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meatbee

gold and schist

In my area of Northen California, placer gold is frequently found in upthrusting viens of slate schist. Is this gold that has been simply trapped there or was the gold formed in between the layers of schist? meatbee
Reno Chris

Good question - impoosible to answer for your particular situation as I know none of the particulars. On the one hand, gold does form in schist sometimes with little or no quartz. On the other, if you are in a stream bed, its most likely that the gold was dropped there by the flowing stream.

Chris
meatbee

Thanks Chris, I am working flowing streambeds, so the gold is probably deposited there from some other source. meatbee
wes

Meatbee, This is a piece I recovered from some shisty slate like you have. It's very thin, only a gram, rough, and has some tiny quartz crystals attached. There was some quartz in the area but not right where it was found. Just an example of what a nugget might look like in that type of rock.




Side view
FlakMagnet

Hi Meatbee,

I also dredged in a river that had an upthrust of slate.
One of the stranger nuggets I found was under about a foot and a half of sheets of slate
that my partner and I chunked out with a crowbar (the sheet had lain over horizontally at
the point we were working).
I was shocked to find this almost 1/4 oz. nugget that deep in the slate...nothing else was found
anywhere that deep.

best,

Flak
Grubstake

I know that there is stuff called BULL QUARTZ, I'm just wondering if there is maybe a little BULL SHIST somewhere? Ha! Ha! Grubstake Rolling Eyes Razz
BIGFOOT

gold and schist

meatbee,
The geological conditions define the type of "Slate Gold" your asking about.The AU of the RP area are of Epithermal origin and that particular area & condition(slate rock that metamorphosed from old ocean floor then later,hydrothermal fluids brought in by a underlying heatsource probly granitic in nature) or geology have produced some flat peices that have a exact negative imprint of the slate surrounding them on BOTH sides of some specimens.This IS a unusual occurence that implys the AU formed directly inside the fissures(sometimes completely without the presence of quartz)from fluids so rich that the AU precipitated in situ DIRECTLY in contact with both walls of the fissure.
However,over in Northern Calif. you have Mesothermal Vein deposition taking place that involve more pressure and thicker host rock units...which does not give the AU the depositional freedoms as in RP.
In N.Calif. I've seen the AU jump from the quartz into the host rock or slate.Also a standard in Geology is the bigger the crystal the slower the cooling that took place.
Bigfoot
rehab

two cents worth. slate is usually baked mud (metamorphic) as is schist (molten and reformed rock). It is quite possible that the gold was from ancient placers trapped in mud, and when uplifted, is now semi exposed for discoverers like you and me.
Most of the bed rock of northern california is uplifted ocean bed.

Schist, in and of itself is usually barren of sizeable gold, but it is an indicator of metamorphic action- the factor that creates ore veins. Being in a metamorphic rock area is what most prospectors look for, in order to start looking for metal ores.

There are geological books about california (simple ones) that can explain this a little better
BIGFOOT

gold and schist

Rehab & others,
Its about time some of us threw some ideals around!
Rehab...you said "slate is usually baked mud (metamorphic) as is schist (molten and reformed rock). It is quite possible that the gold was from ancient placers trapped in mud, and when uplifted, is now semi exposed for discoverers like you and me."...IF this were the case we would have AU pieces trapped(and detected) inside the host rock...not limited to the fissures as at RP.
The nuggs at RP are mostly free in dirt OR ACTUALLY LOCKED (is this an old miners expression?There LOVE is LOCKED in the rocks near "LOVELOCK"?hhhmmm?nah! hmm ) in fissures secondary to the metamorphism.How else can so much rock get altered squeezed heated without deforming pre-existing nuggs?There were no pre-exisiting nuggs prior to metamorphism.Rocks as well as nuggets have thier own story to tell.With perfect imprints of the surrounding walls emmbedded into both sides of the nuggs...its safe to say they formed right there....in situ.I've watched Ed Speir find a nugget out there and it was in fact LOCKED into the fissure....and when it was dislodged from the rock....it had well preserved
faces of both sides of the schist fissure...down to the details of sandy texture,divits,cracks & lumps actually left from the host....or fissure walls.
What suprizes me is even though the bedrock formation(schist)is very old...the AU formation of these nuggs are very young in age.There arent any "slip slide striations"(formed by faulting/compressing)found on any of the in situ fissure pieces.Striation character can indicate a variety of depositional enviroments.Even though striated nuggs can be worn smoothe...striationed(or grooved) specimens would have already been found in such a productive area.
BIGFOOT
shep

