Τίτλος:
Discovery of Se-rich canfieldite, Ag8Sn(S,Se)6 from the Shuangjianzishan Ag-Pb-Zn deposit, NE China: A multimethodic chemical and structural study
Γλώσσες Τεκμηρίου:
Αγγλικά
Περίληψη:
During a study of the ore minerals belonging to the recently discovered Shuangjianzishan Ag-Pb-Zn deposit in NE China, we have discovered exceptional selenium enrichment in canfieldite (up to 11.6 wt.% of Se). Incorporation of Se into canfieldite has been investigated by an integrated approach using field emission scanning electron microscopy, electron microprobe and single-crystal X-ray diffraction. Canfieldite has been identified as one of the dominant Ag-bearing ore minerals in the studied deposit, which occurs mostly in slate-hosted vein type Ag-Pb-Zn ore bodies. Selenium is either homogeneously or, remarkably, heterogeneously distributed in the different canfieldite fragments studied. Chemical variations of Se are mostly attributable to a series of retrograde reactions resulting in diverse decomposition and exsolution of primary phases during cooling, or alternatively, related to influxes of Se-rich fluids during the formation of canfieldite. To evaluate the effects of the Se-for-S substitution in the structure, a crystal of Se-rich canfieldite [Ag7.98Sn1.02(S4.19Se1.81)Σ6.00] was investigated. The unit-cell parameters are: A = 10.8145(8) Å and V = 1264.8(3) Å3. The structure was refined in the space group F3m to R1 = 0.0315 for 194 independent reflections, with 20 parameters. The crystal structure of Se-rich canfieldite was found to be topologically identical to that of pure canfieldite. If the short Ag-Ag contacts are ignored (due to the disorder), the two Ag atoms in the structure can be considered as three-fold (Ag1) and four-fold (Ag2) coordinated. Tin adopts a regular tetrahedral coordination. As in the case of Te-rich canfieldite, the refinement of the site-occupancy factor indicates that Se is disordered over the three anion positions. © 2018 Mineralogical Society of Great Britain and Ireland.
Συγγραφείς:
Zhai, D.
Bindi, L.
Voudouris, P.C.
Liu, J.
Tombros, S.F.
Li, K.
Περιοδικό:
Mineralogical Magazine
Εκδότης:
Cambridge University Press
Λέξεις-κλειδιά:
Binary alloys; Crystal atomic structure; Crystal structure; Deposits; Field emission microscopes; Lead alloys; Lead zinc deposits; Ores; Scanning electron microscopy; Selenium; Single crystals; Ternary alloys; Zinc alloys, Chemical compositions; Field emission scanning electron microscopy; Independent reflections; NE China; Pb-zn deposits; Shuangjianzishan; Single crystal x-ray diffraction; Tetrahedral coordination, Silver alloys, chemical composition; crystal; crystal chemistry; crystal structure; gold; lead; ore body; ore deposit; ore mineral; selenium; zinc, China
DOI:
10.1180/mgm.2018.158
