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    STUDIA GEOLOGIA - Ediţia nr.1 din 2007  
         
  Articol:   CHLORINE ISOTOPE GEOCHEMISTRY.

Autori:  ZACHARY SHARP, JAIME BARNES. 		 
       
         
  Rezumat:  Chlorine is an unusual element. It is neither siderophile, nor chalcophile, nor lithophile. Rather it is generally highly partitioned into aqueous fluids. There are two stable isotopes of Cl, masses 35 and 37. The latter comprises 1/4 of the total, leading to a non-integer molecular weight (this was very significant for physicists in the early 20th century, who were trying to understand the structure of atoms). Chlorine isotope geochemistry was first investigated by Hoering & Parker (1961). He found that there was very little variation in the 37Cl/35Cl ratios of natural materials. In the mid 1990s, a new series of studies were made, where large variations in the δ37Cl values of terrestrial and meteoritic materials were found. We have revisited the chlorine isotope system, modifying existing analytical procedures so that 20 mg samples of Cl can be analyzed on a gas source mass spectrometer using CH3Cl as an analyte. Precision is ±0.14‰. We have measured the δ37Cl values of the major terrestrial and extraterrestrial reservoirs. Mantle samples include pristine mid ocean ridge basalt glasses, and several sub-continental mantle samples. The major crustal reservoirs for Cl are the oceans and evaporites, and these have been thoroughly investigated previously. Four primitive carbonaceous chondrites have also been measured  
         
     
         
         
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