2. REPLACEMENT OF PRIMARY PLAGIOCLASE BY SECONDARY …
2. REPLACEMENT OF PRIMARY PLAGIOCLASE BY SECONDARY K-FELDSPAR AND MYRMEKITE Lorence G. Collins email: [email protected] November 21, 1996; revised February 17, 1997 The following illustrations in this presentation show four photomicrographs of cathodoluminescent images, two black-and-white scanning electron microscope
Myrmekite - Wikipedia
L.G. Collins explains the formation of myrmekite by: the K-metasomatic replacement of deformed primary plagioclase by secondary K-feldspar; different varieties of Ca- and Na-Ca-metasomatism acting mainly upon deformed primary alkali feldspar, an exception being the replacement of deformed plagioclase in anorthosite. See also. Granophyre
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Myrmekite formation at Temecula, California, revisited: A photomicrographic essay illustrating replacement textures ... This parallelism strongly suggests that the microcline is not primary orthoclase that inverted to microcline but is secondary replacement microcline that has ... 1997b, Replacement of primary plagioclase by secondary K ...
Replacement of primary plagioclase by secondary k ... - CORE
Abstract. The following illustrations in this presentation show four photomicrographs of cathodoluminescent images, two black-and-white scanning electron microscope images, and six photomicrographs of thin sections in which various stages of replacement of primary plagioclase by secondary microcline and myrmekite occur.
Hydrothermal alteration of plagioclase and growth of ...
May 30, 2002 · (b) In a sample from 800 m, the igneous plagioclase is less zoned and the appearance of secondary feldspar can be confirmed (five fragments analysed). (c) Analyses of sample from 2000-m depth show three compositional clusters representing igneous plagioclase, secondary Na …
Becker, K., Sakai, H., et al., 1989 Proceedings of the ...
The effect of alteration is recognized as the partial or total replacement of primary minerals (olivine, clinopyroxene, and Plagioclase) by secondary minerals and as the development of secondary minerals in open spaces (e.g., veins, frac tures, vugs, or breccia matrix).
K-, Na-, and Ca-metasomatism characteristics of ...
Where secondary K-feldspar forms by K-metasomatism of primary plagioclase, Ca, Na, and some Al are extracted from the plagioclase silicate lattice prior to the introduction of K to form K-feldspar.
Phyllic alteration and the implications of fluid ...
Primary K-feldspars are white to vitreous gray (Fig. 2a), whereas the secondary K-feldspars are white or pink and turbid (Fig. 2b). Prior to this study, two periods of phyllic alteration, referred to as pre-brecciation and post-brecciation phyllic alteration, were described by Dunn (1982).
SECONDARY MINERALS - Ocean Drilling Program
Clay minerals are ubiquitous and are the most abundant secondary products, present in all four modes discussed above. Clay minerals were determined optically, following the criteria of Honnorez et al. (1983) and Laverne et al. (1996), by XRD data, including those of air-dried and glycolated powder mounts, and by microprobe quantitative and semiquantitative analyses.
(PDF) Hydrothermal replacement of feldspars in igneous ...
K-feldspar is partly or completely replaced by myrmekite-like quartz-plagioclase intergrowths (QPI) and primary plagioclase by secondary, quartz-free plagioclase. Both types of secondary ...
myrmekite : definition of myrmekite and synonyms of ...
L.G. Collins explains the formation of myrmekite by: the K-metasomatic replacement of deformed primary plagioclase by secondary K-feldspar; different varieties of Ca- and Na-Ca-metasomatism acting mainly upon deformed primary alkali feldspar, an exception being …
EVIDENCE FROM SECONDARY MINERALS FOR THREE STAGES …
Primary plagioclase has compositions from endmember anor-thite to endmember albite. Through the type 3 se-quence (3.0-3.9), secondary plagioclase becomes in-creasingly abundant in chondrules as it crystalizes from mesostasis glass [2]. The composition of secondary plagioclase generally follows the composition of the
The replacement of plagioclase feldspars by albite ...
The replacement of plagioclase feldspars by albite: observations from hydrothermal experiments ... primary mechanism of mineral replacement reactions in the presence of a fluid phase (Putnis 2002). Recently, several ... the replacement of plagioclase by albite occurs via an
Hydrothermal alteration of plagioclase in granitic rocks ...
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.
Fabric and origin of gneissic layers in anorthositic rocks ...
The gneissosity is defined by a dimensional preferred orientation of biotite, hornblende, and secondary plagioclase. The formation of the secondary plagioclase is attributed largely to growth by stone boundary diffusion and, to a lesser extent, by replacement of primary plagioclase by stone boundary migration.
Impact-induced replacement of plagioclase by K-feldspar in ...
Impact-induced replacement of plagioclase by K-feldspar in granitoids and amphibolites at the Kärdla Crater, Estonia. Authors; Authors and affiliations ... in addition to medium- to coarse-grained microcline present in primary rocks. SEM, EDS and EPMA studies reveal that the main secondary minerals are orthoclase, replacing plagioclase in ...
Impact-induced replacement of plagioclase by K-feldspar in ...
Impact-induced replacement of plagioclase by K-feldspar in granitoids and amphibolites at the Kärdla Crater, Estonia: ... in addition to medium- to coarse-grained microcline present in primary rocks. SEM, EDS and EPMA studies reveal that the main secondary minerals are orthoclase, replacing plagioclase in granites and amphibolites, and ...
The Petrology and Diagenetic History of the Phacoides ...
Precipitation of carbonates and clays, rearranging of broken grains, and formation of pseudomatrix reduced primary porosity. Secondary porosity is common and formed initially by the dissolution of plagioclase (excluding albite) and volcanic fragments, and later by dissolution of calcite, dolomite, and detrital K-feldspars.
Plagioclase - Wikipedia
Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific stone composition, plagioclase is a continuous solid solution series, more properly known as the plagioclase feldspar series (from the Ancient Greek for "oblique fracture", in reference to its two cleavage angles).