An Article In Meteorite-Times Magazine
by Robert Verish

Dutch Flat (IIAB)

Another low-Iridium iron meteorite. But, is it paired to Sikhote-Alin?


Image courtesy of and by Rob Matson.

The purpose of this article is to post the above image, here on the Internet, and to continue an on-going discussion about possible pairings of the Dutch Flat meteorite with other irons, based upon this image.

Over the past few years the Dutch Flat meteorite, an iron find from Arizona, has been mentioned often whenever there are discussions about the numerous small irons being found within the strewn field of the Franconia meteorite. But, in a recent article in GCA by John Wasson, it was suggested by the authors that, based upon similar trace element composition (namely, low-Iridium content) the Dutch Flat should be considered as paired to Sikhote-Alin.

It is my opinion, as well as the opinion of several others who have seen the above image, that this iron is far too weathered to be paired to the fall of the Sikhote-Alin meteorite. For the same reason, Dutch Flat does not look like a good pairing with the numerous small irons being found within the Franconia strewn field. But, regardless of any perceived difference in weathering grade, one of the larger specimens of these "Franconia irons" was recently classified and the results confirm its chondritic origin (personal communication with finder).

If the terrestrial age of the Dutch Flat iron were to be measured, it could be conclusive evidence in determining whether it is paired/unpaird to the Sikhote-Alin iron, which fell just 60 years ago this past February. Admittedly, the degree of weathering grade is no indicator of terrestrial age. But experts in the weathering of meteorites can tell the difference between an iron oxide rust that formed after 60 years of exposure in a tundra, versus a magnetite-rich patina on a rind which developed over a much longer period of time in a hot desert. In fact, during my recent conversation with John Wasson, he stated that, "if it can be shown that the exterior of the Dutch Flat iron formed in a desert environment, and was of sufficient age, then it would clearly indicate that it isn't paired to the Sikhote-Alin iron."

So, in a manner of speaking, this article is a "want-ad" seeking just such an expert in terrestrial age-determination of weathered iron meteorites. The candidate expert could benefit from this exercise by having the opportunity to author a paper that alternatively, either confirms that Dutch Flat is paired to Sikhote-Alin, or that Dutch Flat, like the Ainsworth iron, fell before the Sikhote-Alin iron, and is another low-Iridium IIAB, yet all three are unpaired!

Post script:

Prior to writing this article, I corresponded with Rob Matson regarding this subject and other related issues. Rob is the person that acquired the Dutch Flat iron from the finders and had it classified by John Wasson at UCLA. The Meteoritical Bulletin in its description of the Dutch Flat meteorite, makes reference to the Ainsworth iron as being ALSO "very similar to Sikhote-Alin". The implication here is that, if the IIAB group can have two "very similar meteorites" that are unpaired, then why can't it have a third? A good question would be, "Just how similar are these three irons with each other?" In an effort to answer that question, Rob felt that a side-by-side comparison was in order. With Rob's permission I have quoted his comments on this matter and the results of his comparison below:
"I think the comparative trace element analysis for Ainsworth, Sikhote-Alin, and Dutch Flat 
is interesting because the data suggest that Ainsworth and Sikhote-Alin are more alike 
than Dutch Flat is to either of them.  (See the attached spreadsheet I created a few months back 
based on the Dutch Flat data in Meteoritical Bulletin #88 versus corresponding Sikhote-Alin and
Ainsworth data kindly provided by Dr. Wasson.)  One does have to be mindful that, 
for a variety of reasons, measurement uncertainty and/or compositional variability on some elements 
can be 10-15%, so not all differences are statistically significant.  The key difference here is iridium, 
where Dutch Flat is a slight outlier."
Rob Matson's spreadsheet is transcribed below for the reader's convenience:

  A B C D E F G H I J
1   Sikhote Dutch Flat Ainsworth S-A to D-F A to D-F S-A to A      
Ni 60.3 57.8 57.1 04.33% 01.21% 05.60%      
Ga 53.7 55.5 53.4 03.24% 03.78% 00.56%      
Ir 0.024 0.021 0.024 14.29% 14.29% 0.00%      
Co 4.79 4.89 5.01 02.04% 02.45% 04.39%      
Cu 117 112 106 04.46% 05.36% 10.38%      
As 9.4 9.04 9.29 03.98% 02.77% 01.18%      
W 0.74 0.82 0.69 09.76% 15.85% 07.25%      
Au 1.049 1.03 1.02 01.84% 00.97% 02.84%      
10  rms diff.       19.28% 22.68% 14.86%      


Google Web Search Results 1 - 2 of about 6 for Dutch Flat . (0.09 seconds) 

Meteoritical Bulletin: Entry for Dutch Flat

Search the Meteoritical Bulletin Database. Last update: 15 April 2007 ... Dutch Flat. Information about the name, Name: Dutch Flat ... - 26k

The following references are from the MeteoriteCentral "Meteorite=List":

[meteorite-list] Fredericksburg & Dutch Flat

2007/03/21 Hi Mike and List, I can't speak to the pairing possibilities between the Fredericksburg iron and the Richland iron, but I'm reasonably confident that the Dutch Flat iron is not a repatriated Sikhote. While Dutch Flat is a kissing cousin to Sikhote-Alin for many (but not all) trace elements that were analyzed, it is also quite similar to the Ainsworth iron. -- Matson, Robert

[meteorite-list] Franconia Area Meteorite Photos, Article

2004/07/28 like a Sikhote-Alin. This is sounding more and more like a match to Dutch Flat. Dr. Wasson noted the close similarity of Dutch Flat to Sikhote-Alin (as well as Ainsworth). All three are low-Ir, IIAB irons. Would love to find one of these irons myself -- I'll be returning to Franconia -- Matson, Robert

[meteorite-list] Re: Franconia Area Meteorite Photos, Article

2004/07/28 Rob posted: This is sounding more and more like a match to Dutch Flat. Dr. Wasson noted the close similarity of Dutch Flat to Sikhote-Alin -- Notkin

[meteorite-list] Franconia area chondrites and Irons

2004/07/26 Hi Ruben and List, Wanted to add some info on the Dutch Flat Iron, with regards to these other small irons being found from the Franconia area: ... -- Matson, Robert

[meteorite-list] Franconia area chondrites and Irons

2004/07/26 was not entirely consistent. Of the eight specimens classified, five meteorites had a shock factor of 2 and three meteorites had a shock factor of 1. The tiny irons we've found have not yet been seriously considered as being related to the Dutch Flat Iron . This is partly because a lot of time has -- Ruben Garcia

[meteorite-list] Update: Franconia area meteorite classifications

2004/07/25 the possibility of all these small irons being paired to the Dutch Flat iron meteorite? Is ASU aware that the Dutch Flat meteorite is from this same general area, what is now being called the Franconia area? Bob V. [meteorite-list] Update: Franconia area meteorite classifications Ruben -- Robert Verish

[meteorite-list] Franconia Area Meteorites

2004/04/09 in the classification process since the beginning and therefore this is not merely our opinion but also the opinion those at Arizona State University. Now this is news of particular interest to me, in light of the iron meteorite I had classified this past year (Dutch Flat -- see MB 88 -- Matson, Robert

My previous articles can be found *HERE*

For for more information, please contact me by email: Bolide*chaser