Obvious differences of tempetrature and density aside, igneous and
sandstone intrusions share many characteristics including large-scale
morphology, such as km-scale saucer-shaped sills.
The recent proliferation of 3D seismic data in large tracts of
sedimentary basins has revealed both igneous and clastic plumbing
systems and it is clear that in some basins or stratigraphic intervals
igneous intrusions dominate whilst in others, in particular the North
Sea Paleogene, sandstone intrusions on a seismic scale outnumber igneous
ones by 1000:1 or more.
I draw your attention to papers by de Boer, Frey-Martinez, Hubbard,
Huuse and Jackson in:
Hurst A. & Cartwright J. A. Eds. 2007. Sand Injectites: Implications for
hydrocarbon exploration and production. AAPG Memoir 87
Plus: Cartwright et al. in Journal of Structural Geology 30 (2008)
854–867 and Huuse & Mickelson in Marine and Petroleum Geology 21 (2004)
141–155
All of these papers deal with clastic intrusions (mainly sandstone) that
are measured in cubic kilometres rather than cm.
Given that billions of barrels of oil have been found in these
structures in the North Sea, they are neither small scale nor unimportant.
On the note of mud 'diapirs', it is now clear that many(/most/all) of
these structures are thrust-cored folds with mud volcanoes sometimes
poking through their tops rather than diapirs in their normal sense (see
papers by Van Rensbergen, de Ville and others and upcoming volumes of
Basin Research (summer 2010)).
Best wishes
Mads
------ Forwarded Message
From: Stu Clarke <[log in to unmask]>
Reply-To: Tectonics & structural geology discussion list
<[log in to unmask]>
Date: Thu, 26 Nov 2009 10:23:20 -0000
To: <[log in to unmask]>
Subject: Re: Anderson Stress Meeting: September 2010 reminder
Don't you hate it when someone gets that email in just before you......
I too have no particular stand on terminology, but I too was surprised by
the stated scale of sedimentary intrusions. I have examined large scale
sedimentary intrusions in deltaic settings and currently work with
colleagues using oil-industry datasets on the same thing. I don't think
sedimentary intrusions have to be small scale......
Stu
-----Original Message-----
From: Tectonics & structural geology discussion list
[mailto:[log in to unmask]] On Behalf Of Macdonald, Professor
David I. M.
Sent: 26 November 2009 10:11
To: [log in to unmask]
Subject: Re: Anderson Stress Meeting: September 2010 reminder
Dear Eric
I have no particular stand on the terminology for igneous rocks, but you are
incorrect in your assertions on the scale of sedimentary intrusions. Salt
is a sedimentary rock which can be injected through kilometers of strata in
bodies hundreds of metres to kilometers across. Anyone who has ever worked
on deltas can point to mud diapirism on a similar scale. Even the humble
sand injection feature is much larger than you make out; your description
seems to be of sand filling pre-existing cracks, whereas most sand
injections are of a fluid slurry under pressure. These intrusions can be
huge. In the Mesozoic forearc basin of the Antarctic Peninsula, sandstone
dykes have been mapped with MINIMUM dimensions: 6 km long, cutting 350 m of
strata, and 1 m wide. For more examples, see, among other papers:
Hurst A. & Cartwright J. A. Eds. 2007. Sand Injectites: Implications for
hydrocarbon exploration and production. Memoir 87 American Association of
Petroleum Geologists
Hurst A., Cartwright J. & Duranti D. 2003. Fluidization structures in
produced by upward injection of sand through a sealing lithology. In:
Subsurface sediment mobilization (eds. Van Rensbergen P.,Hillis R.,Maltman
A. J. & Morley,C.K.), Geological Society Of London, London, 123-127
Jonk R., Hurst A., Duranti D., Mazzini A., Fallick A. E. & Parnell J.
