Nighthawk Ridge mine, White Pine Mining District, White Pine County, Nevada, USAi

Regional Level Types
Nighthawk Ridge mine	Mine
White Pine Mining District	Mining District
White Pine County	County
Nevada	State
USA	Country

Structure: Low Amplitude, Open Folds With Axes That Strike Between N-S And N15e. Nighthawk Fault.

Alteration: Silicification, Jasperization, Argillization, Decarbonization. Silicification Is The Most Common Alteration Within The Orebody. Chainman Shale And Pilot Shale Are Argillized And Silicified Adjacent To Nighthawk Fault.

Commodity: Au:ag ratios generally > 50:1.

Deposit: 75% of ore is in chainman shale, 25% in joana limestone. ; info.src : 1 pub lit refer to record re00028 for data on the adjacent decker flats deposit.

Deposit type: Carbonate-hosted Au-Ag

Development: The original easy junior claims staked in 1979 by earth resources co. On the basis of prominent jasperoid outcrops. These claims were acquired by houston international minerals co. In 1980. Himco drilled eight holes totalling 1810 ft. In 1980, but only one hole contained anomalous gold mineralization. Himco subleased easy junior to consolidated mineral resources 1981-1983, during which eight holes totalling 2620 ft. Were drilled. Drill results were discouraging. In 1984, consolidated minerals conveyed interest in easy junior to aaminex for stock, and aaminex sub-leased the property to santa Fe pacific mining co. During 1984-1985, santa Fe completed geologic mapping, a vlf survey and 16 drill holes totaling 9295 ft. Several of these holes intersected narro W zones of gold mineralization, the best being 45 ft./0.059 opt gold. All mineralized intercepts were at the contact of the chainman shale and joana limestone. Santa Fe terminated the lease in 1985, then aaminex returned claims back to tenneco minerals co. Which had since acquired himco. All drilling up to this time had been completed in the vicinity of the outcropping jasperoids. In 1986, tenneco extended the claim block north to include what would become the nighthawk ridge deposit. A soil geochemistry grid identified two linear gold anomalies which led to the discovery of outcrop of folded and silicified chainman shale with abundant barite and minor scorodite along fractures. 36 samples from this outcrop assayed As high As 2.33 ppm gold, but averaged 0.5 ppm gold. Hg,tl, as, and sb were also anomalous. A 41 drill hole program was initiated in september, 1986. The discovery hole was the 39th hole, intersecting 320 ft./0.066 opt gold. ; econ.com: cash cost of production of $240/oz. Gold.

Rock formation(s): Chainman Shale;Joana Limestone


Ore(s): Nighthawk Fault Strikes Northeast, Dips 80 Degrees West And Serves As The Primary Conduit For Mineralizing Fluids. Ore Is Thickest Where Nighthawk Fault Is Offset By Wnw En Echelon Faulting, A Result Of Secondary Porosity In Chainman Shale At The Fault Intersections. Joana Limestone Acted As A Porous Host Since Gold Mineralization Appears Stratabound And Closely Emulates The Fold Pattern.


Structure: Nighthawk Fault Rocks in the mine area have been affected by low amplitude, open folds with axes that strike between N-S and N15E.

Alteration: Silicification is the most common alteration within the orebody. Jasperization, argillization, and decarbonization have also affected the rocks. Chainman Shale and Pilot Shale are argillized and silicified adjacent to the Nighthawk Fault.

Commodity: Commodity Info: AU:AG ratios are generally > 50:1. Ore Materials: micron-sized gold grains Gangue Materials: hematite, limonite, opal, barite, scorodite

Deposit: Sediment-hosted disseminated gold

Deposit type: Carbonate-hosted Au-Ag

Development: The original Easy Junior claims were staked in 1979 by Earth Resources Company on the basis of prominent jasperoid outcrops. These claims were acquired by Houston International Minerals Company (HIMCO) in 1980. HIMCO drilled eight holes totaling 1810 ft in 1980, but only one hole contained anomalous gold mineralization. Himco subleased Easy Junior to Consolidated Mineral Resources from 1981 to 1983, during which eight holes totaling 2620 ft. were drilled. Drill results were discouraging. In 1984, Consolidated Minerals conveyed interest in Easy Junior to AAMINEX for stock, and AAMINEX sub-leased the property to Santa Fe Pacific Mining Co. During 1984-1985, Santa Fe completed geologic mapping, a VLF survey and 16 drill holes totaling 9295 ft. Several of these holes intersected narrow zones of gold mineralization, the best being a 45 ft intercept grading 0.059 opt gold. All mineralized intercepts were at the contact of the Chainman Shale and Joana Limestone. Santa Fe terminated the lease in 1985, after which AAMINEX returned the claims back to Tenneco Minerals Co, which had since acquired HIMCO. All drilling up to this time had been completed in the vicinity of the outcropping jasperoids. In 1986, Tenneco extended the claim block north to include what would become the Nighthawk Ridge deposit. A soil geochemistry grid identified two linear gold anomalies which led to the discovery of outcrop of folded and silicified Chainman Shale with abundant barite and minor scorodite along fractures. 36 samples from this outcrop assayed as high as 2.33 ppm gold, but averaged 0.5 ppm gold, with anomalous Hg, Tl, As, and Sb. A 41 drill hole program was initiated in September, 1986. The discovery hole was the 39th hole, intersecting 320 feet grading 0.066 opt gold.

Geology: All mineralized intercepts were at the contact of the Chainman Shale and Joana Limestone.

Ore(s): The Nighthawk Fault strikes northeast, dips 80 degrees west and serves as the primary conduit for mineralizing fluids. The ore is thickest where the Nighthawk Fault is offset by WNW-trending en echelon faulting, as a result of secondary porosity tat developed in the Chainman Shale at the fault intersections. The Joana Limestone acted as a porous host since gold mineralization appears stratabound and closely emulates the fold pattern.

Other Databases

Link to USGS MRDS:	10310554
Link to USGS MRDS:	10047584

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