Origin of the Kleva Ni-Cu sulphide mineralisation in Småland, southeast Sweden
The Kleva Ni-Cu sulphide deposit is situated within a gabbro-diorite intrusive complex in southeast Sweden. The basement north of the intrusive complex is dominated by 1.81–1.77 Ga granites of the Palaeoproterozoic Transscandinavian Igneous Belt (TIB). Slightly older (1.83–1.82 Ga) rocks of the Oska...
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| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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Department of Geology, Lund University
2015
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| Online Access: | https://lup.lub.lu.se/record/7852663 https://portal.research.lu.se/files/4009167/7852930.pdf |
| Summary: | The Kleva Ni-Cu sulphide deposit is situated within a gabbro-diorite intrusive complex in southeast Sweden. The basement north of the intrusive complex is dominated by 1.81–1.77 Ga granites of the Palaeoproterozoic Transscandinavian Igneous Belt (TIB). Slightly older (1.83–1.82 Ga) rocks of the Oskarshamn Jönköping Belt, which hosts numerous syngenetic and epigenetic base metal mineralisations, occur just south of the Kleva intrusive complex. The aim of this PhD-thesis is to deduce the origin of the Kleva deposit, the mineralisation itself as well as its host rocks through geochemical, geochronological and petrological studies. U-Pb age determination of zircon dates igneous crystallisation to 1.79 Ga, which is the age of the Kleva intrusive complex and confirms its temporal association with the voluminous TIB magmatism. Major- and trace element systematics are in accordance with a basaltic magma that formed through partial melting of a metasomatically refertilised mantle wedge underneath an Andean-type continental magmatic arc. Lu-Hf signatures of zircon, together with other rocks of Palaeoproterozoic Fennoscandia indicate alternating stages of extension and compression across the subduction zone, facilitating ascent of the mafic magma. Evidence for contamination of the magma through crustal assimilation during its ascent are inconclusive. Low IPGE/Ni together with high S/Se, indicate sulphide melt saturation prior to final emplacement, possibly induced by crustal contamination. Nb/La vs La/Sm indicate contamination with mid-crustal rocks, and radiogenic Os of magmatic pyrite suggests <10% contamination with Archean crust. OJB aged rocks are thus unlikely contaminants, despite the numerous rock inclusions of similar geochemical composition within the intrusive complex. δ34S of Kleva mineralised rocks and the country rocks corresponds with the mantle range, and local or mantle origin of S can neither be proven nor rejected. Sulphide melt segregated from an evolved magma and partially accumulated into massive ... |
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