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

Nevada Mineral Industry 2013 now available!

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Title: The Nevada mineral industry 2013
Author:
John L. Muntean, David A. Davis, Lisa Shevenell, and Alexandra Reid
Year: 2015
Series: Mineral Industry MI-2013
Format: 158 pages, includes color

Starting in 1979, NBMG has issued annual reports that describe mineral and geothermal activities and accomplishments in Nevada, and include statistics of known gold and silver deposits. This report describes mineral, oil and gas, and geothermal activities and accomplishments in Nevada in 2013: production statistics, exploration and development including drilling for petroleum and geothermal resources, discoveries of orebodies, new mines opened, and expansion and other activities of existing mines. Statistics of known gold and silver deposits, and directories of mines and mills are included.

View or purchase MI-2013 here:
http://pubs.nbmg.unr.edu/The-NV-mineral-industry-2013-p/mi2013.htm

New Geologic Map: Lookout Mountain, Ratto Ridge, and Rocky Canyon, Eureka County

Open-File Report 14-8
Preliminary geologic and alteration maps of Lookout Mountain, Ratto Ridge and Rocky Canyon, southern Eureka mining district, Eureka County, Nevada

by Russell V. Di Fiori, Sean P. Long, John L. Muntean, and Gary P. Edmondo, 2014

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Identification of favorable structural settings for Carlin-type gold deposits is fundamental for future exploration.  In this study, mapping and structural analysis were performed in the southern part of the Eureka mining district in east-central Nevada, in order to understand geometric and temporal relationships between structural systems and Carlin-type mineralization.  Geologic and alteration maps at a scale of 1:10,000 of a ~3.5 km (east-west) by ~8 km (north-south) region were generated, along with cross sections that illustrate pre- and post-extensional deformation geometry.  This project bridges a gap between recent 1:24,000-scale mapping and <1:500-scale mapping performed in an active exploration campaign.

The stratigraphy of the map area consists of ~4 km of Cambrian-Devonian carbonate and siliciclastic rocks, which are unconformably overlain and intruded by late Eocene silicic volcanic rocks.  Four structural systems are identified, consisting of Early Cretaceous contractional structures and three separate sets of normal faults: 1) 1st-order, kilometer-scale offset, down-to-the-west normal faults, including the Lookout Mountain and Dugout Tunnel faults, 2) 2nd-order, 10’s to 100’s meter-scale offset, north-striking normal faults, including the Rocky Canyon, Oswego, and East Ratto Ridge fault systems, and 3) a set of 3rd-order, meter-scale offset, east-striking normal faults that cut jasperoid bodies of presumed late Eocene age.  The 1st- and 2nd-order faults are interpreted to be contemporary, cut Late Cretaceous intrusions and an associated contact metamorphic aureole, and are overlapped by a late Eocene, subvolcanic unconformity.

In addition to lithology and structure, specific types of hydrothermal alteration and mineralization were mapped, including silicification, decarbonatization, dolomitization, quartz/calcite-veining, argillization, and the introduction of sulfides and their limonite weathering products.  Carlin-type replacement mineralization, primarily hosted within Cambrian carbonate rocks, occurs in a series of deposits in the southern part of the map area.  The deposits are associated with decarbonatization, silicification and jasperoid formation, and argillization, and are constrained to late Eocene or older by the overlap and intrusion of dated volcanic rocks.

The map area contains a km-scale, faulted relay-ramp of 2nd-order faults that transfer slip between synthetic 1st-order faults. Within accommodation zones, wall-damage zones are predicted to provide hydrothermal fluid pathways and therefore localize mineralization.  The footwall of the Lookout Mountain fault, which contains the majority of Carlin-type deposits identified in the map area, contains a set of antithetic, 2nd-order normal faults, which is interpreted as a wall-damage zone that was responsible for controlling fluid flow that led to mineralization.

The southern Eureka mining district contains several favorable structural conditions for Carlin-type gold mineralization, including: 1) normal fault systems that predate or are contemporary with late Eocene gold mineralization, and 2) complex normal fault interactions in an accommodation zone, including zones of dense fault intersections, antithetic normal faults, and fault-damage zones.  These structural conditions were fundamental for generating a network of open-system fluid pathways, which created an ideal structural architecture for Carlin-type mineralization, and can be used as predictive tools for exploration elsewhere.

