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20 The 1.49 Ga old Norra Kärr complex in Southern Sweden contains rocks characterized by a 21 very high ratio of (Na+K)/Al ≥ 1.2 and a complex and highly unusual mineralogy, including 22 rock-forming catapleiite, eudialyte-group minerals as well as minor rinkiteand britholite23 group minerals. In contrast to other well-studied examples of agpaitic rocks, the Norra Kärr 24 rocks have been deformed and partially metamorphosed during the 25 Sveconorvegian/Grenvillian orogeny, and are now preserved in a westward dipping synform. 26 Magmatic and metamorphic processes at the Norra Kärr complex are distinguished by 27 combining rock fabrics of clinopyroxene and eudialyte-group minerals. Both mineral groups 28 are stable over a large P-T range, which makes them excellent monitors of the geochemical 29 evolution of such systems and enables the reconstruction of magmatic and subsequent 30 metamorphic conditions. 31 The magmatic mineral assemblage crystallized from a subsolvus syenite at 32 continuously decreasing temperatures (700 450oC) and silica activity (0.6 0.3). Due to 33 initially relatively low peralkalinity and reducing conditions, Zr was first incorporated in Zr34 aegirine. Subsequent destabilization of the latter indicates increasing peralkalinity, oxygen 35 fugacity and water activity, which resulted in the crystallization of early magmatic catapleiite. 36 Crystallization of presumably later magmatic Mnand REE-poor eudialyte-group minerals, 37 happened as soon as sufficient Cl, REE and HFSE were enriched in the residual melt. 38 Metamorphic conditions during the Sveconorvegian/Grenvillian orogeny are 39 constrained to T between 400 550oC and aSiO2 range of 0.25 0.4. Due to deformation and 40 interaction with fluids, post-magmatic Al-rich aegirine as well as post-magmatic eudialyte41 group minerals enriched in REE, Y and Mn formed. Subsequently, the eudialyte-group 42 minerals were destabilized and decomposed to post-magmatic catapleiite and secondary REE43 bearing minerals. During the whole history of the complex, aSiO2 remains very similar, 44 indicating very little interaction with the surrounding granitic rocks. 45 Regardless of the intense deformation due to folding of the Norra Kärr body during 46 the Sveconorvegian/Grenvillian orogeny, indications for primary magmatic layering of the 47 intrusion are retained on the deposit scale. In addition, the compositional changes of 48 magmatic eudialyte-group minerals from the outer to the inner subunit indicate a primary 49 geochemical evolution feature due to fractional crystallization. 50

journal of petrology

Distinguishing Magmatic and Metamorphic Processes in Peralkaline Rocks of the Norra Kärr Complex (Southern Sweden) Using Textural and Compositional Variations of Clinopyroxene and Eudialyte-group Minerals