Hey Bigfoot, I'm not very bright when it comes to Geology. Like the RP area, but could never figure out why the gold was so sporatically located. Appreciate your input. Please keep it up!
Thanks,Shep
BIGFOOT

gold and schist

Shep,
Good comment...sporadic distribution through-out RP.There are some patterns to notice...but it involves the surrounding areas as well...The entire Humbolt Range(east of RP)is one long Anticline running North to South.This mountain range was formed by pressure from the East&West causing a prominent buckle or pinch and has a prominent arch to it if veiwed East to West.From there to West of RP one can see the forces of hydrothermal activity and its influence on deposition ALL directions from the RP lake proper.When one combines the "MOUNTAIN MOVING" AND HEAT SOURCES together it leads towards a better understanding of WHATs There &Why its there.
The geothermal activity is remenant of a dieing pulse of large scale "BAKING" of the old ocean floor...its a very THIN SKINNED crust in RP which adds to a large area of sporadic heating/deposition throughout.This "thin crust" is more easily permiable by heat underlying this state...which makes for better conditions for deposits of all kinds.People have no ideal that NEVADA is like no other PLACE on earth GEOLOGICALY speaking.Mountains have been twisted,turned upside down and shoved distances over 60 miles up & over OTHER mountains!
Anyways...Geology Of The Great Basin by Bill Fiero is my fav for learning the basics of THIS states geology...easy to understand yet detailed...CHECK IT OUT!
BIGFOOT

"The Great Basin, explored on its terms, is a fascinating expanse of unique geology, as Bill Fiero, a professor of geology at the University of Nevada-Las Vegas, shows you in this fine book. Written in easily read style, and understandable to anyone who has gone to high school, the book takes you on a general tour of the wonders of Great Basin, including well-known Bonneville Salt Flats, a remnant of an Ice Age lake bigger than Lake Michigan. You will also read about recent volcanoes, earthquake activity and faults, deep trenches such as Death Valley, ancient, dried up rivers, and fossil sand dunes. Canyons, badlands, and mountains are also part of this region, and author Fiero takes you through these areas as well, all the while explaining how and why all of these features came to exist as they do.

The book not only has excellent color and black and white photographs, following side-by-side with the narratives, but gives the reader an excellent background on physical geology in general, Indeed, it could easily be used as an introductory college text. Remember that one advantage to the Great Basin is its aridity, which enables you to see and understand the rocks and what they tell much better."
RexB

Nevada is the “motherload” of the great basin and range province. It is the only state that is completely covered by it. Utah has quite a bit of basin and range territory as well. The basin and range province in a nutshell is basically an area of the crust that is actually expanding or pulling apart. Bigfoot is right, the crust is some of the thinnest in the world. As you approach the western end of the province the deformation becomes more extreme. Areas are downthrust and upthrust forming faults along the mountain ranges.

Rex
rehab

There are many facets of geology or gold origins that no human could ever comprehend or discover. we do know about origins of base rock, and how the outer mantle plays a big part on crust formation, but fail to understand how gold is found in one locale (as part of similar rock formations) and not in another with like formations.

We do not understand how native gold is found without encrustations (such as the picture depicted on this thread) in slate or schist cracks. there are several other things that do not make sense- hence the word "uncomformity" where one rock sequence lies in direct contact with another type, perhaps a million years apart in formation.

The Canadian work "GEOCHEMISTRY OF GOLD" has a lot of information if one cares to wade through complex technical and academic terminology. But, for the most part, "ROADSIDE GEOLOGY OF..." renders a service to explain certain geology, and for all intent, the ability to recognize rock formations where native gold or gold ore exists, should be the intent of gold prospectors, rather than delving into technical abstracts.

Experience in finding gold becomes a knowledge base to help one later understand the process by which it got where it was found. Though native gold is the object of most detectorists, and their geological comprehension is basic, more sophisticated miners and prospectors look at the whole picture and study mineral combinations far beyond native showings; for those chemical combinations in ore bodies can be lucrative, provided the extraction process and dedicated machinery is without fault.

Most detectorists use advanced technology for locating simple globules of native metal, and do not have any desire (or capital) to delve into complex mining theory, fault process that affects(ed) the ore concentration or enrichment, nor will most detectorist become full-fledged miners. In other words, the metal detector prospector is on a 'grab and run' cycle geared towards a specific mineral form; while a miner is looking at income based on chemical reduction of all variables.

As bigfoot pointed out, the gold was younger than the host formation. gold works its way down to bedrock (whatever impervious layer stands in the way to block downward movement). Rock is plastic, and moves and cracks, and whatever heavy, fairly inert gold that is on top will fall into the cracks and ride along, seeking a deeper position. Which tells me one thing: formations that once existed far above the slate bed, containing gold veins, have since eroded, and what we see now as surface rock, was once buried thousands of feet or miles below, and is now uncovered.

Yet, when we can recognize certain metamorphic intrusions or structures, we also recognize the native gold potential of the area. If we are finding native gold in such an area, it would be prudent in my opinion, to obtain a colored geological map and search other areas with like formations. Any body with a basic knowledge that can locate a geological map of one productive area, find the rock formation and structure there on the map, then compare its color and symbols to adjacent areas on the map or other maps, then has a key to potential and possibly other virgin or productive areas in order to locate nuggets or native gold particles. nothing fancy, nothing complex, just comparing one map with another, then making a field search of similar terrain.

