The Caledonian granites of the British Isles have NH+4 contents in the range of 0–167 parts per million. High contents (>60 ppm) are confined to muscovite-rich granites, occurring principally in a restricted area, namely SE Ireland and the Isle of Man. Their magmas are inferred to have formed by the partial melting of a sedimentary protolith rich in organic matter. There is no apparent correlation between NH+4 content and initial 87Sr/86Sr ratios.

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