How Hot Is Hot?

[Steve Herschbach]

7 hours ago, Gold Catcher said:

One thing to remember is that gold is rarely associated with mild soils.

Great post GC, but that line is not entirely accurate. There are very large low mineral areas that carry plenty of gold. It's just that people focus on their own experiences, and unless you have found gold all around the world, well, then you only see what you see.

Alaska has some of the largest low mineral terrains in the world. Bedrocks comprised of low grade metamorphic and sedimentary rocks like slates, shales, siltstones, graywacke and conglomerates with almost no magnetite content. I could run a 6" gold dredge for a 10 hour day and have no more than a few spoonfuls of magnetite. Yet the bedrock is cut with low temperature quartz veins that carry gold and glaciers have dispersed it over a wide region. The area I am talking about is as large as many other states in the U.S.

"The sedimentary rocks of the Seward-Sunrise region consist principally of interbedded dark-colored graywackes and black or bluish-black slates and argillites, with a few interstratified beds of conglomerate and quartzite and still fewer beds of dark-gray limestone. The thickness of the slate and graywacke beds varies from a few inches to many feet. The relative proportions of the slates, argillites, graywackes, and conglomerates differ considerably from place to place, conglomerates being the least abundant. The slates and argillites need no particular description. The graywackes are massive sedimentary rocks, composed chiefly of angular fragments of quartz and feldspar, usually orthoclase and acidic plagioclase. Flat angular fragments of slaty rock appear in many of the beds. Because of their uniform width and longitudinal extent these graywacke beds are often called " dikes " by prospectors. In local usage they are also often referred to as diorites, but the sedimentary origin is in most places readily discernible. The conglomerates contain well-rounded pebbles of argillaceous rocks, granite, quartzites, and quartz."

"The ores are simple in composition. The gangue is quartz with here and there a little calcite, and the ores contain sulphides in various amounts. The principal sulphide is arsenopyrite, but galena, pyrite, and sphalerite occur in subordinate quantities. Pyrrhotite, molybdenite, and chalcopyrite are also present in some of the ores, and gold tellurides have been reported. The ores are free milling. The gold occurs free in the quartz and also in close association with the sulphides, some of it being included in the galena and arsenopyrite grains." Source

However, Alaska is huge and it certainly has some very high mineral locations, including the worst graphitic hot rocks I've seen anywhere. They read exactly like gold and will completely defeat a VLF detector.

Our own phrunt here is hunting in New Zealand, which shares almost exactly the same geological characteristics as Southcentral Alaska. Very low mineral ground, and this is good in both cases as the gold nuggets are not very large, with nuggets over a gram being big stuff.

Lots of fairly low mineral ground here in Nevada also.

Long story short the old adage of "gold is where you find it" applies, and gold occurs in a very wide range of mineralization backgrounds. In my detecting career gold from low mineral locations has been as prevalent if not more so than gold from highly mineralized locations.

Models and Exploration methods for Major Gold Deposit Types

7 hours ago, Gold Catcher said:

The 6000 was not an improvement in this regard! In fact, it is very hot rock sensitive, does'nt really matter much whether with mono or 14DD. The Axiom seems to perform much better here from what I have read, but the sensitivity to small gold in close vicinity to hot rocks might also be reduced.

There is a degree of overlap in gold, ground, and hot rocks. Eliminating ANY ground signal and ANY hot rocks will most likely also eliminate or reduce certain gold signals. The more aggressive the ground and hot rock elimination, the greater the risk. That's just the way it is and anyone that thinks they are not leaving some nuggets in the ground does not understand the technology we are using.

[Gold Catcher]

Thanks, Steve. Great reply, always something to learn. I guess the Minelab treasure talk write up mostly reflects on the CA and AZ situations ("In fact, the worse the soil is and the more hot rocks there are, the better the odds of walking over a nugget.")

