Some topological relationships in multisystems of n+3 phases; [Part] 2, Unary and binary metastable sequences

We describe strain localization by a mixed process of reaction and microstructural softening in a lower greenschist facies ductile fault zone that transposes and replaces middle to upper amphibolite facies fabrics and mineral assemblages in the host schist of the Littleton Formation near Claremont, New Hampshire. Here, Na-poor muscovite and chlorite progressively replace first staurolite, then garnet, and finally biotite porphyroblasts as the core of the fault zone is approached. Across the transect, higher grade fabric-forming Na-rich muscovite is also progressively replaced by fabric-forming Napoor muscovite. The mineralogy of the new phyllonitic fault-rock produced is dominated by Na-poor muscovite and chlorite together with late albite porphyroblasts. The replacement of the amphibolite facies porphyroblasts by muscovite and chlorite is pseudomorphic in some samples and shows that the chemical metastability of the porphyroblasts is sufficient to drive replacement. In contrast, element mapping shows that fabric-forming Na-rich muscovite is selectively replaced at high-strain microstructural sites, indicating that strain energy played an important role in activating the dissolution of the compositionally metastable muscovite. The replacement of strong, high-grade porphyroblasts by weaker Na-poor muscovite and chlorite constitutes reaction softening. The crystallization of parallel and contiguous mica in the retrograde foliation at the expense of the earlier and locally crenulated Na-rich muscovite-defined foliation destroys not only the metastable high-grade mineralogy, but also its stronger geometry. This process constitutes both reaction and microstructural softening. The deformation mechanism here was thus one of dissolution-precipitation creep, activated at considerably lower stresses than might be predicted in quartzofeldspathic rocks at the same lower greenschist facies conditions. AnalysisSamples were analysed at Indiana University using a Bruker D8 diffractometer fitted with a Sol-X energy-

Section: Scale Of Equilibrationmentioning

confidence: 99%

Reaction softening by dissolution–precipitation creep in a retrograde greenschist facies ductile shear zone, New Hampshire, USA

McAleer

Bish

Kunk

et al. 2016

“…As we know, any equilibrium assemblage, being either invariant, univariant, or divariant, has different levels of stability or metastability (Kujawa & Eugster, 1966;Zen, 1967). In a real phase diagram or a more abstract closed-netdiagram, we can determine those assemblages that appear in each field on different levels of metastability by extending the stable portions of univariant lines.…”

Section: N ! K !mentioning

confidence: 99%

“…In a real phase diagram or a more abstract closed-netdiagram, we can determine those assemblages that appear in each field on different levels of metastability by extending the stable portions of univariant lines. One of the typical examples was exhibited by Zen, who constructed unary and binary n + 3 phase multisystem closed nets showing every level of metastability of univariant lines (Zen, 1967, fig. 3 and fig.…”

Section: N ! K !mentioning

confidence: 99%

See 1 more Smart Citation

Topological relations in multisystems of more than n+ 3 phases ¹

Guo

1984

Multisystems of n + k ( k > 3) phases are very complicated and knowledge of them has suffered as a result. The successful solution of the topological relationships in n + 3 phase multisystems ,by Zen (1966, 1967) and Zen & Roseboom (1972) has aroused much interest regarding what will happen in a multisystem of more than n + 3 phases. Since 1979, some important research results on this topic have been published. These results have expounded the substantial rules governing the appearance of phase relations in phase diagrams of n + k ( k > 3) phase multisystems. The most significant conclusions include: ( I ) I t is impossible to incorporate all the possible phase relations in an n + k

“…In past decades, many contributions have been made to the related study of closed nets of multisystems, e.g. Day (1972Day ( , 1976Day ( , 1978, Braun & Stout (1975), Barron & Barron (1977), Burt (1978), Chesworth (1980), Guo (1979Guo ( , 1980aGuo ( ,b,c, 1981aGuo ( ,b, 1984Guo ( , 1985, Cai (1981Cai ( , 1982, Cheng (1983Cheng ( , 1986, , Korzhinskii (1959); Kujava et al (1965), Kujava & Eugster (1966), Zen (1966aZen ( , 1967Zen ( , 1974, Guo & Jin (1980), Mohr & Stout (1980), Wang (1980), Guo & Cai (1982), Guo & Wang (1982), Roseboom & Zen (1982), Vielzeuf & Boivin (1984), Stout (1985Stout ( , 1990, Usdansky (1987Usdansky ( , 1989, , Tan (1990), Stout & Guo (1994), Hu (1998); Kletetschka & Stout (1999), Hu et al (2000), Guy & Pla (2002), Zharikov (1961), Zen & Roseboom (1972), etc. Zen (1966a) proposed the n...…”

Section: Introductionmentioning

confidence: 99%

A new method for the derivation of the closed nets in the phase diagram space of multisystems. I. The absent phase substitution method

Hu¹,

Duan²

2004

A new convenient combinatorial method is developed here to derive the invariant points in multisystem closed nets -the absent phase substitution (APS) method. It substantially simplifies the derivation of the closed nets in multisystems with many components and phases. For the multisystems whose total phase number (N PS ) £ twice the number of the absent phases (m) in an invariant assemblage, the method can yield regular closed nets with or without globally absent phases; for other multisystems, the method can yield the regular closed nets with globally absent phases. As examples, the APS method was used to predict: (1) the regular closed nets of unary to quinary n + 4-phase multisystems, unary 6-phase multisystem and ternary 8-phase multisystem; (2) the basic properties of the regular closed nets of the quaternary and quinary multisystems with n + 4 and n + 5 phases. Two multisystems were chosen to demonstrate how to select a realistic closed net from the numerous possible closed nets of a complex multisystem, and how to derive a realistic partially closed-net, closed-net-diagram and the related realistic straight-line-net-diagram. Comparisons of our APS method for the derivation of complicated closed nets with other methods indicate that this method is much simpler and more efficient.