Augite phase

Figure 5,25 Phase stability relations for natural pyroxenes in the quadrilateral. (A) Magmatic pyroxenes (not reequilibrated at low 7). (B) Three-phase region for pyroxenes of stratihed complexes and magmatic series. (C) Pyroxenes reequilibrated in subsolidus conditions. = Pbca orthopyroxene V = augite C2lc) A = pigeonite (P2jlc) 0 = olivine. From Huebner (1982). Reprinted with permission of The Mineralogical Society of America.

Plutonic rocks from the Emerald Lake pluton, Yukon, comprise four phases (/) augite syenite, (//) hornblende quartz... 

Ross and Huebner (1979) found that dislocations were often present In the augite-orthopyroxene interface, presumably to relieve stress due to the difference in the unit cell sizes of the two phases. 

Figure 8.49. Microstructure of an orthopyroxene from the Siilwater Complex showing large (100) augite lamellae A, intermediate phase B, and a fine distribution of platelets that nucleated homogeneously. (From Champness 1977.)...

Ureilites contain a variety of trace accessory phases. Metallic spherules composed of cohenite, metal, and sulfide are included in olivine and pigeonite of a few ureilites, and metal, phosphide, and sulfide are present as interstitial phases in most. The interstitial regions also commonly contain fine-grained silicates, including low-calcium pyroxene, augite and Si-Al-alkali glass. 

Northwest Africa Oil (NWA 011) has briefly been described by Afanasiev et al. (2000) and more extensively by Yamaguchi et al. (2002), the source of most information presented here. NWA Oil is composed of relatively coarse, anhedral pigeonite and augite, and fine-grained, mostly interstitial plagioclase with a recrystallized texture, interpreted to indicate that it is a recrystallized breccia. Minor phases are silica, chromite, ilmenite, calcium phosphate, ferroan olivine, troilite, and baddeleyite. Pyroxenes make up... 

The olivine- Grove et al. (1982, 1983) developed a projection scheme to present low-pressure clinopyroxene- experimental data for andesites in which the phases pkgioclase, olivine, augite, silica projection pigeonite and orthopyroxene are present. The diagram is useful for caJc-alkali series of Grove et al. rocks but may not be applicable for low-alkali-silica-rich suites. The projection (1982) scheme is similar to that of Walker et al. (1979) for tholeiitic basalts. It is based upon a modification of the CMAS projection in which wt% oxide values are converted to molecular proportions, alkalis and alumina are converted to NaO g 5j, K0 0 5] and AlO j, and the mineral components are calculated as molecular proportions as follows ... 

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