U–Pb ion microprobe investigations of zircons from gneisses, granites and migmatites of the pre-Devonian Smerenburgfjorden and Richarddalen Complexes constrain the tectonic evolution and origin of Svalbard's Northwestern Terrane. Field relationships combined with U–Pb age data indicate that a late Meso- to Neoproterozoic metapelitic protolith was intruded by Tonian (c. 960 Ma) granitoids and suggest that the entire Northwestern Terrane is underlain by early Neoproterozoic granitoids intruding older metasediments. Both rock types were later involved in Caledonian deformation, with subsequent migmatization and granite genesis at c. 435–420 Ma. Ages of inherited zircons in granites and migmatites reflect anatexis of this late Meso- to Neoproterozoic protolith, with zircon xenocrysts ranging in age from c. 1030 to 1820 Ma. Pronounced lithological, geochronological and tectonothermal similarities to NE Svalbard (Nordaustlandet) and the Krummedal supracrustal sequence of East Greenland suggest a strong correlation between Svalbard and East Greenland prior to Caledonian orogenesis.

Mineral-chemical data of metapelites from the Proterozoic Krossfjorden Complex constrain the Late Caledonian tectonic evolution of Svalbard’s Northwestern Terrane and record a clockwise P-T path. The oldest deformation event (D2) related to orogenesis in the Northwestern Terrane records crustal thickening and incipient melting of the crust at c. 430 Ma. Continued heating during prograde metamorphism at c. 420 Ma resulted in the main migmatization event (D3) and related granitoid genesis at c. 850 °C and >6 kbars. Following the peak P-T conditions, the crust was uplifted and cooled to 645-683 °C and 3-5k bars. Unconformably above the Late Silurian aged high-T rocks and granitoid intrusives are Early Devonian (c. 416-411) cover sequences indicating rapid exhumation of the crystalline basement. This suggests that the peak metamorphic conditions were followed by near isothermal decompression. The clockwise P-T-t path of the Krossfjorden Complex of Svalbard’s Northwestern Terrane is remarkably similar to rocks from the Krummedal Sequence and Smallefjord Sequence of central East Greenland, confirming the close link between these areas prior to the Late Caledonian orogeny.

Svalbard is pivotal for defining the northern extent of the Grenville/Sveconorwegian orogenic belt. Consequently, to constrain the origin of Svalbard’s Northwestern Terrane (NWT), detrital zircon populations from samples of the Krossfjorden Group and Smerenburgfjorden complex, northwestern Svalbard, were analyzed by U-Pb Laser ablation ICP-MS. These data indicate that the NWT’s metasedimentary basement, the Krossfjorden Group, was deposited between c. 1020-995 Ma and indicates that the Smerenburgfjorden complex may represent a migmatized and deformed part of the Krossfjorden Group. Statistically, the source area of the Krossfjorden Group can not be distinguished from other late Mesoproterozoic to early Neoproterozoic siliciclastic sequences exposed in the Caledonian orogenic belt and their detrital populations are compatible with derivation from the Eastern Grenville Province (EGP), dominated by ages coinciding with the Labradorian event (1710-1600 Ma). The diachronous tectonothermal evolution of these Meso-to Neoproterozoic metasedimentary sequences suggests deposition in a spatially linked peripheral foreland and remnant ocean basins located east of EGP, which migrated eastwards during the final suturing of Rodina. Thus, they do not represent a northern branch of the Grenvillian/Sveconorwegian Orogeny.

Detrital zircon populations from Silurian-Devonian clastic rocks of NW Svalbard were analysed by U-Pb laser ablation inductively coupled plasma mass spectrometry to investigate the pre-Caledonian provenance of Svalbard's Northwestern Terrane. Changes in the resulting age spectra suggest a major shift in sources from the Laurentian-Avalonian suture in the latest Silurian to the local metasedimentary basement of the Northwestern Terrane in the Late Silurian-Early Devonian, and in the Lochkovian to Grenvillian-Sveconorwegian sources. These data, together with structural, additional geochronological and metamorphic data from Svalbard, East Greenland and Avalonia, support the amalgamation of Svalbard as the result of long-distance transport along sinistral strike-slip faults. A unifying model for the final amalgamation of Svalbard, consistent with the stratigraphical and tectonothermal history of Svalbard, involves fragments from the Grampian orogen and Avalonian crust originally accreted to the Laurentian margin being subsequently transported northward along sinistral strike-slip faults during Scandian deformation.