Monday, February 4, 2019

Green Valley, Payson, Arizona

When I moved to Arizona from Wyoming, I figured I would have many new gold and gemstone deposits and districts to explore. And so far, Arizona has not let me down. However, the geology of Arizona is quite different and it takes time to get use to new geological formation names, geological structures and provinces. Wyoming is primarily underlain by a disrupted, yet stabilized, Archean craton (continental core more than 2.5 billion years old) that is covered by thick layers of sedimentary rock that fill broad basins bounded by Precambrian cored mountain ranges. The old rocks of the Wyoming Craton are geologically favorable for a variety of deposits including diamond pipes, colored aluminous gemstones (i.e, ruby, sapphire, iolite, andalusite, sillimanite, kyanite, garnet), beryl, jade, gold, iron ore, rare earths, titaniferous magnetite, nickel, iolite, moonstone and spectrolite (labradorite) to name a few. In the younger, non-cratonic rocks deposited on the ancient basement terrain, gold, fluorspar, rare earths, coal, uranium, oil and gas are found. 

After spending much of my geological career in Wyoming with sporadic sojourns to other parts of the lower 48 and Alaska, I had some success in finding mineral deposits such as a significant colored gemstone deposits at Palmer Canyon and Grizzly Creek, Wyoming, a world-class gold deposit (with six other geologists) at Donlin Creek, Alaska, and a major gold district in the Rattlesnake Hills, Wyoming. When I began searching, Wyoming had many overlooked mineral deposits and it likely has many more to be found. 

Arizona on the other hand has a younger geological basement (geological basements are the oldest preserved crustal rocks) that is Proterozoic in age (less than 2.5 to about 0.6 billion years old). The oldest rocks in this basement terrain are about 1.8 billion years old, or nearly 2 billion years younger than the oldest rocks in the Wyoming Craton. Arizona’s basement is overlain by younger sedimentary and volcanic rocks and the state is separated into three geological/geographical provinces known as the Colorado Plateau to the north, the central highlands transition zone, and the Basin and Range province to the south. Arizona has many giant base metal deposits with copper, lead, zinc, molybdenum, gold, silver and other metals that are known as porphyry copper deposits, some massive sulfide deposits with copper, zinc, gold and silver, and scattered gold and silver veins and a few disseminated gold deposits along with lapidary to near gem deposits. Coal, oil, gas, and uranium occur in the Colorado plateau area, whereas the porphyry copper, massive sulfide, and lode gold deposits are found south of the Colorado Plateau.

So I began a search of the geological literature with follow-up cursory reconnaissance of the State’s mining districts that will keep me busy for years. Some investigations so far, have taken me to the Vulture mine, the Verde-Jerome district, the Pearce Mineralized area, the Oatman district, the Superstition Mountains, the Tombstone district and others. My most recent investigation was the gold deposits of the Green Valley district near Payson.

The Green Valley district is in central Arizona south of Payson in the foothills of the Mazatzal Mountains. Geographically, this area is part of the central highlands located between the Colorado Plateau to the north, which the southern extent is marked by the Mogollon Escarpment just a few miles north of Payson, and the Basin and Range marked by a series of distinct basins and ranges several miles south of Payson. 

Payson is reached by driving northeast along Highway 87-N (Beeline Highway) from the east valley of Phoenix. The Green Valley district is underlain by the Payson Ophiolite, a sequence of Precambrian rocks that date at 1.73 Ga that include volcanics, sheeted dike swarms, diorite, gabbro and tonalite. These lie on a 1.75 billion year old basement complex formed of granitic rocks that include felsic volcanics (igneous rocks rich in quartz and feldspar such as rhyolite) and volcaniclastic rocks. Ophiolites are chunks of the earth’s oceanic crust and underlying upper mantle that consist mainly of mafic igneous rocks (rocks rich in magnesium and iron such as basalt and gabbro) that have been uplifted above sea level in the geological past and emplaced in continental rocks. And yes, Arizona was under the ocean in the past as the continents drifted around the hemisphere.

