Chapter 9. STABILITY, PHASE RELATIONS, AND THERMODYNAMIC PROPERTIES OF CHLORITE AND SERPENTINE GROUP MINERALS

Experimental aqueous alteration of the Allende meteorite under oxidizing conditions: Constraints on asteroidal alteration

“…However, the absence of fibrous or concentric textures in our serpentines indicates that chrysotile is absent and lizardite is dominant. We interpret this observation as indicating that olivine has been replaced by metastable lizardite, the serpentine polymorph which is regarded as being stable at low temperatures, but higher pressures than chrysotile (Chernosky et al, 1988). This behavior is consistent with studies of terrestrial serpentinization (Moody, 1976;OÕHanley et al, 1989), in which olivine is replaced by lizardite.…”

“…Under the conditions of our experiments (low P, low T), chrysotile would be expected to be the stable alteration product of olivine (Chernosky et al, 1988). However, the absence of fibrous or concentric textures in our serpentines indicates that chrysotile is absent and lizardite is dominant.…”

“…We do not see any evidence of such a transformation in our experiments, probably due to the fact that stabilization of antigorite requires higher pressures and higher temperatures than our experimental conditions. In addition, it is well-recognized that antigorite is extremely difficult to synthesize experimentally, due to formation of both lizardite and chrysotile that persist metastably for long periods of time (Chernosky et al, 1988).…”

Geochemical models of metasomatism in ultramafic systems: serpentinization, rodingitization, and sea floor carbonate chimney precipitation

“…Given that antigorite may contain on the order of 1.0 wt. % Al 2 O 3 , (e.g., Deer et al, 1992;Ulmer and Trommsdorff, 1995), and that solid solution extends from lizardite to amesite (Chernosky et al, 1988;Wicks and O'Hanley, 1988), natural serpentinization (Table 3) by meteoric water (Table 2), equilibrium composition vs. log w/r. A key to the mineral abbreviations is given in Table 1 at 300°C likely results in precipitation of chlorite or aluminous antigorite or lizardite, rather than in amesite.…”

Carboniferous dykes as monitors of post-Caledonian fluid events in West Connacht, Ireland

“…Alteration during post-intrusion cooling may have occurred at any temperature below the maximum at which chlorite can form (~575°C at 0-2 kb P H2 o; Chernosky et al 1988). Alteration at ~ 210 Ma caused development of assemblages including sericite, saussurite, chlorite, calcite and prehnite, indicating temperatures < 300°C.…”