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Tertiary Rivers

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Anyone know of a good example in AZ? Story in the Nov. issue of LT talks about the ancient rivers in CA and I really don't remember a topic about Az and ancient rivers. I saw a place in the Bradshaws But it was more of an up lifted creek, not very big.

Bunk

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(steelpan - sorry I messed up your post accidently. my mistake Ooops! - Reno Chris)

:opps:

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Bunk -

California has a number of uplifted old rivers now stranded high on a mountain top.

Arizona and a lot of other states (including Calif) have uplifted old benches of gravel where the stream once flowed, but they are not old enough to be tertiary.

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If I remember right, at one time in the past, all the rivers in Calf. and some in NV. ran from the north to the south, now since the up lift, they run from the northeast to the south west. And the new rivers have cut through the old channels to expose the old gravels. Grubstake

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Bunk - I am assuming you are interested in gold bearing gravels, not just some conmglomerate gravel of tertiary age somewhere in AZ. Plus there ia a difference between traceable river channels and deltas of gravel.

The different thing about the California rivers is that they were buried in lava and thereby preserved for a long time. Most placers are younger than tertiary as the normal processes of erosion just wash them away.

Yep, the Sierra block tilted. Before most rivers ran N-S, after tilting, most run E-W. These images are from my upcoming book:

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Speaking of uplifted placer, I've found a spot where I've pulled quite a few ounces of larger nuggets, up to an ounce, that has an area above it where the ground is all angular, except for quite a few obviously river worn, rounded quartz rocks...none of the none quartz rocks are rounded, just the quartz...I don't have a clue what I'm on to, but I've found well over six ounces of gold, with the nuggets ranging generally ffrom 1/4 to 1 ozt...Some are solid slugs and some are beautiful picture speci....Any thoughts? ...Cheers, Yer Unc in the Dubyah

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http://www.google.com/search?hl=en&rlz...art=10&sa=N you may find some info here on one of these pages.Hell,why not do a good sampling and checkout of any uplifted or suspected buried gravel,even a smallish appearing area.....Many tens of miles of tertiary channels,here in Calaveras County,Ca...the motherlode...Some are lava capped as Chris mentioned,others are exposed at current elevation levels for miles and are hundreds of feet deep.Some have major faulting and pieces of the channels are who knows where.Others were eroded into more modern day placers.In some areas here are channels lying on top of other channels,some gold bearing,some not.Some channels intersect others and have robbed them of their gold.In one town,Mokelumne Hill..there are eight or nine known channels,very rich which emptied into the Ione sea delta of eons ago.Road side geology comes into play here as one driving about can see many examples of the tertiary period...exposwed rhyolite ash with gravel below and gravel on top of it,etc. Table mountain,and many volcanic ridges.In a few spots one of the rivers was a mile wide.

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Bunk, you might find the article "Tracking Arizona's Ancient Landscapes" to be useful and informative.

Try this link for a pdf of the article/magazine: http://www.azgs.az.gov/arizona_geology/Fall_Winter_08.pdf

Otherwise do a search for the article.

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Ron, ever check the area just South of 60/89?? Sort of across the road from the gravel pit along LSD wash. I remember years ago exploring the old mines and washes before it dumps into the Hassayampa. I think it was west of the RR bridge. This was back in the early 80's when I lived in Wittmann, about half mile due West from the old dragstrip. I have no idea whats there now.

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a few obviously river worn, rounded quartz rocks...none of the none quartz rocks are rounded, just the quartz

Hi - hey this sounds interesting and might make for a good discussion, but could you explain this again?

Chris

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Chris... here is another to ponder. While in Brazil (Central Highlands), we would run into area that the ground is literally coated with rough broken quartz (old Vain?) . In the area will also be a single river worn rock, quartz or other. same areas can have smooth nuggets or rough nuggets. No sign anywhere of old river worn rocks.

IMG_3812.jpg

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The study of Tertiary Geologic Time(s) will give you a great understanding of your gold fields. In our neck of the woods which is more than 100 miles long and about 50 miles wide (give or take). We have sections of the old Jura River, Feather, Yuba and American Rivers and their feeder creeks. During the different Teritary Times they changed course to East/West/South a few rich shallow placers still run North. Each period of time will carry different gravel and rock depending on it's new cut through the new uplifted valley it ran through or the contents from volcanics, to the California central valley sea/gulf. Many places we detect you can find quartz gold, course nuggets and smooth river run nuggets in the same patch(s). The oldtimers put these clues together, so if you have some old diggings in your area take note of the geology/mineralogy. Get out and hump the hills, they didn't find all the gold...there's a patch out there with your name on it. Until our next hunt!