The earliest report of gold in the Green Valley district was in 1875, which was followed by more discoveries over the next few years. The discovery of rich, free-milling gold-quartz veins resulted in an influx of a few hundred miners and prospectors. However, veins in the district were limited in size and the easily recoverable gold in the oxidized portions of the veins gave way to refractory, low-grade, sulfide-bearing quartz below the water table at depths less than 200 feet. Thus, no major mines developed and production records were not kept. Even so, both lode and placer gold were found.

The district is highly fractured and faulted and some fissures provided pathways for gold-quartz vein injections: many of the veins strike N15oW to N65oW and dip northeast. If you examine the area immediately southwest of Payson on Google Earth near the Delaware and Little Maude mines (map numbers 11 and 12) you will see dozens of linear drainages that are structurally controlled by fractures and faults: most trend N70oW to N35oE. Similar distinct polygonal fractures are seen throughout the district and most intersect at right to near right angles, others produce rhombohedral fracture sets. Examine the area around 34°11'15"N; 111°22’30”W on Google Earth by first searching for ‘Payson, AZ’ and then search for matching GPS coordinates at the bottom of the Google Earth page to view many of these fracture-controlled, linear drainages.

In the 19th century, visible gold was found in veins at the Gowan, Oxbow, Golden Wonder and Zulu mines, and detrital (placer) gold was found downslope from the Oxbow mine four miles south of Payson. The placer gold included minute flakes and flat nuggets up to 0.25 inch long. 

Minor deposits of copper and silver were also found. Where found, wire and horn silver occurred in the oxidized part of the vein at the Silver Butte mine. The silver was associated with galena (lead-sulfide) and tetrahedrite (copper-iron-antimony-sulfide). Chalcopyrite (bronze metallic copper-pyrite) was also found at both Silver Butte and also at Bishops Knoll south of Payson, where some tetrahedrite, bornite (iridescent blue to lavender copper-iron-sulfide), covellite (iridescent blue copper-sulfide), chalcocite (black copper-sulfide), malachite (green copper-carbonate-hydroxide), azurite (blue copper-carbonate-hydroxide), chrysocolla (blue hydrated-copper-polysilicate) and dioptase (emerald-green copper-cyclosilicate) were described. Copper in the Green Valley deposits included lenses of tetrahedrite and some disseminated chalcopyrite and bornite in greenstones, and also disseminated pyrite, chalcopyrite and chalcocite in schist and mafic (gabbro and diorite) dikes.

Most gold-bearing quartz veins found in the district were fracture fillings in faults enclosed by crushed quartz zones along their margins. Since the host rocks were often extensively weathered, portions of the veins stood out as positive, resistant, outcrops. The gold-bearing veins ranged from a few inches wide to the vein at the Gowan mine that was as much as 12 feet wide.

Gold was found associated with hematite and limonite in the oxidized portions of the veins. Below the water table, visible gold was absent and the gold values were lower and the precious metal appeared to be hidden in pyrite and chalcopyrite. Above the water table, free milling gold was found suggesting that the precious metal was tied up in the sulfides. 

Further evidence was provided by some vein samples that were described to contain tiny gold flakes in secondary hematite and limonite in quartz above the water table. Additionally, limonite pseudomorphs after pyrite were identified at the Oxbow mine. It was noted by miners that higher gold values correlated with higher limonite and hematite. 

At the Golden Wonder mine, some relatively recent explorers suggested that some of the gold was associated with high bismuth and tellurium content possibly indicating some gold was hosted in tellurium minerals (i.e., calaverite, petzite, or sylvanite) and possibly native bismuth that had been missed by past miners.

