dolerite dykes

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dolerite dykes

Post  davent on Wed Nov 25, 2015 5:01 pm

Ok, so Ive found a place full of steep valleys. The sides of the valleys are granite, steep and smooth with a few patches of vegetation on the sides, but only on a very thin layer of top soil.
On nearly every one of these granite slabs are viens of quartz. I don,t get a signal from any of them with a detector .....yet.
These valleys all end up as spurs that lead to flat ground at the front. the flat ground stays flat for a few kms, and slightly works down hill on a very gentle, almost un noticeable decline.
These valleys lay on the outer of known gold fields, with most finds and commercial mines to the north.
OK, now for the newbie questions!!!!

Should I concentrate to the low ground to the south, or make my way through the valleys, to the north.
The area im talking, would take several lifetimes to cover on foot.

Any advice would be appreciated.

Cheers Dave.

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Re: dolerite dykes

Post  davsgold on Wed Nov 25, 2015 6:42 pm

G'day davent

I don't know the area your talking about but I do know that gold can be found around Granite and Granite contacts.

If your new to detecting and gold finding in general you need to look closely at where gold has been found in the past to get a feel for the type of ground, and then explore similar.

Even if you soil sample (pan) some of the dirt to get an idea if gold even is coming from the rock formations your describing, then you need to work out if the gold is nuggety enough for a detector to find.

cheers dave
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Re: dolerite dykes

Post  davent on Wed Nov 25, 2015 6:50 pm

yep, this what you describe. It is similar to known fields, in the pine creek orogen, its still in the orogen. have panned a sample from a re-entrant in a valley that I was certain would hold some color, but none found.
I have heard this entire area described as nugget or nuthin country. just thought that the low ground would be logical, but hopeing that a savvy geo might point me in the right direction.
I did get some signals on VLF machine, but inexperience clouded my judgment, and I ignored most, as I was getting weak iron signals and hot rocks.

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where's the gold...

Post  mungoman on Thu Nov 26, 2015 7:28 am

G'day Davent. What I would do is start panning at the confluences of the areas coming out of the gullies - this would give me an idea if that particular part of the country was gold shedding. As the gorges are steep, there will be more erosion going on than deposition - where the gully meets up with another gully, there should be sufficient sediment to establish if and which gully is shedding its gold.
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Re: dolerite dykes

Post  davent on Thu Nov 26, 2015 8:00 am

Thanks mungoman, thats what I was looking for, in an answer I mean, and thaks to all that have offered advice, cheers.
I might get one more chance to explore the area before the wet sets in.

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Re: dolerite dykes

Post  Tributer on Thu Nov 26, 2015 9:35 am

Hi Davent, My advice is to spend a few hours doing internet research on the area. Check out the geology maps and exploration reports on the region. The research may lead you to old diggings, mines or may tell you what rocks the gold is originating from, or whether it is only alluvial gold released from the rocks millions of years ago. Without research you may be wasting a lot of time prospecting goldless areas.

If the area is large I would start prospecting on areas downslope with shallow sediment/soil on bedrock. If there is any gold in the area, there will be at least some of it trapped on bedrock in lower areas that you can find with a pan or detector. Shale and deep cracks in flatish granite bedrock are good gold traps. Dolerite on slopes is normally not good at holding up gold, however Dolerite bedrock in low flat areas can be a good impervious base to trap gold.

PS Disclaimer: Australia being an ancient land means ancient gold can be left in spots where none of the surrounding rocks for some distance around actually shed the gold. So if you have time and there is some reported gold in the area check out many locations.
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Re: dolerite dykes

Post  davent on Thu Nov 26, 2015 5:00 pm

Ok, trib, ta. The dolorite dykes ive found so far, are on steep angles, on the sides of valleys. The country is relativly young country. The mass im talking about is riddled with mines and diggings from the 1873 gold rush years. The area im looking at is at the opposite side of that. Cant give too much away, but I have not found any trash what so ever, no beer cans, no wire from fences, no nails, no ciggy buts, no tyre marks, no foot prints, no signs of human activity at all. However, it is in the right country. For those of you unfamilier owith the NT, the entire territory has a population of 210,000, with about 120k in and around darwin, most into barra fishing and hunting, not too many into digging holes. There is a major gold mine about 25km from the area im looking at, and its the same country. Im also pretty close to a fault line.....im not completley clueless, but relativly new, and the top end, is very different country to NSW, FNQ or Victoria.
Just tossing up, do I go deeper into the hills, or opposite to the plains......

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Re: dolerite dykes

Post  gef50 on Sun Dec 06, 2015 9:05 pm

Not sure if I've met you or not Dave .. were you at the prospector barbi last week ...
Anyhow yes dolerite has been known to hold gold .. when there are faults running thru it you will get a quartz seem and sometime this will hold gold .. yes talking about the pine creek oregen ..this is not true for all dolerite sills thou ..
am also in Darwin area here ..
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Re: dolerite dykes

Post  davent on Sun Dec 06, 2015 10:17 pm

Gday gef, no don't think we've met, I wasn't at the bbq, no.
Thanks for the reply. Only doing some "close to home" trips at the moment, going to get wet ! Lightning reeks havoc with my TDI....

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Re: dolerite dykes

Post  gef50 on Sun Dec 06, 2015 10:42 pm

your not Katherine based are you ...
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Re: dolerite dykes

Post  davent on Sun Dec 06, 2015 11:24 pm

Karama

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Re: dolerite dykes

Post  gef50 on Mon Dec 07, 2015 4:17 pm

palmo here thou work nearer you ..
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Re: dolerite dykes

Post  davent on Mon Dec 14, 2015 12:15 pm

Gef,thurs fri off  this week, or any time after 6.30 pm......doing 12 hour shifts atm.
Cheers dave

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