Cheers,

GC

[Steve Herschbach]

I do think that the best gold areas do tend to be the higher mineral areas. The Alaska and New Zealand examples are fairly low grade low production gold locations, with large nugget being rare. Just lots of little stuff. So "In fact, the worse the soil is and the more hot rocks there are, the better the odds of walking over a nugget." is not inaccurate as a generality, but that is all it is. I think sometimes it's being open to the exceptions that makes for the best prospecting. 

[phrunt]

If you strike it lucky, put in the hard yards to get out of the most commonly known areas and go a bit more remote you can do quite well, this has been a patch JW has found a couple of weeks ago remote in the mountains, he tends to drive there and sleep and detect the next day, then he's been going back to on the weekends to finish it off

He was just showing some visitors the area for an exploration day and he took the GM along for a bit of fun and found these in 20 minutes

Went back the next day again with the GM to the same spot and got these in 5 hours.

All looking very promising so in come the big guns, the next day with the GM and 6000.

Noticeable how the gold jumps when the 6000 comes to the party, the smaller bits are the GM checking dig holes.

His wife even had a go with the 6000 and did pretty good for a short time, her first nugget was after 5 minutes

It was getting a lot harder to find anything now so he went back with the GPZ and 15" CC

And this was Friday just gone again with the GPZ and 15"CC with the tiny bits with the GM from the dig holes.

And the GPZ didn't disappoint with a whopper for NZ on that last day

So while yes we mostly have small gold, there is good gold to be found if you can get off the beaten track a bit, that is just not easy to do, the easy to access areas are just finding the bits missed over the years with older technology or by chance, once you get out away from civilization a bit things can improve dramatically.

A small gold mining operation a short drive from my house pulled 75,000 oz of alluvial gold out of what was basically lush green farm paddocks over recent years.   Unfortunately for me the gold is small, and very deep so not detectable gold.

Alaska sounds so much like New Zealand it's crazy, the soil types, the geography, even the photos 😉 I guess it's why Parker from Gold Rush came here for in the hunt for his wash plant as the ones made here suited his needs, Tony Beets always has his Kiwi gear too.   The two areas seem very similar.

A mine on the North Island is pulling 35,000 – 45,000 oz gold a year at the moment, it's been there for a long time, a big open pit, and there is another mine in the South Island about 3 hours drive from my house is pulling 145,000 – 155,000 oz gold a year at a place called Macraes.

Again, just in farmland.

We do have insane black sand beaches though and they're the most mineralized places I ever detect and they just shut down any detector, Tarsacci made a coil specifically for our NZ black sand beaches called their NZ coil for the MDT 8000 detector, from what I can tell it wasn't a success, the only guy I know that bought one was disappointed.  The most success I've had was with the GPX 4500 and 5000 where they could actually work on the beaches, the Equinox just overloads and gets about 2cm depth 😛

On the South Island’s West Coast, black sand beaches such as this have successfully been mined for gold. The sands also contain other heavy minerals eroded from the Southern Alps and concentrated on beaches through wave action. In the North Island the black sands are derived from volcanic rocks and dominate the 750 km of shoreline between Taranaki and Cape Rēinga in the far north. Auckland’s black sands are mined and smelted into iron.

The same beach close up

A lot of New Zealand is national park, and the gold is locked up forever safe in place you're not allowed to mine it, or even detect it, 30% of the entire country is National Park.  The other areas are just too difficult to get approval to mine, it's a very difficult thing to do even for the hobbyist with a little dredge, very costly and difficult to get approval anywhere.

So while we are known as the land of mild soils, we also have large areas of soils no detector can handle and hot rocks that near kill any detector with the best I've seen so far the GPX 5000 in the hot rocks, although still troubled at least works without sounding off on them when buried as if they were a small nugget, I'm looking at you GPX 6000.

[Gold Catcher]

Great pictures, Phrunt. Thanks for sharing!