Perhaps Bigfoot and RexB (who seem to be real geologists) could elaborate on my novice theories.
BIGFOOT

gold and schist

rehab,
Thats not a novice elaboration you posted there!lol Anyways,The occurrence of gold is not allways haphazzard or as random as you suggest...at least to a modern prospector with the present technological advantages out there today...till theory/geology goes several (over 6)miles deep below the surface.True,there will allways be a UNKNOWN or "exception to the rule" extremes in any field...the HUNT is becoming more advanced with better results dependent on ones technique,skill and luck but... at the same time...the easier surface gold IS dwindling.Its presence in various rocks and its occurrence under differing environmental conditions follow natural laws and as detectorist's/geologists increase their knowledge of the mineralizing processes, they improve their ability to find gold...in different...sometimes un-orthodox ways........but...WHO CARES AS LONG AS YE GET THE GOLD!!!..........RIGHT?.......YES!
For Example!!!:Many different kinds of info are used in different ways and may be worthless to some and valuable to others.IF applicable to me & my area of hunting:Which GROUP WORKED WHICH STRETCH OF LAND?You say WHO CARES??!GOOOOD!...because I do!WHY?Think of it this way........would ya rather detect a area CLEANED by "Caffiene Crazed" Chinese miners using toothbrushes and everthing else that was highly effective at that time ...OR....hit a area thats been worked by CONSTANTLY HUNGOVER/INTOXICATED white miners that had tool shortages and a high rate of AU loss in the tailings?WHY did the losses occur and were there areas that had more losses than others ect....hhhhmmmmm....I KNOW which area I'd preffer!.True this was not the consensus people's jobs...but the info is out there AND in some cases is worth just as much as the gold it helped you find.Hey,if a historical acrcheologist will go through hell just to find out WHERE the out-house was to "find duh finds" (and other "things") you can find out AU related info as well...GO GET ER!
Rehab,the IN SITU nuggs I spoke about out at RP is NOT concentrated in those fissures by a gravitational process...they were born inside those fissures.Just thought I'd make my ideal/opinion better understood or more clear because one of the BIGGEST mistake's all of us make here on the net is "thinking" we understand whats being said/written.......when IN FACT we dont.......all ya gotta do is ask to find out.
Rehab,You gave some simple advice and examples(in the above last paragraph)that not too many here actually take the time to do...and thats tooo bad for them because its THAT curiosity and slutheness that better the odds of making a find.When I heard about the Eugene finds(8 years ago) I know some of us were trying figure out why,where&what was causing this on the geo maps......the corrolations,the new piece to the puzzle while the majority were hunting over there to the south/west... pounding Majuba and vicinity.Even then I STILL felt as though I were late in the chase...VERY VERY LATE knowing the more successfull folks were out "making" thier own trails & patches in N.Nevada... just following up with a VLF wasnt/isnt good enough at times for me.Searching more ground in different ways for longer runs may convince me again that its gonna take a lil while to get all of nevada underneath my 10" eliptical coil.
Good Luck out there! Rolling Eyes
BIGFOOT
rehab

great post! No miner ever gets all the goods. they just dig one hole here or there, based upon the law of economics and cash to keep the food on the plate before or after they go to work.

Having an investigative mind and eye is key to locating a reward. Some knowledge of geology is a must, as is some knowledge of gravity. Like seawater that has gold in it, one has to have enough knowledge to determine what the economical threshold is, and how to leave one thing behind and turn their attention to a better chance and a higher return,

Like bigfoot said about depth, except for some gold mines in South Africa approaching 2+ miles deep, most any other cause is but a nick. We do know that some gold (many very highgrade deposits) lie right on the surface, and do not get better with depth. Actually, the deeper one gets, the more complex the ore or the challenges of dealing with rock layer dynamics, faults, slips, and ground movement.

There are coal mines in Chile that stretch out for 17 miles or so under the Pacific Ocean, and gold and copper mines in the Andes that require high altitude aclimation or oxygen masks just to extract the ore, all while the earth shakes everyday as part of a plate subduction zone. (It can be quite disconcerting to experience a tremor while underground, thiinking about all that seawater or whatever that could crack and ... in any mine, there is usually one way in and one way out, and if it gets blocked, tough sh-t).

Luckily for us, it seems the gold nuggets are vastly closer to the surface than below it, and much of the really good finds can be accessed with a quad, a pick, a shovel, and a metal detector. beyond that, recovery gets increasingly complex.

With that said, develop your investigative instincts and abilities. The ability to recognize potential from afar is more than half the battle. Figuring out how the equipment works best to find the target is most of the rest of the effort.
IronMike

Grubstake wrote:
I know that there is stuff called BULL QUARTZ, I'm just wondering if there is maybe a little BULL SHIST somewhere? Ha! Ha! Grubstake Rolling Eyes Razz


I believe that most of the BULL SHIST is down in the Mariposia area with a bit up around the Auburn area. Twisted Evil Twisted Evil Twisted Evil Laughing
Grubstake

Yeh your right Mike, there is plenty of BULL SHIST to go around down here, between Shep, my uncle and Pondmn, we make and put out a lot of it! Want to buy some? Since you have a shortage? Ha! Ha! Grubstake
BIGFOOT

gold and schist

......Imagine that............coming all the way over here just to "talk" bull shist......ar-ar-ar sleep orc

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