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09-10-2012, 09:23 AM
I guess I'm about the only one interested in where the Centennial Nugget came from and the source of it's relatives.:confused:

So, here's a map that shows all of the geophysical anomalies in a nine square mile area:


image courtesy of Alaska DNR DGGS portion of pdf1998_017c_sh001.pdf

Please also note, The survey was conducted using a system that is calibrated and repeatable. Tie lines are ran perpendicular to the parallel lines to confirm that the system is able to repeat the measurements.

09-10-2012, 10:42 AM
I've been keeping my mouth shut because I still have a lot to learn.

Seems to me a person needs a topog map with mylar overlays showing magnetic anomalies, maybe a gravimetric overlay and for sure another with fault lines. Then a high altitude aerial photo of the same scale might be right handy.

When I worked for state forestry, we had a whole slew of mylar overlays and they really helped get a better idea of what was out there before we put boots on the ground.

But like I said, a lot to still learn. I am reading your posts and pondering. I, for one, thank you.


09-10-2012, 10:52 AM

You are welcome. Look carefully. The above image is superimposed on a topo map with 3x3 sections (9 sq. miles) centered on section 26, the center of Swift Creek. :)

This image narrows down the search from over 9000 anomalies to less than 150. Is one of them the source of the Centennial nugget?

Next, we move ahead to a tabulation of the anomalies with precise latitude and Longitude including quantitative measure of size and type (surficial or bedrock) of conductor.

Then, a "method" of displaying "electromagnetic spectrum" that provides "discrimination" of conductive mineralization.

Reno Chris
09-10-2012, 01:29 PM
Is one of them (150 anomalies) the source of the Centennial nugget?

Maybe, maybe not. Gold in Alaska can be associated with dikes, sills and mineralized fault zones that are way too small to show up on a flyover map. Geologic structures 5 or 10 feet wide can generate some serious gold, and will typically be far too small to see on a map like this. The way Alaska's surface soils heave, creep and slide around it makes surface interpretation tough, even when standing right on the ground. I expect Alaska has loads of undiscovered deposits, but the reason they have not already been found is that they are not easy to see.

09-10-2012, 01:58 PM
That's the reason for using geophysics. Only one percent of this mining district is exposed. The low altitude used in this survey combined with the sampling rate and precision positioning provides a high resolution of measurement.

The average airspeed was 94 miles per hour. That translates to 137.87 feet per second. The sample rate was 10 samples per second. So, samples were taken with a resolution of 13.787 feet. The samples also overlap because this isn't a pin-pointer coil system.

- Geowizard

09-10-2012, 02:13 PM
If you look closely, you can see 16 diagonal lines going from upper left to lower right. These are the actual flight lines of the helicopter. The round circles on the lines are where the anomalies are. Every anomaly is different. Just like metal detecting, there are different signals that mean different things. Conductive formations in the earth have many different possible positions (angles) of dip and strike. Thickness and depth are additional variables. Type of conductive mineralization is also a variable.

Conductor model:

D Discrete Bedrock Conductor; 2,822 responses
B Discrete Bedrock Conductor; 5,032 responses
S Conductive Cover 1,025 responses
E Edge of wide conductor 9 responses
H Rock Unit or Thick Cover; 76 responses
M Magnetite 68 responses
L Culture; 1 response

Conductor Grade:

7 > 100 (9)
6 50 - 100 (11)
5 20 -50 (63)
4 10 - 20 (136)
3 5 - 10 (351)
2 1 - 5 (3,099)
1 <1 (4,373)
* Indeterminate (991)

- Geowizard

09-10-2012, 10:54 PM
Yes, I see that the magnetic is overlaid on a topog map, but everything in black and white makes it hard to discern which is what.

Reckon I'm old school using mylar for the overlays. Well that and I like to use colored sharpie pens to ink in certain things on the mylar. Then mix and match overlays until I get it figured out.

09-11-2012, 07:00 AM

I agree. I have also used the mylar overlays. There are a few of the magnetic contours that are labeled on this map. It's already a "busy" map. This map was intended to show the flightlines and provide an overlay of the magnetic contour lines with interpretation of where the peaks (anomalies) occurred along the flight lines. It's just like ordinary metal detecting with the advantage of having interpretation of the signals.

Each circle shown along the flight lines represents an abnormal signal that has been interpreted as a source of conductive mineralization. Veins or faults that cross the flightlines will provide a line of circles across a series of flightlines. There are other maps that show a colored representation of the conductive mineralized zones. Those will be posted next then a final interpretation that shows where "the fault line" is.