Below the water table veins with pyrite and chalcopyrite typically assayed less than 1 opt Au (ounce per tonne gold). In the oxidized vein above the water table at the Oxbow mine, samples yielded 0.24 to 3.87 opt Au, and values at the Gowan vein above the water table were as high as 4.85 opt Au. Most host rocks were described as diorite altered to chlorite, sericite and secondary quartz over a width of several feet on either side of the veins.

There are several mines and prospects in the district. Some of these include Bishop's Knoll, Callahan (34°12'21"N; 111°22’55”W), Crackerjack, Delaware (34°10'49"N; 111°22’20”W), Eighty-five, Excursion, Gowan, Gold Rock, Golden Wonder, Lincoln, Little Green (34°11'11"N; 111°23’48"W), Little Maude (34°10'41"N; 111°22’41”W), Maggie, Mankin, Midget (34°9'48"N; 111°21’32”W), Oxbow, Payrock (34°12'40"N; 111°22’5”W), Rocky Ford (34°12'1"N; 111°22’18”W), Silver Butte, Silver King (34°13'34"N; 111°21’45"W), Single Standard (34°11'48"N; 111°22’8”W), Summit, Thompson, Zulu, and White Mountain (34°16'3"N; 111°24’12"W). A few properties appear to have been prospected over relatively large areas since the second world war such as the Golden Wonder, Maggie, Oxbow, and Zulu. These, in particular, should be examined for large tonnage gold mineralization. And these and other veins could provide opportunities for nugget hunters as well as for detrital gold downslope from the veins.

Placers are uncommon due to a lack of active streams. Some placer gold was recovered in drainages below the Oxbow mine during the rainy season when surface water was available. Much of the gold was found in surface gravel, but in 1939, placer gold was described in deeper gravels in an old channel unrelated to the current stream channel.

Some mined ore was hauled to the nearby Verde River where the gold was recovered by amalgamation in arrastra mills and later in stamp mills. And some attractive agates and chalcedony were also reported in the area including banded agate (34°12’45''N, 111°22’13’’W) and fire agate (34°12’40''N, 111°13’2’'W). 

Crackerjack prospect. SW¼NE¼ section 22, T11N, R9E (34°17'4"N; 111°25’18”W). The Crackerjack was a former underground copper-silver-lead-gold prospect located about 0.75 mile south of Cracker Jack Mesa on National Forest land (map number 17). The property was also known as the Copper King. Mineralization was found in a 3- to 5-foot-wide vein with lenses cut by cross fractures. The mine workings included a 350-foot tunnel on the vein about 150 feet down from the hill top, and a second tunnel was dug into the footwall of the vein. A 45-foot deep shaft was sunk at the top of the hill.

The fissure vein strikes N80oW and dips 80oN and is hosted by Precambrian felsic rock that shows moderate chlorite alteration near the vein. The Crackerjack mine lies along a fault zone separating Larsen Spring Formation (1.75 Ga) felsic volcanics and volcaniclastics from much younger Tertiary rocks to the southwest. Gold, malachite, brochantite (green copper-sulfate), chalcopyrite, cuprite (red copper-oxide), chalcocite, bornite, quartz and limonite were reported on the mine dump. Two ore cars shipped from the property contained an average of 7.7% Cu and 8.7% Cu.

Gowan (Excursion?) mine. N/2 section 23, T10N, R9E (34°11’50”N; 111°24’12”W) (map number 9). Eleven patented claims were granted for this property (patented claims means that the property is privately owned). The footwall of the Gowen vein was described as altered hornblende diorite intruded by porphyry granite. Sycamore Creek sandstone (Devonian) was reported to sit on the igneous rocks, and was down-dropped along a fault. The vein strikes N15oW and dips 32oNE and has a maximum width of 12 feet. Some free gold was reported in the vein. 

The property was at one time operated by the Excursion mining company and included several thousand feet of development work. The gold ore was processed using a 10 stamp mill and was free milling and reported to average about 2.5 opt Au. Cuts on the surface and in outcrop show the vein to be continuous for at least 900 feet with an average width of 3 feet.

