Low-Temperature Alteration Processes

Because of their high glass contents and very fine grain size, volcanic rocks are very susceptible to low-temperature processes such as hydration and weathering, which are characterized by large 0-emichment effects in the altered rocks. 

In general, it is probable that Tertiary and older volcanic rocks will exhibit O-isotope compositions that have been modified to higher ratios from 

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Kojima T., Yada S., and Tomeoka K. (1995) Ca-Al-rich inclusion in three Antarctic C03 chondrites, Yamato 81020, Yamato-82050, and Yamato-790992 record of low temperature alteration processes. Proc. NIPR Symp. Antarct. Meteorit. 8, 79-86. 

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