Discovery of and research on babingtonite in the drusy cavities of basalt

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Marco E. Ciriotti
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Discovery of and research on babingtonite in the drusy cavities of basalt

Messaggio da Marco E. Ciriotti » ven 08 feb, 2019 10:25

Referenza:
▪ Zhang, L., Ruan, Q., Rao, C., Zhang, C., Lri, W., Liao, B., He, T. (2018): Discovery of and research on babingtonite in the drusy cavities of basalt. Acta Mineralogica Sinica, 2008, 578.

Abstract:
Based on X-ray power analysis, X-ray monocrystal diffraction analysis, infrared spectroscopic analysis, electron-probe wave spectrum (EPM) analysis, scanning electron microscope (SEM) analysis and energy spectrum (EDS) analysis, the black tabular crystals occurring within the interlayer-gliding(fractured) drusy cavities of altered basalt were determined to be babingtonite of the triclinic crystal system. It is a new genetic type of babingtonite discovered for the first time in the Emeishan basalt in China. By crystal measurement, it is a tabular crystal consisting of eight parallel dihedra among which the monohedra of {100} and {001} are more developed, with FeO* ≈ 20%, Fe2O3FeO, CaO ≈ 20%, SiO2 52% and a small amount of MnO (2%~3%). It is a rare calcium-iron inosilicate mineral. Babingtonite of the first generation is present in the form of coarse-crystallized tabular crystals measured 25 mm × 20 mm × 10 mm in size. It is interlocking with columnar rock crystals; babingtonite of the second generation is present in the form of fine-grained bright-black tabular-columnar crystals. It is interlocking with bipyramidal transparent crystals. On the basis of the characteristics of the occurrence, paragenetic minerals and chemical composition, it is indicated that babingtonite was formed under the conditions of low temperature and weakly oxidized and more alkaline environment. The ore-forming solution is a Ca and Fe-enriched SiO2 solution of high-degree saturation. It is mainly derived from Ca-and Fe-bearing SiO2 solution formed from plagioclase, pyroxene, olivine and "specularite" as a result of retrograde metamorphism under the condition of later tectonic stress.
Marco E. Ciriotti

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