Physical and chemical evidence of the 1850 Ma Sudbury impact event in the Baraga Group, Michigan
Peir K. Pufahl, Acadia University, Earth and Environmental Science, Wolfville, Nova Scotia B4P 2R6, Canada; et al. Pages 827-830.
A catastrophic extraterrestrial impact 1850 million years ago produced the Sudbury crater, the second largest known impact site on Earth. Pufahl et al.’s discovery of debris in northern Michigan, USA, produced from this impact has provided new information regarding the nature of this event. A prominent iridium anomaly in impact-generated tsunami deposits containing shocked quartz, spherules, tektites, and accretionary lapilli demonstrate that the extraterrestrial body was a meteorite and not a comet, as previously proposed. The Sudbury event was larger than those responsible for later major extinction events, and may prove important in the evolution of early life on Earth.
Two of the three largest impact craters on Earth have nearly the same size and structure, researchers say, but one was caused by a comet while the other was caused by an asteroid. These surprising results could have implications for where scientists might look for evidence of primitive life on Mars.
Susan Kieffer of the University of Illinois at Urbana-Champaign, Kevin Pope of Geo Eco Arc Research and Doreen Ames of Natural Resources Canada analyzed the structure and stratigraphy of the 65 million-year-old Chicxulub crater in Mexico and the 1.8 billion-year-old Sudbury crater in Canada.
Chicxulub is well preserved, but buried, and can be studied only by geophysical means, remote sensing and at a few distant sites on land where some ejecta is preserved. In contrast, Sudbury has experienced up to 4-6 kilometers of erosion, and is well exposed and highly studied by mining exploration companies because of its rich mineral resources.
RIO DE JANEIRO, Brazil, June 21, 2007 /PRNewswire-FirstCall via COMTEX/ -- Companhia Vale do Rio Doce (CVRD) announces that exploration drilling at Creighton, a more than century-old nickel mine near Sudbury, province of Ontario, Canada, is confirming mineralization at depth that has the potential to extend the mine life well into the future and continue its longstanding economic contribution to its wholly-owned subsidiary, CVRD Inco Ltd. (CVRD Inco) Ontario operations.The Creighton Deep Project, a deep mine exploration program, has the potential to almost double the proven and probable reserves at Creighton from 17 million metric tons grading 3.1% nickel and 2.5% copper to up to 32 million metric tons grading 1.9 to 2.2% nickel and 2 to 2.3% copper.
In operation since 1901, Creighton has delivered a total of 173 million metric tons over its life with an average grade of 1.52% nickel and 1.22% of copper.Exploration and advanced exploration diamond drilling have shown significant high-grade nickel, copper and platinum group elements (PGE) mineralization between the 2,150 and 3,200 meter levels at the mine.
The exploration program continues, and three exploration stations located 1.5 kilometers have been constructed to support further economic study of the findings to date. These latest stations are excavated further into the footwall beyond current infrastructure, allowing exploration to the 3,200- meter level across the entire strike length of all ore bodies.
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