Geochemistry of mafic dykes in the Corrovarre Nappe, Troms, North Norway
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Tholeiitic metadolerite dyke rocks in the Corrovarre Nappe of the Kalak Nappe Complex in North Troms show chemical traits which indicate T-MORB affinities, with fairly flat, chondrite-normalised REE patterns in a (La\/Nb)N just over 1. The low initial 87Sr\/86Sr ratio, 0.7030, and lack of Th enrichment suggest that the magma was not contaminated to any extent during upward passage from a secondarily slightly LIL element-enriched but primarily depleted mantle source. Element abundamces and ratios and the low initial Sr ratio are compar- able to those from Tertiary T-MORB dykes and lavas from the Vøring Plateau. It is suggested that the Corrovarre dykes, Sm\/Nd-dated to c. 580 Ma, penetrated a continental crust which had thinned appreciably since the time of initial rifting. The dykes probably intruded just prior to the actual inception of sea- floor spreading along this segment of the Baltoscandian margin.