Australian BIF 'tiger iron' - info?

[Wrangellian]

I'm sure you've all seen that banded iron tiger eye stuff from Australia:

(pic from Mindat)

Does anyone know with confidence anything about it - especially the age and formation name?

I find various info online, some of which conflicts. Some say Archean, 2.7by, some say Early Proterozoic... and is it currently accepted as Nimingarra Formation or what? Can anyone find a stratigraphic column showing where this stuff is situated? I can't. I just want the basic info about it, but from a more trustworthy source than the usual websites that get their info from who-knows-where. I know some of you are good at finding literature on sundry subjects.

I understand there are two sites in Western Australia that the stuff we find in lapidary shops/etc is likely to be from (see mindat). I don't suppose there's a way to tell which spot the piece you've got came from. If both sites are the same formation I guess it doesn't matter much.

And is it stromatolitic, or just sediments containing precipitated iron/iron oxide?

[doushantuo]

I'd hazard a guess you mean something by Allwood or van Kranendonk you read? 

[Wrangellian]

That does not look familiar....

I'm pretty sure the stuff I'm talking about is no older than Late Archean.

[doushantuo]

Whatever its relevance &/or use might be

 

 

 

from:

[doushantuo]

destructive analysis might be the order of the day,like I insinuated earlier

[doushantuo]

A lot of those Australian BIF's have suffered massive hydrothermal alteration,and that obfuscates the "biogenicity" issue

[Wrangellian]

And apparently tectonic deformation...

Can you find anything that just describes the stratigraphy/age of the stuff called 'Tiger Iron'? The locations mentioned on Mindat are:

1) Ord Ranges, De Grey Station, Port Hedland Shire, WA, Aus.

2) Brockman tiger eye mine (Marra Mamba), Mt Brockman, Ashburton Shire, WA.

I guess you'd say they are Hamersley Province...

[doushantuo]

euh

[doushantuo]

??

(Turee Creek)

fortescue

[doushantuo]

Gerardetal

[doushantuo]

Plavsky,2010.pdf

[doushantuo]

need i post this?

 

[Wrangellian]

Maybe...

 

[Wrangellian]

If the 'Brockman Iron Fm' is applicable to both mines, or at least the Brockman tiger eye mine, then the Plavsky paper has this about it:

 

A.3. 2.45 Ga Brockman Iron Formation, Dales Gorge
Member, Australia
The Brockman Iron Formation is a part of the Hamersley
Supergroup located in the northwestern part of Australia
(Cheney, 1996). The precursor sediments to BIF are
interpreted to have been hydrothermal muds that were
deposited on the flanks of submarine volcanoes and resedimented
by density currents (Krapezˇ et al., 2003). The age
of the Brockman Iron Formation is well-constrained by
U–Pb ages of zircons from ash beds within the iron formation
(Pickard, 2002).
 

[Wrangellian]

Aha...

Strat column I already had in my files (I forget the source paper, maybe the TSC 2012 publication?):

Brockman Fm, Dales Gorge Mbr, just above the Archean/Proterozoic boundary (black arrow)..

Not sure which mbr the tiger iron is from, anybody know?

 

[doushantuo]

This Krapez

[doushantuo]

heck

SIMS_analyses_of_silicon_and_oxygen_isot.pdf

Two very relevant paper remain paywalled

[Wrangellian]

The opening paragraphs of that last one are pertinent:

 

"Banded iron formations (BIFs) are chemical marine sediments
composed of alternating iron-rich (oxide, carbonate,
sulfide) and silicon-rich (chert, jasper) layers. BIFs are
largely restricted to the Precambrian with the oldest BIFs exposed
in supracrustal belts of the North American craton as
part of the oldest3.8 billion year old (Ga) metasedimentary
outcrops at Isua, West Greenland (Moorbath et al., 1973)
and Nuvvuagittuq, northern Que´bec (David et al., 2002,
2009; Cates and Mojzsis, 2007). BIF deposition peaked at
2.5 Ga including the largest BIFs, the coeval Transvaal
Supergroup in South Africa, and Hamersley Group in
Western Australia, then abruptly ceased after deposition of

