Dislocation formation and albitization in alkali feldspars from the Shap Granite

Lee, Martin; Parsons, Ian

doi:10.2138/am-1997-5-616

Cited by 103 publications

(65 citation statements)

References 29 publications

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“…The former can be named as a 'small type of patch microperthite', according to the nomenclature (Parsons and Brown, 1984;Brown and Parsons, 1994). The typical patch microperthite was described in detail for the alkali feldspar in the Shap granite Lee and Parsons, 1997), and such microperthites may be also common in other granites (Hashimoto et al, 2005a;Yuguchi and Nishiyama, 2007). However, the microperthite of C11 is rather different from those microperthites.…”

Section: C11 Alkali Feldsparmentioning

confidence: 99%

“…'Patch microperthites' in granites are generally thought to be formed by low-temperature hydrothermal (deuteric) interaction (below 400°C ) through dissolution-reprecipitation between feldspar and fluid (Parsons, 1978;Parsons and Brown, 1984;Smith and Brown, 1988;Parsons, 1994, Lee et al, 1995;Lee and Parsons, 1997;Nakano et al, 1997Nakano et al, , 2002Nakano et al, , 2005Nakano, 1998;Deer et al, 2001;Hashimoto et al, 2005a;Parsons and Lee, 2009;Yuguchi and Nishiyama, 2007). Sasaki et al (2003) defined that the hydrothermal convection zone is limited above 3350 m in depth at Kakkonda, and so the C11 alkali feldspar was within hydrothermal convection zone and the C13 alkali feldspar was within the thermal conduction zone.…”

Section: Microperthitic Texture In the C11 Alkali Feldsparmentioning

confidence: 99%

“…In other words, primary plagioclase grains may have been resorbed into plagioclase flakes of irregular and variable shape during the growth of alkali feldspar to form the microperthitic texture during the cooling of the sample C11. On the basis of the cooling environment at Kakkonda (Sasaki et al, 2003), the origin of the bead microperthite in the C11 alkali feldspar may be attributed to hydrothermal coarsening of cryptoperthite to microperthite like the ordinary patch microperthites Lee and Parsons, 1997;Hashimoto et al, 2005a;Parsons and Lee, 2009). The bead microperthite, however, is not associated with the microscopic turbidity that is evidence of hydrothermal recrystallization, and its spotted appearance due to the presence of microscopically larger pores and inclusions is quite different from the well known turbidity (Fig.…”

Section: Microperthitic Texture In the C11 Alkali Feldsparmentioning

confidence: 99%

“…On the contrary, most of alkali feldspars in granites are reorganized to form patch microperthites with pervasive turbidity over a grain (e.g., Lee et al, 1995;Lee and Parsons, 1997;Hashimoto et al, 2005a;Yuguchi and Nishiyama, 2007), although relatively pristine part of cryptoperthite is still few remained Lee and Parsons, 1997). Thus, perthitic textures of alkali feldspars become a very important tool to clarify the cooling histo-ries of host plutons during magmatic to hydrothermal stages (Brown and Parsons, 1994;Parsons and Lee, 2009).…”

Section: Introductionmentioning

confidence: 99%

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Microtexture and compositional variation of alkali feldspars from the Kakkonda granitic pluton, northeast Japan: Implications to the formation processes of granitic texture

Nakano

Sawaki

Sasaki

2014

Journal of Mineralogical and Petrological Sciences

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This paper describes textures and chemical compositions of alkali feldspars to get a clue of the cooling history of the Kakkonda granitic pluton. The Kakkonda pluton of tonalite-granodiorite contains two types of alkali feldspar: one is microperthitic alkali feldspar in the lower-temperature granodiorite of 370°C at the shallower depth (sample C11, 2936-2939 m) and the other is non-microperthitic alkali feldspar in the higher-temperature tonalite over 500°C at the deeper depth (sample C13, 3726-3729 m). The two types of alkali feldspars were examined using an electron microprobe analyzer with an attached cathodoluminescence spectrometer system. The former alkali feldspar is spotted due to microscopic pores and several types of inclusions with microperthitic texture, and the latter is clear and featureless under a microscope. Concentric and/or domain Ba zoning patterns with irregular veins were newly found in both the alkali feldspars. The microperthitic texture in the lower-temperature granodiorite contains two types of Ab-rich plagioclase: one is a bead type of smaller size with rather rounded shape, and the other is a flake type of larger size with irregular shape. The appearance of the microperthitic alkali feldspar is quite different from ordinary patch microperthites with turbidity in granitic rocks described to date. Based on the microperthitic textures and Ba-distribution patterns, resorption of primary plagioclase during the growth of interstitial alkali feldspar might contribute to the formation of the microperthitic alkali feldspar in the granodiorite of C11. Barium-zoning patterns are principally magmatic (C13 alkali feldspar), but they were modified during the formation of microperthite (C11 alkali feldspar) at cooling.

