The Petrogenetic Significance of the Contact Relationships of the Donegal Granite in Gweedore and Cloghaneely

Whitten, E. H. Timothy

doi:10.1017/s0016756800068278

Cited by 5 publications

(2 citation statements)

References 12 publications

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“…progressive basification toward wall rocks is generally ascribed to cooler host rocks at the time of intrusion and the magmas response of crystallizing its most basic composition first (e.g. Vance 1961;Lipman 1963;MacColl 1964;Whitten 1957Whitten . 1959Whitten , and 1961.…”

Section: Introductionmentioning

confidence: 99%

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Zonal structure of the Perth Road monzonite, Grenville Province, Ontario

Ermanovics¹

1970

Can. J. Earth Sci.

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The Perth Road pluton is a lenticular, grossly conformable body emplaced in metasedimentary rocks of the Grenville series during a period in which the enclosing gneisses deformed by plastic flow. The body is zoned and from the center outward comprises gabbro, diorite, monzonite (the dominant rock-type), quartz monzbnite, and granite. The change from one rocktype to the next is gradual and the progressive acidification toward all the contacts, without regard to the type of enclosing gneiss, is taken as an indication of cogenesis of the plutonic assemblage; modal mineral variations of quartz, alkali-feldspar, plagioclase, and color index demonstrate this mineral progression.The enclosing crystalline metasedimentary rocks have been metamorphosed to the hornblende granulite facies, and although recrystallization has kept pace with deformation some cahclasis pervades all rocks. The pluton occupies a flattened crestal position of a doubly plunging fold, and all folds show a combination of fold-styles depending on the relative competence of the various rock-types. Flow models demonstrate that Ihe early magmatic precipitates collected in regions of maximum velocity of the magma during folding of the enclosing envelope of gneisses and that syntectonic differentiation in this manner obtains for the Perth Road and other plutons in the area.

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Section: Introductionmentioning

confidence: 99%

“…Vance 1961;Lipman 1963;MacColl 1964;Whitten 1957Whitten . 1959Whitten , and 1961. Alternatively, basification; by viitue of loss'of alkalies and silica into the wall rock (e.g.…”

Section: Introductionmentioning

confidence: 99%

Zonal structure of the Perth Road monzonite, Grenville Province, Ontario

Ermanovics¹

1970

Can. J. Earth Sci.

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Rb‐Sr isochron study of the Thorr and Main Donegal Granites, Ireland

et al. 1982

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A Rb-Sr whole-rock isochron study indicates that the entire Donegal granite suite was emplaced into orthotectonic Caledonian (Dalradian) rocks over a short interval during mid-Silurian to earliestDevonian times. The Thorr pluton, probably the earliest member of the suite, yields an age of 418 f 26 Myr and initial 87Sr/86Sr ratio of 0.7055 f 4, while the latest member, the Main Donegal pluton has an age of 407 i 23 Myr and initial g7Sr/86Sr ratio of 0.7063 f 5 (P'Rb = 1.42 x lo-" y-').Errors on both the age and initial Sr isotope ratios incorporate both a prion' and geological scatter components and are quoted at the 2-sigma level. The low and restricted range of initial Sr isotope ratios suggests small but significant differences in the composition of the parental granitic magmas which were derived from a low RWSr, low "Sr/86Sr source.

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Composition trends in a granite: Mmodal variation and ghost stratigraphy in part of the Donegal granite, Eire

Whitten¹

1959

J. Geophys. Res.

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Modal variation of quartz, color index, (potash feldspar/plagioclase), and total feldspar within a 25 square mile area of the ‘older granite’ of Donegal was analyzed on the basia of 71 specimens. Non‐orthogonal polynomial analysis was used to compute linear and quadratic trend surfaces and deviations for each variable. The IBM 650 was used for all computations. Each variable behaved differently. Single modes gave excellent trend surfaces for color index, whereas averaging data within each square mile sometimes masked important residuals. Realistic trend surfaces for quartz or total feldspar were only derived from averaged data. With averaged data the four linear trend surfaces have almost parallel strikes, and such uniform regional trends have significance in the interpretation of geological gradients in relation to the petrogenesis of the granite. Some deviations have been linked to observed geologic factors. Other deviations are consistent for all variables. These deviations reflect ghost stratigraphy; the latter group indicate ghost stratigraphy previously unsuspected in this area which is harmonious with the well‐known regional picture.

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The Petrogenetic Significance of the Contact Relationships of the Donegal Granite in Gweedore and Cloghaneely

Cited by 5 publications

References 12 publications

Zonal structure of the Perth Road monzonite, Grenville Province, Ontario

Zonal structure of the Perth Road monzonite, Grenville Province, Ontario

Rb‐Sr isochron study of the Thorr and Main Donegal Granites, Ireland

Composition trends in a granite: Mmodal variation and ghost stratigraphy in part of the Donegal granite, Eire

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