The emplacement of the Palaeogene Mourne Granite Centres, Northern Ireland: new results from the Western Mourne Centre

Stevenson, Carl; Bennett, Neil

doi:10.1144/0016-76492010-123

Cited by 22 publications

(14 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Permian, Triassic, Jurassic and Cretaceous sequences are found in north-east Ireland's Rathlin Trough and Lough Neagh-Larne Basin (McCann, 1988(McCann, , 1990Naylor, 1992) Naylor, 1992). Tertiary igneous complexes relating to the rifting of North America and Eurasia and the opening of the Atlantic Ocean are present in north-east Ireland (Jolley and Bell, 2002;Stevenson and Bennett, 2011). The vast basaltic lavas of Co. Antrim date to this period (Lyle, 1980;Lyle and Preston, 1993), whilst the Mourne granites of Co. Down were also emplaced at this time (McCormick et al, 1993;Stevenson and Bennett, 2011).…”

Section: Post-variscanmentioning

confidence: 99%

The genesis of gold mineralisation hosted by orogenic belts: A lead isotope investigation of Irish gold deposits

et al. 2014

View full text Add to dashboard Cite

Lead isotope analyses have been performed on 109 gold and 23 sulphide samples from 34 Irish gold occurrences, including 27 placers, and used to shed light on the sources of mineralising fluids and metals associated with gold mineralisation hosted by orogenic belts. The Pb isotope ratios of lode and placer gold range from 206 Pb/ 204 Pb = 17. 287-18.679, 207 Pb/ 204 and 208 Pb/ 204 Pb = 37.517-38.635, consistent with the Pb isotopic data on previously reported Irish sulphide mineralisation. There is no evidence that gold mineralisation is associated with distinctive source regions, and it appears to have been derived from similar sources to those responsible for the widespread sulphide mineralisation in Ireland. It is inferred that the principal controls on the Au mineralisation are structural and not related to the distribution of Au in their source rocks. The range of Pb isotope ratios favours the interaction of multiple source reservoirs predominantly during the Caledonian Orogeny (c.475-380 Ma). Underlying basement was the primary control on two key sources of Pb. Gold occurrences located to the south-east of the Iapetus Suture are characterised by Pb compositions that derive predominantly from the Late Proterozoic crustal basement or overlying Lower Palaeozoic sediments, whilst those located north-west of the Iapetus Suture are characterised by less radiogenic Pb signatures derived predominantly from Late Proterozoic or older crustal basement. A third source, relatively enriched in radiogenic Pb, also played a role in the formation of a number of Irish gold occurrences, and may have been associated with syn-to postorogenic intrusives. Magmatic processes may therefore have played an important role in the formation of some gold occurrences located in orogenic settings.

show abstract

Section: Post-variscanmentioning

confidence: 99%

The genesis of gold mineralisation hosted by orogenic belts: A lead isotope investigation of Irish gold deposits

et al. 2014

View full text Add to dashboard Cite

show abstract

“…For example, Stevenson et al . [] and Stevenson and Bennett [] used AMS fabrics to demonstrate that the Mourne Mountains (NE Ireland) granite intrusions were emplaced laterally, instead of forming through in situ cauldron subsidence related to caldera collapse. Regardless of source, studies of various intrusive elements of the BPIP have documented lateral movement of magma over many 10's of kilometers away from the magma ascent site.…”

