Geologic Map of the Washoe City Quadrangle, Washoe County, Nevada

Authors: Chad W. Carlson, Richard D. Koehler, and Christopher D. Henry
Year: 2019
Series: Open-File Report 2019-04
Version: supersedes Urban Maps UM5Ag and UM5Ak
Format: plate: 34.5 x 37 inches, color; text: 7 pages, b/w
Scale: 1:24,000

View, download, or purchase the Washoe City Quadrangle map.

This quadrangle encompasses Washoe Valley, an internally drained basin located between the Reno/Sparks and Carson City urban areas in northern Nevada. The seismically active eastern range front of the Sierra Nevada (Carson Range) extends along the western side of the quadrangle. Washoe Lake, a popular recreational area, extends from the south into the central part of the quadrangle. The eastern side of the quadrangle contains the rural communities of New Washoe City and Pleasant Valley, located along the western foothills of the Virginia Range. Major infrastructure within the quadrangle includes Interstate 580 concurrent with U.S. Highway 395, which extends north-south through the quadrangle west of Washoe Lake, and the ~73 megawatt Steamboat Hills geothermal power plants, with expansion plans for an additional 20 megawatts, occupying the northeasternmost part of the quadrangle.

Bedrock exposures in the quadrangle consist of Jurassic to Triassic metasedimentary and metavolcanic rocks of the Gardnerville Formation, Cretaceous granite and granodiorite, and Tertiary volcanic and sedimentary rocks. The Tertiary section includes Oligocene ash-flow tuffs and a complex section of Miocene volcanic rocks, intrusions, and volcaniclastic sedimentary rocks. Miocene volcanic rocks are basaltic to dacitic lavas and breccias interfingering across the northern parts of the quadrangle. The volcanic rocks were part of an ancestral Cascades arc that consisted of two recognized pulses in the Washoe City quadrangle: ~5.5–7.1 Ma lavas and breccias that extend east from the Mount Rose quadrangle into the Steamboat Hills and ~15 Ma lavas and breccias that extend west from the Virginia City quadrangle. Quaternary, 1.2 Ma rhyolite lava and tuff and 2.2 Ma basaltic andesite lava in the Steamboat Hills are some of the youngest volcanic rocks in western Nevada. Holocene sinter is being deposited by the active Steamboat geothermal system.

Principle Quaternary surficial deposits include middle Pleistocene to modern alluvial fan, landslide, and debris-flow deposits, middle to late Pleistocene glacial outwash and moraine deposits, late Pleistocene to modern lacustrine and eolian deposits, as well as active alluvial and colluvial deposits. A major debris flow complex sourced from the flank of Slide Mountain (Mount Rose) occupies the Ophir Creek canyon and is associated with at least five distinct flows including the 1983 debris flow, which caused significant damage to residential structures and infrastructure. Numerous other debris-flow deposits occur within smaller drainages of the eastern Carson Range. A massive landslide deposit along the northeastern side of Pleasant Valley is associated with large intact blocks of bedrock. The Mount Rose fan complex sourced from Jones, Whites, and Galena creeks records a long history of fan deposition (early to late Pleistocene) that includes fan deposits eroded from the Cascades arc volcanic rocks and multiple pulses of glacial outwash.

The east-dipping Carson Range fault bounds the eastern flank of the Carson Range and displaces Quaternary alluvial-fan, debris-flow, and glacial deposits across east-facing scarps that range in height from 2 to over 60 m. North of Washoe Valley, the Carson Range fault becomes distributed and is characterized by a broad zone of west- and east-facing scarps and grabens. The east-dipping Little Valley fault within the Carson Range displaces glacial outwash and moraines. A component of right-lateral displacement along the Little Valley fault is suggested by offset drainages along the eastern flank of Slide Mountain. West-dipping faults mapped and interpreted from gravity data along the eastern boundary of Washoe Valley similarly diffuse and anastamose with east-dipping faults in the northern part of the quadrangle to develop a structural accommodation zone occupied by the Steamboat Hills geothermal power plants.

This geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program under STATEMAP award number G18AC00198, 2019.

Geologic Map of the Independence Valley NW Quadrangle, Elko County, Nevada

Authors: Andrew V. ZuzaSeth DeeChristopher D. Henry, Michael W. Ressel, and Charles H. Thorman
Year: 2019
Series: Open-File Report 2019-03
Version: partially supersedes Open-File Report 2017-06
Format: plate: 40.5 x 28.5 inches, color; text: 18 pages, color
Scale: 1:24,000

View, download, or purchase the Independence Valley NW Quadrangle map.

