Oscillatory Epitactic-Growth Zoning in Biotite and Muscovite From the Lake Lewis Leucogranite, South Mountain Batholith, Nova Scotia, Canada

Clarke, D. Barrie; Bogutyn, Patrick A.

doi:10.2113/gscanmin.41.4.1027

Cited by 33 publications

(18 citation statements)

References 42 publications

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“…Clarke and Bogutyn 2003). In the case of miaroles from El Portezuelo Pluton, the very fine scale of the zoning would imply many cycles of pressure build-up and release.…”

Section: The Evolution Of the Granite-pegmatite System: Inferences Frmentioning

confidence: 99%

Mineralogy and crystal chemistry of micas from the A-type El Portezuelo Granite and related pegmatites, Catamarca (NW Argentina)

Colombo¹,

Lira²,

Dorais³

2012

J. Geosci.

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The A-type El Portezuelo Pluton (Catamarca, NW Argentina) is parental to an intragranitic suite of pegmatites of NYFtype affiliation (miarolitic class, miarolitic-rare earth element subclass, with features more similar to those reported for the gadolinite-fergusonite type). This study was performed on samples from the host granite and several zones of pegmatites, including crystals growing in miarolitic cavities and fine-grained overgrowths. Micas from the granite and massive pegmatites are rather homogeneous, but crystals coming from miarolitic cavities are usually sharply zoned with monocrystalline trioctahedral inner zones overgrown by polycrystalline dioctahedral rims. Dioctahedral micas are always paragenetically later. Micas from the granite are intermediate members of the annite-siderophyllite series. From the outer pegmatite zones inwards the substitution (SiLi)( Si)([4] Al [6] Al) -1 , where R 2+ = Fe, Mg, Mn; there is a compositional gap between dioctahedral and trioctahedral micas. Zoned individual crystals have trioctahedral cores enriched in Fe, Mn and F; Na, Li and Ti are usually also enriched in the cores, whereas Mg is usually depleted compared with the dioctahedral rims. Micas in El Portezuelo are the most important F-bearing species (for their elevated F contents and their modal abundance) and they also have a major role in the distribution of Li and Rb. The overall evolutionary trend is very similar to that found at the Pikes Peak Batholith (Colorado USA) and is characteristic of NYF-type granite-miarolitic pegmatite systems.

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“…Clarke and Bogutyn 2003). In the case of miaroles from El Portezuelo Pluton, the very fine scale of the zoning would imply many cycles of pressure build-up and release.…”

Section: The Evolution Of the Granite-pegmatite System: Inferences Frmentioning

confidence: 99%

Mineralogy and crystal chemistry of micas from the A-type El Portezuelo Granite and related pegmatites, Catamarca (NW Argentina)

Colombo¹,

Lira²,

Dorais³

2012

J. Geosci.

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“…The K/Rb ratio of micas, together with the content in Li or F and some trace elements such as Cs, Sn, Ba, and Zn, have been used frequently as petrogenetic indicators of the degree of pegmatite evolution (e.g., Gaupp et al 1984;Foord et al 1995;Wise 1995;Roda et al 1995Roda et al , 2006Roda et al , 2007aRoda et al , 2007bKile and Foord 1998;Clarke and Bogutyn 2003;Černý 2004). In general, micas show the same general evolutionary trends as those of feldspars, with an increase in Li, Rb, Cs, and F and a decrease in Ba with decreasing K/Rb ratio.…”

Section: Petrogenetic Implicationsmentioning

confidence: 99%

Chemical variation and significance of micas from the Fregeneda-Almendra pegmatitic field (Central-Iberian Zone, Spain and Portugal)

