Prospectors & Developers Association of Canada (PDAC)—March 1–4

Look for NBMG at Booth 7017N.

A message from the Nevada Mineral Exploration Coalition (NMEC): “The NMEC in partnership with the NDOM [Nevada Division of Minerals], NBMG [Nevada Bureau of Mines and Geology], NvMA [Nevada Mining Association], GSN [Geological Society of Nevada] and the State Office of the BLM will once again have a large island display booth [7017N] in the North Hall of the Convention Center.

As part of our effort, we will have a series of brief presentations by Nevada explorers, suppliers and government agencies.”

https://www.nvmec.org/

“Welcome to the registration and housing website of PDAC 2020 annual convention. The Prospectors & Developers Association of Canada (PDAC) 2020 annual convention will be held from 1-4 March, 2020 in Toronto, ON, Canada. The Prospectors & Developers Association of Canada (PDAC) is the leading voice of the mineral exploration and development community. With over 7,500 members around the world, PDAC’s work centers on supporting a competitive, responsible mineral sector. PDAC is known worldwide for its annual PDAC Convention—the premier international event for the industry—that has attracted over 25,000 people from 135 countries. The mission of PDAC’s is to promote a globally-responsible, vibrant and sustainable mineral sector that encourages leading practices in technical, operational, environmental, safety and social performance.”

https://www.pdac.ca/convention

Geological Society of Nevada 2020 Symposium, May 14–24, 2020

Early Registration Ends Friday, February 28, 2020!
Geological Society of Nevada 2020 Symposium, May 14-24, 2020

4 full days of Technical Sessions!
6 Field Trips!
11 Short Courses!

Keynote Speakers:  Rich Goldfarb, Quinton Hennigh, Joe Mazumdar, Keith Meldahl, Elizabeth Miller, John Prochnau, Eric Seedorff, Dick Sillitoe, Moira Smith, and Chuck Thorman.

Presentations, Field Trips, and Short Courses by NBMG Faculty:  Jim Faulds, Andrew Zuza, John Muntean, Bridget Ayling, Mike Ressel, Chris Henry, Rich Koehler, Mark Coolbaugh, and students Justin Milliard and James Ingraffia.

NBMG is a CO-HOST! Look for NBMG at Booth 69.

The Symposium is being held at the Nugget Casino Resort, Reno/Sparks, Nevada.

REGISTER NOW
Call for information:  775-433-8758.

Earth Science Week Trip Guide

combinationTitle: Lode and Behold! Geology and Natural Resources of the Truckee Meadows and Virginia City (Guide for the Earth Science Week Field Trip, October 12, 2019)
Authors: Mike Ressel, Rachel Micander, Jack Hursh, Steve Russell, and Matthew Sophy
Year: 2019
Series: Educational Series 65
Format: 25 pages, color
View/download/purchase the 2019 Earth Science Week field trip guide!

Geoscientists from Nevada Bureau of Mines and Geology explain the geology of the Truckee Meadows and Virginia City areas, in celebration of Earth Science Week 2019 and the importance of earth sciences to the people of the state of Nevada.

Major stops on this field trip included the following:

  • Ormat geothermal plant in south Reno
  • Chollar Mine (open pit mine site) in Virginia City

NBMG coordinates annual geology field trips for the public during, or near, Earth Science Week. These field trips are fun, educational, family oriented, and always free. NBMG has been an active participant in Earth Science Week since it began in 1998.

Geologic Map of the Granite Peak Quadrangle, Washoe County, Nevada

Author: Seth Dee
Year: 2019
Series: Open-File Report 2019-05
Version: supersedes Open-File Report 1987-08
Format: plate: 28 x 32.5 inches, color; text: 5 pages, color
Scale: 1:24,000

View, download, or purchase the Granite Peak Quadrangle map.

The Granite Peak 7.5-minute quadrangle is located immediately north of Reno, and abuts the Nevada-California state line in an area known as the ‘North Valleys’. The quadrangle includes the summits of Petersen Mountain and Granite Peak, and portions of Red Rock Valley and Cold Springs valley. The bedrock exposures in the quadrangle consist primarily of Cretaceous granitic rocks related to the Sierra Nevadan batholith. The granitic rocks include three distinct lithologies with relative ages constrained by clear crosscutting relationships. Miocene to Pliocene clastic and fluvio-lacustrine sediments are deposited in a shallow basin west of Freds Mountain in the easternmost part of the quadrangle. On the western flank of Petersen Mountain, west-dipping Oligocene ash-flow tuff deposits nonconformably overlie Cretaceous granite. Quaternary sediments largely consist of alluvial fans and several large landslide deposits (up to 2.7 sq. km.).

The quadrangle is bisected by the Petersen Mountain fault zone. The fault zone consists of two subparallel traces (western and eastern) that extend from Cold Springs valley in the south to Seven Lakes Mountain in the north. The western trace of the fault strikes generally north-south along the eastern range front of Petersen Mountain, dips steeply east, and locally displaces surficial deposits as young as Holocene. The eastern trace consists of several north-south striking strands that displace surficial deposits as young as late Pleistocene and locally forms a narrow graben infilled by faulted fanglomerate material. Fault surfaces on the eastern trace have subhorizontal slickenlines demonstrating a history of dextral-oblique motion. Long-term late Cenozoic normal displacement across the western trace is demonstrated by the high relief of the Petersen Mountain range front (>500 m) as well as the accumulation of Miocene-Pliocene sediments to the east that were likely deposited into a basin controlled by early displacement along the fault. This is in contrast to the eastern strand, which has been active since at least the middle Pleistocene but for much of its length does not bound basins with significant accumulations of late Cenozoic deposits. These map relationships suggest the Petersen Mountain fault zone initially developed as a Basin and Range extensional structure with displacement primarily along the western fault trace, and has evolved into a Walker Lane structure with dextral-oblique motion focused on the eastern trace.

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

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).

NBMG Geologic Map T-Shirts—Taking Preorders

“Geologic Map of Nevada” T-shirts will soon be back in stock, and we are taking preorders this week. It is best to place a preorder if you want to be sure to get a certain size and/or color. If you want to order a size that is not on the drop-down menu, please give us a call by Friday, December 13 at 775-682-8766.

We hope the shirts will arrive before we close on December 23 but cannot guarantee the date. Priority will be given to those who place a preorder since we will have those shirts printed first.