KALEDONSKE FJELLKJEDE

In the first part of the report, a synopsis is presented of the general geology and tectonostratigraphy of this part of Central Norway, with a slightly more detailed account given of the geology of Fosen Peninsula. The second part comprises an excursion guide, spanning 3 days, covering the southern district of Fosen from Rørvik to Ørland and to the outer coast near Sandnes; and then continuing along the Verran Fault (Møre-Trøndelag Fault Complex) via Verrabotn and Beitstadfjorden to Steinkjer. The last day of the excursion takes in selected localities along the southeastern side of Trondheimsfjorden, finishing at Storvika close to Trondheim airport Værnes. The excursion aims to show the variety of rock-types at different tectonostratigraphic levels in this part of the Caledonides, and demonstrates the significance of faulting and diversity of fault trends, fault rocks and vein systems of a variety of ages in this onshore region adjacent to the Mid-Norwegian continental shelf. A preliminary version of this report and guide was distributed to participants during the actual excursion, 2-4 September 1998 - days blessed by warm, sunny weather. The excursion was the first in the project "Basin analysis and applied thermochronology on the Mid-Norwegian Shelf", otherwise known as the "BAT project".

Samples of pervasively cleaved mudstones and claystones from two different parts of the Gaissa Nappe Complex in Finnmark were subjected to Rb-Sr analytical investigation with the aim of trying to dtermine the metamorphic age of the rocks in this thrust sheet. Although neither of the two groups of samples yielded atrue isochron (i.e., MSWD 2.5), the data do support the concept of a probable isochron age at around 480-500 Ma, as can be discerned from the "isochron fits" of various combinations of the analytical data. Together with the relatively high 87Sr/86Sr initial ratios, this results strongly suggests that a Sr-isotopic resetting event occurred at around 480-500 Ma. This event is throuht to reflect an iverall, pervasive metamorphic imprint on the rock formations of the Gaissa Nappe Complex. Previous radiometric dating evidence from the Gaissa Nappe Complex has given ambiguous results, some pointing to Finnmarkian (Late Cambrian-Early Ordovician) deformation whereas other data hace indicated a Scandian (late Silurian-Early Devonian) age. The Rb-Sr analytical data reported here do tend to favour a likely Finnmarkian age for the very low-grade mertamorphism; and this fits with viverse isotopic data obtained from the overlying nappe complexes, as well as with the biostratigraphic evidence where the youngest rocks in the Gaissa thrust sheet are of Early Tremadoc age.

The report presents the results of diamond drilling carried out by MoMin AS in the Mofjellet Mine in 2005, and also some reinterpretation of older data. Twelve boreholes were drilled in 2005, distributed in three profiles, with the main target to further define an economic gold-rich mineralization related to the main sulfide ore bodies.
The most interesting results from the work in 2005 were found in the western half of the deposit, where drilling in profile 43480Y revealed a possible gold-rich sulfide zone following the AKP structure, about 70-80 m long and 1-3 m wide containing on average 4,4% Cu+Pb+Zn, 20 ppm Ag and 0.9 ppm Au. More work is recommended in this area by drilling short holes from an old reailway tunnel.
Interpretation of old data from the westernmost 800 m of the deposit show average grades of 3% Cu+Pb+Zn, 21 ppm Ag and 0.9 ppm Au over an average thickness of nearly 3 m. More work, including further interpretation of old data, structural geology and drilling is highly recommended in this part of the deposit to define economic resources,

The Fongen-Hyllingen complex, situated 60 km southeast of Trondheim, Norway, comprises the 160 km2 Fongen-Hyllingen layered mafic intrusion (FH1) and the slightly younger, minor (3 km2) mafic to ultramafic Treknattan intrusion. The FH1 was emplaced synorogenically in the Scandinavian Caledonides -435 Ma ago. Folding and subsequent uplift and erosion allow access to the floor, walls and roof of the magma chamber. The complex itself has been affected to some extent by deformation and metamorphism, but sufficient primary features remain to study magma chamber processes in detail.

The Mofjell project commenced in 2008 as a cooperation between GEXCO Norge AS, the county administration of Nordland and NGU. As GEXCO faced financial difficulties the external funding ended in 2009. The project area included Mofjellet and the eastern part of Plurdalen, an area with a large potential for economic sulfide deposits with Zn, Cu, Pb, Ag and Au.
NGU has focused on establishing the geological setting of the Mofjell Group and its relation to ore formation. Another very important goal has been to assess the potential for economic ore deposits in the area, including enrichment of precious metals.
On the basis of lithological observations and geochemistry, the Mofjell Group consists of a largely bimodal volcanic-sedimentary assemblage formed in an island-arc to back-arc setting. The data also show that the proportion of felsic volcanic rocks is much higher than previously described. A bimodal volcanic suite mixed with sediments is a geological environment which is regarded as favorable for both rich and large sulfide deposits.

Det har vært utført geologisk og malmgeologisk kartlegging i den nordøstlige del av Hattfjelldal kommune i perioden 2014-2016. Arbeidet skal sluttrapporteres i 2017 og dette er en rapport for status i prosjektet pr. desember 2016.
Prosjektet ble i 2014 og 2015 i sin helhet finansiert gjennom NGUs MINN-program. For 2016 og 2017 har Nordland Fylkeskommune bidratt til å finansiere Hattfjelldalsprosjektet med kr. 750 000,-. Disse midlene går til å dekke kostnader ved feltarbeidet, analysekostnader ved ekstern lab, samt timekostnader. Prosjektet har bakgrunn i at det har vært utstrakt leteaktivitet i området av flere selskaper. Disse selskapene har etterspurt grunnlagsdata i form av blant annet berggrunnsgeologi og geofysikk. Til nå har det i stor grad kun eksistert berggrunnskart i 1 :250 000 skala. Et mål med prosjektet er å benytte geofysisk, geokjemisk og geologisk kartlegging og detaljstudier til å utpeke områder med størst potensial for å finne større malmforekomster.

The report gives a description of the geology and field relationships of Ni-Cu mineralisation in 7 ore fields that occur in the Uppermost Allochthon (UmA) of the Scandinavian Caledonides in Nordland where they occur associated with a variety of metamorphosed and/or metasomatically altered mafic-ultramafic rock units. The occurrences in Markafjell in Brønnøy commune, Esjeholmene in Lurøy commune and Utvikåsen in Bodø commune are associated with ultramafic rocks in dismembered ophiolites whereas the ore-bearing ultramafic intrusion at Tverrbrennfjellet in Bodø commune comprises pyroxenites that have become “gabbroic” by mingling with a tonalitic magma. Mineralisation hosted by gabbroic intrusions are comprised by the Høgsetdalen showing in Gildeskål commune and the Lilleålegden deposit in Beiarn commune, as well as the Måløy deposit in Steigen commune. The latter two deposits have been the sites of small-scale mining in the past due to high-grade ores exceeding 1 wt. % (locally massive pentlandite with ca. 33 wt. % Ni). The Steinåga mineralisation in Beiarn commune comprising low-base metal pyrrhotite ore (< 0.1 wt % Ni or Cu) is hosted by ultramafic amphibolites possibly representing meta-volcanites.

Det har vært utført geologisk og malmgeologisk kartlegging i den nordøstlige del av Hattfjelldal kommune i perioden 2014-2016. Arbeidet skal ferdigstilles i 2018 og rapporten her oppsummerer resultatene fra prosjektet pr. februar 2018. Prosjektet ble i 2014 og 2015 i sin helhet finansiert gjennom NGUs MINN-program. For 2016 og 2017 har Nordland Fylkeskommune bidratt til å finansiere Hattfjelldalsprosjektet med kr.750 000,-. Prosjektet har sin bakgrunn i utstrakt leteaktivitet av flere selskaper i området. Disse selskapene har etterspurt grunnlagsdata i form av blant annet berggrunnsgeologi og geofysikk. Hele området ble målt med høyoppløselig geofysikk i 2014 under MINN-programmet. Et mål med prosjektet er å benytte geofysisk, geokjemisk og geologisk kartlegging og detaljstudier til å utpeke områder med størst potensial for å finne større malmforekomster.

New magnetotelluric (MT) data were acquired in the southern Scandinavian mountains to study the crustal structure of the Late Caledonian Gudbrandsdalen Anticline including the Atnsjø tectonic window and the adjacent Middle and Upper Allochthon. The project focuses on investigating the structure of the upper Precambrian basement in the area related to the Western Gneiss Region (WGR), surrounded by the Caledonian nappes. One problem we are addressing is the depth extension of the Devonian detachments related to the late Caledonian gravity collapse and their influence on the old passive continental margin beneath the Caledonian Orogen.

This guidebook was prepared for the Norwegian part (seven days) of Excursion no. 34 ofthe 33" IGC, Oslo, 2008, to give participants from outside the region as comprehensive a view as possible within 10 days of the stratigraphy, paleontology, tectonostratigraphy, structural geology, igneous and metamorphic petrology, geochronology, tectonics and geophysics, in a traverse across this major thrust-assembled orogen from the foreland in Sweden to places deep in the hinterland in coastal Norway with evidence of ultra-high-pressure metamorphism and melting. The flrst three days in Sweden (Part I of report 2008.064) were led by David Gee and Per-Gunnar Andreasson, with co-leaders Erik Sturkell and Anna Ladenburger. The last seven days (Part II: this report) were led by Peter Robinson and David Roberts with co-leaders Arne Solli, Kurt Hollocher, Per Terje Osmundsen, Tor Grenne, Herman Van Roermund, Michael Terry and Hans Vrijmoed, with contributions by David Gee, Bob Tucker, Tom Kroghl, Alan Krill, Emily Walsh and Megan Regel. It was divided by day as follows:
Day 4: Trondheim Nappe Complex and subjacent units: Storlien to Trondheim.
Day 5: Scandian geology of the Outer Trondheimsfjord region.
Day 6: Part I: Geology of the Hølonda-Horg-Løkken area.
Day 6: Part II: Geology of Trollheimen.
Day 7: Garnet peridotites in the northern UHP domain af the Western Gneiss Region, Otrøy.
Day 7: Mafic dikes and basement-cover relationships, southern coast of the islands of Midsund.
Day 8: Structural and metamorphic relationships between Caledonian nappes and Fennoscandian basement on the mainland near Brattvåg. Day 9: Geology of Haramsøy, Flemsøy and Lepsøy.
Day 10: Geology on the route Lepsøya-Brattvåg-Solholmen-Svartberget-Atlantic Highway-Averøy-Halsa-Trondheim