Monday, January 10, 2011

Puzzler Hill palladium-nickel-gold discovery, Wyoming

Mineralized terrains and mining districts in Wyoming from
Hausel (1997).
The Encampment mining district was described by researchers of the 19th and 20th century to cover the entire Sierra Madre Mountains and include parts of the adjacent Medicine Bow Mountains. This district is primarily a base metal district with copper, lead, zinc mineralization and associated gold and silver along with some layered mafic complexes and an ultramafic massif with some gold, silver, palladium, platinum, chromium, vanadium, titanium and nicke anomalies.

Located 6.5 miles northwest of Encampment Wyomng at Puzzler Hill. Puzzler Hill is formed of a pyroxenite massif hosted by Late Archean gneiss north of the Cheyenne Belt suture zone. The extent of the complex has not been determined as the complex continues to the northeast under sedimentary cover. Anomalous platinum, palladium and nickel were discovered in 1995 but the property remains unevaluated for these mineral resources.

Puzzler Hill is an ultramafic massif with sporadic highly anomalous mineralization located in sections 24, 26, 35 & 36. The pyroxenite (CO1-94) and associated actinolite-chlorite schist (CO5-94) country rock are highly magnesian (Hausel, 1995b).



                                     Oxide/Element                                 Sample number
                                    (Weight percent)                         CO1-94                   CO5-94
                                                SiO2                                    45.5                        48.75
                                                TiO2                                    0.59                         0.44
                                                Al2O3                                  8.48                         8.57
                                                Fe2O3                                 11.76                       12.09
                                                MnO                                    0.17                         0.19
                                                MgO                                   19.39                       16.43
                                                CaO                                     8.01                         6.65
                                                Na2O                                   0.83                         0.79
                                                K2O                                     0.07                         0.09
                                                P2O5                                   0.05                        <0.03
                                                Cr2O3                                  0.35                         0.28
                                                LOI                                      3.59                         4.24
                                                TOTAL                               98.79                       98.52
                                                Au (ppb)                                3                             14
                                                Pt (ppb)                                  8                             <5
                                                Pd (ppb)                                15                             8
                                                Cu (ppm)                              159                          248
                                                Ni (ppm)                              343                          178
                                                Co (ppm)                               29                            28

Other samples collected from the massif from 28 a small group of mines and prospects also contained anomalous metals. The samples yielded 0.01% to 4.43% Cu, 66 ppm to 3.72% Ni, 14 ppb to 0.29 opt Au, <5 ppb to 0.027 opt Pt, 5 ppb to 0.12 opt Pd, <0.1 ppm to 0.19 opt Ag, 21 ppm to 831 ppm Co, 64 ppm to 294 ppm Cr, and trace lead and zinc. These samples included limonite-stained breccia (CO2-94) from a mine dump in the S/2 section 26 that yielded anomalous copper, nickel, platinum and palladium. Samples of massive specular and earthy hematite with copper carbonate, minor bornite and chalcopyrite in chlorite-actinolite-talc schist from the Charter Oak mine dump (CO3-94 and CO4-94) yielded anomalous copper and gold. A sample (CO6-94) of quartz breccia cemented by sideritic limonite with fuchsite collected from a mine dump in the center of section 26 was poorly mineralized.

Assays from the Puzzler Hill massif (Hausel, 1995b).
Sample             Cu               Ni            Co           Cr           Au            Pt            Pd           Ag           Pb           Zn            
   No                 (%)           (ppm)     (ppm)     (ppm)      (ppb)      (ppb)      (ppb)      (ppm)     (ppm)     (ppm)
CO2-94            4.43           37200        831          244           95           828         4042          2.9           57            55
CO3-94            3.52              66            27            71          7718          <5            11            3.8           10            14
CO4-94            2.39             127           82            64          9862          <5            14            6.6            9              9
CO6-94            0.01             162           21           294           14            <5             5           <0.1            -               -

Early reports suggested that the mine was located in a northerly-trending, easterly-dipping quartz vein on the east side of a broad synform in granite-gneiss, schist and diorite country rock. The vein contains iron- and copper-sulfides which impregnate the fractured country rock. Chalcopyrite, chalcocite, bornite and azurite were identified in a gangue of quartz, jasperoid, schistose wall rock, calcite and some chalcedony (Spencer, 1904). Some high-grade gold was found on the property (Beeler, 1905a) and some secularite from the Charter Oak mine dump is gem-quality and used to produce some attractive specularite cabochons with traces of copper (Hausel and Sutherland, 2000).
A 7.73 carat specularite cabochon cut from samples from Puzzler Hill.
Specimen was placed on display at the Wyoming Geological Survey Building
at the University of Wyoming in Laramie.
The mineralized zone was traced 2 miles on the surface and varied in width from 14 feet at the Charter Oak shaft (section 24, T15N, R85W) to 100 feet elsewhere. Where the mineralized structure is widest, the ore apparently consisted of quartz stringers mixed with low grade material. An open cut near the top of Puzzler Hill showed a "huge ledge of mineralized diorite" stained with copper-carbonate (Beeler, 1906g). It has been reported that the Charter Oak also has some cobalt (as much as 4 to 5% Co) (Armstrong, 1970), although we were unable to verify these high values even though anomalous cobalt was detected in our samples (Hausel, 1995b). 

The Charter Oak shaft was sunk to a depth of 488 feet (Beeler, 1905a). Three shafts were developed on the property with more than four levels. In total, the Charter Oak had >2,300 feet of shafts, winzes, raises and tunnels (Saratoga Sun, 1907). The Saratoga Sun contradicted Beeler's (1906g) assessment of the ore body and stated the ore body ranged from 3 to 10 feet thick. An ore reserve was estimated at 680,000 tons to a depth of 300 feet and reported to be high-grade and to have a 6-foot thickness. This property, and the rest of Puzzler Hill, definitely deserves more research and it would be very surprising if significant nickel and palladium were not detected in the massive sulfide in the Charter Oak mine workings.

Massive specimen from the Charter Oak mine dump showing specularite with chalcopyrite and possibly some niccolite(?) and annabergite(?). The specularite is high-quality lapidary material and fasionable into cabochons for jewelry.

The 7.73-carat specularite cabochon from Puzzler Hill