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 Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie

nachricht Modeling magma to find copper
13.01.2017 | Université de Genève

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

How gut bacteria can make us ill

18.01.2017 | Life Sciences

On track to heal leukaemia

18.01.2017 | Health and Medicine

Water - as the underlying driver of the Earth’s carbon cycle

17.01.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>