2005.The origin and timing of sand injection, petroleum migration and
diagenesis: the Tertiary petroleum system of the South Viking Graben, North
Sea. AAPG Bulletin, 89, 329-357
Hurst A. & Duranti D. 2004. Fluidisation and injection in the deep-water
sandstones of the Eocene Alba Formation (UK North Sea). Sedimentology, 51,
3, 503-529
Hope this helps
David Macdonald
-----Original Message-----
From: Tectonics & structural geology discussion list
[mailto:[log in to unmask]] On Behalf Of Eric Essene
Sent: 26 November 2009 07:39
To: [log in to unmask]
Subject: Re: Anderson Stress Meeting: September 2010 reminder
Rob,
The term igneous intrusions is functionally a terrible term, a
distinction without a difference. More than 99.9% (or more?) of the
time it means igneous rocks where the term is redundant. If one talks
about sedimentary intrusions it is on a meter scale feature, commonly
even less--I have seen some down to cm scale. When they formed and
well afterward they did not look like dikes, just fractures filled
with loose sediment. I discount the poor term "sandstone dikes" as
needing yet another confusing term.
On the other hand salt domes are metamorphic (recrystallized) but
not molten rock, well a little brine. They were not in the
sedimentary group during formation. Yes, we have diapirs of
metamorphic rock, although a lot of those gneiss domes probably have a
little melt. I would agree about metamorphic diapirs but simply would
not call them metamorphic intrusions to avoid confusion on a
transitional rock. Gneiss domes are a nice description for them.
It must be exceedingly rare for igneous petrologists/geochemists
to be presenting data on "sand dikes". Salt domes are much larger
but are as they form. Do you know of any igneous petrologist/
geochemist who would report on them in your symposium? So "sandstone
dikes" are fractures filled with loose clastic material and water,
salt diapirs are all metamorphic and may have brine, gneiss domes are
often partial melts then at least partly igneous, and the term
"igneous intrusion" is clearly redundant to the average passerby. Is
this really a useful terminology?
cheers,
eric
On Nov 26, 2009, at 12:17 AM, Butler, Robert wrote:
> Eric
> Actually - there are lots of non-igenous intrusions in basins -
> sandstone dykes through 100s metres of strata. Not to mention mud
> diapirs, salt etc etc.... gas chimneys....
> go google!
> Cheers
> Rob
>
> ________________________________________
> From: Tectonics & structural geology discussion list
[[log in to unmask]
> ] On Behalf Of Eric Essene [[log in to unmask]]
> Sent: 26 November 2009 05:09
> To: [log in to unmask]
> Subject: Re: Anderson Stress Meeting: September 2010 reminder
>
> Rob, Zoe, and all,
> Igneous intrusions as opposed to all those sedimentary plutons?
> The phrase is nearly always meaningless and should not be used.
> Sounds like a great trip.
> cheers,
> eric
>
>
> On Nov 25, 2009, at 11:28 PM, Butler, Robert wrote:
>
>> Dear all
>> As we get our diaries together for 2010 we thought it timely to
>> remind you of the conference next year:
>>
>> Stress controls on faulting, fracturing and igneous intrusion in the
>> Earth's crust
>>
>> A meeting to commemorate the work of Ernest Masson Anderson on the
>> 50th anniversary of his death.
>>
>> 6-8 September 2010 at the University of Glasgow, UK
>>
>> Organisers: Zoe Shipton, Rick Sibson, Dave Healy, Rob Butler
>>
>> We will send out details of the meeting ("First Circular") in
>> January -
>> Abstract deadline will be end April with a preliminary programme
>> drawn up through May.
>> We are also planning a fieldtrip to the Hebrides and NW Scotland to
>> examine a variety of faults and the Tertiary igneous complexes.
>> Again - further information will be included in the first circular.
>>
>> Hope to see a bunch of you in Scotland next September!
>> Zoe, Rick, Dave and Rob.
>>
>>
>> The University of Aberdeen is a charity registered in Scotland, No
>> SC013683..
>>
>>
>
>
> The University of Aberdeen is a charity registered in Scotland, No
> SC013683..
>
>
The University of Aberdeen is a charity registered in Scotland, No SC013683.
------ End of Forwarded Message
--
Mads Huuse, PhD
Reader of Geophysics
Basin Studies Group
School of Earth, Ocean and Atmospheric Sciences (SEAES)
The University of Manchester
Willimason Building, Oxford Road
Manchester M13 9PL
England
[log in to unmask]
http://www.seaes.manchester.ac.uk/research/groups/basin/
|