Geometry of sheath folds and related fabrics at the Luikonlahti mine, Svecokarelides, eastern Finland

Park, Adrian F.

doi:10.1016/0191-8141(88)90036-3

Cited by 16 publications

(5 citation statements)

References 11 publications

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“…The formation of one or several F 2 sheath folds enriched in sulphides at the deposit, incorporating the reclined fold geometry discussed above, is suggested as an explanation for these concentric patterns that developed perpendicular to the stretching direction. The occurrence of sheath folds has been reported previously in the Outokumpu ore district in the Fennoscandian Shield (Park 1988) as well as in other Precambrian ore districts affected by ductile deformation and metamorphism such as Itabira in Brazil (Giuliani et al 1990;Olivo et al 1995), the Manitouwadge greenstone Belt in Canada (Zaleski and Peterson 1995) and Broken Hill in Australia (Forbes et al 2004). …”

Section: Discussionmentioning

confidence: 97%

3D modelling and sheath folding at the Falun pyritic Zn-Pb-Cu-(Au-Ag) sulphide deposit and implications for exploration in a 1.9 Ga ore district, Fennoscandian Shield, Sweden

2016

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Altered and mineralized rocks at the Falun pyritic Zn-Pb-Cu-(Au-Ag) sulphide deposit, situated in the Palaeoproterozoic Bergslagen ore district in the southwestern part of the Fennoscandian Shield, have been metamorphosed at low-pressure, amphibolite-facies conditions and affected by ductile deformation. Using combined surface mapping of lithology and structure, drill core logging and microstructural work, the polyphase (D 1 and D 2 ) ductile deformation is demonstrated and a 3D model for the deposit created. Mineral associations include quartz, biotite, cordierite, anthophyllite, and minor almandine, andalusite and chlorite in silicate-rich altered rock, calcite or dolomite in marble and tremolite-actinolite or diopside-hedenbergite in skarn. The silicate minerals show varying growth patterns during the different phases of the tectonothermal evolution, with considerable static grain growth occurring between D 1 and D 2 , and even after D 2 . F 2 sheath folding along axes that plunge steeply to the SSE, parallel to a mineral stretching lineation and the dip direction of the S 2 foliation, is suggested as a key deformation mechanism forming steeply plunging, cone-to rod-shaped mineralized bodies. This contrasts with a previous structural model invoking fold interference. A major shear zone with talc-chlorite-(quartz-biotite) mineral association separates the northern and southern structural domains at the deposit and bounds the polymetallic massive sulphides to the north.

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Section: Discussionmentioning

confidence: 97%

3D modelling and sheath folding at the Falun pyritic Zn-Pb-Cu-(Au-Ag) sulphide deposit and implications for exploration in a 1.9 Ga ore district, Fennoscandian Shield, Sweden

2016

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“…The presence of mesoscopic sheath folds at numerous localities and abundant evidence for such high-strain conditions support the possibility for large-scale sheath folding occurring during thrusting. Kilometre-scale sheath folding is not uncommon in thrust regimes and terranes that experienced significant shortening (Henderson, 1981;Lacassin & Mattauer, 1985;Hibbard & Karig, 1987;Park, 1988;Goscombe, 1991). F 3b folds and steep shear zones (Fig.…”

Section: A Origin Of Folding and Deformation Within Thrust Blocksmentioning

confidence: 97%

Thrusting in the lower crust: evidence from the Oygarden Islands, Kemp Land, East Antarctica

et al. 2000

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Layered orthogneisses of the Oygarden Islands preserve evidence for four high-grade deformation events (D 1 to D 4 ). Archaean D 1 and D 2 structures are only patchily preserved due to extensive recrystallization during D 3 and D 4 , which represent effects of the c. 1000 Ma Rayner Structural Episode. Ductile thrusting at middle to lower crustal levels occurred during D 3 , which is separated into two mutually cross-cutting phases based on structural geometry; the two phases represent changes in finite strain that developed during progressive deformation. East-directed transport during D 3a developed subhorizontal thrusts that contain co-axial, east-trending F 3a folds and L 3a lineations. Buckling as a consequence of constriction in thrust duplexes developed upright F 3b folds coaxial to F 3a folds, and steeply south-dipping D 3b shear zones. Garnet-clinopyroxene-and garnet-orthopyroxene-bearing assemblages in mafic lithologies, and garnet-sillimanite-bearing assemblages in pelitic lithologies reflect D 3 conditions of P = 9 kbar and T = 800-850°C. The well-exposed D 3 duplex structures indicate that shortening of the lower crust may be accommodated by extensive strain partitioning to develop contemporary kilometre-scale thrust stacking and ductile flow.

