DIGHEM Interp...

[Geowizard]

Hi Guys and Gals,


Interpretation is based on the signals.

- Geowizard

[Geowizard]

A good place to start;



- Geowizard

[Geowizard]

Depth to Top;


- Geowizard

[Jim_Alaska]

It must just be me. You said the interpretation has been done and you provided the charts. Seems simple enough, but my poor old brain just can't sort it all out. Perhaps folks with a higher education will find it simple, but my education level is waaay below most.

I see you talking about the math that goes into this process and it may as well be Greek, I can't understand it at all. I hope others reading this thread get more out of it, the information is there for anyone that needs it.

[Micropedes1]

Jim, lets try this from a different tact.

If you are looking for conductive anomalies, then your first indicator might be the magnetic strength registered as the magnetometer took its "snapshot" of the ground below. The earth in the general area of the survey exerts a magnetic field, anywhere from 60,000 nT (nanoteslas) at the poles to 30,000nT at the equator. This is measured by a base station located within the general survey area. Conductive ore bodies cause a deflection in this baseline magnetic field. This deflection is compared (or subtracted??) from the base station signal. The magnitude of the deflection is based largely upon the conductivity of the mineral deposit. Magnetite and certain other magnetic elements can cause a significant deflection in this reading. So, just because you find a location with a high magnetic signature does not mean that you have discovered a gold lode.

Faulting within an area tends to concentrate surface magnetite, sometimes to great depths, so that you get a narrow, brief signal with a strong magnetometer response. It makes you think that you have discovered an intrusive dike. So, in addition to reading the EM survey, you need to know something about the geology of your area.

[Micropedes1]

Suppose that you have found an anomaly with a magnetic signature that is much higher than many of the other anomalies (although all anomalies can be important and bear investigation). As mentioned above, there are 3 different coplanar coil sets (transmit and receive). These are 900Hz, 7200Hz, and 56,000Hz (roughly multiples of 8). Each of these frequencies has a different depth of penetration reading, with 900Hz reading the deepest). So, if you get a strong signal that corresponds to the 900Hz signal and little or no response on the other two channels, then you can figure that what you have discovered is a bit too deep to reach with a shovel. Depending upon what is above the conductor, this distance can be several hundred meters down.

[Micropedes1]

I do not usually do my own depth to conductor calculation, but rely upon the survey interpretation results. I am usually satisfied that there is actually an ore signature that is shallow enough that I can sample with a shovel. However, I do compare CPI to CPX to determine the extent of the conductor. I have not yet figured out how to tell which side of the flight line that the conductor extends. 3D graphing software gives a good visualization but is not always accurate.

[Geowizard]

It must just be me. You said the interpretation has been done and you provided the charts. Seems simple enough, but my poor old brain just can't sort it all out. Perhaps folks with a higher education will find it simple, but my education level is waaay below most.

I see you talking about the math that goes into this process and it may as well be Greek, I can't understand it at all. I hope others reading this thread get more out of it, the information is there for anyone that needs it.

Jim,

There's NO math. I intentionally avoided math.

Look at the report.

The Column that says the numbers greater than 0 are anomalies. Low numbers are like faint tone on a metal detector!

- Geowizard

[Geowizard]

Keep it simple;

To begin with, look at the column.

Go down the column and find numbers greater than 0. That's an Anomaly.

- Geowizard

[Geowizard]

Numbers are listed in the right column...

See "derived units"

- Geowizard