Jenkin, Gawen R. T., Mohr, Paul, Mitchell, John G., Fallick, Anthony E. (1997) Carboniferous dykes as monitors of post-Caledonian fluid events in West Connacht, Ireland. Transactions of the Royal Society of Edinburgh: Earth Sciences, 88 (4) 225-243 doi:10.1017/s0263593300006969
| Reference Type | Journal (article/letter/editorial) | ||
|---|---|---|---|
| Title | Carboniferous dykes as monitors of post-Caledonian fluid events in West Connacht, Ireland | ||
| Journal | Transactions of the Royal Society of Edinburgh: Earth Sciences | ||
| Authors | Jenkin, Gawen R. T. | Author | |
| Mohr, Paul | Author | ||
| Mitchell, John G. | Author | ||
| Fallick, Anthony E. | Author | ||
| Year | 1997 | Volume | 88 |
| Issue | 4 | ||
| Publisher | Cambridge University Press (CUP) | ||
| DOI | doi:10.1017/s0263593300006969Search in ResearchGate | ||
| Generate Citation Formats | |||
| Mindat Ref. ID | 494518 | Long-form Identifier | mindat:1:5:494518:9 |
| GUID | 0 | ||
| Full Reference | Jenkin, Gawen R. T., Mohr, Paul, Mitchell, John G., Fallick, Anthony E. (1997) Carboniferous dykes as monitors of post-Caledonian fluid events in West Connacht, Ireland. Transactions of the Royal Society of Edinburgh: Earth Sciences, 88 (4) 225-243 doi:10.1017/s0263593300006969 | ||
| Plain Text | Jenkin, Gawen R. T., Mohr, Paul, Mitchell, John G., Fallick, Anthony E. (1997) Carboniferous dykes as monitors of post-Caledonian fluid events in West Connacht, Ireland. Transactions of the Royal Society of Edinburgh: Earth Sciences, 88 (4) 225-243 doi:10.1017/s0263593300006969 | ||
| In | (1997) Transactions of the Royal Society of Edinburgh: Earth Sciences Vol. 88 (4) Cambridge University Press (CUP) | ||
| Abstract/Notes | AbstractThe causes of hydrothermal alteration in dolerite dykes intruding Caledonian rocks of W Connacht are investigated using stable isotope, water content and K–Ar data for whole rocks and mineral separates. Using an isochron approach the Logmór dyke in the north is re-dated to 308±4 Ma; previously determined older whole-rock ages reflect excess 40Ar. The ∼ 305 Ma age previously proposed for the Teach Dóite suite in the south is reinforced by a 305 Ma age on a pyroxene separate, although the severe resetting of most samples is emphasised by other pyroxene and plagioclase ages of ∼210 Ma. Pyroxene δ18O values for these Upper Carboniferous dykes are mostly 5·5 to 6·1%, indicating negligible crustal contamination. Logmór whole-rock samples have water contents of 1·7–2·1 wt.%, δ5D= 59 to –47‰ and δ18O = 9·4 to 9·6‰; plagioclase shows little mineralogical alteration but its δ18O is 9·7‰. Hydrothermal alteration involving a local formation or metamorphic water took place at high fluid/rock ratios and high temperature during cooling after intrusion, most probably in a thermally-driven convection system. Teach Dóite dykes have water contents of 2·0–4·2 wt.%. δD= –58 to –38‰ and δ18O = 3·6 to 9·2‰, and were mostly altered in two stages; hydration upon intrusion to ∼ 2 wt.% water by contemporaneous meteoric water at low fluid/rock ratios was followed by extensive chemical and isotopic alteration at ∼210 Ma (Upper Triassic) by surface waters. This latter event could also have caused the extensive alteration observed in the host rocks. | ||
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