Mynydd Mawr Intrusion

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Journal Article
Published: 01 April 1999
Journal of the Geological Society (1999) 156 (2): 301–316.
...). The Nanhoron Suite comprises the most evolved igneous rocks in central Lly n but has no direct 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...
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 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 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 February 1991
Journal of the Geological Society (1991) 148 (1): 5–8.
... Anelog (SH 147275), viewed to the NE. (c) Clasts 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...
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 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, Geology of Series, Geological Society, London, Geology of Series
Published: 01 January 2006
DOI: 10.1144/GOEWP.3
EISBN: 9781862393882
... setting. The relatively minor volumes of intermediate andesite–rhyodacite magmas were the result of low-pressure fractional crystallization of the tholeiitic basalts. However, their small volumes, together with the lack of geophysical evidence for large mafic intrusions, have been used to suggest...
FIGURES | View All (47)
Series: Geological Society, London, Special Publications
Published: 30 August 2019
DOI: 10.1144/MPAR4.4
EISBN: 9781786204684
... lies within the Silbersberg Series, which consists essentially of greywackes, phyllites and greenschists, with small outcrops of porphyry and basaltic rock. A large intrusion of quartz porphyry lies a few hundred metres west of the peralkaline gneiss ( Phadke 1967 , fig. 1). The gneiss appears...
FIGURES | View All (127)