LuckyLundy

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Hi Steve:

Lots of prospectors know that angular sharp gold means that it cant have travelled far - and thats true. The other side of that coin, that all smooth nuggets are always formed by years of rolling around in some stream to round them is NOT true. Some nuggets form in the ground in a smoothed condition, and are "born" smooth. Geologically, this happens when the fluids that are depositing and forming gold change, and start dissolving the gold. Then by the process of dissoving, the nuggets are smoothed during the formation process. THis explains how you can be in an area with angular rocks like quartz, that produces mostly angular gold, and yet a few smooth gold nuggets are found. I was out at Rye Patch this weekend and most of the gold found was sharp and angular, but one guy found a nugget that was all smooth and looked like it rolled around in a river for years. Like the rest of our nuggets, it had not been in a river - it was just formed smooth.

There are also places like Lundy mentioned that have dual sources - an old river channel and nearby sources erroding out of the ground. One can contribute angular gold out of the ground and the other smooth gold that has been river rounded. Wtih these sources you should see a good percentage of river rounded rocks that are coming from the old river.

So why is the quartz covering the ground in your picture? Same reason we have big areas with lots of quartz out near Rye Patch. Quartz is VERY resistant to chemical weathering from rain and air. The surrounding rocks are not so resistant and break down into clays and silts on exposure to the weather. The clays are washed away (or blown away by wind in Nevada). This leaves the vein quartz, still angular and not worn, just sitting there, accumulating on the surface.

Chris

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Ron,

I have a few patches where the nuggets are rough and some round too. These areas are obviously a mixture of alluvial and elluvial. The rough stuff is weathered out of hardrock more recently than the older slugs. The district has a lot of local sources of veins striking the surface, some traversing canyons and ravines. Each one of the these local sources is actually a part of the entire deposit weathering system and each local source has weathered differently to a lesser extent than the entire area. sometimes the contemparary weathering (water bar) may be cutting right through an alluvial or elluvial and innermixing material. I never thought this was unusual, because the eyesight geology lead me to its conclusion. In this area I make it a point to hunt in areas where I find innermixing of gravels (angular and rounded). Areas like these get me excited. :winking0011:

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In some areas the quartz has blown out when formed?,such as Chapparal hill in Calaveras County,Ca...this across the road from ths famous Carson Hill mine.Quartz over a quarter mile and few veins that surfaced.In a small glory hole below the peak are dense wide mostly barren quartz veins/vein systems.Perhaps the rock was much softer near the surface when the solutions rose up,thus lot's of quartz,angular and otherwise.Very little is written or discussed about the quartz veins buried under these tertiary gravels.How rich some areas must be!...........Dave

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That makes very good sense. When I used to dredge Screwauger Creek (Headwaters to the North Fork Of the Middle Fork of the American), We used to find rotten quartz veins in bedrock they were all very angular quartz. When we broke them up and there were very very smooth and dense slugs of gold that had to form in the quartz. I was told by a professional Geologist (who also graduated from UNR) that those nuggets grew in the quartz.

The last picture was defiantly a very large decomposing vein on a mountain in Brasil. 4 times larger then anything at RP......

This is one of those screwauger nuggets

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Hi Reno Chris,

As far as some of the smooth nuggets found at RP, those type of nuggets are generally found fairly high, in my experience.

That day you came by, and chatted with me, I found a nice nugget that was smooth on one side and coarse on the other, most likely coarse from being retained by the host rock, then ultimately released at some more recent time, while the other side was likely polished smooth by the wave action of beach sands of the ancient lake shore, as seen from satellite images...

Would you buy into that notion?

Thanks, hope to see you this fall!

~LARGO~

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Would you buy into that notion?

Not at RP. I've seen a number of smoothed nuggets, but never any smooth, round quartz cobbles like you see by the millions in the tertiary rivers of Calif. If wave action was rounding the gold, you'd see rounded quartz along those ancient shores as well, and you just dont see that. If there were loads of round quartz pebbles around, then I'd say that rounding by rivers or waves might well be a possibility.

Very little of the RP gold was ever formed inside quartz veins - I've seen far more rounded nuggets from RP than I've seen RP quartz specimens filled with gold - yet there is quartz all over the ground and its fresh and angular. Most RP gold comes from little iron bearing seams and cracks in the rock - it hasnt had time to break and pop out of quartz if it had been formed that way. The big quartz veins at RP are practically barren. In spite of all the placer gold I've never heard of any hard rock ore from the placer area. If the placer was coming out of the quartz veins, quartz specimens would be the most common finds, but instead they are extremely rare at RP.

