A Study on the Mineralogy and Volatile Fraction of Scapolite from Mogok, Myanmar

Abstract

The Mogok metamorphic belt (MMB) of Myanmar is a famous geographical origin acknowledged by the whole world for its large mineral resources. In this study, basic gemological tests (density, UV fluorescence, refractive index, etc.), spectroscopic tests (infrared spectrum, Raman spectrum, and ultra-violet visible spectrum) and chemical composition analysis (electron microprobe and laser ablation inductively coupled plasma mass spectrometer) were carried out on scapolites from Myanmar. This paper explores the mineralogical characteristics of Burmese scapolites and provides additional information on its origin. Burmese scapolites are colorless and transparent with a yellow tone and belong to Cl-rich dipyre. The infrared spectra of the samples show the vibrations of Si-O and Al-O (400–1300 cm−1), (CO3)2− (1400–300 cm−1), and OH (3048 cm−1 and 3568 cm−1). The Raman spectra are mainly the vibrational spectra of Si (Al)-O-Si (Al) and the absorption peaks at 992 cm−1 and 1110 cm−1 caused by the vibrations of sulfate and carbonate ions, respectively. Black inclusions were found inside the scapolites, and the dark inclusions were identified as graphite by Raman spectroscopy. Moreover, the composition of the scapolite could be influenced by the αCl−/α(CO3)2− of the fluid. The Cl activity degree could control the scapolite content as the ion exchange between scapolite and plagioclase was gradually balanced. The enrichment of rare earth elements and the apparent positive Eu anomaly indicate that Burmese scapolites have a high degree of light and heavy rare earth element differentiation and an oxidizing environment of mineralization.