Featured Research

from universities, journals, and other organizations

Iron in primeval seas rusted by bacteria

Date:
April 23, 2013
Source:
Universitaet Tübingen
Summary:
Researchers have been able to show for the first time how microorganisms contributed to the formation of the world's biggest iron ore deposits. The biggest known deposits -- in South Africa and Australia -- are geological formations billions of years old. They are mainly composed of iron oxides -- minerals we know from the rusting process. These iron ores not only make up most of the world demand for iron -- the formations also help us to better understand the evolution of the atmosphere and climate, and provide important information on the activity of microorganisms in the early history of life on Earth.

Iron ore mine in the Hamersley region, Western Australia.
Credit: Professor K.O. Konhauser

Researchers from the University of Tübingen have been able to show for the first time how microorganisms contributed to the formation of the world's biggest iron ore deposits. The biggest known deposits -- in South Africa and Australia -- are geological formations billions of years old. They are mainly composed of iron oxides -- minerals we know from the rusting process. These iron ores not only make up most of the world demand for iron -- the formations also help us to better understand the evolution of the atmosphere and climate, and provide important information on the activity of microorganisms in the early history of life on Earth.

The extent to which microbes in the Earth's ancient oceans contributed to the formation of iron deposits was previously unknown. Now an international team of researchers from the US, Canada and Germany has published new findings in the journal Nature Communications. Led by University of Tübingen geomicrobiologist Professor Andreas Kappler of the Center for Applied Geoscience, they found evidence of which microbes contributed to the formation of the iron ores, and were able to show how different metabolic processes can be distinguished in the rock formations today.

The iron in the Earth's ancient oceans was spat out of hot springs on the seafloor as dissolved, reduced ferrous [Fe(II)] iron. But most of today's iron ore is oxidized, ferric [Fe(III)] iron in the form of "rust minerals" -- indicating that the Fe(II) was oxidized as it was deposited. The classic model for the formation of iron deposits suggested that the Fe(II) from the Earth's core was oxidized by the oxygen produced by cyanobacteria (blue-green algae). This process can happen either chemically (as in the formation of rust) or by the action of microaerophilic iron-oxidizing bacteria.

But scientists are still debating at what point the Earth's atmosphere contained enough oxygen (produced by cyanobacteria) to allow the formation of big iron deposits. The oldest known iron ores were deposited in the Precambrian period and are up to four billion years old (the Earth itself is estimated to be about 4.6 billion years old). At this very early stage in geological history, there was little or no oxygen in the atmosphere. So the very oldest banded iron formations cannot be the result of O2-dependent oxidation.

In 1993, bacteria were discovered which do not need oxygen but can oxidize Fe(II) by using energy from light (anoxygenic phototrophic iron-oxidizing bacteria). Studies by Professor Kappler's team in 2005 and 2010 showed that these bacteria transform dissolved ferric iron into iron oxide (rust) -- like the material in the early iron ores. Now, the geomicrobiologists from Tübingen have been able to demonstrate that, by examining the identity and structural properties of the iron minerals, it is possible to tell that the minerals were deposited by iron-oxidizing microbes and not by oxygen made available by the action of cyanobacteria. To do this, the researchers placed different amounts of organic material together with iron minerals into gold capsules and increased the pressure and temperature to simulate the transformation of the minerals over geological time. They ended up with structures of iron carbonate minerals (siderite, FeCO3), just as they occur in geological iron formations. In particular, they were able to distinguish iron carbonate structures which had been formed in the presence of a rather small amount of organic compounds (microbial biomass) from those formed in the presence of a larger amount.

This research not only provides the first clear evidence that microorganisms were directly involved in the deposition of Earth's oldest iron formations; it also indicates that large populations of oxygen-producing cyanobacteria were at work in the shallow areas of the ancient oceans, while deeper water still reached by the light (the photic zone) tended to be populated by anoxyenic or micro-aerophilic iron-oxidizing bacteria which formed the iron deposits.


Story Source:

The above story is based on materials provided by Universitaet Tübingen. Note: Materials may be edited for content and length.


Journal Reference:

  1. Inga Köhler, Kurt O Konhauser, Dominic Papineau, Andrey Bekker, Andreas Kappler. Biological carbon precursor to diagenetic siderite with spherical structures in iron formations. Nature Communications, 2013; 4: 1741 DOI: 10.1038/ncomms2770

Cite This Page:

Universitaet Tübingen. "Iron in primeval seas rusted by bacteria." ScienceDaily. ScienceDaily, 23 April 2013. <www.sciencedaily.com/releases/2013/04/130423110750.htm>.
Universitaet Tübingen. (2013, April 23). Iron in primeval seas rusted by bacteria. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2013/04/130423110750.htm
Universitaet Tübingen. "Iron in primeval seas rusted by bacteria." ScienceDaily. www.sciencedaily.com/releases/2013/04/130423110750.htm (accessed July 31, 2014).

Share This




More Earth & Climate News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Visitors Feel Part of the Pack at Wolf Preserve

Visitors Feel Part of the Pack at Wolf Preserve

AP (July 31, 2014) — Seacrest Wolf Preserve on the northern Florida panhandle allows more than 10,000 visitors each year to get up close and personal with Arctic and British Columbian Wolves. (July 31) Video provided by AP
Powered by NewsLook.com
Big Waves In Arctic Ocean Threaten Polar Ice

Big Waves In Arctic Ocean Threaten Polar Ice

Newsy (July 30, 2014) — Big waves in parts of the Arctic Ocean are unprecedented, mainly because they used to be covered in ice. Video provided by Newsy
Powered by NewsLook.com
Raw: Thousands Flocking to German Crop Circle

Raw: Thousands Flocking to German Crop Circle

AP (July 30, 2014) — Thousands of people are trekking to a Bavarian farmer's field to check out a mysterious set of crop circles. (July 30) Video provided by AP
Powered by NewsLook.com
Weather Kills 2K A Year, But Storms Aren't The Main Offender

Weather Kills 2K A Year, But Storms Aren't The Main Offender

Newsy (July 30, 2014) — Health officials say 2,000 deaths occur each year in the U.S. due to weather, but it's excessive heat and cold that claim the most lives. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

    Environment News

    Technology News



    Save/Print:
    Share:  

    Free Subscriptions


    Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

    Get Social & Mobile


    Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

    Have Feedback?


    Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
    Mobile iPhone Android Web
    Follow Facebook Twitter Google+
    Subscribe RSS Feeds Email Newsletters
    Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins