Environmental Engineering Reference
In-Depth Information
12
Volatile generation and release from continental
large igneous provinces
henrik svensen, kirsten e. fristad, alexander g. polozov and
sverre planke
12.1 Introduction
The temporal and causal link between large igneous provinces (LIPs) and rapid
changes in the environment and the biosphere has been explored and debated
for decades (Wignall,
2001
;Stothers,
1993
). Early studies suggested that violent
sulfur-rich LIP eruptions could have caused global cooling on short annual timescales
and that simultaneous release of mantle carbon from lava
flows could have initiated
global warming on longer centurial timescales, resulting in a potentially chaotically
varying global climate (Wignall,
2001
). However, upon detailed investigation of
sedimentary sections, it was suggested that any carbon release to the atmosphere was
characterized by vast quantities of
12
C-enriched gas. Since mantle CO
2
is relatively
12
C-depleted, gas hydrates were introduced as a potential source to explain the isotope
excursions associated with the Palaeocene
Eocene Thermal Maximum (PETM), the
Toarcian event and the end-Permian event (Hesselbo
et al
.,
2000
; Dickens
et al
.,
1997
). As a consequence, focus turned away from the role of LIP processes.
In the 1990s, regional metamorphic processes were suggested as potential drivers
of climate change. Pioneering work by Derrill M. Kerrick and co-workers attempted
to link Cenozoic greenhouse events (the PETM and others) to large-scale CO
2
degassing generated by prograde metamorphism of carbonate-bearing rocks
(Nesbitt
et al
.,
1995
; Kerrick
et al
.,
1995
). The 5
-
10-million-year timescale of
orogeny or crustal extension can, however, not explain rapid (10
-
100 kyr)
and transient climatic events and thus regional metamorphism is unlikely to affect
short-term global climate change. In 2004, Svensen
et al
. suggested that processes
in the sub-volcanic parts of the North Atlantic Igneous Province (NAIP) could have
triggered the PETM by greenhouse-gas generation and release from contact aure-
oles around sills. Similar processes were later suggested to have been involved in
-