Golden Wonder mine. Center section 18, T10N, R10E (34°12'41"N; 111°22’19”W) (map number 3 between 4 and 5). This property (also known as the Eighty-Five and Gold Rock) is underlain by altered hornblende diorite and gabbro. A quartz vein strikes northwest and has a near vertical dip with a maximum width of 4 feet. The oxidized portion of the vein was mined for free milling gold, but was not minable below the water table because the vein had lower ore value.

In a press release (1/30/2013), Golden Wonder Mine, LLC, reported excavation of 90,000 yds3 of ore on the property and reported assays of 0.13, 2.6, 12.4 to 100 opt Au. The company indicated gold was closely associated with higher bismuth and tellurium content at depth.

The mine had been initially developed by several hundred feet of underground workings and low grade ore was reportedly stored in the old stopes. Mine production was estimated at about 5,000 ounces of free-milling gold by 1909. The nearby Maggie prospect lies a short distance west and the Payrock a short distance east (on strike) suggesting the vein(s) could have a strike length as much as 0.6 mile. Part of the Golden Wonder was mined by open cut and more recent trenching is apparent on aerial photography.

Maggie Vein. W/2 section 18, T10N, R10E (34°12’32”N; 111°22’34”W) (map number 5). This is likely the southwestern extension of the Golden Wonder mine. A 125-foot ore shoot was explored along a 4-foot-wide vein. Two samples from a stope averaged 1.9 opt Au over a 1-foot width.

Oxbow Mine. NW section 32, T10N, R10E (34°10'5"N; 111°21’16”W). The Oxbow lies west of Oxbow Hill and about a mile west of Highway 87 (map number 1). The property lies on two patented claims that enclose a vein within the Payson Ophiolite. The property includes a highly altered rhyolite dike and some fine-grained diorite dikes. 

The Oxbow vein occupies a roughly N-S trending fault fissure that has curved geometry, similar to an oxbow in a stream. At the main portal, the vein is 4 feet wide and swells to 6 feet: wider portions of the vein have higher gold values. Where the vein narrowed to a few inches, the fracture was occupied by inward projecting quartz crystals. Adjacent to the vein, quartz stringers projected into the hanging wall. The mined ore was reported to contain as much as 1.7 to 2.25 opt Au. 

The water table was intersected at 175 feet below the collar of the two compartment shaft sunk to a depth of 176 feet in 1925. In addition, more than 500 feet of tunnel was dug from an adit. According to mindat.org, the property has a mineralized zone that is 1,950 feet long, by 5.9 feet wide and is 515 feet thick. The vein has a 45 to 85oW dip, and at least 5 ore shoots were recognized. Numerous cross veinlets were intersected during past exploration and some placer gold was found on the property. Fluorspar was also described on the property. 

Single Standard mine. Center section 19, T10N, R10E (34°11’48"N; 111°22’8”W) (map number 13). According to topographic maps, the Single Standard is located south of the Golden Wonder mine; however, Lausen and Wilson (1925) indicated the mine was a mile to the west at the approximate location of the Callahan mine (34°12'21"N; 111°22’55”W). The vein cuts the host rock (diorite) which itself is cut by fine-grained diorite dikes. The vein strikes N65oW and dips 55oNE. Where the vein outcrops it is only about 12 inches wide and consists of massive quartz with some hematite and limonite. 

Summit Mine. E/2 SE section 36, T11N, R9E (34°15’1”N; 111°22’39”W). The Summit vein (map number 8) was discovered in 1881 and a patent was granted on the property in 1890. It was reported in 1925: “considerable ore is said to have been produced and a large dump is stated to average $7 in gold”. In 1925, gold prices were $20.67/ounce, thus this would be equivalent to 0.34 opt Au. 

In the 1940s, work continued on the mine. It was reported that the main vein had a strike trend of N21oW and consisted of quartz with schist gangue (Payson Roundup, 2009).

