DOI 10.1130/GES01565.1 Recently it has been argued that the Sveconorwegian orogeny in southwest Fennoscandia comprised a series of accretionary events between 1140 and 920 Ma, behind a long-lived, active continental margin characterized by voluminous magmatism and high-grade metamorphism. Voluminous magnesian granitic magmatism is recorded between 1070 and 1010 Ma (Sirdal Magmatic Belt, SMB), with an apparent drop in activity ca. 1010-1000 Ma. Granitic magmatism resumed ca. 1000-990 Ma, but with more ferroan (A type) compositions (hornblende-biotite granites). This ferroan granitic magmatism was continuous until 920 Ma, and included emplacement of an AMCG (anorthosite-mangerite-charnockite-granite) complex (Rogaland Igneous Complex). Mafic rocks with ages corresponding to the spatially associated granites suggest that heat from underplated mafic magma was the main driving force for lower crustal melting and long-lived granitic magmatism. The change from magnesian to ferroan compositions may reflect an increasingly depleted and dehydrated lower crustal source. High-grade metamorphic rocks more than similar to 20 km away from the Rogaland Igneous Complex yield meta-morphic ages of 1070-1015 Ma, corresponding to SMB magmatism, whereas similar rocks closer to the Rogaland Igneous Complex yield ages between 1100 and 920 Ma, with an apparent age peak ca. 1000 Ma. Ti-in zircon temperatures from these rocks increase from similar to 760 to 820 degrees C ca. 970 Ma, well before the inferred emplacement age of the Rogaland Igneous Complex (930 Ma), suggesting that long-lived, high-grade metamorphism was not directly linked to the emplacement of the latter, but rather to the same mafic underplating that was driving lower crustal melting. Structural data suggest that the present-day regional distribution of high-and low-grade rocks reflects late-stage orogenic doming.
| File | Pages | Size | Access | |
|---|---|---|---|---|
Publisher's official version | 22 | 4 Mo | ||
Suppl A - Methods | 4 | 159 Ko | ||
Suppl B - Geochron data, sample by sample | 20 | 372 Ko | ||
Suppl C - SMB and HBG U-Pb zircon data | - | 288 Ko | ||
Suppl D - magmatic U-Pb zircon data | - | 128 Ko | ||
Suppl E - metamorphic U-Pb zircon data | - | 869 Ko | ||
Suppl F - metamorphic U-Pb zircon data ca.1.25 Ga rocks NEW | - | 337 Ko | ||
Suppl G - Sample coordinates and age summary NEW | - | 85 Ko | ||
Fig ES.B.1 TW plots SMB granites | 2 | 911 Ko | ||
Fig ES.B.2 TW plots HBG granites | 2 | 956 Ko | ||
Fig ES.B.3 prev fig7 CL images mafic magmatism | 1 | 742 Ko | ||
Fig ES.B.4 prev fig8 TW plots mafic magmatism | 1 | 511 Ko | ||
Fig ES.B.5 prev fig9 CL images HAOM, Sjelset | 1 | 473 Ko | ||
Fig ES.B.6 prev fig10 TW plots HAOM and Sjelset | 1 | 457 Ko | ||
Fig ES.B.7 prev fig11 CL meta rocks outside core area | 1 | 1014 Ko | ||
Fig ES.B.8 prev fig12 TW rocks outside core area | 2 | 772 Ko | ||
Fig ES.B.9 prev fig13 TS-photosUHTmetalm | 1 | 46 Mo | ||
Fig ES.B.10 prev fig14 CL rocks in core area | 1 | 1 Mo | ||
Fig ES.B.11 prev fig15 TW rocks in core area | 2 | 692 Ko | ||
Fig ES.B.12 prev fig16 alpha dose and Ti-in-zrn temp | 1 | 418 Ko |
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