Rev. Mineral. Geochem. 69. 61-120

Improving our understanding of magma plumbing and storage remains one of the major challenges for petrologists and volcanologists today. This is especially true for explosive volcanoes, where constraints on magma plumbing are essential for predicting dynamic changes in future activity and thus for hazard mitigation. This study aims to investigate the magma plumbing system at Anak Krakatau; the post-collapse cone situated on the rim of the 1883 Krakatau caldera. Since 1927, Anak Krakatau has been highly active, growing at a rate of ∼8 cm/week. The methods employed are a.) clinopyroxene-melt thermo-barometr

Granitic magmatism by melting of juvenile continental crust: new constraints on the source of Palaeoproterozoic granitoids in Fennoscandia from Hf isotopes in zircon

<p>Zircons from nine Palaeoproterozoic granitoid intrusions within the southern part of the Fennoscandian Shield have been studied by laser ablation inductively coupled plasma source mass spectrometry to obtain U–Pb ages (in the range 1.88–1.68 Ga) and Hf isotope compositions. Six granitoids are from the 1.85–1.65 Ga Transscandinavian Igneous Belt; during that period more than 10⁶km³ of granitoid magma intruded the pre-existing crust. The large majority of magmatic zircons from the nine granitoids have a limited initial range, ¹⁷⁶Hf/¹⁷⁷Hf = 0.2816–0.2818, and define an evolutionary trend given by an initial value of ε_Hf(1.88Ga) ≈ +2 ± 3 at an average ¹⁷⁶Lu/¹⁷⁷Hf = 0.015. These data show that a geographically extensive, long-lived, relatively homogeneous, and dominant magma source resided within 2.1–1.86 Ga Svecofennian juvenile crust between 1.88 and 1.68 Ga. Zircon xenocrysts (1.91–1.98 Ga) with initial ε_Hf = +0 to +2.5 from one of the intrusions provide additional evidence for such a long-lived crustal source of granitic magmas in central Fennoscandia. The granitoids were emplaced during a period of active mafic underplating that supplied heat to the anatectic zone in the lower–middle crust, but little or no mantle-derived Hf to the granitic magmas, in contrast to many mixed intermediate rocks. </p

Emendment to the term complex in: “Guide for geological nomenclature in Sweden” (Kumpulainen 2016)

Since the publication of Kumpulainen (2016), the Committeehave been alerted by the investigation and subsequent changesto the North American Stratigraphic Code concerning thelithodemic unit“complex”(Easton et al.2016; North Ameri-can Commission on Stratigraphic Nomenclature (NACSN)2017). These changes concern the introduction of the nomen-clature unit“Intrusive Complex”. In the original version(NACSN1983), as well as in the Swedish Guide for nomencla-ture (Kumpulainen2016), the unit“complex”is defined ascontaining at least two genetic classes of rocks, i.e., igneous,sedimentary, or metamorphic