| Autor: |
Macdonald, R., Rock, N. M. S., Rundle, C. C., Russell, O. J. |
| Zdroj: |
Mineralogical Magazine; December 1986, Vol. 50 Issue: 358 p547-557, 11p |
| Abstrakt: |
AbstractThe 2 km × 5 m Newmains Dyke in the Scottish Southern Uplands consists mainly of primitive (mg number > 70), at least partly mantle-derived lamprophyre (vogesite spessartite, SiO250–60%), with hornblende-pyroxene-rich cumulates (SiO2< 50%) and small amounts of quartz syenitic to granite residua (60–73% SiO2). The lamprophyres and cumulates yield an Rb-Sr whole-rock isochron age of 395±9 Ma (MSWD 2.0), and (87Sr/86Sr)i0.70514±5—identical values to the nearby Criffell granitic pluton. After some 65% hornblende + clinopyroxene fractionation of parent lamprophyre magma, a volatile phase separated and metasomatically enriched the country rock greywackes in K, Ba, and Rb. The remaining quartz syenitic liquids became contaminated by 87Sr from these greywackes, which have a mean (87Sr/86Sr)395value of 0.70789±114. Further fractionation of the contaminated syenitic liquids gave the granitic rocks, which have (87Sr/86Sr)395values of 0.7056–64. The dyke appears to demonstrate in situsome of the hidden processes previously invoked to explain the evolution of the Criffell pluton itself. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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