No abstract

No abstract

Sulfide melt inclusions entrapped in primitive olivine phenocrysts can be used to understand the compositions of early sulfide melts that may ultimately contribute to magmatic sulfide ore deposits. Sulfide globules hosted in olivine (86-92 mol% Fo) from the Tolbachik basalt (the 1941 eruption) are characterized in terms of their major and trace element abundances using electron microscopy and LA-ICP-MS analysis. Distribution of major elements within individual sulfide globules varies from homogeneous to heterogeneous. Phases include monosulfide solid solution (MSS) and intermediate solid solution (ISS) intergrowths and exsolved low-temperature minerals such as pyrrhotite, pentlandite, chalcopyrite and cubanite. Trace elements (platinum-group elements-PGE, Ag, Te, Au, Pb and Bi) are also present in solid solution in sulfide phases and as micronsized particles ("nuggets"). Such nuggets of dominantly Au, Pt, Au-Pd and Pd-Te are contained randomly within sulfide matrices or, more commonly, at phase boundaries. Nuggets are also attached to outer surfaces of sulfide globules. Concentrations of PGE in sulfides follow a log normal distribution over four orders of magnitude. The highest measured noble metal

No abstract

A new hydrocarbonhydrographitewith the composition close to CH is shown to form from graphite and gaseous hydrogen at pressures above 2 GPa and temperatures from 450 to 700°C. Hydrographite is a black solid thermally stable under ambient conditions. If heated in vacuum, it decomposes into graphite and molecular hydrogen at temperatures from 500 to 650°C. Powder X-ray diffraction characterizes hydrographite as a multilayer "graphane II" phase predicted by ab initio calculations [Wen X-D et al. PNAS 2011;108:6833] and consisting of graphane sheets in the chair conformation stacked along the hexagonal c axis in the −ABAB− sequence. The crystal structure of the synthesized phase belongs to the P6 3 mc space group. The unit cell parameters are a = 2.53(1) Å and c = 9.54(1) Å and therefore exceed the corresponding parameters of graphite by 2.4(2)% and 42.0(3)%. Stretching vibrations of C-H groups on the surface of the hydrographite particles are examined by infrared spectroscopy.