| An efficient method is developed to construct potential solutions of phase diagrams, using dual networks. A dual network is a graph composed of divariant fields linked together by univariant lines. The assemblages observed in thin section define the chemography of the System. Once the chemography is known, the invariant points and divariant fields can be constructed and the divariant fields are used to construct the dual network. A potential solution for the phase diagram is obtained by inverting the dual network.; Dual networks and chemographic analysis are used to investigate the stability of lizardite and chrysotile in the simplest multisystem that describes serpentinization. Phase diagrams for Mg serpentinites described by MgO-SiO(,2)-H(,2)O are constructed for systems of five, six and seven phases using dual networks. The seven-phase system brucite, forsterite, lizardite, chrysotile, antigorite, enstatite and talc describes the serpentinization of Mg peridotites.; The chrysotile asbestos deposits of southeastern Quebec occur in serpentinized per idotites of Ordovician ophiolites. The asbestos is localized in veins within blocks of partly serpentinized peridotite bounded by zones containing schistose serpentinite and granitic masses. These zones are thought to have localized shear and to provide the channelways by which water entered the peridotite. Different generations of chrysotile veins can be identified locally by cross-cutting relationships but these observations cannot be generalized regionally. The asbestos was produced late during the deformation of the peridotite, filling extensional fractures in the peridotite induced by stresses resulting from motion along the shear zones.; A simple, rapid microscopic test was designed to obtain semi-quantitative measurements of the bending strength of acicular or fibrous crystals. The instrument was tested on samples of asbestiform tremolite from Baltimore, Maryland, and non-asbestiform tremolite from the Warren Head mine in New Hampshire. The samples ranged in size from 0.3 to 0.8 mm in length and 0.9 to 15 (mu)m in diameter. The asbestiform tremolite was stronger than the non-asbestiform tremolite at every diameter, with an order of magnitude higher strength at small diameters. This indicates that asbestiform tremolite behaves as a whisker, whereas non-asbestiform tremolite does not. |