GC

[Norvic]

Reading Steves post of Alaska, the Palmer River Alluvial Goldfield FNQ geology is much similar with sedimentary slates, shales, siltstones etc. (Hodgkinson Basin Geology) Much of it is very quiet ground but it also is intruded on by igneous and metamorphics and has some hot to extremely hot areas with those extremely annoying hot rocks, but the main Palmer River alluvials are quiet to our detectors mostly. Like Alaska tons of gold come out of the early gold rush of the Palmer River Goldfield and the ongoing Electronic gold rush. I`ve just about given up on theories of where it is as theories mostly turn out to be just blinkers on the eyes that instead of putting you onto gold, lead you away from it, only certainty is as Steve says is where it is, old Irish truism "Gold Tis where tis". 

Whatever, Off Grid, it would be a massive challenge to compile meaningful data to us electronic prospectors on how hot is hot.

GC I think Bruce Candy has branched off from only timings with the 6Ks GEO Sense PI, hopefully that may take us to the dead quiet only light weight gold signaling detector we yearn for.😉

[jrbeatty]

On 2/17/2023 at 1:01 PM, Aureous said:

 John HS's claim at Beggary Hills in Wedderburn was similar. I was astounded at the lack of punch there too.....as well as the sheer noise!

Yes indeed Aureous, Beggary Hills is often stated to be archetypal "hot" Victorian ground but as you know there are many lesser known "scorchers" in the "GT" which equal and may even exceed it for detecting difficulty.

One that springs to mind is Roberts Gully, Kingower. Pushed back in VLF days, both JHS and Jim Stewart regarded it as superb ground for testing prototype detector technology - and it still is.

Amusingly, I found my first ever gold (an oz piece) on John's Beggary Hills claim back in the 80's with a newly released GT 16000.

.....should have seen the look on his face!!

 

[Off Grid]

On 2/18/2023 at 8:35 PM, phrunt said:

If you strike it lucky, put in the hard yards to get out of the most commonly known areas and go a bit more remote you can do quite well, this has been a patch JW has found a couple of weeks ago remote in the mountains, he tends to drive there and sleep and detect the next day, then he's been going back to on the weekends to finish it off

Thanks for the post Phrunt. I was really interested to see the incremental finds from this patch. The nuggets look more elluvial than alluvial; is that so? Any idea to what extent the extra finds were due to the 6000 & 7000 seeing deeper in previously searched ground, the size of the patch expanding over time or something else? 

[phrunt]

8 hours ago, Off Grid said:

Thanks for the post Phrunt. I was really interested to see the incremental finds from this patch. The nuggets look more elluvial than alluvial; is that so? Any idea to what extent the extra finds were due to the 6000 & 7000 seeing deeper in previously searched ground, the size of the patch expanding over time or something else? 

Sorry they were not my finds, it was a friend so I don't know the finer details.  They were found high up on a mountain range.   I haven't been up there, one of my 4x4's wouldn't make it with not enough ground clearance, the other probably would but I'm not a confident enough off road driving to take it on, the dirt track to get up there is pretty wild.  I've been considering trying it one day soon but I fear I'll get stuck, and if the weather changes I'm in real trouble, the soil turns to glue if it gets wet.

The GPZ outfitted with the 15" Concentric coil he was using is just a very deep coil on smaller gold targets, a 15" transmit outside flat winding around the circumference of the coil with the  inner receive windings really push the GPZ's depth on smaller gold at depth.   We are in a very mild soil environment here which also helps being able to crank the detectors right up.   I believe we've both found over time the GPZ with that 15" coil is just the deeper detector than the 6000, the 6000 is great at what it does plucking the smaller bits out of the ground but when depth is required it's always the GPZ doing the heavy lifting.  He could have just started with the GPZ and got virtually everything except the very tiniest bits the Gold Monster was used for but it's nice to use different detectors and the 6000 is just a nice light fun detector to use and because he wasn't expecting to do any serious prospecting he just took the GM1000 along on the first day for a play around on some bedrock, then it found the patch and it was all on from there 🙂