Search

Copyright of Journal of Earth Sciences & Environment is the property of Journal of Earth Sciences & Environment and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

BACKGROUND: As a new kind of jade, yellow - green alunite jade is difficult to positively identify and evaluate due to the lack of research. Yellow - green alunite jade is a new type of jade that has appeared on the market in recent years. At present, there is relatively insufficient research on its gemological mineralogical characteristics, which makes it difficult for its scientific identification and quality evaluation. OBJECTIVES: To study the mineralogical characteristics and coloration mechanism of yellow - green alunite jade. METHODS: Infrared spectroscopy, X - ray diffraction, Raman spectroscopy, scanning electron microscope, laser ablation - inductively coupled plasma - mass spectrometry and ultraviolet - visible spectroscopy were applied to analyze the mineral component, micro texture, and chemical composition. RESULTS: The main mineral component of yellow - green alunite jade was alunite with a cryptocrystalline texture and grain size of less than 5 µm. The very fine texture identified it as a delicate jade, but due to lack of interwoven fibric or scaly texture, its toughness was relatively poor. The alunite jade was composed of 0, Al, S and K. The contents of transition metals such as V, Fe, Cr were relatively high, with average contents of 23591. 52µ.g/ g, 4717. 99 µg/ g and 2077. 67 µg/ g, respectively. Combined with the absorption spectrum in the ultraviolet region of 500nm and 826nm in the ultraviolet - visible spectroscopy, it was concluded that the isomorphous substitution of Al3+ by V3+, Cr3+ and Fe3+ was the main cause of the yellow - green color. The texture of weathering crust of alunite jade was relatively coarse. The mineral components were alunite, quartz, goethite with minor anatase. Yellowish - brown color of weathering crust was due to the serious pigmentation by limonite, and especially goethite. CONCLUSIONS: The study confirmed the mineralogical characteristics and coloration mechanism of yellow - green alunite jade, which provides a theoretical basis for the scientific identification and further quality evaluation. [ABSTRACT FROM AUTHOR]

Basaltic magma, which is found in whole process of plate tectonic evolution and the critical stages, is a most important tectonogeochemical indicator in all igneous rocks. Therefore, the diagrams and ratios of related elements in basalts become the first choice to investigate the igneous diagenesis and tectonic setting. Ta, Hf, Th, La, Zr and Nb, which are high-field strength elements and stronger incompatible elements, have similar geochemical properties and regular changes in basaltic diagenesis, thus, they are most frequently used in basalt genesis and discrimination diagrams of tectonic setting. Moreover, the ratios of contents between the each one of elements can better distinguish the tectonic settings of formation. Based on the double-log discrimination diagrams of Th/Hf-Ta/Hf, Th/Zr-Nb/Zr and La/Zr-Nb/Zr in basalt yielded by previous research, the ratios of Ta/Hf, Th/Ta, Th/Hf, Nb/Zr, Th/Nb, La/Nb values were proposed to distinguish the basalts in various common tectonic settings, and the ratio discrimination table was put forward. The table extremely distinguishes basalt in most common variety of tectonic environments and is a great supplement for the double-log discrimination diagrams. [ABSTRACT FROM AUTHOR]