In some mining districts the placer gold really is formed in quartz veins, and in those places gold-quartz specimens are fairly common. Nuggets can also form, like Steve noted in pockets of iron in the quartz veins.

I know this stuff grates against what lots of guys have been told over the years, but its true in a lot of areas, not just RP. Just like crystal specimens that have been etched and disolved by geothermal waters, gold is also re-disolved sometimes. I'd say your piece was partly protected by rock and the exposed area disolved away during the formation process deep in the earth.

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Gold usually occurs either liberated or in the alteration products of pyrite and other sulphidic minerals. The most common of these are the iron oxides, such as hematite, magnetite, goethite and limonite, although gold can be associated with manganese oxides/hydroxides. supergene and residual deposits Mineralization formed deep in the Earth's crust can be exposed to the surface environment by uplift and erosion of its host rocks. The high oxygen content of the Earth's atmosphere and the presence of water result in chemical reactions that break down ore minerals that are not chemically stable under surface conditions.

Sulphide minerals are particularly susceptible to chemical weathering, which results in the release of their contained metals and sulphur. The oxidation of the sulphur produces large quantities of acid which then promotes further breakdown of other more stable minerals. In the air-saturated zone near the surface, valuable metals can be dissolved into groundwater because of oxidizing conditions in this region of the soil. When the groundwater percolates down to the water-table, conditions become more reducing and the metals can no longer remain dissolved and are precipitated as supergene minerals. Over time, large accumulations of supergene minerals can form and constitute a supergene deposit.

In straight talk, vein structures that carry gold & sulfides outcrop at the surface. Under the right circumstance supergene enrichment can take place, which will form flakes, nuggets, even slabs of solid gold. Over time erosion strips away the oxidized surface rock, exposing that gold at or near the surface in native form. The result can be, you can find “nuggets” where no streams, or river ever existed. Other times rich surface, or near surface pockets are found. The Gold Hill pocket mine in Oregon comes to mind, as well as Briggs, Steamboat & several others in SW Oregon.

QUICK CUT/PASTE BELOW

Hicks Lead: The first gold "pocket," also the first gold lode, discovered in Oregon was the so-called Hicks Lead found on the left fork of Jackson Creekabove Farmers Flat in Jackson County. Sonora Hicks, the discoverer, workingwith his brother, took out $1,000 in two hours, according to the Jacksonville Sentinel of that time. Walling (1884, p. 328) relates that Hicks sold his claimto Maury, Davis, and Taylor, owners of the adjoining claim, who then builtthe first arrastra in Oregon in order to treat the Hicks ore. The yield from theHicks claim was $2,000.

Gold Hill Pocket: The most famous of all was the astonishing Gold HillPocket, discovered in January, 1857 by Emigrant Graham and partners nearthe top of the hill 2 miles northeast of the town of Gold Hill in SW41\1E34 sec.14, T. 36 S., R. 3 W., Jackson County, at about 2,000 feet elevation. According to available records (Oregon Dept. Geology & Mineral Ind., 1943,p. 70), the outcropping rock was so full of gold that it could scarcely be brok-en by sledging. The crystallized quartz associated with the gold was not honey-combed as it generally is where sulfides have leached out of the rock, leavingsprays of gold in the cavity. The gold in this pocket went down only 15 feetand occurred in a fissure vein striking about N. 20° V'/., dipping about 80° E.,with a vertical gash vein cutting the fissure nearly due east. The fissure veinaverages 5 feet between walls with 1 to 2 feet of gouge on the footwall, whichcontains calcite and quartz mixed with a little pyrite, in spots containing freegold. A mass of granite, about 5 feet wide by 200 feet long, crops out in thefootwall side of the fissure. The country rock is pyroxenite. It is said that this pocket produced at least $700,000.Revenue Pocket:

Another large "pocket" was named the Revenue. It was found and mined out (date unknown) by the Rhotan brothers 5 miles south of Gold Hill on Kane Creek in sec. 11, T. 37 S., R. 3 W., Jackson County, atan elevation of about 2,570 feet. Reportedly it produced $100,000 (Parks andSwartley, 1916, p. 193) and was one of the larger pockets discovered by Rho-tan brothers, who evidently were well-known pocket hunters.

