Golds Path Down A Slope.

[Stocky111]

Say you find a nugget low down on a slope heading into a gully. Looking up the slope there is a reef at the top that at some time shed a good quantity of gold. When I'm trying to track how the nugget got to be in this particular spot, l tend to imagine how water would have to travel down the hill to arrive here, taking into account all the little side slopes and dips within the general grade. Is this sound theory, or am I off track in my thinking.

 

[Moneybox]

Say you find a nugget low down on a slope heading into a gully. Looking up the slope there is a reef at the top that at some time shed a good quantity of gold. When I'm trying to track how the nugget got to be in this particular spot, l tend to imagine how water would have to travel down the hill to arrive here, taking into account all the little side slopes and dips within the general grade. Is this sound theory, or am I off track in my thinking.

Well that's the way I see it Stocky but my theory doesn't seem to work a lot of the time. If you take note of some of the places you find sea shells for example, they are often right up there on top of the mountain. To me that looks like movements in the geology since the gold was formed might have the run of gold heading in an altogether different direction. The only sure way is to swing that detector far and wide. Of course before the days of metal detectors those prospectors sampled the soil at likely locations by panning or dry blowing. I think they had more success than I have with a metal detector because I can't track the fine gold.

 

[Zengeo]

Sounds right to me Stocky (a completely inexperienced prospector but experienced Geo).
Gold will shed off a reef down a slope under the effects of gravity and water but it depends what the landforms looked like when it did. If that makes sense?

And Moneybox, you cant find fine gold because youre too busy finding ounce nuggets! :lol:

 

[Stocky111]

It's just that then I start a search upwards and below to see if other pieces were liberated at a similar time,and followed the same or similar path. Maybe rake a track up the imagined pathway and give it a good working over. All based on gravitys and erosion s effect. Haven't found any siblings as yet. Puzzling. Maybe others did??

 

[Perth Tim]

It depends, maybe you dug it out of an old river channel?
I'd grid the area not just up and down the slope.

 

[user 14190]

A few months ago we found about 5 small nuggets (around 4 grams total) at the bottom of a gentle slope, at the time we were having a few problems with coils and settings so nothing else was done. Have returned with better coils and settings and found one at 3.4 grams (wife found it) and one at .27g and one at .33g and when we look at where the latest ones were found they are almost straight above the original ones, about 30 to 40 meters up the slope. All the bits that have been found in this location were rough/prickly, do not look like it has traveled far. We have now worked that area fairly well and nothing more has shown up so will wait until we can purchase a more powerful detector (we are using older GPX4500) to try for a bit more in the future. Photo was taken with a phone that we know nothing much about.

Graham

 

[Stocky111]

Great results Graham, your experience seems to support the theory that I subscribe to; right or wrongly. I just think that when I find a nugget, then what? Just wander off and find another one somewhere? Or use the new knowledge to your advantage if possible. Knowing where you found it , and knowing where it came from, must be to some advantage over just wandering around good areas looking for more, even if the results don't always bear the fruit. Steve

 

[Aussiedigs]

Stocky, its the way i see it.

Erosion happens quite quickly so my thinking is you are looking for elluvial gold from the down slopes and gullys from the main reef. Its also worth swinging above and below the old reef in case there are undetected reef sections present. There is one particular ridge ill be running down as there are workings scattered in patches all along as well as the leaching side and gullys. Where the sides come into a flat where the gold would stop falling is worth swinging over also.

 

[BigWave]

In general, I think you're correct, although the gold in the Eastern states formed around 640 million years back, and that in WA nearly 4 times longer.
Therefore, older gold could be anywhere (as in WA), though more recently released gold in the East is generally easier to trace. Older Vic gold can have traveled a long way in that time and is likely beyond reach of all but deep mines, whereas recently released gold (last 100 to 1000 years) would likely follow your description IMHO.

 

[DykeHead]

Golds path down a slope, fine gold spreads coarse gold takes the most direct path usually.
Never hurts to take a sample and pan it. You can learn a lot about golds whereabouts with a pan.

 

[20x]

Golds path down a slope, fine gold spreads coarse gold takes the most direct path usually.
Never hurts to take a sample and pan it. You can learn a lot about golds whereabouts with a pan.

Bingo!!

 

[DykeHead]

Hi 20x, Congrats on 1000 posts! Nothing beats following the yellow to it's source. When the colours are rising I have a grin.

 

[user 4386]

In general, I think you're correct, although the gold in the Eastern states formed around 640 million years back, and that in WA nearly 4 times longer.
Therefore, older gold could be anywhere (as in WA), though more recently released gold in the East is generally easier to trace. Older Vic gold can have traveled a long way in that time and is likely beyond reach of all but deep mines, whereas recently released gold (last 100 to 1000 years) would likely follow your description IMHO.

The basic idea is correct, and although there are complications at times, the fact that gold formed around 400 million years ago in the eastern states is a bit irrelevant. Kilometres of mountain elevation have been removed since then. The dispersion of gold that you see now on hillslopes is mostly only millions of years old at most, even tens of thousands of years - not hundreds of millions of years. So in the main, nuggets will simply be downslope from the quartz veins that are their source. We actually KNOW that is true, by mapping the large nuggets in the Ballarat goldfield relative to their sources- most are only hundreds of metres at most downslope of the quartz veins they formed in. Those quartz veins and their gold formed 5 to 10 km below the ground, yet are now exposed at surface.