Section: Discussionmentioning

confidence: 92%

Emplacement of the early Miocene Pinto Peak intrusion, Southwest Utah, USA

Petronis

O’Driscoll

2013

Geochem Geophys Geosyst

View full text Add to dashboard Cite

[1] In this contribution, we report rock magnetic, petrographic, and anisotropy of magnetic susceptibility (AMS) data from the Pinto Peak intrusion, all of which bear on volcanic construction. Rock magnetic data indicate that the dominant magnetic mineral phase is low-Ti titanomagnetite of multidomain grain size, the composition of which varies spatially across the intrusion. The intrusion is a porphyritic andesite dominated by Ca-rich plagioclase (>60%) as well as biotite, amphibole, olivine, and opaque minerals. Reflected light petrography reveals mostly euhedral-subhedral (titano)magnetite crystals that often form clustered glomerocrysts and stringers of equant crystals, without exhibiting a consistent mineral alignment fabric. Moderate-to-shallow plunging prolate magnetic susceptibility ellipsoids dominate the northern part of the intrusion while steeply dipping/plunging magnetic susceptibility ellipsoids are generally restricted to the southern part of the intrusion. The vent facies rocks yield moderate-to-steep oblate susceptibility ellipsoids. We interpret the flow pattern in the north to reflect subhorizontal flow of magma, filling a tabular sheet-like body associated with propagation of the intrusion to the north. We argue that the southern part of the intrusion represents the ascent site of the magma rising to shallow crustal levels along a steep feeder system. The oblate magnetic fabrics in the vent area plausibly represent flattening against the conduit walls as evidenced by a weak planar flow foliation observed in the vent conduit rocks. On reaching shallow crustal levels, the magma deformed and uplifted the roof rocks leading to gravitational instability. As the slide mass released from the roof, an explosive eruption ensued resulting in the emplacement of the Rocks of Paradise tuff and associated effusive lava flows. Following eruption, magma pressure decreased and the magma drained northward forming the northern intrusive phase.

show abstract

“…The granite pluton has been treated as two separate magmatic centers, an eastern and western center ( Fig. 2A) (Emeleus, 1955;Hood, 1981;Gibson, 1984;Meighan et al, 1984;Cooper and Johnston, 2004;Stevenson et al, 2007;Stevenson and Bennett, 2011 mapping has shown that the granites form a connected pluton (Richey, 1927;Emeleus, 1955;Hood, 1981;Gibson, 1984). The oldest granites, G1 to G3, form the eastern part of the pluton, and the younger granites, G4 and G5, form the western part ( Fig.…”

Section: The Mourne Mountains Magmatic Centermentioning

confidence: 99%

“…Richey (1927) therefore interpreted the northeastern contact to the Eastern Mourne pluton to represent part of the feeding ring dike to the granite pluton. Stevenson et al (2007) and Stevenson and Bennett (2011) analyzed magnetic (AMS) fabrics in the Mourne Mountains granites. The magnetic fabric in the Mourne granite pluton is dominantly oblate to triaxial.…”

Section: The Mourne Mountains Magmatic Centermentioning

confidence: 99%

Host-rock deformation during the emplacement of the Mourne Mountains granite pluton: Insights from the regional fracture pattern

et al. 2019

View full text Add to dashboard Cite

The Mourne Mountains magmatic center in Northern Ireland consists of five successively intruded granites emplaced in the upper crust. The Mourne granite pluton has classically been viewed as a type locality of a magma body emplaced by cauldron subsidence. Cauldron subsidence makes space for magma through the emplacement of ring dikes and floor subsidence. However, the Mourne granites were more recently re-interpreted as laccoliths and bysmaliths. Laccolith intrusions form by inflation and dome their host rock. Here we perform a detailed study of the deformation in the host rock to the Mourne granite pluton in order to test its emplacement mechanism. We use the host-rock fracture pattern as a passive marker and microstructures in the contact-metamorphic aureole to constrain large-scale magma emplacement-related deformation. The dip and azimuth of the fractures are very consistent on the roof of the intrusion and can be separated into four steeply inclined sets dominantly striking SE, S, NE, and E, which rules out pluton-wide doming. In contrast, fracture orientations in the northeastern wall to the granites suggest shear parallel to the contact. Additionally, contact-metamorphic segregations along the northeastern contact are brecciated. Based on the host-rock fracture pattern, the contact aureole deformation, and the north-eastward–inclined granite-granite contacts, we propose that mechanisms involving either asymmetric “trap-door” floor subsidence or laccolith and bysmalith intrusion along an inclined or curved floor accommodated the emplacement of the granites and led to deflection of the northeastern wall of the intrusion.

show abstract

The emplacement of the Palaeogene Mourne Granite Centres, Northern Ireland: new results from the Western Mourne Centre

Cited by 22 publications

References 34 publications

The genesis of gold mineralisation hosted by orogenic belts: A lead isotope investigation of Irish gold deposits

The genesis of gold mineralisation hosted by orogenic belts: A lead isotope investigation of Irish gold deposits

Emplacement of the early Miocene Pinto Peak intrusion, Southwest Utah, USA

Host-rock deformation during the emplacement of the Mourne Mountains granite pluton: Insights from the regional fracture pattern

Contact Info

Product

Resources

About