bands. The textural features suggest the following formation process: gamma ->gamma + Sch ->gamma + Sch + alpha, and then gamma ->alpha(2) + gamma. The metallographic cooling rate of Huoyanshan iron was determined to be 3-50 degrees C/Myr using both the taenite Ni profile-matching and taenite central Ni content methods, with the bandwidths corrected for crystallographic orientation by electron backscatter diffraction (EBSD). The cooling rate of Huoyanshan is consistent with other sLH irons and confirms the slow cooling history of the IAB low-Au subgroups. These slow cooling rates require immediate re-accretion with a thick brecciated fragments layer in the parent body after the impact melting event. The depleted but unfractionated Re, Os, Ir, Ru, and Pt and the enriched Pd and Au abundances of Huoyanshan iron and other sLH subgroup irons show complementary feature to that of refractory metal nuggets in Ca-, Al-rich inclusions (CAIs), which could be explained by extracting the metallic Fe-Ni with HSE predominantly remained in CAIs from a CAI-bearing asteroid. The very high Ni content of sLH subgroup and its Mo isotope evidence (Worsham et al., 2017, ) suggest it has an oxidized parent body with non-carbonaceous chondrite-like precursor composition. We propose that the sLH subgroup was produced by impact melting of a LL like and CAI-bearing asteroid, followed by fast burying of thick and porous silicate breccia.
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