Carlin Anniversary—May 4, 1965, First Gold Bar Poured at the Carlin Mill from the Carlin Mine

“The discovery of the Carlin deposit is one of the most significant events in worldwide mining and in the history of Nevada.

Named for a town on the banks of the Humboldt River, the Carlin deposit was overlooked by the ’49ers who rushed by, along the Emigrant Trail, on their way to the gold fields in California. Because of the extremely fine grain size of its gold particles, Carlin was missed by the ’49ers and by the prospectors that combed the hills of the western United States in the late 1800s. A few gold deposits of what would later be known as the Carlin type were found in the late 1800s and early 1900s, but their significance was not recognized until the Carlin discovery in 1961 and the opening of the Carlin mine in 1965.

Closely following Carlin were discoveries of other deposits along the Carlin trend, a 50-mile long, 5-mile wide belt that now includes more than 20 major deposits. The Carlin trend has developed into one of the premier gold fields of the world. Known resources are immense, tens of billions of dollars worth of gold, and growing, as new discoveries continue to be made. The deposits of the Carlin trend and other Carlin-type deposits have catapulted Nevada into the lead among gold producing states and have made the United States a major gold-producing country and net exporter of gold.

Discoveries of Carlin-type deposits have helped to diversify the Nevada economy. Gold mining directly provides thousands of jobs for Nevadans, indirectly provides thousands more, helps build and maintain infrastructure in rural parts of the state, and broadens the tax base for education and other government programs. Highly skilled miners, including heavy equipment operators and mechanics, engineers, and individuals well versed in computer operations, earn the highest average wages of any industry within the state.

Deposits on the Carlin trend have set new standards for gold mining throughout the world. Large-scale mining, heap leaching, and automation at various levels in the mining, milling, and assaying processes have cut overall costs and allowed lower and lower grades of ore to be mined.

This report, written and reviewed by some of the individuals involved, provides a first-hand account of the Carlin discovery, a milestone in the history of Nevada and in the history of mining.” (“Foreward” by Jonathan G. Price, from NBMG Special Publication 13 by J. Alan Coope)

Read the entire history here:
Carlin Trend Exploration History: Discovery of the Carlin Deposit
http://pubs.nbmg.unr.edu/Carlin-trend-exploration-histor-p/sp013.htm

More publications on the Carlin trend:
http://pubs.nbmg.unr.edu/SearchResults.asp?Search=Carlin

Exploration Resourcescheck out resources on the NBMG Open Data page:
https://data-nbmg.opendata.arcgis.com/pages/exploration-resources

New NBMG standard reference materials available

NBMG is announcing the sale of new standard reference materials for three Carlin-type gold ores:NBM-8a is a low-grade oxide ore standard having a recommended gold concentration of 0.049 ounces/ton. NBM-8b is a high-grade oxide ore standard having …

NBMG is announcing the sale of new standard reference materials for three Carlin-type gold ores:

NBM-8a is a low-grade oxide ore standard having a recommended gold concentration of 0.049 ounces/ton.

NBM-8b is a high-grade oxide ore standard having a recommended gold concentration of 0.290 ounces/ton.

NBM-8c is a high-grade refractory ore standard having a recommended gold concentration on 0.397 ounces/ton with very high arsenic concentration.

All three standards have a broad suite of trace-element data reported. These new SRMs are available in 300-gram bottles for $100.00 or 30-gram bags for $15.00.

NBMG standard reference materials:

http://www.nbmg.unr.edu/Departments/AnalyticalLab/SRM.html

John Muntean speaks at GSN-Friday, September 9, 2011

Who: Dr. John Muntean, Nevada Bureau of Mines and Geology, Research Economic GeologistWhat: Geological Society of Nevada meetingTopic: Ferroan carbonates in Carlin-type gold deposits: Real time detection of an important ore control by carbonate st…

Who: Dr. John Muntean, Nevada Bureau of Mines and Geology, Research Economic Geologist

What: Geological Society of Nevada meeting

Topic: Ferroan carbonates in Carlin-type gold deposits: Real time detection of an important ore control by carbonate staining

When: Friday September 9 (The date change is due to a conflict with the Elks Club, so remember GSN at the Elks on September 9th. Other than the date, the time and venue are the same as usual.)

6:00 PM– Social

7:00 PM– Dinner, $17.00

8:00 PM–Speaker

Where:
Elks Lodge
597 Kumle Lane
Reno, NV

Questions:  Please call Laura Ruud at 775-323-3500.

Abstract (by John Muntean, NBMG; Michael Cassinerio, Barrick Gold Corp.; and Lucia Patterson, Timberline Resources Corp.):

Carbonate staining is an inexpensive, real time tool to detect ferroan carbonate, an important ore control in Carlin-type gold deposits. Studies are increasingly showing a close spatial association between ore and wall rocks containing ferroan dolomite or ferroan calcite. These ferroan carbonates are important in that when they are dissolved by acidic, gold-bearing hydrothermal fluids, they release iron which reacts with reduced sulfide in the fluid, destabilizing gold-sulfide aqueous complexes, resulting in deposition of gold-bearing pyrite. This process, known as sulfidation, is widely regarded as the principal depositional mechanism for gold in Carlin-type deposits. Carbonates can be stained by dilute hydrochloric acid containing both alizarin red S and potassium ferricyanide to differentiate between calcite, ferroan calcite, ferroan dolomite and dolomite. Staining needs to be done carefully in conjunction with a good hand lens, because other iron-bearing phases in the rock, such as pyrite and iron-bearing clays, can cause “iron-bleeding” and misleading results. Electron microprobe analyses of carbonates show the staining is sensitive down to 0.1 wt% Fe.

Detailed carbonate staining by the authors at the Turquoise Ridge deposit reveals a distinct spatial relationship between gold, ferroan calcite, and the southern margin of a thick Paleozoic basalt. High-grade gold ore in the HGB zone occurs exclusively within ferroan calcite-bearing host rocks. The transition from ferroan calcite (mainly 0.1-1 wt% Fe) to calcite (mainly <0.1 wt% Fe) occurs at the base of the HGB. Staining of carbonates at the base of the Roberts Mountain Formation along the Saval discontinuity in drill holes across the entire Jerritt Canyon district shows a close spatial association between the gold deposits and host rocks containing ferroan dolomite (mainly 0.5-2.75 wt% Fe). Others have reported a spatial association between ferroan dolomite and gold at Twin Creeks, Meikle, Storm, and Deep Star. At Twin Creeks, ferroan dolomite was interpreted to form during Cretaceous sericitization of Paleozoic basalts, which mobilized iron into interbedded carbonates. We envision an analogous process at Turquoise Ridge. At Meikle ferroan dolomite was interpreted to form by either syn-sedimentary exhalative processes or by a late Paleozoic brine. Such a late Paleozoic brine event was probably also responsible for formation of ferroan dolomite at Jerritt Canyon. In every case, ferroan carbonate is interpreted to form prior to Eocene-age Carlin-type gold mineralization, and, in effect, is critical pre-ore chemical rock preparation for subsequent ore formation. We highly recommend routine carbonate staining of prospective host rocks in exploration for carbonate-hosted gold deposits of all types.

NBMG geologist talks with UNR President on “A Few Minutes with Milt”

NBMG Research Geologist, John Muntean, interviews with UNR President, Milt Glick, about his NBMG research on the origin of Carlin-type gold deposits and the future of mining in Nevada. Listen to the broadcast…

NBMG Research Geologist, John Muntean, interviews with UNR President, Milt Glick, about his NBMG research on the origin of Carlin-type gold deposits and the future of mining in Nevada.  Listen to the broadcast

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