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Mynydd Mawr Intrusion

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Journal Article
Published: 01 August 1991
Journal of the Geological Society (1991) 148 (4): 703–710.
... that are reset, but also those of the andesites. This shows that resetting is not caused by anything inherent in the rhyolite texture such as devitrification of original glass. Intrusive rocks The Bera Bach microdiorite, the Mynydd Mawr microgran- ite and Gurn Ddu microgranodiorite (Fig. 2 g, j, and m) give ages...
Journal Article
Published: 01 April 1999
Journal of the Geological Society (1999) 156 (2): 301–316.
... eruptive equivalent (see geochemistry section below). One of the best known Lly n intrusions, the Mynydd Tir-y-cwmwd porphyritic granophyric microgranite that forms the oval coastal hill at Llanbedrog (Fig. 1b), is the intrusive equivalent of the Carneddol Rhyolitic TuV Formation. These intrusions are seen...
Journal Article
Published: 01 August 1985
Journal of the Geological Society (1985) 142 (4): 615–624.
... of the unconformity, although, thereafter, grade rises generally towards the north and west. 2. There is approximate concordance between iso- crysts on either side of the trace of the unconformity along much of the northwestern limb of the major Snowdonia Syncline (Roberts 1979), although between Mynydd Mawr and Nant...
Journal Article
Published: 01 September 1985
Journal of the Geological Society (1985) 142 (5): 875–888.
... intrusions post-dating the rhyolite domes have not been proved. The nearby microgranitic pluton of Mynydd Mawr is of Caradoc age (J. Evans, pers. comm.) and has associated sulphide mineralization at its northern margin. Its chemistry is closely comparable to that of the rhyolite domes of the LRTF caldera...
Journal Article
Published: 01 February 1991
Journal of the Geological Society (1991) 148 (1): 5–8.
... of sandstone and Gwyddel Beds in the melange lying immediately above the Braich y Pwll block of Gwyddel Beds on the south flank of Mynydd Mawr (SH 13802550). Harbour Group rocks is parallel to, and indistinguishable from, the anatomosing foliation within the overlying Gwna Group melange. DiPenssion...
Journal Article
Published: 01 September 1988
Journal of the Geological Society (1988) 145 (5): 759–775.
... silicic intrusion (Mynydd Moel Granophyre: Fig. 3). Above this, a major site of eruption developed where thick rhyolitic ash-flow tuffs (Upper Acid Group) were cut by coeval rhyolites. Numerous NNE, NNW, and N-S faults dissect the volcanic rocks here and in the area just to the west (Fig. 3; see Davies...
Journal Article
Published: 01 July 1972
Journal of the Geological Society (1972) 128 (4): 407–420.
... undertaken a number of detailed minera- logical studies, first with Zeis, on a new barium feldspar and then on the occurrence of acmite in the riebeckite microgranite of Mynydd Mawr, Caernarvonshire. You have also given an account of the mineralogy of the replacement veins in the Mourne Mountain granite...
Series: Geological Society, London, Special Publications
Published: 13 January 2021
DOI: 10.1144/SP503-2020-9
EISBN: 9781786209917
...-facies metamorphism ( Strachan et al. 2007 ), while the Gwalchmai and Mynydd Bodafon sediments are presumed to have been deposited after metamorphism at <666 Ma and before intrusion at >613 Ma. More recent research has revealed similarities in succession, provenance and basement composition...
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Series: Geological Society, London, Geology of Series
Published: 01 January 2006
DOI: 10.1144/GOEWP.3
EISBN: 9781862393882
... sills, up to 100 m thick, represent multiple intrusions with precursor basic margins and cores of either feldspar porphyry or rhyolite which grade, in the thicker sills, into microgranite. In central Snowdonia there are three acid plutons, at Tan y Grisiau, Mynydd Mawr and Ogwen. The Tan y Grisiau...
FIGURES | View All (47)
Series: Geological Society, London, Special Publications
Published: 30 August 2019
DOI: 10.1144/MPAR4.4
EISBN: 9781786204684
... whole-rock analyses, and notably data for Zr and Nb, led Leat et al. (1986) to conclude that a proportion of the rhyolites were originally comendites. At Mynydd Mawr, located c. 7 km west of Snowdon, the highest peak in the area, is an intrusion of peralkaline microgranite with an area of c. 3...
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