 

[DykeHead]

I thought gold formed at the beginning of our solar system through nuclear fusion 4.5 Billion years ago.
Then it was deposited around 400 million years ago?

 

[Guest]

Gday

The way that gold nuggets can run from a source can vary so it is worth remembering this for future reference, sometimes you can find the bulk of the nuggets that are virtually in a straight line across a slope with fewer pieces above or below that point, other times they will run in almost a straight line down the slope, and also will fan out across the slope the top point of the fan being the closet point to the source.

It would depend on the way the gold shed from the source and what the terrain was like at the time as it could have been very different than what you can see today, but for the most part the way the gold has run is how you can sometimes identify the probable location of the source if its not obvious like a quartz blow or reef structure that is visible, sometimes the source can not be easily located even though some quantity of free gold was found in one spot, but some things remain constant and that is if the nuggets are well worn and rounded then they have travelled some way from the source, if the nuggets are coarse and prickly the they have not travelled far and the source can be close by.

Also you can find that the bigger pieces will be deeper and specimens can be some way from the source so the idea is to thoroughly scan the whole slope by chaining or gridding, and then go out onto the flats below the slope, if you only do a quick troll of the spot and then wander away you could very well be missing the best gold, so its always worth spending a good amount of time working the area either trying to locate the source or to see if any larger bits or species are present.

cheers

stayyerAU

 

[20x]

Hi 20x, Congrats on 1000 posts! Nothing beats following the yellow to it's source. When the colours are rising I have a grin.

Hi mate, cheers..didn't realise that was my 1000th.
Sources are like solving a puzzle, aquired evidence of everything, think back in millions of years of decomposition just like Goldie says and put humpty Dumpty back together again in your head.
A piece of this puzzle I haven't yet worked on is to work out how much gold is swallowed up by the decomposing cracks in the host/country rock below the source as everything commutes with gravity..
With my current prospect there are a few old workings up to 5m below the source. Don't know if they were looking for deep shed gold or another fault.
From this point down slope there are no workings or test holes until the bottom of the gully approx 50m where workings are extensive.
The picture I get from this is that the load/shoot of gold in the fault was in a position quite higher from the current surface level..

 

[user 4386]

I thought gold formed at the beginning of our solar system through nuclear fusion 4.5 Billion years ago.
Then it was deposited around 400 million years ago?

No. it did form billions of years ago but did not form in our solar system but was probably added later, possibly even after our solar system had already started to form. But that is formation of the element gold, it has nothing much to do with forming gold deposits - it simply brought gold into existence when there was none previously. It then got incorporated into our solar system and into our planet at a later date. However the Earth rocks containing it only had an average concentration of perhaps 2 parts gold to a billion parts rock. To form a gold deposit, we then had to have that concentrated more than a thousand-fold on average (2 to 30 parts per million = grams per tonne). That is the process of forming gold ore deposits (which can form by a number of processes, mostly from molten magmas or from hot metamorphic waters rising to near surface - few gold deposits form much deeper than 10 km below surface). This occurred at many different times throughout geological history. For example, mostly around 2700 million years ago in the eastern goldfield of WA, a couple of billion years later around Olympic Dam, Tennant Creek, Cloncurry and Telfer (eg 1700 million years), around 435 and 380 million years in much of central Victoria and central west NSW, and even younger in New England (e.g. Hillgrove) and in much of Queensland close to the coast (Mt Morgan, Gympie). To name but a few. Most of this ceased more than 66 million years ago in Australia, but it continued to much younger ages elsewhere. For example New Zealand such as Coromandel (=Waihi), Mexico and western USA (e.g. Nevada), Philippines, Alaska and Indonesia - in the "ring of fire".

Most of these deposits formed at this time were then eroded at surface by rain, wind and ice, forming important alluvial gold deposits only a few tens of millions of years ago up to the present day. Although this was a continuous process, it also tended to occur in major bursts (eg little happens when land is flat, uplift it by faulting and form hills and the hills are rapidly worn down by streams and sheet-wash processes, alluvial gold being deposited in the streams. Once it is flat, lift it up again and you get another period of formation of alluvial gold deposits. For example these were probably around 35 million years ago and a bit greater than 15 million years ago in Victoria (two main pulses related to uplift, although minor deposits formed in-between and later). A few were earlier in NSW, perhaps prior to 66 million years (eg Tibooburra, some minor gold west of Mudgee).

 

[DykeHead]

Envision this, a large gold specimen on the ground.Then the ground it's on and the surrounding country erodes away at varying degrees until a depth of 10km's is eroded away. It is hard to fathom as it's size would have greatly diminished and it may have been moved by floods in a stream etc.Over those types of ages a 5oz specimen might now be a kidney bean in a deep lead buried inside a mountain. The more recent events are most important as Goldie is saying that gold on hill slopes is mostly only become freed from it's source in the last few millions of years at most. We have a chance at tracing this more recent dispersion.

 

[DykeHead]

You know your stuff Goldierocks!

 

[DykeHead]

20x you write "few old workings up to 5m below the source" What is it you are calling the source? Did they sink on the source?