Find in Library
Search millions of books, articles, and more
Indexed Open Access Databases
Mineralogical Characteristics and Genesis of Green Nephrite from the World
oleh: LIU Xi-feng, ZHANG Hong-qing, LIU Yan, ZHANG Yong, LI Zi-jing, ZHANG Jin-hong, ZHENG Fen
Format: | Article |
---|---|
Diterbitkan: | Science Press, PR China 2018-09-01 |
Deskripsi
BACKGROUND In previous studies, due to the limited samples with specific origins and limited methods for measurement, the genesis of serpentinite-related green nephrite and its relationship with dolomite-related nephrite were unclear. OBJECTIVES To understand the genesis of serpentinite-related green nephrite. METHODS Green serpentinite-related nephrite deposits have been collected from Qinghai province in China, Russia, Canada, Australia, New Zealand and Pakistan for systematic analysis. X-ray Diffraction (XRD), Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), Electron Microprobe Analysis (EMPA), X-ray Fluorescence Spectrometry (XRF) and Stable Isotope Mass Spectrometry were employed. RESULTS ① Serpentinite-related green nephrite is mainly composed of tremolite with minor quartz, talc, biotite, chromite, chlorite, and garnet. ② O-H isotopic values of samples (δD=-69.763‰--29.251‰, δ18O=4.7‰-13.4‰) indicate that the ore-forming fluids are mainly metamorphic water. ③ whole-rock major elements of Fe2+/(Mg+Fe2+)values range from 0.11 to 0.32. The contents of Cr range from 22.9 to 3400 μg/g, whereas Ni ranges from 700 to 1800 μg/g. All of these geochemical characteristics indicate the input of the mantle material in the formation of serpentinite-related nephrite. CONCLUSIONS Geochemical characteristics of serpentinite-related and dolomite-related nephrite are different, which are related to the geological environment. For example, the composition of dolomite-related nephrite is controlled by the granite and dolomite marble, whereas the composition of serpentinite-related green nephrite is related to the mantle material and metamorphic fluids.