Strontium Isotope Studies related to Petrogenesis in the Caledonian Basic Igneous Province of NE. Scotland |
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| Authors: | PANKHURST R J |
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| Institution: | Department of Geology and Mineralogy, University of Oxford United Kingdom |
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| Abstract: | Rubidium-strontium isotope analyses are reported for 90 whole-rocksfrom the Newer Gabbros and associated rocks of NE. Scotland.The Sr87/Sr86 ratio of the regional gabbro magma at Insch andBelhelvie underwent a progressive increase, in the former casefrom 0·703 to 0·712 during differentiation tosyenogabbros and syenites. This is ascribed to a process ofisotopic equilibration with country rocks of the Dalradian Series.The wider implications of a process by which the Sr87/Sr86 ratioof a basic magma can be increased in the crust without any othersigns of petrological contamination are considered. Cordierite-noritesand related rocks of the Haddo House and Arnage masses haveinitial Sr87sol;Sr86 ratios of 0·720–0·730,essentially the same range as for the country rocks at the timeof intrusion. This is interpreted as support for the hypothesisthat such rocks were formed by the partial fusion of peliticsediments adjacent to the basic igneous sheet. |
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