Forwarded from Laura Ruud at GSN:
James E. Faulds, State Geologist and Director of NBMG, will be giving a two-part talk at October’s Geological Society of Nevada meeting in Reno.
Part 1. Nevada Bureau of Mines and Geology: Analyzing and Educating for Nevada’s Future
Nevada is richly endowed with natural resources and stunning landscapes, ranging from high alpine mountains to enchanting deserts. It has more mountain ranges, gold, and geothermal resources than any other state. It has some of the largest gold deposits in the world, and its vast geothermal potential could one day be harnessed to produce enormous quantities of electricity. Nevada owes its unique setting to its location within the Pacific-North American plate boundary, where tectonic stresses drive crustal blocks to slide past one another along major faults, akin and related to the San Andreas Fault in California, and also to crustal stretching in the horizontal dimension. These motions make Nevada literally the fastest growing state in the country, as the stretching adds new land at the rate of two acres every decade. Some models predict that the San Andreas fault will eventually shift inland in a few million years and make Nevada home, ultimately allowing the Gulf of California to grow northward and create beachfront property near Reno. All of this activity makes Nevada the third most seismically active state after California and Alaska, with a number of large M 7 earthquakes in our recent past. So large earthquakes are a looming natural hazard that Nevada will continue to face in the coming years.
Studies of Nevada’s geology are therefore important for both public safety in its large dynamic cities (Las Vegas and Reno) and rural communities and to support economic development throughout the state, especially for its mining and renewable energy industries.
The Nevada Bureau of Mines and Geology is responsible for understanding Nevada’s geology and landscapes, assessing its natural resources, and analyzing its earthquake potential and other natural hazards. NBMG is Nevada’s state geological survey. Every state has a geological survey, with 1/3 of them residing at a major university. In Nevada, NBMG resides in the College of Science at the University of Nevada, Reno. The university relationship allows us to be intimately involved in both cutting edge research and education of the next generation of geoscience experts.
Although NBMG resides at UNR, we are a statewide agency that applies its expertise to all corners of the state, including the burgeoning city of Las Vegas in the south, the major gold resources of the northeast, and the earthquake hazards and geothermal resources of the west and northwest within and near the Reno-Carson City urban corridor. Thus, NBMG is relevant to nearly every Nevada citizen, and its work is making Nevada a safer and more attractive home for its people and industries.
Part 2. Favorable Structural Settings of Active Geothermal Systems in the Great Basin Region: Implications for Fluid Flow, Normal Faulting Mechanisms, and Geothermal and Epithermal Mineral Exploration
Active amagmatic geothermal systems of the Great Basin, USA are used to generate electricity and have temperatures overlapping formation of some epithermal mineral deposits (up to and >200°C). We recently completed an inventory of structural settings of known geothermal systems (426 total) in the extensional Great Basin region. Of ~250 categorized fields, step-overs or relay ramps in normal fault zones are the most favorable setting, hosting ~32% of the systems. Such areas have overlapping fault strands, increased fracture density, and thus enhanced permeability. Other common settings include a) normal fault tips (25%), where horse-tailing generates closely-spaced faults and increased permeability; b) fault intersections (22%), where multiple minor faults typically connect major faults and fluids can flow readily through highly fractured, dilational quadrants; and c) accommodation zones (9%), where oppositely dipping normal fault systems intermesh in belts of multiple fault tips and intersections. 3D modeling indicates subvertical conduits of high fracture density in these settings. The primary segments of major faults only host ~1% of the geothermal fields. Quaternary faults lie within or near most fields.
The paucity of geothermal systems along primary fault segments may result from reduced permeability in thick clay gouge and periodic stress release in major earthquakes. Step-overs, terminations, intersections, and accommodation zones represent critically stressed areas, where fluid pathways more likely remain open in breccia-dominated fracture networks. Because stress is not relieved by major earthquakes, abundant microseismicity characterizes fault interaction areas, which precludes pervasive healing of fractures and thus facilitates fluid flow. Increased pore-pressure may also provide a positive feedback mechanism that promotes more frequent but lesser magnitude earthquakes. The association of some young (
The GSN October Membership meeting is this Friday, October 17th at the Reno Elks Lodge, 597 Kumle Lane, Reno, Nevada. Drinks begin at 6 p.m., Dinner at 7 p.m., and Talk begins at 8 p.m.
Meeting details from Laura Ruud, GSN Office Manager:
- Dinner cost is $25/each and reservations are due by 4:00 p.m. on WEDNESDAY, OCTOBER 15TH!
- Please email your reservation to Laura at: email@example.com or call 775-323-3500.
- Any Nevada GSN Student member can eat for free if they make a reservation by the deadline of 4 pm on October 15th.
- The Bar Sponsor for OCTOBER is RUEN DRILLING INC.