“Post-Depositional Tectonic Modification of VMS Deposits and its Economic Significance, Based on Iberian Examples”
Monday, October 3, 2011
Davidson Mathematics and Science Center, Room 104 (on the southeastern part of UNR campus)
Professor Ricardo Castroviejo
Escuela Técnica Superior de Minas
Universidad Politécnica de Madrid, Spain
Students, professors, and industry colleagues who attend the lecture are invited to a party in Ricardo’s honor immediately following the lecture, at the home of Beth and Jon Price, 2210 Andromeda Way, Reno 89509 (on the southwest side of Reno, 0.5 mile southwest of the intersection of Plumb Lane and Hunter Lake Drive; call 329-8011 if lost).
Ricardo will be visiting UNR throughout October during his sabbatical leave from the School of Mines at the Polytechnical University in Madrid. He will also be giving a presentation on “A Fully Automated System for Multispectral Ore Microscopy” at 1:00 p.m. on Tuesday, October 4, to students and others interested in ore petrology in SEM 401, the conference room of the Nevada Bureau of Mines and Geology. Ricardo recently led a successful master’s degree program in economic geology and sustainable development, focusing on Latin America and based in Lima, Peru. An expert in ore microscopy and several types of mineral deposits (including VMS, volcanogenic massive sulfides), Ricardo will also be visiting several mines in northern Nevada and will be prepared to present a talk on “Ophiolites in the Eastern Cordillera of the Central Peruvian Andes” during those visits. If you would like to arrange some extra time to speak with Ricardo, please contact Jon Price at email@example.com or call 775-784-6691 x 5.
OF11-2 – Qualitative petroleum potential map of Nevada
by Larry J. Garside and Ronald H. Hess
plate: 24 x 36 inches, text: 9 b/w pages, $18.00
Who: Mary Roach, Author
Title: “Packing for Mars: The Curious Science of Life in Space”
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
597 Kumle Lane
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.
Who: Dr. Graham Kent; Director, Nevada Seismological Laboratory, University of Nevada, Reno
What: Nevada Petroleum Society meeting
Title: M7 in the Tahoe basin: An exploration of recent seismic CHIRP and airborne LiDAR imagery
When: Thursday, September 8, 2011
RSVP by MONDAY, Sept. 5 to Diane Phillips (775) 267-4663 or firstname.lastname@example.org
Cocktails: 6:30 PM; Dinner Served at 7:00 PM
NPS Members $20; Non-Members $23; Students $10
Menu: Buffet style including chicken & beef entrees with side dishes and salad
Ramada Reno Hotel (Washoe Room)
1000 East 6th Street
Reno, NV 89512
The Ramada Reno Hotel & Casino is located one mile from the junction of Interstate 80 and Highway 395 on 6th Street. From Interstate 80:Take Exit 14, Wells Avenue. Travel one block and turn left onto 6th Street.