Alfredo -
You might have a look at the papers by Michel Jebrak, and Clark and James
(below). Particle size distributions and clast roughness are new ways to
look at breccias that show promise of being able to distinguishing
brecciation mechanisms.
The Mt Isa inlier possibly has some of the most extensive areas of
brecciated rocks in the world, including carbonates, which may me related to
granitic plutonism, and include clast sizes up to the values that you
mention.
Tom
Jébrak, M. 1997. Hydrothermal breccias in vein-type ore deposits: A review
of mechanisms, morphology and size distribution. Ore Geology Reviews 12,
111-134.
Hydrothermal brecciation due to fluid pressure fluctuations:
examples from the Olary Domain, South Australia
Christopher Clark*, Patrick James Tectonophysics 366 (2003) 187 206
> Alfredo,
> Where are the rocks located? I have heard of this situation in
> the Western Alps.
> You can see lots of tectonic breccias and mylonites in Grenville
> marbles along the major extensional zones.
> eric
>
>
> On Apr 18, 2005, at 5:07 PM, Alfredo Camacho wrote:
>
>> Dear all,
>>
>> I require help in distinguishing between different types of breccias,
>> in particular between tectonic
>> breccias and breccias that could have been caused by the intrusion of
>> dykes into carbonate
>> sequences. I have looked around but cannot find any clear cut
>> criteria.
>>
>> The breccias that I am looking at have irregular boundaries and are
>> not clearly related to faults.
>> Where faults are present, they are to one side and some distance away,
>> usually a few metres. In
>> addition, some of the breccia bodies are quite large, range in size
>> from a few metres to 20 m in
>> diameter and contain clasts (both angular and rounded) of carbonate
>> and igneous rocks upto 1 m
>> across.
>>
>> These do not look like any of the psudotahylyte and cataclasite
>> breccias that I have seen.
>>
>> Any help will be much appreciated.
>>
>> Regards
>>
>> Alfredo Camacho
>>
>> --
>> --
>> Alfredo Camacho
>> Geological Sciences and Geological Engineering
>> Queen's University
>> Kingston,
>> Ontario, K7L 3N6
>> CANADA
>>
>> Phone 1-613-533 6169
>> Fax 1-613-533 6592
>>
>>
Tom Blenkinsop, Email [log in to unmask]
School of Earth Sciences, Tel. 617 4781 4318
James Cook University, FAX 617 4725 1501
Townsville, http://www.es.jcu.edu.au/
QLD4811, Deformation Microstructures and Mechanisms
in Rocks
Australia http://www.wkap.nl/prod/b/0-412-73480-
http://www.es.jcu.edu.au/STOMP
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