A review of the occurrence, form and origin of C-bearing species in the Khibiny Alkaline Igneous Complex, Kola Peninsula, NW Russia

Bitumen biomarkers in the Mid-Proterozoic Ilímaussaq intrusion, Southwest Greenland – A challenge to the mantle gas theory

“…Free gas was measured in two ways; either by extraction from drill-core samples by thermo-vacuum degassing or by direct sampling from newly drilled shot-holes (Nivin et al, 2005). The highest levels of free gas from both cores and boreholes, high level referring to high initial flow rate in a borehole, were recorded in zones with the highest contents of occluded gas; occluded gas being the amount of gas released by crushing (Nivin et al, 2005). Nivin et al (2005) observed the gas composition from nonventilated mines over space and time and found that a slow diffusional outflow of gas occurs from the rocks.…”

Geochemistry of coal-measure source rocks and natural gases in deep formations in Songliao Basin, NE China

“…Acceptably, the trend that 13 C depleted with the increasing of carbon number (i.e., δ 13 C 1 b δ 13 C 2 b δ 13 C 3 b δ 13 C 4 ) may indicate organic origin of hydrocarbons, the inversed trend of carbon isotope for CH 4 and its homologs may support the other possibility (the inorganic origin). While the carbon isotope distributing pattern of some hydrocarbon gas identified as inorganic origin or synthesized in lab through inorganic means do not show rigorously reverse pattern (Hu et al, 1998;Lancet and Anders, 1970;McCollom and Seewald, 2006;Nivin et al, 2005;Potter et al, 2004). Meanwhile the carbon isotope distributing pattern of several organic gas containing CH 4 and its homologs unexpectedly presents partial reversal.…”

The Ilímaussaq Alkaline Complex, South Greenland

“…Despite many studies, there was and is considerable debate whether such fluids are of a magmatic origin and represent primary high-temperature conditions (mantle gas theory) or are the result of various secondary processes (e.g., Konnerup-Madsen 2001;Potter and Konnerup-Madsen 2003;Krumrei et al 2007;Beeskow et al 2006;Nivin et al 1995Nivin et al , 2001Nivin et al , 2005Potter et al 1998Potter et al , 2004Potter and Longstaffe 2007), but scientists agreed on the abiogenic origin of the methane-rich fluids found in the Ilímaussaq rocks and in similar agpaitic complexes in Russia (see above). This was, however, largely questioned by Laier and Nytoft (2012) who argued that the hydrocarbons of Ilímaussaq are of biogenic origin and migrated to Ilímaussaq from deep oil seeps offshore west of Greenland during the Cretaceous.…”

“…They concluded that a biogenic origin would be consistent with published stable isotope data for the bitumen, and even re-interpreted the published stable isotope characteristics of hydrocarbon gases from Ilímaussaq and from the agpaitic Khibina and Lovozero complexes in Russia mostly as of biogenic origin. Loss of hydrocarbon gases via diffusion (as reported from Khibina and Lovozero by Nivin et al 2001Nivin et al , 2005) may significantly change their isotopic composition (Zhang and Kross 2001) and this process is invoked by Laier and Nytoft (2012) to be the reason that hydrocarbon gases from Ilímaussaq, Khibina and Lovozero could be mistaken as abiogenic gases. This theory is in stark contrast to numerous detailed fluid inclusions studies (see above) and has to be regarded as dubious until it can be documented that such fluids have also been trapped in minerals outside the Ilímaussaq complex as one would expect, if they migrated from deep oil seeps offshore west of Greenland.…”