Vieira

Roda-Robles

Pesquera

et al. 2011

American Mineralogist

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Field, textural, paragenetic, and chemical data for micas from pegmatites of the Fregeneda-Almendra pegmatitic field (Central-Iberian Zone) are used to characterize and evaluate their petrogenesis. These pegmatites show a zonal distribution from barren to evolved, with an increase in degree of evolution with increasing distance from the Mêda-Penedono-Lumbrales leucogranite. Five types of evolved pegmatites have been recognized: (1) petalite-rich, (2) spodumene-rich, (3) Li-mica + spodumenerich, (4) Li-mica-rich, and (5) cassiterite-rich pegmatites, plus six types of barren and intermediate pegmatites. Representative micas from the different pegmatite types and from the leucogranite were analyzed for major and trace elements. All micas belong to the muscovite-lepidolite series. Lithium is incorporated into Li-micas via the Li 3 Al -1 o -2 and Si 2 LiAl -3 substitutions, where o represents vacancies. The Al 4 Si -3 o -1 and Al 2 o 1 R 2+ -3 substitutions, where R 2+ = (Fe + Mg + Mn), account for the compositional variability of micas from the Li-mica-free pegmatites. The Li, Rb, Cs, Be, Ta, and Nb contents of micas increase in the order: leucogranites and barren pegmatites < intermediate pegmatites < spodumene-bearing and petalite-bearing dikes < Li-mica-bearing pegmatites. The Ba content decreases in the same order, and Sn and Zn are relatively abundant in the intermediate pegmatites.These variations are consistent with rare-element enrichment via fractionation processes combined with partitioning of rare elements from the pegmatite melt into the minerals and volatile phases. However, some pegmatite types occurring in this area, such as the cassiterite-rich dikes, do not seem to form part of the same evolutionary trend.

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“…These inclusions resemble rare melt inclusions in peralkaline rhyolites from the Pantelleria Island, Italy, described by Naumov et al (1987). Further examples of granites with "abnormally" high water concentration in the melt inclusions were found in the Precambrian Kymi granite, Finland (Lukkari et al 2009) and in the Lake Lewis Leucogranite in the South Mountain Batholith, Nova Scotia, Canada (Clarke and Bogutyn 2003). The last example is interesting, because the primary melt inclusions in the granite quartz were generally partially decrepitated during the structural uplift on the way to the intrusion level.…”

Section: Melt Inclusions In Granitic Rocksmentioning

confidence: 98%

The missing link between granites and granitic pegmatites

Thomas¹,

Davidson²

2013

Jour. Geosci.

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In this contribution we provide evidence for the extraction of volatile and incompatible element enriched melts from common granites. This provides a mechanism showing that at least a large proportion of granitic pegmatites could be genetically directly connected to a main granite body. In granites there are often two principal types of melt inclusions: (i) those that represent the bulk chemistry of the granite and (ii) those with very different compositions. In the Variscan Erzgebirge granites, the second type is characterized by the abundance of fluorine. However, in other geodynamic settings inclusions in granites can contain high concentrations of other elements which may take over the function of fluorine. From textural relationships the second inclusion type represents intergranular melts enriched in all elements incompatible with the ideal haplogranite system. Due to the high volatile content of such melts, the viscosity can be several orders of magnitude lower than the quasi-solid bulk system and can therefore move rapidly through the partially or totally crystallized host, and flow together into a separate system forming pegmatite bodies inside or outside the granite body. Another important effect of the high volatile content is the phase separation resulting from the speciation changes OH -→ H 2 O or CO 3 2-→ CO 2 due to temperature and/or pressure changes at different locations within the granite-intergranular melt system. Since melt inclusions provide a means of conserving original un-degassed compositions, they yield important evidence for closing the gap between granites and granitic pegmatites. The paper is dedicated to two Czech colleagues -Petr Černý and Milan Novák -who have devoted their lives to the study of granitic pegmatites.

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Oscillatory Epitactic-Growth Zoning in Biotite and Muscovite From the Lake Lewis Leucogranite, South Mountain Batholith, Nova Scotia, Canada

Cited by 33 publications

References 42 publications

Mineralogy and crystal chemistry of micas from the A-type El Portezuelo Granite and related pegmatites, Catamarca (NW Argentina)

Mineralogy and crystal chemistry of micas from the A-type El Portezuelo Granite and related pegmatites, Catamarca (NW Argentina)

Chemical variation and significance of micas from the Fregeneda-Almendra pegmatitic field (Central-Iberian Zone, Spain and Portugal)

The missing link between granites and granitic pegmatites

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