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“…Geological map showing the division of stratigraphic sequences and structural units in the Ogcheon Belt(modified from Kang, 1994a) (Kang et al, 1993). (Park, 1988;Skjernaa, 1989)(Fig. 5b).…”

Section: Vol 21 No 2 2012mentioning

confidence: 96%

Tectonic evolution of the Central Ogcheon Belt, Korea

Kang¹,

Hayasaka²,

Ryoo³

2012

The Journal of the Petrological Society of Korea

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The tectonic evolution of the Central Ogcheon Belt has been newly analyzed in this paper from the detailed geological maps by lithofacies classification, the development processes of geological structures, microstructures, and the time-relationship between deformation and metamorphism in the Ogcheon, Cheongsan, Mungyeong Buunnyeong, Busan areas, Korea and the fossil and radiometric age data of the Ogcheon Supergroup(OSG). The 1st tectonic phase(D*) is marked by the rifting of the original Gyeonggi Massif into North Gyeonggi Massif(present Gyeonggi Massif) and South Gyeonggi Massif (Bakdallyeong and Busan gneiss complexes). The Joseon Supergroup(JSG) and the lower unit(quartzose psammitic, pelitic, calcareous and basic rocks) of OSG were deposited in the Ogcheon rift basin during Early Paleozoic time, and the Pyeongan Supergroup(PSG) and its upper unit(conglomerate and pelitic rocks and acidic rocks) appeared in Late Paleozoic time. The 2nd tectonic phase(Ogcheon-Cheongsan phase/Songnim orogeny: D1), which occurred during Late Permian-Middle Triassic age, is characterized by the closing of Ogcheon rift basin(= the coupling of the North and South Gyeonggi Massifs) in the earlier phase(Ogcheon subphase: D1a), and by the coupling of South China block(Gyeonggi Massif and Ogcheon Zone) and North China block(Yeongnam Massif and Taebaksan Zone) in the later phase(Cheongsan subphase: D1b). At the earlier stage of D1a occurred the M1 medium-pressure type metamorphism of OSG related to the growth of coarse biotites, garnets, staurolites. At its later stage, the medium-pressure type metamorphic rocks were exhumed as some nappes with SE-vergence, and the giant-scale sheath fold, regional foliation, stretching lineation were formed in the OSG. At the D1b subphase which occurs under (N)NE-(S)SW compression, the thrusts with NNE-or/and SSW-vergence were formed in the front and rear parts of couple, and the NNE-trending Cheongsan shear zone of dextral strike-slip and the NNE-trending upright folds of the JSG and PSG were also formed in its flank part, and Daedong basin was built in Korean Peninsula. After that, Daedong Group(DG) of the Late Triassic-Early Jurassic was depoisited. The 3rd tectonic phase(Honam phase/Daebo orogeny: D2) occurred by the transpression tectonics of NNEtrending Honam dextral strike-slip shearing in Early~Late Jurassic time, and formed the asymmetric crenulated fold in the OSG and the NNE-trending recumbent folds in the JSG and PSG and the thrust faults with ESE-vergence in which pre-Late Triassic Supergroups override DG. The M2 contact metamorphism of andalusite-sillimanite type by the intrusion of Daebo granitoids occurred at the D2 intertectonic phase of Middle Jurassic age. The 4th tectonic phase(Cheongmari phase: D3) occurred under the N-S compression at Early Cretaceous time, and formed the pull-apart Cretaceous sedimentary basins accompanying the NNE-trending sinistral strike-slip shearing. The M3 retrograde metamorphism of OSG associated with the crystallization of chlorite porphyroblasts mainly o...

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Geometry of sheath folds and related fabrics at the Luikonlahti mine, Svecokarelides, eastern Finland

Cited by 16 publications

References 11 publications

3D modelling and sheath folding at the Falun pyritic Zn-Pb-Cu-(Au-Ag) sulphide deposit and implications for exploration in a 1.9 Ga ore district, Fennoscandian Shield, Sweden

3D modelling and sheath folding at the Falun pyritic Zn-Pb-Cu-(Au-Ag) sulphide deposit and implications for exploration in a 1.9 Ga ore district, Fennoscandian Shield, Sweden

Thrusting in the lower crust: evidence from the Oygarden Islands, Kemp Land, East Antarctica

Tectonic evolution of the Central Ogcheon Belt, Korea

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