This project was supported by Timberline Resources Corporation and the Geological Society of America.

Open-File Report 14-8, two plates, scale 1:10,000; plate one: 56 x 41 inches, plate two: 29 x 41 inches; folded or rolled, $35.00

Available free on the Web or purchase here: http://www.nbmg.unr.edu/sales/pbsdtls.php?sku=OF14-%208

Nevada Mineral Industry 2012

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MI-2012: The Nevada Mineral Industry 2012, by John L. Muntean, David A. Davis, Lisa Shevenell, and Benjamin McDonald, 2014

Starting in 1979, NBMG has issued annual reports that describe mineral and geothermal activities and accomplishments in Nevada, and include statistics of known gold and silver deposits.

This report describes mineral, oil and gas, and geothermal activities and accomplishments in Nevada in 2012: production statistics, exploration and development including drilling for petroleum and geothermal resources, discoveries of orebodies, new mines opened, and expansion and other activities of existing mines. Statistics of known gold and silver deposits, and directories of mines and mills are included.

Available free on the Web: http://www.nbmg.unr.edu/dox/mi/12.pdf

Special Publication MI-2012, 177 pages (includes 19 pages in color)

Lecture by John Muntean—Friday Jan. 18, rsvp by noon Wednesday Jan. 16

Speaker: Dr. John Muntean (Director, Ralph J. Roberts Center for Research in Economic Geology; Research Economic Geologist, Nevada Bureau of Mines and Geology) Title: Exploration for Gold in a Mature Terrain: Maintaining Nevada’s Gold Rush What: G…

Speaker: Dr. John Muntean (Director, Ralph J. Roberts Center for Research in Economic Geology; Research Economic Geologist, Nevada Bureau of Mines and Geology)

Title: Exploration for Gold in a Mature Terrain: Maintaining Nevada’s Gold Rush

What: Geological Society of Nevada monthly meeting

When: Friday January 18, 2013 (drinks at 6:00 PM, dinner at 7:00 PM, and talk at 8:00 PM)

Where: Reno Elks Lodge, 597 Kumle Lane, Reno, NV

Contact: Dinner reservations must be made by NOON, Wednesday January 16. Contact Laura Ruud, Geological Society of Nevada, at (775) 323-3500 or email gsn@gsnv.org for reservations.

Abstract:

Gold production in Nevada increased in 2011 for the second year in a row, to a total of 5.54 million ounces.  However, production has decreased 10 of the last 13 years from its peak in 1998, when a record 8.82 million ounces were produced.  Exploration spending in Nevada remained high in 2011 with over $600 million in expenditures, the majority of which was by junior companies exploring for gold.  Nevertheless, since the price of gold bottomed out at $279/ounce in 2000, only five new >2 million ounce deposits have been found (Cortez Hills, Long Canyon, South Arturo, Long Canyon, and Gold Rush), a much lower rate of discovery than the previous two decades.  Current exploration continues to focus on known areas, many of which contain known resources that have benefitted from the current high price of gold.  Is Nevada at the beginning of a long decline that mature terrains inevitably experience?  The main geologic challenge in maintaining Nevada’s gold production is exploration under cover.  Half of Nevada is covered by alluvium, and significant additional areas are covered by pre-ore and post-ore thrust plates and volcanic rocks.  The talk will focus on gaps in our knowledge of Nevada’s gold deposits that bear on two basic questions facing explorationists: 1) Where to look? and 2) How to detect? Emphasis will be on Carlin-type gold deposits that account for about 80% of Nevada’s production.  Meeting the challenges of finding new deposits in the future will require a new generation of highly skilled, creative explorationists.  Opportunities exist for companies, universities, and government to cooperate in the training of future explorationists and in undertaking studies from the atomic to regional scale to fill the knowledge gaps.  The traditional practice of individual researchers working with individual companies needs to evolve.  The challenges should be prioritized into individual cooperative projects between multiple companies and research institutions that share results.  Models for such cooperative research exist (e.g., CODES, MDRU, AMIRA, CAMIRO).