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

The Ilímaussaq Alkaline Complex, South Greenland

“…Hydrocarbons in the Ilímaussaq rocks are in agreement with the predicted behavior of the C-O-H system under the extremely reduced crystallization conditions reported for the Ilímaussaq magmas (e.g., Holloway and Jakobsson 1986;Scott 2004;Zhang and Duan 2010;Mysen and Yamashita 2010). So far the idea of Laier and Nytoft (2012) has to be regarded as highly unlikely and it is the responsibility of Laier, Nytoft and their followers to present the supporting evidence that the application of biomarker distributions to such magmatic to hydrothermal rocks is a reliable source of information. Obviously, the source and origin of the hydrocarbons and especially that of the so-far little studied bitumen in Ilímaussaq (and other agpaitic complexes) is an exciting topic which needs further investigation.…”

“…14.8f). Furthermore, bitumens are known from some Ilímaussaq rocks (Petersilie and Sørensen 1970;Konnerup-Madsen et al 1988;Laier and Nytoft 2012). They occur finely dispersed (not visible with the naked eye) in most Ilímaussaq rocks and are also found as milimetre-sized droplets (Konnerup-Madsen et al 1988).…”

“…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. Laier and Nytoft (2012) investigated the biomarker distribution in finely dispersed bitumens in the Ilímaussaq rocks.…”

“…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. Laier and Nytoft (2012) investigated the biomarker distribution in finely dispersed bitumens in the Ilímaussaq rocks. 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.…”

“…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.…”