4 Responses to “Meteor Impacts”

1. Jim Metzner Says:
   August 1st, 2007 at 10:22 am

   Dear Charles:
   Thanks for your email, which I am ccing to professor Mungall.

   Regards;
   Jim Metzner

2. Jim Mungall Says:
   August 1st, 2007 at 6:58 pm

   Not all breccias are impact-related, so it would be interesting to know what material constitutes the matrix to your breccia. If it is glassy or devitrified glass or if it is an igneous rock with a composition unlike ordinary terrestrial magmas, it could be related to an impact. If it is carbonate minerals or other phases deposited from percolating aqueous solutions, then an impact origin seems less likely. Other localities that I can think of off the top of my head are the Slate Islands in Lake Superior, and the Wanapitei structure immediately to the east of Sudbury.

   cheers
   Jim Mungall

   ps for a list of impact sites and other interesting stuff regarding impacts, check out the following two websites:
   http://www.unb.ca/passc/ImpactDatabase/
   http://keith.aa.washington.edu...../index.htm

3. Jim Metzner Says:
   August 1st, 2007 at 7:35 pm

   Jim: Thanks for your reply!

4. Jim Mungall Says:
   August 1st, 2007 at 10:44 pm

   No problem. When I reread this thread I also recalled that a colleague of mine at U of Toronto recently contributed to a paper documenting the presence of fallout from the Sudbury structure in bedrock near Gunflint too. Perhaps there is a connection there.

   cheers
   Jim

   …here is the title and abstract etc

   Discovery of distal ejecta from the 1850 Ma Sudbury impact event
   William D. Addison* R.R. 2, Kakabeka Falls, Ontario P0T 1W0, Canada
   Gregory R. Brumpton 211 Henry Street, Thunder Bay, Ontario P7E 4Y7, Canada
   Daniela A. Vallini
   Neal J. McNaughton
   Centre for Global Metallogeny, School of Earth and Geographic Sciences, University of Western Australia, Nedlands, Western Australia 6009, Australia
   Don W. Davis Department of Geology, Earth Sciences Centre, University of Toronto, 22 Russell Street, Toronto, Ontario M5S 3B1, Canada
   Stephen A. Kissin
   Philip W. Fralick
   Anne L. Hammond

   Department of Geology, Lakehead University, Thunder Bay, Ontario P7B 5E1, Canada

   ABSTRACT
   A 25–70-cm-thick, laterally correlative layer near the contact between the Paleoproterozoic sedimentary Gunflint Iron Formation and overlying Rove Formation and between the Biwabik Iron Formation and overlying Virginia Formation, western Lake Superior region, contains shocked quartz and feldspar grains found within accretionary lapilli, accreted grain clusters, and spherule masses, demonstrating that the layer contains hypervelocity impact ejecta. Zircon geochronologic data from tuffaceous horizons bracketing the layer reveal that it formed between ca. 1878 Ma and 1836 Ma. The Sudbury impact event, which occurred 650–875 km to the east at 1850 6 1 Ma, is therefore the likely ejecta source, making these the oldest ejecta linked to a specific impact. Shock features, particularly planar deformation features, are remarkably well preserved in localized zones within the ejecta, whereas in other zones, mineral replacement, primarily carbonate, has significantly altered or destroyed ejecta features.

   published in Geology; March 2005; v. 33; no. 3; p. 193–196; doi:
   10.1130/G21048.1; 4 figures; Data Repository item 2005036.

Leave a Reply

Name (required)

Mail (will not be published) (required)

Website