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2. Replacement Of Primary Plagioclase By Secondary K-feldspar And Myrmekite. 3. Microscopic And Megascopic Relationships For Myrmekite-bearing Granitic Rocks Formed By K-metasomatism. 4. Myrmekite Formed By Ca-metasomatism. 5. Myrmekite Formed By Exsolution? 6. Myrmekite As A Clue To Metasomatism On A Plutonic Scale; Origin Of …
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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 ...
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1) and (b) where broken plagioclase crystals are surrounded by the K-feldspar so that plagioclase islands are created in parallel optic continuity with the adjacent, larger, unbroken plagioclase crystal (Appendix: Microfracturing, Figures 12 and 18). In early stage of K-feldspar replacement of plagioclase, the K-feldspar occurs
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The hydrothermal minerals occur as replacement minerals on most primary This mineral was found in well TR2 Most of the plagioclase Primary and secondary30/09/2011· Primary vs Secondary Succession "Succession" is a series of complex processes taking place in the environment due to various driving forces governed by Difference Between Primary ...
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Oligoclase and labradorite crystals have been experimentally replaced by albite in an aqueous sodium silicate solution at 600°C and 2 kbars. The replacement is pseudomorphic and is characterised by a sharp chemical interface which progresses through the feldspar while preserving the crystallographic orientation. Reaction rims of …
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There is a clear progression of alteration modes from replacement of calcic plagioclase by sodalite/scapolite in subtypes 3.2–3.6, nephelinization in subtypes 3.4–3.9, to albitization in types 3.6–5. ... Starting at about petrologic type 3.6, replacement of primary and secondary calcic plagioclase, formed from the devitrification of ...
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For example, replacement of the Cpx schists by Na-rich plagioclase and hornblende was induced by Na-rich fluid infiltration from the pegmatites at 690–730°C and 0.30–0.45 GPa, which caused gains of Na 2 O (0.83%) and H 2 O (0.30%) and loss of CaO (3.17%) for every 100 g of unaltered wall rock . The dissolution of An-rich plagioclase is ...
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1. Origin Of Myrmekite And Metasomatic Granite. 2. Replacement Of Primary Plagioclase By Secondary K-feldspar And Myrmekite. 3. Microscopic And Megascopic Relationships …
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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 ...
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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
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The minerals replaced hetero-orientedly by K-feldspathization are mainly plagioclase and K-feldspar. 1.1.2.1 K-feldspar Hetero-Orientedly Replaces …
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REPLACEMENT OF PRIMARY PLAGIOCLASE BY SECONDARY K-FELDSPAR AND MYRMEKITE Lorence G. Collins email: lorencec@sysmatrix November 21, 1996; revised February 17, 1997 …
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of secondary plagioclase (2.63) relative to the lesser density of K-feldspar (2.56) requires that silica cannot be released but is consumed in forming the secondary plagioclase that fills the space once occupied by the K-feldspar. Thus, although the balanced mass-for-mass equations appear to be quite logical, they cannot be used
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introduced K begins to recrystallize in the plagioclase lattice as a K-feldspar, the residual Si and Al atoms become re-ordered, distorting the lattice and producing the gridiron twinning characteristic of microcline. In that way, primary triclinic microcline is formed naturally from the primary triclinic plagioclase rather than by
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This parallelism strongly suggests that the microcline is not primary orthoclase that inverted to microcline but is secondary replacement microcline that has inherited its lattice from a former altered ... Collins, L. G., 1997b, Replacement of primary plagioclase by secondary K-feldspar and myrmekite: Myrmekite, ISSN 1526-5757 ...
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The following illustrations in this presentation show four photomicrographs of cathodoluminescent images, two black-and-white scanning electron microscope images, …
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REPLACEMENT OF PRIMARY PLAGIOCLASE BY SECONDARY K- FELDSPAR AND MYRMEKITE Lorence G. Collins email: 103725.3674@compuserve It is recommended that you read the previous presentation before proceeding.. The following illustrations show four photomicrographs of cathodoluminescent images, two black-and-white scanning …
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We describe the details of mineral assemblages, textural relations, and chemical compositions of primary tourmaline and individual secondary minerals after tourmaline and other associated minerals (plagioclase, quartz) to reveal replacement reactions, PTX conditions of alteration processes, geochemical signature and sources of …
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The secondary, nearly pure albite (Ab ~ 99 mol.%) with weak to dark-brown cathodoluminescence replaces primary plagioclase (~ An 37–50 Ab 47–58 Or 2–4) along the cleavage and/or twinning planes during Al 3+ –conservative reaction. The accessory apatite is marked by swallow-tail terminations indicative of rapid cooling formation …
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Myrmekite, an intergrowth of plagioclase and quartz vermicules, often occurs in felsic-to-intermediate, calc-alkalic plutonic and gneissic rocks. Several hypotheses for myrmekite genesis are briefly reviewed and discussed. The proportional relationship between the volume of quartz vermicules and the An value of plagioclase is consistent with the …
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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 …
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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.
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The fluid was probably also enriched in CO 2 and reaction between the fluid and Ca-rich plagioclase lead to the formation of secondary calcite and small calcite veins (see Section 2.1).
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The syenite porphyry samples LJ-37 and ST-11-5 close to orebodies show obvious signs of potassic alteration, reflected mainly by the replacement of primary perthite by secondary K-feldspar. Table 2 presents scanning electron microscope EDS analyses of primary and secondary K-feldspars. Discordant two-feldspar temperatures between …
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This difference suggests that Ca is lost from the primary high-grade gneisses and granodiorite of the pluton during orthoclase- and myrmekite-replacement of the plagioclase. The increase of Na from 1.48 wt % Na 2 O in the core granodiorite to 1.66-1.86 wt % Na 2 O in the replaced rocks indicates the retention of some of the Na in …
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K-rich alkali feldspar replacement of plagioclase develops also as anastomosing veinlet networks through primary plagioclase but these spread contrary to the direction of the Na-rich veinlets. These are nucleated in the replaced rims of the phenocrysts that are evident in Fig. 5, Fig. 6 .
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SELECTIVE STAINING of K-FELDSPAR and PLAGIOCLASE on ROCK SLABS and THIN SECTIONS* Eocen H; Igneous Mars: Crust and Mantle Evolution As Seen by Rover Geochemistry, Martian Meteorites, and Remote Sensing; 2. Replacement of Primary Plagioclase by Secondary K-Feldspar and Myrmekite; 26. the Microcline-Orthoclase …
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In samples where secondary feldspar is more coarse grained or more abundant, three different compositional clusters are resolved, representing true …
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Experimental studies show that K replacement of Na in triclinic plagioclase under hydrothermal conditions results directly in triclinic microcline without forming intermediate monoclinic orthoclase. ... L. G., 1996a, Replacement of primary plagioclase by secondary K-feldspar and myrmekite: Myrmekite and Metasomatic Granite, ISSN 1526 …
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