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Structure refinements of coquimbite and paracoquimbite from the Hongshan Cu-Au deposit, NW China
Yang, Zhuming1,2; Giester, Gerald3
2018-07-01
发表期刊EUROPEAN JOURNAL OF MINERALOGY
ISSN0935-1221
卷号30期号:4页码:849-858
摘要The crystal structures of coquimbite and paracoquimbite from the Hongshan Cu-Au deposit, NW China, were refined by single-crystal X-ray diffraction, including the positions of all non-H atoms and hydrogen atoms. The unit-cell parameters of coquimbite are a = 10.9644(15), c = 17.090(3) angstrom, and V = 1769.6(5) angstrom(3), Z = 4 with space group P (3) over bar 1c. The crystal structure was refined based on 1352 unique reflections to R1(F) = 0.0301, yielding the formula Fe1.64Al0.36(SO4)(3)center dot 9H(2)O. Among the three cation positions of coquimbite, the isolated octahedral one is dominantly occupied by Al, i.e. Al0.660(3)Fe0.340(3). Consequently, the average Al-O interatomic distance is 1.9155 angstrom, smaller than the Fe-O distances, 2.002 angstrom for Fe(1), and 1.989 angstrom for Fe(2). Based on the structure data available for coquimbite in the literature, the ideal formula should be expressed as AlFe3(SO4)(6)center dot 18H(2)O (Z = 2) or Fe2-xAlx(SO4)(3)center dot 9H(2)O, x similar to 0.5 rather than Fe-2(3+)(SO4)(3)center dot 9H(2)O. The simplified formula for coquimbite from Hongshan is (Al0.66Fe0.34)Fe-3(SO4)(6)center dot 18H(2)O(4). The unit-cell parameters of paracoquimbite are a = 10.9631(16), c = 51.473(10) angstrom, and V = 5357.7(15) A(3) Z = 12 with space group R (3) over bar. The crystal structure was refined using 2733 unique reflections to R1(F) = 0.0550, which led to the formula Fe1.91Al0.09(SO4)(3)center dot 9H(2)O. There are five non-equivalent octahedrally coordinated metal sites for Fe in the structure of paracoquimbite. The range of Fe-[6]-O interatomic distances in paracoquimbite (1.966 angstrom-2.016 angstrom) can well be compared with those found in various sulfate minerals of ferric iron. Both minerals are characterized by a complex system of hydrogen bonds involving three types of H2O molecules, respectively: those of [Fe-3(SO4)(6) (H2O)(6)](3) clusters, of isolated [Fe(H2O)(6)](3+) or [Al(H2O)(6)](3+) octahedra and further interstitial (H2O) groups. The interstitial H2O molecules resemble a cyclohexane-like chair and are held in the structure solely by hydrogen bonding. In coquimbite H(2)Ow(2) is disordered with two alternative orientations (H2B1 and H2B2), in paracoquimbite interstitial H2O consists of two H2O molecules, H(2)Ow(3) and H(2)Ow (4). The range of the O-H stretching frequencies between similar to 2750 and 3650 cm(-1) from infrared spectroscopy for paracoquimbite is in fair accordance with the calculated values between similar to 2874 and similar to 3600 cm(-1) from both the d(O center dot center dot center dot O) lengths and the d(H center dot center dot center dot O) lengths.
关键词coquimbite paracoquimbite crystal-structure refinement hydrogen bonding formula revision NW China
DOI10.1127/ejm/2018/0030-2752
资助者National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China
关键词[WOS]HYDRATED FERRIC SULFATES ; CRYSTAL-STRUCTURE ; MINERAL CHEMISTRY ; EASTERN TIANSHAN ; BOND-VALENCE ; PROVINCE
语种英语
资助项目National Natural Science Foundation of China[41272063]
资助者National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China
WOS研究方向Mineralogy
WOS类目Mineralogy
WOS记录号WOS:000449622000017
出版者E SCHWEIZERBARTSCHE VERLAGSBUCHHANDLUNG
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文献类型期刊论文
条目标识符http://ir.iggcas.ac.cn/handle/132A11/89437
专题其他部门
通讯作者Giester, Gerald
作者单位1.Chinese Acad Sci, Inst Geol & Geophys, Beijing 100029, Peoples R China
2.Chinese Acad Sci, Inst Earth Sci, Beijing, Peoples R China
3.Univ Wien, Inst Mineral & Kristallog, Althanstr 14, A-1090 Vienna, Austria
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Yang, Zhuming,Giester, Gerald. Structure refinements of coquimbite and paracoquimbite from the Hongshan Cu-Au deposit, NW China[J]. EUROPEAN JOURNAL OF MINERALOGY,2018,30(4):849-858.
APA Yang, Zhuming,&Giester, Gerald.(2018).Structure refinements of coquimbite and paracoquimbite from the Hongshan Cu-Au deposit, NW China.EUROPEAN JOURNAL OF MINERALOGY,30(4),849-858.
MLA Yang, Zhuming,et al."Structure refinements of coquimbite and paracoquimbite from the Hongshan Cu-Au deposit, NW China".EUROPEAN JOURNAL OF MINERALOGY 30.4(2018):849-858.
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