2. REPLACEMENT OF PRIMARY PLAGIOCLASE BY SECONDARY …
replacement of primary plagioclase by secondary microcline and myrmekite occur. Cathodoluminescent images were made by Karl Ramseyer in Switzerland. Temecula, California (USA). Fig. 1. This photo shows a cathodoluminescent image of a normally zoned plagioclase crystal where the host diorite is only slightly deformed. Relatively
Myrmekite - Wikipedia
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.
Replacement of primary plagioclase by secondary k-feldspar ...
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.
37. Overlooked experimental evidence for K-replacements of ...
Nevertheless, using the experimental studies of Orville (1962), 1963), Collins demonstrated reasons why the secondary origin for K-feldspar by replacement of plagioclase is possible and expected. Applications of experiments to geologic terranes
37. Overlooked experimental evidence for K-replacements of ...
why the secondary origin for K-feldspar by replacement of plagioclase is possible and expected. Applications of experiments to geologic terranes The application of the overlooked experiments by Wyart and Sabatier (1956), which show that triclinic microcline is formed directly by K-metasomatism of plagioclase, is far reaching.
Hydrothermal alteration of plagioclase and growth of ...
May 30, 2002 · Replacement of igneous plagioclase by K-feldspar rather than Na-feldspar is occasionally seen . The intensity of alteration is in general high although a trace of relict igneous plagioclase was analysed in all samples except in samples from 1300 and 1700 m.
Impact-induced replacement of plagioclase by K-feldspar in ...
Nov 16, 2005 · SEM, EDS and EPMA studies reveal that the main secondary minerals are orthoclase, replacing plagioclase in granites and amphibolites, and chlorite, replacing hornblende in amphibolites. The extent of stone and mineralogical alteration is closely related to microfractures. However, alteration has selectively changed the minerals.
The replacement of plagioclase feldspars by albite ...
Jun 24, 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.
The replacement of plagioclase feldspars by albite ...
The replacement of plagioclase feldspars by albite: observations ... albitisation and secondary ore mineralisation which is common in nature. ... primary mechanism of mineral replacement reactions in the presence of a fluid phase (Putnis 2002). Recently, several
42. A study of intergrowth textures and their possible ...
replacement of plagioclase by K-feldspar, (4) replacement of plagioclase by quartz, (5) growth of blastic plagioclase around residual, recrystallized quartz, (6) exsolution of myrmekite from a high-temperature K-feldspar, and (7) combinations
Hydrothermal alteration of plagioclase in granitic rocks ...
Apr 28, 2020 · K-feldspar is partly or completely replaced by myrmekite-like quartz-plagioclase intergrowths (QPI) and primary plagioclase by secondary, quartz-free plagioclase.
20. FAILURE OF THE EXSOLUTION SILICA-PUMP MODEL FOR …
deformed rocks where incomplete interior replacement of plagioclase by secondary K-feldspar occurs (see presentations 1, 2, and 3 in this web site). The K needed to form this secondary K-feldspar is readily available from coexisting, deformed, abundant biotite that is replaced by quartz.
Hydrothermal anorthitization of plagioclase within the ...
Oct 01, 1998 · Most primary plagioclase in the vein halos is completely replaced by secondary plagioclase, except near the outer edge of halos where the replacement is incomplete. Secondary cathodoluminescent plagioclase varies from An 55 to An 78 , which is considerably more calcic than the secondary feldspars reported previously for the sheeted dikes of Oman [34] .
10. K- AND Si-METASOMATISM IN THE DONEGAL GRANITES …
of twinning, and interior replacement of plagioclase by undeformed K-feldspar occur (Hall, 1966). 5. Myrmekite. All Donegal granites containing K-feldspar also contain myrmekite. The interior replacement features of primary plagioclase by secondary K-feldspar accompany myrmekite formation and are observed in zones of gradation from
Geochemistry, Mineralization and Alteration Zones of ...
Primary minerals show zones replace large part of plagioclase and sometimes associated with white micas composition. Igneous biotite is replaced by secondary biotite which crystallizes in …
(PDF) A study of intergrowth textures and their possible ...
Formation of flame perthite can be explained by replacement reaction mechanism (Na-K exchange) between K-feldspar and plagioclase under low to moderate differential stress condition during rapid ...
(PDF) 56. Origin of myrmekite as it relates to K-, Na ...
Where secondary K-feldspar forms b y K-metasomatism of primar y plagioclase, Ca, Na, and some Al are extracted from the plagioclase silicate lattice prior to the introduction of K to form K-f eldspar.