NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Collections About News Help Login
Back to Results
Ar-40/Ar-39 Age of Hornblende-bearing R Chondrite LAP 04840Chondrites have a complex chronology due to several variables affecting and operating on chondritic parent bodies such as radiogenic heating, pressure and temperature variation with depth, aqueous alteration, and shock or impact heating [1]. Unbrecciated chondrites can record ages from 4.56 to 4.4 Ga that represent cooling in small parent bodies. Some brecciated chondrites exhibit younger ages (<<4 to 4.4 Ga) that may reflect the age of brecciation, disturbance, or shock and impact events (<< 4 Ga). A unique R chondrite was recently found in the LaPaz Icefield of Antarctica - LAP 04840 [2]. This chondrite contains approx.15% hornblende and trace amounts of biotite, making it the first of its kind. Studies have revealed an equigranular texture, mineral equilibria yielding equilibration near 650-700 C and 250-500 bars, hornblende that is dominantly OH-bearing (very little Cl or F), and high D/H ratios [8,9,10]. To help gain a better understanding of the origin of this unique sample, we have measured the Ar-40/Ar-39 age. Age of 4.290 +/- 0.030 Ga is younger than one would expect for a sample that has cooled within a small body [4], and one might instead attribute the age to a younger shock event, On the other hand, there is no evidence for extensive shock in this meteorite (shock stage S2; [3]), so this sample may have been reannealed after the shock event. This age is similar to Ar-Ar ages determined for some other R chondrites
Document ID
20140003557
Acquisition Source
Johnson Space Center
Document Type
Conference Paper
Authors
Righter, K. (NASA Johnson Space Center Houston, TX, United States)
Cosca, M. (Geological Survey Denver, CO, United States)
Date Acquired
April 24, 2014
Publication Date
January 1, 2014
Subject Category
Geophysics
Report/Patent Number
JSC-CN-30744
Meeting Information
Meeting: 2014 Goldschmidt Conference
Location: Sacremento, CA
Country: United States
Start Date: June 8, 2014
End Date: June 13, 2014
Sponsors: Geochemical Society
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

Related Records

There are no records associated with this record.
No Preview Available