The Independence Valley NW 7.5-minute quadrangle covers a part of the western Pequop Mountains and adjacent Independence Valley in eastern Elko County. The east-tilted Pequop Mountains have newly recognized Carlin-type gold deposits in a geographic and geologic setting distinct from similar deposits elsewhere in Nevada. Southeast-dipping Cambrian through Ordovician sedimentary rocks are exposed in the range front along the eastern edge of the map area. Eocene rhyolite dikes and sills, and Cretaceous granitic sills and pods locally intrude the oldest Cambrian stratigraphy. The Eocene intrusions may be part of a magmatic system that produced the heat source for the nearby Carlin-type mineralization. The range front is bound on the west by two west-dipping normal fault systems that accommodated late Cenozoic exhumation. Exposed in the hanging wall of the eastern fault system are late Cenozoic basin deposits that uncomfortably overlie Cambrian through Ordovician sedimentary rocks. Logs from three boreholes drilled into the Paleozoic rocks of the hanging wall during mineral exploration were used to help develop cross section A–A”. One of the boreholes encountered an approximately 60-m-thick zone of fault gouge and a fault sliver with repeated Ordovician stratigraphy. This fault zone may be correlative with the enigmatic Pequop fault observed in adjacent quadrangles. Another borehole advanced through the eastern range-front fault constrains its dip to 34° west. Correlation of stratigraphy across the eastern range-front fault suggests approximately 4 km of total dip-slip displacement during Cenozoic exhumation.

The oldest Cenozoic basin deposits exposed between the two range-front fault systems are Miocene tuffaceous sediments with a maximum measured bedding dip of 34° east. New 40Ar/39Ar dates bracket the age of the deposit between approximately 6 Ma and 10.8 Ma. The tuffaceous sediments are overlain by a megabreccia landslide deposit with individual bedrock blocks over 200 m long. The individual blocks have lithologic and textural characteristics similar to rocks exposed along the western flank of the modern Pequop Mountains, which may have been the source of these megabreccia deposits. The megabreccia is overlain by Pliocene fanglomerate deposits with nearly horizontal bedding. New 40Ar/39Ar dates from detrital sanidine grains constrain the age of the fanglomerate to younger than ca. 4.8 Ma. New dating of the Cenozoic basin deposits records the timing of the east-tilting of the range along range-bounding faults.

The western range-front fault, named the Independence Valley fault zone, has evidence for late Quaternary activity. In the footwall of the fault, alluvial-fan deposits of probable middle Pleistocene age are beveled onto the Cenozoic sediments. Late Quaternary displacement along the Independence Valley fault zone has uplifted these fan deposits a minimum of 30 m. The youngest fan deposits offset by the fault zone are of probable latest Pleistocene age, and are displaced by fault scarps up to 3 m high. In Independence Valley, lacustrine gravels are deposited on shorelines, beach bars, and spits recording the highstand and recessional stages of latest Pleistocene Lake Clover. An older lacustrine gravel deposit with a well-developed pedogenic carbonate soil horizon was mapped topographically above the latest Pleistocene shorelines along the western edge of the map area.

This map completes a suite of three new geologic maps in the Pequop Mountains including the Independence Valley NE and Pequop Summit 7.5-minute quadrangles. Together these maps and associated analytical datasets build upon prior research to address basic (characteristics and timing of major contraction, metamorphism, and extension) and applied (origin of Carlin-type gold deposits) geologic research questions. Contraction and metamorphism, which had been attributed to either the Jurassic Elko or Cretaceous Sevier orogenies, is likely Jurassic because of a newly mapped lamprophyre sill that intruded along the major thrust of the range. Although the lamprophyre that intruded the thrust is not yet dated, our dating of similar mafic intrusions across the range all yielded similar ca. 160 Ma ages. Furthermore, a continuous metamorphic gradient from amphibolite-grade Cambrian rocks to non-metamorphosed Permian rocks in the lower plate of the thrust raises questions about previous interpretations of overlying thrust plates that buried rocks to great depths and pressures. New thermochronology reveals three significant overprinting thermal pulses that affected the range—Middle Jurassic, Late Cretaceous, and Eocene—that resulted in the metamorphism and economic mineralization.

This geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program under STATEMAP award number G16AC00186 (2017) and G18AC00198 (2019).

GSN December Meeting— Wednesday, December 18

Speaker: Greg Crouch
Topic: The Bonanza King: John Mackay and the Battle Over the Greatest Fortune in the American West

GSN CHRISTMAS MEETING, SILENT AUCTION & RAFFLE

“Mark your calendars and register now for the GSN [Geological Society of Nevada] Christmas Meeting, Raffle and Silent Auction being held in the Grand Ballroom at the Nugget Casino Resort in Sparks, NV.  The date is Wednesday, December 18, 2019 with festivities beginning at 6 p.m. 