the correlative 1.9 Ga Biwabik, Gunflint, and other BIFs in
the Lake Superior district of Canada and the US.
BIFs have been linked with the rise of oxygen in the atmosphere
from 2.4 to 2.2 Ga, which is proposed to have caused
deep ocean waters to become fully oxygenated (Holland,
1984). An alternate hypothesis attributes the depletion of
deep water Fe2+ and Fe3+ to increasing concentrations of
biogenic H2S, a reactant that removed Fe2+ from the ocean
and formed Fe sulfides, lowering the concentration of ferric
hydroxides and subsequently halting BIF formation for 1
billion years (Canfield, 1998). BIFs reappear in the Neoproterozoic
from 0.8 to 0.6 Ga during the “Snowball Earth” glaciations
(Kirschvink, 1992). Subsequently, chemical
conditions of the deep ocean, in particular free oxygen, removed
dissolved iron thus thereafter preventing further
BIF deposition (e.g., Holland, 1984; Canfield, 2005).
BIFs as chemical sediments provide a unique record of
the chemistry of Precambrian ocean waters. Silicon concentrations
in ocean water as silicic acid (H4SiO4) are thought
to be high (60–120 ppm; Siever, 1992; Morris, 1993) close to
saturation with respect to amorphous silica due of the absence
of silica secreting organisms in the Precambrian (Siever,
1992). Additionally, Fe2+ concentrations were high (2–
50 ppm; Ewers, 1983; Sumner, 1997; Canfield, 2005) due to
very low oxygen and sulfate concentrations in the Paleoproterozoic
(e.g., Canfield, 2005). In the absence of oxygen,
Fe2+ hydrous precipitates could have formed directly,
whereas Fe3+ hydroxides (ferrihydrite) formed via oxidation
of Fe2+ by biologic and/or abiologic processes (Lepp
and Goldich, 1964; Garrels et al., 1973; Cairns-Smith,
1978; Johnson et al., 2008)."

 

[doushantuo]

dumb question maybe but tiger iron is NOT the same as tiger eye?

edit:

"banded iron tiger eye"

Tiger eye aetiology has been discussed be e.g.Heaney(2003)

[Wrangellian]

'Tiger Iron' is banded iron with tiger eye in it.

[Wrangellian]

Well that Krapez paper throws doubt on the idea that suspended/dissolved iron precipitated out as it was oxidized by the rising O2 levels made by photosynthesizing organisms... unless I read it wrong? Seems the iron and iron oxide was already in sediment around submarine volcanoes that was transported some distance by currents and underwater landslides and deposited in cycles thereof. So much for the stromatolite idea.

Still would like to know what formation(s)/member(s) the 'tiger iron' come(s) from.

[Wrangellian]

Even for the ages/formations I'm still getting conflicting info... Seems the scientists can't agree on anything, and it's still being sorted out.

 

From what I've been able to sleuth together, the 2 location are quite different in age:

If it's from the Ord Ranges, it is Nimingarra Iron Fm or Cleaverville Fm (different names for the same thing, depending who you consult), of the Gorge Creek Gp/DeGrey Supergp. Mesoarchean in age, either 3.4 b.y. to 3.020 or 3.1 b.y. I'll go with the latter based on: http://www.sciencedirect.com/science/article/pii/S030192681630523X

If it's from the Brockman Tiger Eye Mine, it's Marra Mamba Fm (Neoarchean ~2.6by) (or would it be Brockman Iron Fm, Paleoproterozoic 2.45~2.5 b.y.?) both of Hamersley Gp.

I guess the associated name 'Marra Mamba' with the Brockman mine implies it is of the Marra Mamba Formation.

According to Mindat, if it has more tiger eye, it's more likely from the 2nd location. I'm not sure where my specimens fall on that spectrum.

 

If anyone can confirm or clarify any of this, I'd appreciate it.