Here is a link to a complete explanation of the survey and two maps that show interpretation:


09-11-2012, 09:50 AM
Here are Swift Creek Magnetic survey, Geologic Units, and Geologic map:

Image courtesy of Alaska DNR DGGS r11998_004_sh001.pdf

Image courtesy of Alaska DNR DGGS ri1998_011_sh001.pdf

Image courtesy Alaska DNR DGGS ri1998_011_sh001.pdf

What we can see...

In the original flightline image at the beginning of the thread, a magnetic anomaly between section 22 and 23.

This correlates with the colorized totalmagnetic image above... a large magnetic "low".

Of greater importance... observe two magnetic "highs" in section 36 in both images.

The two magnetic highs are on each side of the historic gold mining (tailings) on Willow Creek!

- Geowizard

09-11-2012, 05:30 PM
I guess I'm about the only one interested in where the Centennial Nugget came from and the source of it's relatives.
Been there done that. I've spent a lot of time in the Ruby area looking a big nugget. ...and I'll be back!

09-11-2012, 05:44 PM
Hi Walt,

I've been waiting for you to join in! Do you usually land at Long? Can you share any inside information? :)

- Geowizard

09-12-2012, 07:12 AM
Hi Walt,

I've been waiting for you to join in! Do you usually land at Long? Can you share any inside information? :)

- Geowizard
The strip at Long is overgrown with just over 600 feet available. As my plane is self insured I don't push it. The road makes a better landing strip as its state maintained. Either that or if I plan to be there for a week or more I'll fly into Ruby where I have a friend with a place to stay, a hot shower, and a vehicle I can use.

I wish I had some inside information. My friend Barry, who found the 294 ouncer 14 years ago, is still looking for it's mate so he doesn't have the inside information either.

When the price of gold shot up someone "papered" over the whole area so now everything is claimed. I regret not staking more ground when I had the chance. There were some places that I wanted to investigate but now their off limits; except for... oh never mind.

09-12-2012, 07:40 AM
Hi Walt,

People always ask me for inside information too. Usually I really don't have any information either. :)

Swift Creek is the first of several exercises where we are Chasing Big Gold in Alaska. There is now enough information to evaluate any surveyed locality and determine the probability of where much of the lode gold deposits are.

Yes, I am aware that much of the area is already staked. We can still do the investigation and negotiate a lease with the current claimant(s).

- Geowizard

09-12-2012, 08:34 AM
One problem with the Ruby district is that bedrock is deep in many places. When you have to go down a hundred feet or better it's difficult to sample and expensive to mine. As in many mining areas the easy ground has already been worked.

09-12-2012, 12:48 PM
Hi Walt,

When I drill, it will be ONE hole on ONE target with almost 100 percent certainty of hitting hardrock GOLD in bedrock.

It isn't a placer crap shoot! :)

- Geowizard

09-14-2012, 06:25 AM
As it turns out, Swift Creek isn't actually "Swift Creek". Swift Creek is Code for another Creek. :)

- Geowizard

09-23-2012, 10:13 AM
Ok... "Swift Creek" is code for "Willow Creek". Part of any Indiana Jones adventure is de-cyphering the crypt. :)

Also, please keep in mind that the lode may be on mountainous terrain with little or no overburden.

Watch the you-tube link I provided on the Oconnor Creek Happy Dance thread!

Within days...There may be a Swift Creek Happy Dance! :)

- Geowizard

09-27-2012, 11:11 AM
"Maybe maybe not"...

Well, if the airborne geophysics shows a conductive anomaly, it's just like getting a hit with a metal detector. "Maybe... Maybe not..." :)

You can make a rational decision based on the signal that justifies digging or you can blow it off and wait to see if someone digs it. The geophysical methods are based on scientific methods that are accepted in the mining industry and proven to work.


There are NO other clues! The gold is buried beneath cover as Walt has pointed out and as is known and documented in all of the literature written over the past 100 plus years.

Fact: The LARGEST Gold nugget ever found in Alaska was discovered here! It was named the "Centennial Nugget".

Where did the Centennial Nugget come from? Can we narrow it down to one of twenty anomalies with 80 percent certainty?

Watch! :)

09-27-2012, 12:01 PM
Did this nugget come from a terrestrial source?

Can we assume the Centennial nugget (the nugget) was an erosional product?

Can we assume it eroded down hill?

Can we assume it travelled less than one mile?

- Geowizard

Bill Bohan
09-27-2012, 12:41 PM
We can assume the centennial nugget has a grid coordinate as to exactly where it was found. That would be a good starting point.

09-27-2012, 01:11 PM

That's a good point! Without the grid coordinates, what can we assume as far as it's discovery location?

We know it was discovered while bulldozing a road.

We can assume with reasonable certainty the road was on the swift Creek mine in section 25.

Do you think this is correct?