Our speaker this year is Greg Crouch, author of “The Bonanza King: John Mackay and the Battle Over the Greatest Riches in the American West”.  “A monumentally researched biography of one of the nineteenth century’s wealthiest self-made Americans…Well-written and worthwhile” (The Wall Street Journal) it’s the rags-to-riches frontier tale of an Irish immigrant who outwits, outworks, and outmaneuvers thousands of rivals to take control of Nevada’s Comstock Lode. This should be an amazing talk and interesting to all who attend! “

TO PRE-PAY DINNER AND BUY RAFFLE TICKETS, CLICK ON THIS LINK:
https://www.gsnv.org/dinner-reservations/

GSN student members are free!

RSVP by Friday, December 13th! We only have space for 300 guests so it is best to reserve now!

Schedule for the evening:
6:00 PM – Open Bar, Raffle, and Silent Auction opens
7:00 PM – Dinner will be served (Buffet style including salads, vegetables, 3 entrees and an assortment of desserts)
7:45 PM – Live auction in the dining room
8:00 PM – Presentation begins (Silent Auction ends and raffle prizes will be drawn starting at this time.)

OUR GENEROUS SPONSOR FOR THE EVENING IS: Envirotech Drilling LLC – Thanks Steve Neilsen!

Earth’s Heat Gives States Another Option for Clean Energy Goals

  • Nevada exploring geothermal’s potential for electricity, heating
  • Cost, risk impede development

By Brenna Goth, July 15, 2019 06:01AM ET, Bloomberg Law.
Read the full story here: Earth’s Heat Gives States Another Option for Clean Energy Goals.

“Tapping heat beneath the Earth’s surface for electricity and other uses is gaining ground among policy makers, especially out West, as states seek to expand their options for meeting more aggressive renewable energy goals.

Geothermal energy’s promise lies in its ability to constantly produce power with limited environmental impacts, unlike resources such as wind or solar that are weather-dependent and have other challenges.

It also has the potential “to power the global electric grid many times over” with a nearly unlimited supply, Susan G. Hamm, director of the Energy Department’s geothermal technologies office, says in the introduction to its analysis on the subject.

While geothermal energy represents a small fraction of the power used in the U.S., production could increase by more than 26 times over roughly three decades with the right technology and policy changes, the analysis said. But the risk and cost of developing new projects could hamper the industry’s growth.

One major state player, Nevada, wants to tackle those issues as its utilities move toward getting half their electricity from renewable sources by 2030.

A new initiative in the state, which is second only to California in U.S. geothermal electricity generation, directs lawmakers to audit geothermal potential and propose changes that could boost the resource.

Environmental considerations for geothermal projects vary by technology and include water use, greenhouse gas emissions higher than for wind or solar, and seismic hazards. Utilities, though, face few choices for energy sources that both meet their climate change goals and can stabilize the grid, said Paul Thomsen, vice president of business development for the Americas at renewable energy company Ormat Technologies.

“This renewable resource really is a problem solver,” said Thomsen, who also chairs the Geothermal Resources Council policy committee.

Nevada Resort Shows Potential

Nevada is taking a broad approach to analyzing its geothermal potential and impediments. Policy proposals will go to the Legislature for approval.

Lawmakers and researchers will weigh how to map geothermal resources, and the necessary technology and financial support to use them. They will consider applications like using geothermal directly to heat public buildings, and figure out how to integrate the power source with the solar, mining, and lithium industries.

Increasing geothermal use is a matter of national security for state Sen. Pat Spearman (D), who sponsored the initiative. Breaking reliance on foreign oil became a priority following her military career, she said.

“I need the experts working on this with me,” Spearman said.

Some state leaders see potential in a Reno resort’s use of geothermal for heating, which can use underground water at lower temperatures than are needed to produce electricity. The 1,621-room Peppermill Resort Spa Casino produces all of its own heat from its onsite geothermal plant.

Geothermal use at the property dates back to the 1970s. A 4,400-foot-deep production well drilled more than a decade ago replaced boilers and now saves the property $2.2 million per year on its natural gas bills, according to Peppermill representatives. Its carbon dioxide emissions also decreased by 12,000 metric tons per year.

“We were on a known aquifer. So we knew the water was down there and we were able to utilize it,” said John Kassai, the resort’s central plant and geothermal engineering manager.

Risk Reduction, Faster Permitting on Table

Market demand for geothermal is increasing with higher state renewable energy requirements, particularly in places awash with solar, said Thomsen, from the Geothermal Resources Council. The Department of Energy is among agencies looking at how to make development cheaper and faster.

Exploring and developing resources deep underground poses unique challenges. Permitting and land access issues can also increase cost and project length.

The geothermal industry doesn’t have the research and development budget to address those issues, Thomsen said. Legislation proposed in Congress seeks to help, as does federally-funded research.

A project out of Nevada aims to reduce the risk of geothermal exploration to make the energy more economical, said James Faulds, director of the Nevada Bureau of Mines and Geology at the University of Nevada, Reno, that is leading the Energy Department-funded research.

