196 Hg/ 202 Hg ratio and Hg content in meteorites and terrestrial standard rocks: a RNAA study

• Main Authors: Kumar, Pradeep, Ebihara, Mitsuru, Bhattacharya, S. K.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Terra Scientific Publishing Company, Tokyo 2001
• Subjects: QE Geology; Yamato; Antarc*; Antarctica
• Online Access: http://repository.ias.ac.in/87288/; http://www.terrapub.co.jp/journals/GJ/abstract/3502/35020101.html

Radiochemical neutron activation was applied for the determination of mercury isotopic ratios ( 196 Hg/ 202 Hg) for standard rock samples and meteorite samples. After neutron activation, Hg was released upon heating from 100°C to 500°C at 100°C steps and the activity ratio of 197 Hg/ 203 Hg was measured for each released fraction. After the correction for the interfering g-rays of 75 Se to 203 Hg, the ratios obtained from the Dhajala meteorite (bulk and magnetically separated samples) were identical to those of the Hg monitor as well as standard rock samples (JB-1, basalt, and JG-1, granodiorite). An apparently low ratio of 196 Hg/ 202 Hg was observed at high temperature (500°C) for the Allende meteorite reference sample. As such a low value was not reproduced in another run, the presence of isotopically anomalous Hg in the Allende reference sample can not be concluded. Hg/Se ratio was observed to be very high in the non-magnetic fraction of Dhajala compared with that in the magnetic fraction, suggesting that Hg is less chalcophile than Se. Yamato 82050 (CO3) has an anomalously high content of Hg with a normal 196 Hg/ 202 Hg ratio, being at least an order of magnitude higher than the expected value. This meteorite must have been contaminated with Hg, presumably on Antarctica.