Discovery and Significance of Diamonds and Moissanites in Chromitite within the Skenderbeu Massif of the Mirdita Zone Ophiolite, West Albania

• Published in: Acta geologica Sinica (Beijing) 2017-06, Vol.91 (3), p.882-897
• Main Authors: WU, Weiwei, YANG, Jingsui, MA, Changqian, MILUSHI, Ibrahim, LIAN, Dongyang, TIAN, Yazhou
• Format: Article
• Language: English
• Subjects: Age; Albania; Alloying elements; Alloys; Aluminum; Carbides; Carbon; Chromium; Crystals; diamond; Diamonds; Electron imaging; Elongation; Energy; Grains; Heavy metals; high–Cr chromitite; Light; Mantle; Mesozoic; Microdiamonds; Minerals; Mirdita zone ophiolite; moissanite; Nitrides; Ophiolites; Raman spectra; Raman spectroscopy; Silicon; Silicon carbide; Spectra; Striations
• ISSN: 1000-9515; 1755-6724
• DOI: 10.1111/1755-6724.13316

In recent years diamonds and other unusual minerals （carbides, nitrides, metal alloys and native elements） have been recovered from mantle peridotites and chromitites （both high-Cr chromitites and high-Al chromitites） from a number of ophiolites of different ages and tectonic settings. Here we report a similar assemblage of minerals from the Skenderbeu massif of the Mirdita zone ophiolite, west Albania. So far, more than 20 grains of microdiamonds and 30 grains of moissanites （SIC） have been separated from the podiform chromitite. The diamonds are mostly light yellow, transparent, euhedral crystals, 200-300μm across, with a range of morphologies; some are octahedral and cuboctahedron and others are elongate and irregular. Secondary electron images show that some grains have well-developed striations. All the diamond grains have been analyzed and yielded typical Raman spectra with a shift at -1325 cm^-1. The moissanite grains recovered from the Skenderben chromitites are mainly light blue to dark blue, but some are yellow to light yellow. All the analyzed grains have typical Raman spectra with shifts at 766 cm^-1, 787 cm^-1, and 967 cm^-1. The energy spectrums of the moissanites confirm that the grains are composed entirely of silicon and carbon. This investigation expands the occurrence of diamonds and moissanites to Mesozoic ophiolites in the Neo-Tethys. Our new findings suggest that diamonds and moissanites are present, and probably ubiquitous in the oceanic mantle and can provide new perspectives and avenues for research on the origin of ophiolites and podiform chromitites.