Raman microspectroscopy of organic inclusions in spodumenes from Nilaw (Nuristan, Afghanistan)

The color varieties of spodumene (green spodumene, kunzite) from Nilaw mine (Nuristan, Afghanistan) have been investigated by microthermometry and Raman spectroscopy analyses. These minerals are rich in primary and secondary fluid inclusions. Measured values of temperature homogenization (Th) and pressure (P) for selected fluid-inclusion assemblages (I–IV) FIA in green spodumene and (I–II) FIA in kunzite ranges from 370 to 430 °C, 1.16 to 1.44 kbar and 300 to 334 °C, 0.81 to 1.12 kbar, respectively. The brine content and concentration varies from 4.3 to 6.6 wt.% eq. NaCl. Numerous and diverse mineral phases (quartz, feldspars, mica, beryl, zirconium, apatite, calcite, gypsum) present in this mineral as solid inclusions were studied by Raman microspectroscopy. Raman spectra of selected fluid, organic and solid inclusions were collected as line or rectangular maps and also depth profiles to study their size and contents. There appeared very interesting calcite (156, 283, 711and 1085 cm−1), beryl (324, 397, 686, 1068 and 3610 cm−1), topaz (231, 285, 707, 780 and 910 cm−1) and spodumene (355, 707 and 1073 cm−1) inclusions accompanied by fluid and/or organic inclusions (liquid and gas hydrocarbons) with bands at 2350 cm−1 (CO2, N2), 2550 cm−1 (H2S) and 2900 cm−1 (C2H6–CH3). Some solid inclusions contain carbonaceous matter (D-band at ca. 1320 cm−1 and/or G-band at ca. 1600 cm−1).