Rock Library

Gas shales samples from three cores in East Texas US from the Haynesville-Bossier formation, have been made available to UCL and UOM by BG group for research purposes and are now stored in a corehouse in Wales. This report is a brief summary of the available samples with related geological and geochemical information obtained by standard analytical techniques as well as recent developments pertaining to simultaneous carbon, nitrogen and noble gases’ elemental and isotopic analyses of bulk rock samples

Characterisation of carbon components and their isotopic composition in gas shales

Shales are an important reservoir of both organic and inorganic carbon that can be decoupled by incremental stepwise combustion without acid treatment. The study of shales from various depths of three cores of Haynesville-Bossier formation of Jurassic period indicates the presence of organic and inorganic carbon with comparable δ13C and nitrogen/carbon (N/C) ratios in all three. Both the isotopic and elemental ratios predominantly indicate a continental source but a minor N/C fraction corresponding to a marine/lacustrine source is also seen. This indicates either mixing from different sources and/or fractionation, perhaps due to preferential loss of nitrogen during organic matter degradation. Because some of the organic component is released at a high temperature of 1000-1200 °C although ungraphitised, it may be locked up in minerals like sulphides and K-feldspars, incorporated during diagenesis and hydrothermal alteration. Carbon locked in these minerals can be isolated from the carbon cycle for a longer period of time

The phase diagram of NiSi under the conditions of small planetary interiors

The phase diagram of NiSi has been determined using in situ synchrotron X-ray powder diffraction multi-anvil experiments to 19 GPa, with further preliminary results in the laser-heated diamond cell reported to 60 GPa. The low-pressure MnP-structured phase transforms to two different high-pressure phases depending on the temperature: the ε-FeSi structure is stable at temperatures above ∼1100 K and a previously reported distorted-CuTi structure (with Pmmn symmetry) is stable at lower temperature. The invariant point is located at 12.8 ± 0.2 GPa and 1100 ± 20 K. At higher pressures, ε -FeSi-structured NiSi transforms to the CsCl structure with CsCl-NiSi as the liquidus phase above 30 GPa. The Clapeyron slope of this transition is -67 MPa/K. The phase boundary between the ε -FeSi and Pmmn structured phases is nearly pressure independent implying there will be a second sub-solidus invariant point between CsCl, ε -FeSi and Pmmn structures at higher pressure than attained in this study. In addition to these stable phases, the MnP structure was observed to spontaneously transform at room temperature to a new orthorhombic structure (also with Pnma symmetry) which had been detailed in previous ab initio simulations. This new phase of NiSi is shown here to be metastable