Zulu mine. N/2 section 1, T9N, R9E (34° 9'32"N; 111°23’5”W). The Zulu property (map number 2) is underlain by rocks of the Payson Ophiolite reported as diorite that was intruded by granite porphyry dikes and fine-grained diorite dikes. A rich, 20-inch wide ore shoot was found in a narrow quartz vein that was explored in a mine shaft. Numerous quartz veinlets extended into the wall rock (Lausen and Wilson, 1925) suggesting a possibility for low-grade gold mineralization surrounding the vein. 

Aerial photos show the property was extensively prospected by dozer cuts over an area of 0.35 by 0.65 mile. This may suggest past operators may have found gold anomalies in the altered wall rock, or that they were searching for hidden veins. 

Mineralization was described to include a 3,900 foot long and 19.5 foot wide zone containing a gold-silver-quartz vein with stingers of ore and barite gangue in fractures. Other reports suggested two ore shoots were intersected at depth that were separated by altered granite in a ore zone about 30 feet wide.

Initially, the mine was developed by a 200-foot-deep two compartment shaft. Later work included minor ore recovery in the 1950s and some heap leaching in 1981 and 1982. Reported assays in 1939 ranged from 0.02 opt Au to 5.94 opt Au. The latter sample was taken in the vein at the 150-foot mine level in a 9-foot wide vein.

In summary, the Green Valley district south of Payson lies within favorable host rocks for gold mineralization and offers potential opportunities for nugget hunters near veins that yielded free milling gold. Past erosion and flash floods likely carried some gold downslope from the veins into the surrounding drainages.

Some deposits likely contained large areas of low-grade gold mineralization that may have been overlooked and little ore was tested below the water table. With the numerous fractures in the area, it is likely some veins have been missed in the past.

Finally, ophiolites are known to host certain types of mineral deposits including copper and gold. For instance, some ophiolites contain platinum-group metals, chromium, manganese, titanium, cobalt, nickel and other metals of interest, but there does not seem to be any reports of prospectors searching for these types of mineral deposits in the past.


References
Arizona Geological Survey, 1986, Miscellaneous reports on the Crackerjack and other properties in the Payson district: May 7, 1986, http://docs.azgs.az.gov/OnlineAccessMineFiles/C-F/CrackerjackGila511a.pdf. 
Hausel, W.D., The GemHunter - Professor Hausel’s guide to finding gemstones, diamonds, gold, rocks and minerals: http://gemHunter.webs.com). 
Hedburg, Ed, 1909, The Greens Valley Mining District: Ming World, December, 25, p. 1245-1256. 
Johnson, M.G., 1972, Placer gold deposits of Arizona: US Geological Survey Bulletin 1355, 103 p. 
Kusky, T.M, 2004, Precambrian Ophiolites and Related Rocks: Developments in Precambrian Geology 13, Elsevier, 772 p.
Lausen, C., and Wilson, E.D., 1925, Gold and copper deposits near Payson, Arizona: University of Arizona, Arizona Bureau of Mines Bulletin 120, no.4, 43 p.
Minedat dot org - various mineral reports on the internet.
Peterson, J.A., 1984, Metallogenic maps of the ophiolite belts of the western United States: US Geological Survey Misc Investigations Series Map I-1506. 
Rhodimer, T., 1939, Assay report on the Zulu mine dated Dec. 9, 1939.




General location map of the Green Valley district, Payson, Arizona, and mines including (1) Oxbox & nearby Midget, (2) Zulu, (3) Golden Wonder, (4) Payrock, (5) Maggie, (6) Callahan, (7) Silver King, (8) Summit, (9) Excursion, (10) Little Green, (11) Delaware, (12) Little Maude, (13) Single Standard, (14) Rock Ford, (15) Bishops Knoll, (16) White Mountain, (17) Crackerjack. The blue line marks the approximate outline of the Payson ophiolite complex.