Steamboat Pocket: This important enrichment in a network of quartz veinsin andesite was found in the Steamboat mine about 1860. The location is onBrush Creek, a tributary of Carberry Creek, 2 miles west of Steamboat and 42 miles by road west of Medford. It is in sec. 20, T. 40 S., R. '4 W., Jackson County. The yield from the pock-et (Parks and Swartley, 1916, p. 212) is reported to have been $350,000.Johnson and Bowden Pockets: Two pockets in the Jacksonville locality aredescribed under the name of Town Mine by Parks and Swartley (1916, p. 136).Date of discovery and extraction is not recorded. The deposits were discoveredat points about 600 feet apart, approximately 2 miles west of the reservoir onJackson Creek in sec. 25, T. 37 S., R. 3 W., Jackson County. ,The Johnson deposit yielded $30,000 and the Bowden $60,000.Roaring Gimlet Pocket:

Diller (1914, p. 46) described a rich deposit knownas the Roaring Gimlet pocket, discovered in 1893. It was found at the mouthof China Gulch, Jackson County, about 21 miles south of the Gold Hill pock-et. The high-grade ore was apparently liberated from oxidized sulfides, leaving very little quartz, and formed an enriched gouge seam from a quarter of aninch to 6 inches thick between a porphyry footwall and a slate hanging wall.At a depth of 40 feet the vein continued down between dioritic walls and con-tained some small kidneys of calcite and quartz with pyrite - a gangue lookingvery much like that of the Gold Hill pocket. Several small pockets were extracted just east of the large Gimlet pocket. The combined yield is said to havebeen $40,000 .

Jewett Ledge Pocket: Known as the Jewett Ledge, this pocket was foundin 1860 by the Jewett brothers on the south side of the Rogue River in sec. 27,28, 33, and 34, T. 36 S., R. 5 W., Josephine County. As reported by Wal-ling (1884, p. 330), the Jewetts were "signally successful" and took out $40,-000. It is said that they exhausted the deposit and ceased work. In later years considerable work was done on the property and seven claims were patented.

Robertson Mine: In more recent times an underground high-grade lens of gold ore was found at the Robertson (or Bunker Hill) mine in March, 1940,somewhat different in character from the surficial deposits previously described.The mine owners, William Robertson and Virgil E. Hull, struck an enrichmentin their quartz vein, and took out 640 ounces of gold valued at about $20,480 in four days of mining. The mine is west of Galice in sec. 2, T. 35 S., R. 9W., Josephine County, at an elevation of 4,500 feet. A specimen of this high-grade ore is on display in the Portland museum of the Oregon Departmentof Geology and Mineral Industries.

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Thanks for all the input, it has made for some real interesting reading!

I gess what started this is I was thinking about All that volcanic cap in the area between Cordes and Black Canyon City. It must be covering up some good gold areas.

When your self taught, you don't learn if you don't ask questions.

Bunk

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Bunk,it would probably be in your interest to get all the old mining reports you can,state,county,USGS etc...you seem to have the main ingrediant for success.....curiousity!....If you do find a patch/stretch of gravel,don't ignore any quartz stringers or veins.Any color at all is worth further checking...........Dave

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Great Topic,Dave as you know the a lot of the mining in(Calmo Shaft) the "Golden River Channel near us was in the "very rich quartz stringers which were in the bedrock several hundred feet down.Also as you know I hit a little paying bedrock stringer dredging in that area.I am still confused though on how I am finding quartz stringers in the supposed false bedrock over the channel????

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Bunk,

There may well be a reason that there is little about gold bearing Tertiary streams in AZ.

I have started reading USGS Bulletin 782, Ore Deposits of the Jerome, Bradshaw Mountains Quadrangles, Arizona (1926). The following is from the introduction to that Bulletin:

The object of this work

was not a detailed investigation of each deposit but rather a coordination and

classification of the occurrences and an attempt to ascertain their origin and

economic importance. Almost all the deposits occur in pre-Cambrian rocks or in

rocks that are not readily differentiated from the pre-Cambrian. In the northern

part of the Jerome quadrangle there are large areas of almost horizontal

Paleozoic beds, and in both quadrangles there are also large areas of lava flows

of Tertiary age. Finally there are wide spaces occupied by Tertiary tuff and

limestone, or by Tertiary and Quaternary wash filling the valleys between the

mountain ranges. But all these rocks except the pre-Cambrian are practically

barren of ore deposits, and the problem therefore narrowed itself to an

examination of the pre-Cambrian areas.

(emphasis mine)

Additionally the Colorado Plateau is largely unfaulted, post-Cambrian sedimentary rock.

Simply put, Ariziona's is a quite different geoevolution from California's.

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I have not done much book learning on this subject. In my travels I see things and wonder. In traveling down I-17 are places that look good for prospecting but the land is covered with lava, for lack of the proper word, and in some places it sure looks to me like theese later "lava" flows really changed the landscape like some of the places in CA. I think what I am wondering, has anyone found a place like this, in AZ, where they have found gold in a aceient stream that was covered with lava?

This is a yes or no question, I am not asking for anyones seceret spot. Thanks, Bunk

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