| Abstract/Notes | An exotic pegmatite classified as a rare-element gadolinite type amazonite pegmatite is situated in Paleozoic sedimentary rocks, and associated with the peralkaline ekerite granites in the Permian Oslo Region. The amazonite pegmatite is approximately 16 meters long and consists of a coarse-grained, subhedral, green microcline feldspar (amazonite), quartz and danalite. Fine grained fabric with abundant sulphides intersect the coarse grained amazonite several places, and indicates a second generation of mineralization. The danalite has a strong reddish color with an intermediate composition of zinc and iron, i.e. composition along the danalite – genthelvite solid-solution series. Abundant pristine subhedral to euhedral phenakite coexist with danalite, and a boron zone in the pegmatite interior contains abundant danburite, tourmaline, and minor nordenskiöldine. Additional löllingite, gadolinite-(Y), biotite, zircon, columbite-(Fe), pyrochlore group minerals, and fluorite occur throughout the pegmatite body. Other pegmatites in the area contain primarily amphibole, pyroxene, microcline, and quartz. Major element variation of the amazonite pegmatite and its neighbor pegmatites correlate; however, trace-element evolution trends diverge in respect to REE, Nb, Y, and Ta. The amazonite pegmatite is clearly enriched in HREE relative to LREE, while Y, Nb, and Ta contents are significantly higher in the amazonite pegmatite than other pegmatites in the area. This evidence, in conjunction with the high boron- and sulphur-content, indicates an enrichment of the original NYF magma by circulating hydrothermal fluids, and chemical exchange with the sedimentary wall-rocks. |
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