Most geothermal resources are “blind”—they don’t have hot springs or other signs at the surface, said Faulds, who is also a professor at the University of Nevada, Reno.

The research looks at multiple characteristics of known geothermal systems, including fault locations, to find patterns that can indicate potential new resources. The goal is to make it quicker and cheaper to find and drill undiscovered systems; Industry would be responsible for actually developing the resource. Recent exploratory drilling at two areas the research identified found new geothermal systems. That result is an “enormous success” and shows promise for reducing risk, according to a statement from the Energy Department’s Geothermal Technologies Office.

To contact the reporter on this story:
Brenna Goth in Phoenix at bgoth@bloomberglaw.com

To contact the editors responsible for this story:
Gregory Henderson at ghenderson@bloombergenvironment.com;
Susan Bruninga at sbruninga@bloombergenvironment.com;
Anna Yukhananov at ayukhananov@bloombergenvironment.com

New Exploration Survey 2017/2018 

Nevada Mineral and Energy Resource Exploration Survey 2017/2018
by Michael W. Ressel

Year: 2019
Series: Exploration Survey ES-2018
Version: previously issued as “Nevada Exploration Survey” by Nevada Division of Minerals; third issue of the new NBMG series “Exploration Survey”
Format: 20 pages, color
View/download/purchase full report:
http://pubs.nbmg.unr.edu/NV-exploration-survey-2018-p/es2018.htm

Exploration survey 2017/2018 flyer:
http://nbmg.unr.edu/_docs/es2018flyer.pdf

The Nevada Bureau of Mines and Geology (NBMG) carried out an online survey of companies exploring for new mineral and geothermal resources in Nevada during 2017 and 2018. The Nevada Commission on Mineral Resources and the Nevada Division of Minerals commissioned and provided partial support for the survey. The economic impact of mineral and energy production in Nevada from existing resources is well known. Indeed, Nevada ranks first in the U.S. in the value of its nonfuel minerals produced in 2017. In spite of its high minerals production, the impact of exploration activities, which focus on discovering new resources in Nevada, is poorly understood due to limited data. Exploration activities are burdened with high risk as substantial investments are not guaranteed to result in mineable resources. Indeed, only rarely do exploration programs result in successful resource extraction, and then only after many years of capital investment and development activities. Despite this, exploration success is imperative for the continued well-being and sustainability of natural resource industries in Nevada.

A goal of this survey was to gather data to better assess the impact of exploration on Nevada’s economy. The survey’s focus was to collect company data on exploration expenditures and the number of employees involved in exploration in 2017 and 2018. Expenditures were subdivided by various categories and participants were asked to rate the relative importance of external factors on their exploration programs. The survey includes data from 172 companies that actively explore for mineral and geothermal resources in the state. The dollars spent and personnel employed in exploration is a minimum, because records suggest as many as 315 companies actively explored in Nevada in recent years.

The results from this 2017–2018 survey show that Nevada’s exploration spending of $461 million in 2018 reflects a 31% increase from 2017 and a 42% increase from 2016 levels. Despite major increases in 2018, spending remained substantially lower than in the commodity boom year of 2011, when more than $674 million was spent on exploration. Results from the current survey are consistent with global exploration trends and reflect a modest increase in most commodity prices since 2016, when the last survey was undertaken. Major findings are included in this publication.

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

NBMG Research Featured in Wired Magazine

An article in WIRED magazine recently released describes cutting-edge research by Jim Faulds, Bill Hammond, and Rich Koehler (Nevada Bureau of Mines and Geology) on fault systems in the Walker Lane and how this region could one day become the primary boundary between the Pacific and North American plates.

Read the story here—or listen to the audio version (following the third paragraph in the full article):

Move Over, San Andreas: There’s an Ominous New Fault in Town

by Geoff Manaugh (WIRED, Science, 4-18-19, 6:00 AM)

https://www.wired.com/story/walker-lane-move-over-san-andreas-fault/?mbid=email_onsiteshare

“U.S. Route 395 is a geologic master class disguised as a road. It runs north from the arid outskirts of Los Angeles, carrying travelers up to Reno along the eastern flank of the Sierra Nevada. On the way, they pass the black cinder cones of Coso Volcanic Field and the eroded scars of a mighty 19th-century earthquake near Lone Pine. In winter, drivers might see steam rising from Hot Creek, where water boils up from an active supervolcano deep underground. About an hour from the Nevada border, Mono Lake appears, with its bulbous and surreal mineral formations known as tufa towers. Even for someone with no particular interest in rocks, these are captivating, otherworldly sights. But for James Faulds, Nevada’s state geologist, they are something more—clues to a great tectonic mystery unfolding in the American West. If he’s right, all of this, from the wastes of the Mojave Desert to the night-lit casinos of Reno, will someday be beachfront property.” (Click on link above for complete story.)