We have investigated 128 14 C-dated ordinary chondrites from Oman for macroscopically visible weathering parameters, for thin section-based weathering degrees, and for chemical weathering parameters as analyzed with handheld X-ray fluorescence. These 128 14 C-dated meteorites show an abundance maximum of terrestrial age at 19.9 ka, with a mean of 21.0 ka and a pronounced lack of samples between 0 and 10 ka. The weathering degree is evaluated in thin section using a refined weathering scale based on the current W0 to W6 classification of Wlotzka (1993), with five newly included intermediate steps resulting in a total of nine (formerly six) steps. We find significant correlations between terrestrial ages and several macroscopic weathering parameters. The correlation of various chemical parameters including Sr and Ba with terrestrial age is not very pronounced. The microscopic weathering degree of metal and sulfides with newly added intermediate steps shows the best correlation with 14 C terrestrial ages, demonstrating the significance of the newly defined weathering steps. We demonstrate that the observed 14 C terrestrial age distribution can be modeled from the abundance of meteorites with different weathering degrees, allowing the evaluation of an age-frequency distribution for the whole meteorite population.

We tested a handheld X‐ray fluorescence instrument with adaptable matrix correction for its suitability in meteoritics. We report here the instrument setup, precision and accuracy and present examples of applications. With a measuring time of 300 s, it is possible to collect accurate data for K, Ca, Ti, Cr, Mn, Fe, Co, Ni, Sr and Ba that are needed for the identification of doubtful meteorites and the nondestructive classification of chondrites and achondrites. The factory‐supplied calibration curve of the instrument was fine tuned for our purposes with the use of well‐analyzed meteorite powders, pressed pellets and meteorite hand specimens as standards. Relative errors of 10% to 20% are reached for the mentioned elements. The instrument was tested in the hot desert of Oman while searching for meteorites and also in the laboratory while doing research on meteorites. The main applications of the instrument are the identification and classification of meteorites, the quantification of terrestrial elemental contamination (Sr and Ba) and detection of Mn‐rich desert varnish. It is possible to discriminate the major meteorite groups using Fe/Mn and Ni values. Handheld X‐ray fluorescence is also useful in identifying meteorites belonging to the same fall event. Copyright © 2011 John Wiley & Sons, Ltd.

Abstract-The common appearance of hygroscopic brine ("sweating") on ordinary chondrites (OCs) from Oman during storage under room conditions initiated a study on the role of water-soluble salts on the weathering of OCs. Analyses of leachates from OCs and soils, combined with petrography of alteration features and a 11-month record of in situ meteorite and soil temperatures, are used to evaluate the role of salts in OC weathering.

No abstract

No abstract