2. REPLACEMENT OF PRIMARY PLAGIOCLASE BY SECONDARY K ...
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
In the second variety Na- and Ca-bearing fluids truly act together. This leads via the replacement of primary K-feldspar (perthitic and non-perthitic microcline) to the formation of plagioclase (albite or oligoclase) and in certain places also to the formation of myrmekite.
42. A study of intergrowth textures and their possible ...
granodiorites and granites, it may have formed by both K- and Ca-metasomatism. The presence of anti-rapakivi texture (K-feldspar overgrowth on plagioclase) in the same rocks may be related to this process, too. Introduction A brief historical review of intergrowth textures and their possible origins is as follows.
Plagioclase | Technology Trends
Accordingly the texture was created as plagioclase formed by exsolution from alkali feldspar during cooling, under conditions in which silicon was mobile in the rock ... 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 ...
(PDF) Hydrothermal alteration of plagioclase in …
Hydrothermal alteration of plagioclase in granitic rocks from Proterozoic basement of SE Sweden. ... BSE image showing albitized plagioclase in which replacement by K-feldspar proceeded inward. (D) ... Electron microprobe analyses of primary and secondary feldspars …
(PDF) Hydrothermal alteration of plagioclase and …
In samples where secondary feldspar is more coarse grained or more abundant, three di¡erent compositional clusters are resolved, representing true composi- tions of primary plagioclase, secondary Na-feld- spar and K-feldspar (Fig. 5c).
17. THE MOBILITY OF IRON, CALCIUM, MAGNESIUM, AND …
replacement of relatively-calcic plagioclase by K-feldspar, myrmekite, and more-sodic plagioclase in the igneous wall rocks (Collins, 1988) would have mobilized both Ca and Al that could have moved to this epidote zone or into the aforesaid epidote veins. (d) Replacement of biotite by muscovite is a fourth indication of the mobility of Al.
Hydrothermal alteration of plagioclase and growth …
(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-rich plagioclase and K …
The replacement of plagioclase feldspars by albite ...
24-6-2009 · Mineral replacement reactions in nature are commonly associated with fluid–rock interaction and metasomatism (Putnis 2002). The replacement of alkali and plagioclase feldspars by albite is a prevalent phenomenon in the Earth’s upper crust.
Impact-induced replacement of plagioclase by K …
Impact-induced replacement of plagioclase by K-feldspar in granitoids and amphibolites at the Kärdla Crater, Estonia. Authors; ... EDS and EPMA studies reveal that the main secondary minerals are orthoclase, replacing plagioclase ... Impact-induced replacement of plagioclase by K-feldspar in granitoids and amphibolites at 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, ... the replacement of plagioclase by albite occurs via an
「Plagioclase」の共起表現(1語右で並び替え) - …
plagioclase- and pyroxene-phyric andesite-basalt lavas (ndant feldspathoids (nepheline or leucite), plagioclase, and augite, together with olivine and less: metasomatic replacement of deformed primary : plagioclase by secondary K-feldspar: ufficiently present so that a fairly calcic : plagioclase can be formed which in turn releases enough
Plagioclase - Wikipedia
Plagioclase series members. The composition of a plagioclase feldspar is typically denoted by its overall fraction of anorthite (%An) or albite (%Ab), and readily determined by measuring the plagioclase crystals refractive index in crushed stone mounts, or its extinction angle in thin section under a …
Impact-induced replacement of plagioclase by K …
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 ...
Replacement of pyroxene by hornblende, …
Lithos, 17 (1984) 247-258 247 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands Replacement of pyroxene by hornblende, isochemically balanced with replacement of plagioclase by garnet, in a metagabbro of upper-amphibolite grade H.W. BARINK Institute of Earth Sciences, Free University, De Boelelaan 1085, 1007 MC Amsterdam ...
A dissolution-reprecipitation mechanism for the ...
Pseudomorphous replacement is replacement in which a secondary mineral inherits some combination of external and/or internal morphological and textural features of the primary mineral it replaces (e.g., crystal form, inclusions). The mechanism by which this kind of replacement occurs, however, is not clear.
(PDF) Hydrothermal alteration of plagioclase in …
Barium is an important component in replacement of plagioclase by K-feldspar were hydrothermal systems, and Ba-feldspar (celsian) can thus strongly controlled by the mineralogical composition form solid solution with orthoclase in secondary K-feldspar of …
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Geochemistry, Mineralization and Alteration Zones …
Geochemistry, Mineralization and Alteration Zones of Darrehzar Porphyry ... Ca, Mn and Fe took place. These changes attended replacement of plagioclase and amphibole by K-feldspar and ... The primary and secondary alterations in granodiorite stock are represented by potassic mineral assemblages developed pervasively and ...
The mineralogical characteristics of the hydrothermal ...
volcanic rocks. The potassic alteration, characterized by the replacement of the primary minerals with secondary biotite, K-feldspar, sericite is associated with sulphides (pyrite, chalcopyrite) and magnetite. This mineral assemblage suggests the presence of a “porphyry copper” system. The potassic feldspar substitutes the plagioclase.