Emil Holtung Gulbransen

• Gulbransen, Emil Holtung; Andersen, Tom; Friis, Henrik & Xuan, Liu (2025). Lead isotope systematics of galena from pegmatites in the Larvik Plutonic Complex (LPC). Lithos. ISSN 0024-4937. 508-509. doi: 10.1016/j.lithos.2025.108079. Full text in Research Archive Show summary

  The Larvik Plutonic Complex (LPC) is situated in the southernmost parts of the Carboniferous-Permian Oslo Rift, Norway. The alkaline complex is host to several suites of pegmatites ranging from miaskitic to agpaitic, and much is unknown of the origin and source of these pegmatites. Compared to granitic pegmatites, alkaline pegmatites are commonly intraplutonic and cogenetic to the host rock. This makes alkaline pegmatites such as the ones in the LPC important indicators of the evolution of the alkaline complexes as a whole, and towards our understanding of their formation and source. This study aims to utilize Pb-Pb isotope geochemistry on galena crystals from selected pegmatites in the LPC, to investigate possible sources to the pluton. The LPC pegmatite data was modelled using a 295 Ma paleoisochron, which represents the lead isotope composition at the time of formation. The 295 Ma paleoisochron is significantly more radiogenic than the upper mantle, indicating a need of another component to the source. This have been investigated by extrapolating the 295 Ma paleoisochron to the intercept point of the global average juvenile lithosphere, which gave an initial lead composition of 206Pb/204Pb = 16.819, 207Pb/204Pb = 15.482 and 208Pb/204Pb = 36.490. The intersection is at ∼1140 Ma which correlates well with the duration of the Sveconorwegian orogeny that occurred between ∼1290–1000 Ma and gives μ2min of 13.880 and μ2max of 14.658 which shows that these values are realistic in terms of what can be expected growth of a LILE-enriched, crustal domain in such a system. Galena from hydrothermal ore at Konnerud has similar lead isotope compositions as in the LPC pegmatites, suggesting an almost purely magmatic source, whereas galena in the Kongsberg silver deposit is more radiogenic, suggesting contamination by Cambrian-Ordovician alum shale.

• Gulbransen, Emil Holtung; Friis, Henrik; Bo, Fabrice Dal & Erambert, Muriel (2022). Illoqite-(Ce), Na2NaBaCeZnSi6O17, a new member of the nordite supergroup from Ilímaussaq alkaline complex, South Greenland. Mineralogical magazine. ISSN 0026-461X. 86(1), p. 141–149. doi: 10.1180/mgm.2021.104. Full text in Research Archive Show summary

  Abstract The new mineral, illoqite-(Ce), with the ideal formula Na 2 NaBaCeZnSi 6 O 17 , has been discovered in the Taseq Slope, Ilímaussaq Alkaline Complex, Southern Greenland. Illoqite-(Ce) occurs in a hyperalkaline ussingite vein closely related to one of the largest ussingite veins in the Ilímaussaq complex. The associated minerals are aegirine, arfvedsonite, a britholite-group mineral, epistolite, chkalovite, lueshite, Mn-rich pectolite group member and steenstrupine-(Ce). Illoqite-(Ce) crystallises as either single euhedral crystals up to 150 μm in size or radiating aggregates consisting of a few or many crystals. The aggregates are up to 200 μm in diameter. Illoqite-(Ce) can occur as scattered small groups of crystals or aggregates, but sometimes they occur in high concentrations creating clusters or bands almost completely consisting of illoqite-(Ce). The empirical formula on the basis of 17 anions is Na 2.00 Na 1.00 (Ba 0.59 Sr 0.32 Ca 0.04 Na 0.03 ) Σ0.98 (Ce 0.68 La 0.31 Nd 0.09 Pr 0.04 ) Σ1.12 (Zn 0.42 Fe 0.34 Li 0.14 Mn 0.09 ) Σ0.99 Si 5.97 O 17 , with the simplified formula being Na 2 Na(Ba,Sr)(Ce,La,Nd)(Zn,Fe,Li)Si 6 O 17 . Illoqite-(Ce) exhibits sector zoning between elements Sr and Ba. The crystal structure was determined using single-crystal X-ray diffraction data and refined to R 1 = 2.46% using 1902 unique reflections. Illoqite-(Ce) is orthorhombic, Pcca , with a = 14.5340(7), b = 5.2213(1), c = 19.8270(4) Å, V = 1507.25(6) Å 3 and Z = 4. The strongest lines of the powder X-ray diffraction pattern [ d , Å ( I , %) ( hkl )] are: 7.266 (79) (200), 4.688 (44) (104), 4.241 (64) (210), 3.486 (79) (114), 3.340 (52) (312), 2.986 (67) (410), 2.882 (100) (314) and 2.789 (44) (016). Illoqite-(Ce) is a new member of the nordite supergroup and is named after the Greenlandic word illoq, meaning cousin, in allusion to the mineral's close relation to nordite-(Ce).

• Bo, Fabrice Dal; Gulbransen, Emil Holtung & Friis, Henrik (2021). New data on nordite-(Ce) and the establishment of the nordite supergroup. Mineralogical magazine. ISSN 0026-461X. 85, p. 431–437. doi: 10.1180/mgm.2021.42. Full text in Research Archive Show summary

  Abstract A nomenclature scheme has been set up for the nordite supergroup of minerals, which have the general formula A 2 BXYZT 6 O 17 and where A = Na; B = Na, Ca; X = Sr, Ca, Ba; Y = REE , Sr; Z = Zn, Fe, Mn, Mg and T = Si. The nordite supergroup includes nordite-(La), nordite-(Ce), ferronordite-(La), ferronordite-(Ce) and manganonordite-(Ce), as well as meieranite which is considered as an unassigned member of the nordite supergroup. In the known nordite-group minerals the Y site is occupied by rare earth elements (REE), while in meieranite the Y site is occupied by Sr. The dominant element on the tetrahedral Z site determines the prefix used in the mineral name. New rootnames must be given to species with a different dominant element on the A , B or X sites. Nordite supergroup minerals are orthorhombic, although nordite-group minerals and meieranite crystallise in the Pcca and P 2 1 nb space groups, respectively. The proposed nomenclature scheme for the nordite supergroup has been approved by the Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical Association (IMA). In addition, new chemical and structural investigations were performed on nordite-(Ce) from Illutalik (Igdlutalik), South Greenland, leading to the first crystal structure refinement for nordite-(Ce).

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• Gulbransen, Emil Holtung; Friis, Henrik; Hutchison, Will & Andersen, Tom (2024). Sulphur isotopes and helvine-group minerals of pegmatites in the Larvik Plutonic Complex (LPC), Norway. Full text in Research Archive
• Gulbransen, Emil Holtung (2024). Byrud Smaragdgruver med Steinklubben. Full text in Research Archive
• Gulbransen, Emil Holtung (2024). Geologiens Dag: Steinorakel. Full text in Research Archive
• Gulbransen, Emil Holtung; Friis, Henrik; Hutchison, William & Andersen, Tom (2023). Helvine-group minerals and sulphur isotopes in the Larvik Plutonic Complex, Norway. Full text in Research Archive
• Gulbransen, Emil Holtung (2023). Helvine-group minerals and sulphur isotopes in the Larvik Plutonic Complex, Norway (LPC). Full text in Research Archive

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