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Section: C11 Alkali Feldsparmentioning

confidence: 99%

Section: Microperthitic Texture In the C11 Alkali Feldsparmentioning

confidence: 99%

Section: Microperthitic Texture In the C11 Alkali Feldsparmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Microtexture and compositional variation of alkali feldspars from the Kakkonda granitic pluton, northeast Japan: Implications to the formation processes of granitic texture

Nakano

Sawaki

Sasaki

2014

Journal of Mineralogical and Petrological Sciences

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“…Fluid-feldspar reactions are the main factor controlling the microtextural evolution of feldspars. Albite that precipitated along microveins through perthite are described by Lee and Parson (1997), who relate their formation to recrystallisation mediated by magmatic fluids and driven by stored elastic energy. Formation of the irregular veins filled by albite, tweed orthoclase and microcline are called unzipping reactions.…”

Section: Fluid-rock Interaction Causing Colour Changementioning

confidence: 99%

Late Pan-African Fluid Infiltration in the Mühlig-Hofmann- and Filchnerfjella of Central Dronning Maud Land, East Antarctica

Engvik

Elvevold

Antarctica

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Abstract. The nunataks of Mühlig-Hofmannfjella and Filchnerfjella in central Dronning Maud Land, East Antarctica, comprise a deepseated metamorphic-plutonic rock complex, dominated by a dark colour due to dark feldspar and containing granulite facies minerals including perthite, plagioclase, orthopyroxene and garnet. The area was affected by a late Pan-African fluid infiltration outcropping as conspicuous light alteration zones restricted to halos around thin granitoid veins. The veins were formed during infiltration of volatile-rich melts, probably originating from underlying magmachambers. The alteration halos were formed by CO 2 -H 2 O-volatiles emanating from the veins into the host rock causing hydration of the granulite facies assemblages. The alteration involves a breakdown of orthopyroxene to biotite and sericitisation of plagioclase at crustal conditions around 350-400°C and 2 kbar. The marked colour change is caused by transformation of feldspars, spread of dusty micas, opaques and fluid inclusions in addition to replacement of coarse to finer grains. The process is locally penetrative indicating that fluid infiltration can affect large rock volumes. The frequent distribution of alteration zones throughout the mountain range independent of lithological variations shows that the fluid infiltration is regionally extensive.

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Hydrothermal alteration of plagioclase in granitic rocks from Proterozoic basement of SE Sweden

et al. 2009

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Petrographic examinations and electron microprobe analyses of Proterozoic granitic rocks, SE Sweden aimed to characterize and unravel the mechanisms and conditions of plagioclase alterations. These alterations include saussuritization, albitization and replacement of plagioclase by K-feldspar. The hydrothermal alterations, which are inferred to have occurred at ca. 250-4008C, resulted in concomitant formation of Alrich titanite, epidote, calcite, pumpellyite, prehnite and iron oxides. Replacement of plagioclase by K-feldspar occurs in red-stained zones, which have developed close to thin fractures owing to the precipitation of tiny Fe-oxide pigment particles within the altered plagioclase, whereas saussuritized plagioclase has less systematic spatial relationships to these fractures. Albitization of plagioclase occurred in rocks that are poor in biotite compared to rocks that suffered extensive saussuritization. The chemical and textural characterization of various types of plagioclase alterations allows elucidation of the granitic hydrothermal systems. Features of feldspar alteration in the granitic rocks are similar to those encountered in feldspathic sandstones and should hence be considered in studies on diagenetic changes of siliciclastic successions during basin evolution.

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Dislocation formation and albitization in alkali feldspars from the Shap Granite

Cited by 103 publications

References 29 publications

Microtexture and compositional variation of alkali feldspars from the Kakkonda granitic pluton, northeast Japan: Implications to the formation processes of granitic texture

Microtexture and compositional variation of alkali feldspars from the Kakkonda granitic pluton, northeast Japan: Implications to the formation processes of granitic texture

Late Pan-African Fluid Infiltration in the Mühlig-Hofmann- and Filchnerfjella of Central Dronning Maud Land, East Antarctica

Hydrothermal alteration of plagioclase in granitic rocks from Proterozoic basement of SE Sweden

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