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Post  TuronYellowFever on Sat May 14, 2011 8:17 pm

Welll I'm off to an old gold field that I gave up on years ago. I found a couple of really nice slugs there but the hot rocks that occur all around the old shallow lead are incredible, probably one hot rock every square foot. The field is an old river bed that sheds from under a basalt cap. Problem is that the vocanic basalt cap seems to include heavy iron type mineralized rocks that sounded exacly like a target with the old GpExtreme. Hoping now that the new upgrade to a Gpx4000 might lessen this problem. Im interested in hearing from other peoples experiences in dealing with hot rocks and the Gpx4000's best type of settings for such rocks. These hot rocks are really unlike any other hot rocks that I have encountered. They are almost always near perfectly round and about the size of an orange, they are a browny colour and when broken up the have a slight purple metalic like appearance. Hoping to overcome the problem.

cheers

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Post  Guest on Sat May 14, 2011 9:17 pm

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Last edited by fencejumper on Sun Aug 12, 2012 10:05 pm; edited 1 time in total

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Post  Tributer on Sat May 14, 2011 11:01 pm

Hi TYF, I spend alot of time detecting the gold from deep leads in the tablelands. Yes there is nothing to compare to signals partly decomposed basalt cobbles produce. You cannot use settings to get rid of the signals in any real way.

I use a small coil 8-11 and try to work all bedrock that is free of the basalt rubble. Many of the creeks below deep leads often have some good gradient and areas of bedrock to detect. Otherwise i simply listen for very distinctive signals that are not basalt. Any signal that has some broadness to it i leave. You will always get caught out by some small cobbles that are a few cm deep however with an 8 inch coil you can pick out the crisp whistles from smaller nuggets and the small coil size means you have some breaks between getting signals from basalt cobbles. Unfortunately any deeper signals from nuggets with some size will be almost impossible to distinguish. I have dug some deep ones because the signal was just slightly different from the dozens of basalts signals i had got in the 10 minutes before the nugget. I have tried inverted and Sen/smooth and many settings however in my humble opinion the only good way is to try get your brain tuned to the difference between the basalt and sharper better defined nugget signals.

I know its basic stuff but with persistence i have become happy to detect basalt areas without suffering brain damage from the neverending basalt signals.

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Post  Jonathan Porter on Sun May 15, 2011 5:26 am

If the actual ground itself has a consistent level of mineralisation (non variable) then try ground balancing to one of the hot rocks (obviously you then need to keep the detector in Fixed GB as well as use one of the more powerful timings) to take the edge off the signal or even ignore it altogether. Some areas this is possible others not so good. Sens Smooth on the 4000 will go someway to helping but Smooth has limited depth on larger gold so is best used in shallower areas.

Another suggestion is to use Sharp or Normal timings, back off the threshold completely (Bogenes method), crank the Gain up flat out and perform a GB on one of the hot rocks, then dig everything that causes even the slightest burp in the threshold there after.

Hope this helps,

JP
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Post  Guest on Sun May 15, 2011 9:41 am

Nar if I az remembed correctly frum va erly dayz wun ov va main sellin points ov va ML PIz iz vat vay dun respond ta hot rocks Very Happy Very Happy Very Happy

Soundz like ya needs a Infinium Very Happy Very Happy Very Happy Shocked Shocked

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Post  TuronYellowFever on Sun May 15, 2011 8:47 pm

Thanks for the help guys, really payed off. The hot rocks still hot on the gpx4000 but the surrounding gullies were very fruitful. 10grams total. Biggest 4.3grams. Loving the 4000 !!!

HOT ROCKS .....GRRRRR Goldd

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Post  llanbric on Sun May 15, 2011 9:05 pm

Go to here http://arizonaoutback.ipbhost.com/index.php? and search for basalt, there should be a couple of good posts about tuning out basalt, it didn't help me, it may help you, there are different types of basalt.

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Post  Nature_Pete on Mon May 16, 2011 7:39 pm

Hi guys,

Forgive my ignorance as I am a newbie to this. I have to ask the simple question:

Is an area of basalt or areas surrounding it, which I am assuming is a 'hotrock', considered a good place to find gold deposits?

Thank you,

Nature Pete. Very Happy Very Happy Very Happy
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Post  Guest on Mon May 16, 2011 7:53 pm

Hot rocks are any of many types of rock that set your detector off! The majority contain no valuable minerals, There are however hot rocks that can contain good amounts of fine gold when crushed and panned? I discovered this fact over in WA. So from my experience it's always worth tacking a couple of hot rocks from a given area, to crush and pan later?
Maybe nothing, Maybe fine Gold.
P.s It really ups the antics on your panning skills!
Cheers Chris.

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Post  Tributer on Mon May 16, 2011 8:23 pm

Hi Nature Pete, as Someday-Chris mentions many different types of rocks (most containing significant iron rich minerals) can be hot rocks and produce a good signal when the coil is passed over them.

In relation to basalt, there are many old river streams containing gold that were covered in basalt (lava). These are usually named "deep leads" Along the great dividing range and Tablelands of NSW and many other places there was alot of volcanic activity from 40-8 million years ago. Very liquid lava oozed from rift type volcanoes associated with faults often and flowed down valleys covering gold bearing gravels and plant material.

Basalt is so resistant to weathering and erosion thatthe hills either side of the basalt filled valleys eroded away over millions of years to become the valleys and left the basalt capped river gravels as the high ridges in the local landscape. The topography has been reversed!.

So there is gold under these basalts and it erodes out and spills down the slopes to the present day creeks, and i chase it. The 1800's miners also chased it and many deep leads have shafts sunk horizontally into them. These mines in river gravels were some of the most dangerous and prone to collapse aided by water movement through the gravels.
Google deep leads for more info

Cheers Tributer
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Post  davsgold on Mon May 16, 2011 8:25 pm

Nature_Pete wrote:Hi guys,

Forgive my ignorance as I am a newbie to this. I have to ask the simple question:

Is an area of basalt or areas surrounding it, which I am assuming is a 'hotrock', considered a good place to find gold deposits?

Thank you,

Nature Pete. Very Happy Very Happy Very Happy

Some of the ancient rivers were capped by basalt flows and trapped any gold under these basalt flows that the old rivers carried, ie: Paleochannels = old river courses.

Now the present drainage/rivers have is some places cut through these old river beds and redistributed the gold. Sometimes these old river beds capped in basalt or lava flows can be seen way up above the present river systems and the old rounded river gravel is scatterd down the hillside.

To answer the question......Basalt is one of the hot rocks in this situation and it gives a good (but very annoying) signal on the detector.

cheers dave

PS: Tributer and I posted at the same time Very Happy


Last edited by davsgold on Mon May 16, 2011 8:27 pm; edited 1 time in total (Reason for editing : added PS)
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Post  Guest on Mon May 16, 2011 9:42 pm

Somebody please hit me over the head with a shovel or something!
Tributer, I never had diddly squat to do with lava so it's a subject I never bothered about! Having said that I now feel sick. West of Ravensthorpe in WA about 10 km from memory
near the Phillips river, I came across a few basalt covered areas in the higher ranges, Due to WA's flatness the erosion process will be slowed dramatically!
You learn something new every day, I didn't need to learn that now thou.
Cheers Chris.
P.s. Thanks Crying or Very sad Crying or Very sad Crying or Very sad

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