Letter | Published:

Volatiles in phyllosilicate minerals

Nature volume 296, pages 551553 (08 April 1982) | Download Citation



Volatiles other than water are known to occur in hydrous ring-structure silicates like beryl and cordierite1,2. However, there has been limited study of volatiles in phyllosilicates. Ammonia has been reported in micas3,4; Banks5 measured sulphur in biotite, sericite and chlorite by electron microprobe; and Norman6 reported evolution of H2S and CO2 when chlorite, sericite and kaolinite were heated to 500 °C. We have studied the thermal evolution of volatiles from phyllosilicates by mass spectrometry. The gases observed were, in approximate order of their abundance, CO2, H2S, H2, SO2, NH3, CO, CH4, N2, Ar and He. These gases represent 0.35–9 wt% of the volatiles observed; the remainder is water. Step-heating studies indicate H2S and CO2 are not generated by the thermal breakdown of sulphide and carbonate minerals. Rather, they are bound within the phyllosilicate structures in a complex way. We show here that gases in chlorite, muscovite and biotite are related to their mode of origin. Phyllosilicates from hydrothermal ore deposits evolve several times more volatiles, principally CO2 and H2/S, than phyllosilicates not from ore deposits.

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  1. New Mexico Institute of Mining and Technology, Socorro, New Mexico 87801, USA

    • David I. Norman
    •  & J. Michael Palin


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