Composition and Spectroscopy of Olivine Xenocrysts from the Hawaiian Tholeiitic Basalts

NMR Spectral Characteristics of Ultrahigh Pressure High Temperature Impact Glasses of the Giant Kara Crater (Pay-Khoy, Russia)

“…The high-resolution 29 Si, 27 Al and 23 Na MAS NMR studies of the impact glass samples were carried out at the Center for Magnetic Resonance (SPbU Research Park) using Bruker Avance III 400 WB spectrometer (9.4 T; operating frequencies 105.87, 104.29, and 79.51 MHz for 23 Na, 27 Al, and 29 Si nuclei, respectively). The KP15-12-115 and KP15-12-118 samples were placed in a rotor with an external diameter of 4 mm and spun at 14 kHz at the magic angle relative to the direction of the magnetic field for the acquisition of 23 Na, 27 Al, and 29 Si MAS NMR spectra. The low amount of the sample required the usage of 4 mm rotors with reduced inner volume so that the whole sample material stayed in the detected volume of the receiver coil.…”

“…The amount of material for the ZH1 and ZH2 samples was enough to fill a standard rotor with an external diameter of 3.2 mm. The resulting samples were spun at 17.5 kHz (for 27 Al and 23 Na NMR spectra) and 12.5 kHz (for 29 Si NMR spectra; lower spinning rate allowed for better detection of spinning sidebands, which were used for phase and baseline correction). In all cases, a single-pulse excitation sequence was used (direct excitation technique).…”

“…In all cases, a single-pulse excitation sequence was used (direct excitation technique). The relaxation delay for 23 Na, 27 Al, and 29 Si nuclei was 2.5, 1, and 5 s, the excitation pulse durations were 2.5 µs, 1.6 µs, and 4 µs, and the number of scans were 2048, 8192, and 4098, respectively. The relaxation delay for 29 Si NMR spectra was optimized, i.e., the preliminary measurements confirmed that 5 s was sufficient for the consistent registration of 29 Si NMR spectra.…”

“…We attribute the short relaxation time to the presence of paramagnetic impurities. Aqueous solutions of NaCl, AlCl, and tetramethylsilane (TMS) were used as external references for 23 Na, 27 Al, and 29 Si nuclei, respectively.…”

“…Among modern methods for studying glass structures, one of the most informative techniques is multinuclear NMR spectroscopy [17,18]. In this paper, the results of studies of the nearest environment of general elements of the aluminosilicate and silicate framework of natural UHP impact glasses of the Kara crater in comparison to natural impact melt glasses of low-pressure (LP) condensation-tektites of the Zhamanshin crater (Kazakhstan) by 29 Si, 27 Al and 23 Na MAS NMR are presented for the first time.…”