Ann: Croydon Exploration Update, page-5

Wow is an effin Ghost town.. npi

I know you and @ludbucker have an adversarial relationship on other forms. I will not go there. I prefer to keep it more respectful.

Again another gem from @Ludbucker on CEO.ca (btw thanks for the kind words) @ stocksluce please pass on my thanks. Also thanks to @Vaughn for dispatching the quartz conquistador, if I may speak for the silent observers and I believe in fredom of speech, but it had to be done.. not the time and place here for that discussion.

Please refer to the full PDF at the bottom but this, pertaining to the fortescue group and the Wits, caught my attention..


The Witwatersrand deposits in comparison to other
conglomerate-hosted gold deposits
Conglomerate-hosted gold mineralization is by no means re-
stricted to the Mesoarchaean Witwatersrand Basin but is a
style of mineralization observed on almost all cratons and is
common to many siliciclastic successions that developed on
Archaean to Palaeoproterozoic basement. In a recent compar-
ative compilation of worldwide Witwatersrand-type deposits
(Frimmel 2014), a number of similarities, all of which confirm
a syngenetic origin, but also some systematic differences came
to the fore. They provide revealing clues as to the principal
gold sources for these various deposits (Table 1).
The overall ore mineralogy of the Witwatersrand-type
deposits/occurrences is strikingly similar, with differences be-
ing related primarily to age. Deposits that are older than the
Great Oxidation Event (GOE) at c. 2.4 Ga are rich in both
detrital and synsedimentary pyrite as well as detrital uraninite,
whereas those younger than the GOE contain detrital Fe-oxides
(haematite, magnetite). Moreover, many of the older Archaean
examples, especially those that are particularly well-endowed
in gold, contain more or less abundant stratiform kerogen layers
(carbon seams) that represent former microbial mats (Hallbauer
1975; Minter 1991; Mossman et al. 2008; Horscroft et al. 2011;
Frimmel 2014). Such carbon seams are conspicuously missing
in all the younger, Palaeoproterozoic examples.
A further significant difference lies in the shape and size of
gold particles in the various deposits. The presence of detrital
gold particles has been ascertained in almost all examples, but
much of that gold had been remobilized into texturally late
positions in those deposits that had experienced low- to
medium-grade metamorphic overprint. This is well document-
ed for the Witwatersrand deposits (Frimmel et al. 1993; Gartz
and Frimmel 1999; Hayward et al. 2005), those in the
Huronian Supergroup (Long et al. 2011), the Jacobina
(Milesi et al. 2002) and Moeda (Koglin et al. 2012)
palaeoplacers (for location maps and stratigraphic columns,
see Figs. A1–A5 in online supplementary material). This not-
withstanding, many of these deposits, except for those in the
Witwatersrand Basin, contain well-preserved gold nuggets
that display variable degrees of mechanical abrasion and de-
formation, thus reflecting a range of transport distances from
their respective sources in a former hinterland. Good examples
are gold particles released by digestion in HF from the Moeda
Formation and from the Roraima Supergroup (Fig. 2a, b, c and
g) as well as gold nuggets of up to >1 mm diameter recovered
from the deposits in the Hardey Formation in the Fortescue
Group (Fig. 2j). Observations of primary gold inclusions with-
in detrital quartz clasts (Fig. 2d) or within greenstone clasts
(Fig. 2i) clearly attest to a greenstone-hosted orogenic-type
gold-quartz vein system as source. Systematic differences in
degree of rounding from proximal to distal depositional envi-
ronments, together with sedimentological analyses, such as
palaeocurrent directions, help in deciphering specific point
sources—eroded former gold deposits in the hinterland.
Such specific sources in the form of older, eroded gold de-
posits, be it greenstone-hosted gold-quartz veins or older
conglomerate-hosted placer deposits, are indicated for many
of the Witwatersrand-type deposits that are younger than
2.8 Ga, such as those in the Fortescue, Caraça, Jacobina and
Tarkwa groups, the Roraima Supergroup, as well as in the
younger deposits in the Kaapvaal Craton, specifically the
Elsberg Reefs, Ventersdorp Contact Reef and the Black
Reef. In contrast, no specific sources are known for the older
examples in the Witwatersrand Supergroup, which has posed
a major problem for the (modified) palaeoplacer model and
has been used as critical argument by those favouring an epi-
genetic gold mineralization (e.g. Phillips and Law 2000).
Although the greenstone belts surrounding the
Witwatersrand Basin host several orogenic-type gold deposits,
some of which in the Barberton greenstone belt even have the
same age (3.08 and 3.04 Ga, Dziggel et al. 2010) as indicated
for the detrital heavy minerals (including some gold) in the
Witwatersrand reefs, several lines of evidence speak against a
derivation of the Witwatersrand gold from such greenstone-
hosted gold-quartz veins. Apart from significant differences in
the chemical composition between Barberton greenstone-
hosted gold and Witwatersrand gold (Hallbauer and Barton
1987; Frimmel et al. 2005a), there is an insurmountable
mass-balance problem. Total gold production from the green-
stone belts in the Kaapvaal Craton (mainly from the Barberton
goldfield) is approximately 385 t. Bearing in mind that the
total area of exposed Archaean greenstone terrains in the cra-
ton is not significantly smaller than that of Central Rand
Group subcrop, the main depository of Witwatersrand gold,
the amount of gold mined from greenstone-hosted orogenic
gold deposits is miniscule in comparison to the >52,000 t of
gold recovered from the Witwatersrand goldfields so far. This
comparison clearly highlights that the hypothetical amount of
orogenic-type gold in the Palaeo- to Mesoarchaean hinterland
is by far not sufficient to explain the huge amount of gold in
the Witwatersrand Basin.

http://novoresources.com/_resources/research-papers/frimmel_hennigh-mindep2015.pdf

I am really impressed with those who do the digging to attempt to understand what in due course, imho, will be revealed. This, just another of those pieces, that eventually add up to...I'll leave that up to you to decide.

Thanks again @Ludbucker and all those on CEO that do hard slog.

DYODD
Cheers