Rb-Sr isotopic determinations and the timing of Tertiary central complex magmatism in NE Ireland

Abstract

Summary Full Rb-Sr isotopic data and whole-rock regressions are presented for each of the Mourne Mountains granites (G1–G5 inclusive) and a set of granophyres/microgranites from the Slieve Gullion central complex. The former were intruded at approximately 56 Ma (G1–G4 inclusive) and later (G5), and may all be younger than the major intrusions of the Slieve Gullion and Carlingford central complexes. The initial Sr isotope ratios are >0.7060 for all five Mourne granites, the Slieve Gullion granophyres/microgranites analyzed and the rhyolitic rocks of the Tardree area (Co. Antrim), and crustal involvement is indicated in their petrogenesis. In the E Mourne Centre the first (the least silicic and most Sr-rich) granite has a significantly higher initial ratio (0.7129 ± 2) than G2 (0.7109 ± 3) and G3 (0.7104 ± 6), and the isotopic data provide further support for the recent revision to the mapping of the first and second granites. Preliminary Rb-Sr isotopic data for a comprehensive suite of Tertiary rhyolites from NE Ireland, some separated by >50 km, define a linear array whose explanation is considered.

Geochronology of the Tardree Rhyolite Complex, Northern Ireland: Implications for zircon fission track studies, the North Atlantic Igneous Province and the age of the Fish Canyon sanidine standard

“…Ma 2 obtained by Chambers (2000; age 4 quoted in Fig. 1d, e) and the unpublished 40 Ar/ 39 Ar plateau age of 60.7 ± 1.2 Ma of Lux and Gibson, quoted in Meighan et al (1988) (not shown in Fig. 1d…”

“…ACCEPTED MANUSCRIPT 5 complex. Meighan et al (1988) report an Rb-Sr whole rock isochron of 60.3 ± 2.8 Ma (age 2 quoted in Fig. 1d, e).…”

Mobility during the neolithic and bronze age in northern ireland explored using strontium isotope analysis of cremated human bone

“…Palaeozoic lithologies (545‐248 Ma) predominate, especially Carboniferous sedimentary rocks (350 − 290 Ma); there are several large granitic bodies and, in Co. Antrim in the northeast, an extensive outcrop of mantle‐derived Tertiary (60 Ma) basaltic lavas. Consequently, and relevant to this research, there is a large range of present‐day strontium isotope compositions, from below 0.7040 in some Antrim basalts to over 1.15 in certain Mourne Mountains granites (Wallace et al, ; Meighan et al, ). The subsurface is composed, among other things, of Holocene peat bogs and glacial till originating mostly from the last deglaciation around 14 kya.…”

Anorogenic granite magma genesis: new isotopic data for the southern sector of the British Tertiary Igneous Province

“…Skye, Mull, Arran, Mourne Mountains). Unfortunately, there are insufficient available Nd isotopic data to allow comment in this context, but for the Mourne Mountains (Table 7) it is interesting that the elevated initial Sr isotope ratio for the G1 granite (Meighan et al 1988) is not accompanied by initial e Nd values significantly different from the later granites (G2-G5 inclusive).…”