Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Geologists map Cartwright country

16.06.2004


’Big Bonanza’ and the Comstock Lode



Remember the burning Ponderosa map at the beginning of the long-running TV show "Bonanza"? It’s up in flames before you can read all the place names.
Now a geologist at Washington University in St. Louis has replaced that map with one of the famous ore site known as the Comstock Lode, a part of which is the "Big Bonanza."

While it’s doubtful that Hoss, Adam and Little Joe – not to mention the sages, Pa and Hop Sing – could make heads nor tails of it, the map is a valuable contribution to geology because it gives an interpretation of the flow of hot waters interacting with rock some 14 million years ago that created the ore district. Between 1859 and 1882, the Comstock Lode produced gold and silver in such quantities that the bullion would be worth several billion dollars in today’s markets.



Robert Criss, Ph.D., professor of earth and planetary sciences in Arts & Sciences, and his former graduate student Michael J. Singleton, Ph.D., now at Lawrence Berkeley National Laboratory, analyzed 327 rock samples collected from a portion of the Comstock Lode as well as historical samples and ones from the Smithsonian Institute and "visualized" a kind of symmetrical flow. They were able to determine the flow thanks to a mathematical technique called kriging that allows computer contouring of oxygen isotope data gleaned from the rock samples.

When water and rock interact in ore deposition they exchange isotopes. Isotopes are different variations of the same element. There are three oxygen isotopes, oxygen-16, -17 and -18. All three behave chemically as oxygen, differing only in their mass. Most is oxygen-16, but about one oxygen atom in 500 is oxygen-18, and only one in about 2,500 is oxygen-17. Rocks are about 50 percent oxygen by weight, water 90 percent. The exchange of isotopes – the researchers measured O-16 and O-18– creates "patterns of disturbance" in the rock, which the researchers can map by combining a lot of field work with lab analysis and computing.

"We can map and interpret these patterns long after the disturbance happened -– 12 to 14 million years ago" said Criss. " The rocks preserve a record of what happened."

Criss said the hydrothermal flow geometry that created the ore district was a longitudinal roll pattern superimposed on a unicellular flow system. Think of the longitudinal rolls as two parallel tubes and the unicellular system as a flat roll. The map is the first evidence showing the longitudinal roll pattern occurring in nature. The system had been predicted by theory but never seen before in an ore district.

"We’ve shown that these modes of convection can occur on Earth under the right circumstances," Criss said. "It’s the first description of such symmetry in an ore district. The ore body positions have an obvious relationship to these rolls. "

The research was published in the April issue of the Journal of Geophysical Research. It was supported by funding from the National Science Foundation.

The finding is important for geologists to understand the creation of ore deposits. These events occur underground and must be analyzed remotely. And it could have economic implications.

"It’s possible, under perfect conditions, to understand currents of fluid that make ore bodies," Criss said. "If this could become part of a predictive tool to locate currents that form ore bodies, that would be a valuable outcome because we don’t have very good theories on how ore bodies are formed. It’s a very peculiar process."

Tony Fitzpatrick | EurekAlert!
Further information:
http://www.wustl.edu/

More articles from Earth Sciences:

nachricht Heidelberg Researchers Study Unique Underwater Stalactites
24.11.2017 | Universität Heidelberg

nachricht Lightning, with a chance of antimatter
24.11.2017 | Kyoto University

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New proton record: Researchers measure magnetic moment with greatest possible precision

High-precision measurement of the g-factor eleven times more precise than before / Results indicate a strong similarity between protons and antiprotons

The magnetic moment of an individual proton is inconceivably small, but can still be quantified. The basis for undertaking this measurement was laid over ten...

Im Focus: Frictional Heat Powers Hydrothermal Activity on Enceladus

Computer simulation shows how the icy moon heats water in a porous rock core

Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...

Im Focus: Nanoparticles help with malaria diagnosis – new rapid test in development

The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.

Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

IceCube experiment finds Earth can block high-energy particles from nuclear reactions

24.11.2017 | Physics and Astronomy

A 'half-hearted' solution to one-sided heart failure

24.11.2017 | Health and Medicine

Heidelberg Researchers Study Unique Underwater Stalactites

24.11.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>