Transitional (2.1 Ga) Fe-tholeiitic-tholeiitic magmatism in the Fennoscandian Shield signifying lithospheric thinning during Palaeoproterozoic extensional tectonics

Nykänen, Vesa; Vuollo, Jouni; Liipo, Jussi; Piirainen, T.

doi:10.1016/0301-9268(94)90020-5

Cited by 34 publications

(29 citation statements)

References 44 publications

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“…The slight enrichment in the LREE relative to HREE, is again suggestive of crustal contamination, or an enriched lithospheric mantle source. This LREE enrichment of the Killara Formation mafic rocks compares well with the continental Fe‐rich tholeiites of the Fennoscandian Palaeoproterozoic rocks ( Nykänen et al 1994 ). The Killara Formation volcanic rocks have high Ce/Yb ratios (>10), which are considered typical of continental tholeiites ( Green 1992).…”

Section: Stratigraphysupporting

confidence: 55%

Three Palaeoproterozoic basins—Yerrida, Bryah and Padbury—Capricorn Orogen, Western Australia

Pirajno

Occhipinti

2000

Australian Journal of Earth Sciences

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The Palaeoproterozoic Yerrida, Bryah and Padbury Basins record periods of sedimentation and magmatism along the northern margin of the Archaean Yilgarn Craton. Each basin is characterised by distinct stratigraphy, igneous activity, structural and metamorphic history and mineral deposit types. The oldest of these basins, the Yerrida Basin (ca 2200 Ma) is floored by rocks of the Archaean Yilgarn Craton. Important features of this basin are the presence of evaporites and continental flood basalts. The ca 2000 Ma Bryah Basin developed on the northern margin of the Yilgarn Craton during backarc sea-floor spreading and rifting, the result of which was the emplacement of voluminous mafic and ultramafic volcanic rocks. During the waning stages of the Bryah Basin this mafic to ultramafic volcanism gave way to deposition of clastic and chemical sedimentary rocks. At a later stage, the Padbury Basin developed as a retroarc foreland basin on top of the Bryah Basin in a fold-and-thrust belt. This resulted from either the collision of the Pilbara and Yilgarn Cratons (Capricorn Orogeny) or the ca 2000 Ma westward collision of the southern part of the Gascoyne Complex and the Yilgarn Craton (Glenburgh Orogeny). During the Capricorn Orogeny the Bryah Group was thrust to the southeast, over the Yerrida Group. Important mineral deposits are contained in the Yerrida, Bryah and Padbury Basins. In the Yerrida Basin a large Pb-carbonate deposit (Magellan) and black shale-hosted gossans containing anomalous abundances of Ba, Cu, Zn and Pd are present. The Pb-carbonate deposit is hosted by the upper units of the Juderina Formation, and the lower unit of the unconformably overlying Earaheedy Group. The Bryah and Padbury Basins contain orogenic gold, copper-gold volcanogenic massive sulfides, manganese and iron ore. The origin of the gold mineralisation is probably related to tectonothermal activity during the Capricorn Orogeny at ca 1800 Ma.

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Section: Stratigraphysupporting

confidence: 55%

Three Palaeoproterozoic basins—Yerrida, Bryah and Padbury—Capricorn Orogen, Western Australia

Pirajno

Occhipinti

2000

Australian Journal of Earth Sciences

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“…The first was associated with tholeiitic mafic volcanism dated at 2.10 and 2.06 Ga (Pekkarinen and Lukkarinen, 1991;Vuollo et al, 1992;Nykänen et al, 1994), and transgression and subsidence recorded by a transition from orthoquartzites and platform carbonates to turbidites of proximal to distal character (Ward, 1987(Ward, , 1988Pekkarinen and Lukkarinen, 1991).…”

Section: Geological Settingmentioning

confidence: 96%

Metamorphism and Chromite in Serpentinized and Carbonate-Silica-Altered Peridotites of the Paleoproterozoic Outokumpu-Jormua Ophiolite Belt, eastern Finland

Säntti

Kontinen

Sorjonen-Ward

et al. 2006

International Geology Review

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The 1.95 Ga Outokumpu-Jormua ophiolite belt of eastern Finland contains numerous mafic-ultramafic, predominantly peridotitic bodies which, despite amphibolite-facies metamorphism and pervasive deformation, retain compelling evidence of a residual mantle origin. These rocks therefore currently represent the oldest documented examples of exhumed mantle lithosphere, so information concerning their primary igneous mineral assemblages and textures and chemical and isotopic characteristics is of considerable scientific value. Although several earlier studies have argued for the preservation of primary mineral assemblages, field and petrographic evidence presented here show that the protolith peridotites had already experienced pervasive low-T serpentinization prior to Svecofennian orogenic deformation, during which they were progressively deserpentinized via antigorite metaserpentinites to olivine-talc-anthophyllite-enstatite-bearing metaperidotites. Evidence is also presented to show that the premetamorphic serpentinization event was closely followed by extensive low-T (< 250°C) metasomatic alteration of the marginal parts of the ultramafic bodies to carbonate-silica rocks which, during the subsequent prograde metamorphism, were converted to the distinctive chromite-bearing carbonate-skarn-quartz rocks comprising the Outokumpu rock assemblage. Because these quartz rocks are intimately associated with the Outokumpu Cu-Co-Zn-Ni deposits and have generally been regarded as metamorphosed siliceous seafloor exhalative deposits, the revised interpretation presented here has important implications for ore formation as well. Equilibrium mineral assemblages in the interior parts of the ultramafic bodies (low XCO 2 ) define four regional metamorphic zones, expressed as an east to west increase in the peak dehydration temperatures from 500° to 775ºC, at 3-5 kbar. Large ultramafic bodies commonly show core to margin zoning from talc via anthophyllite-to enstatite-bearing assemblages, reflecting synmetamorphic core-margin gradients in XCO 2 , attributed to infiltration of CO 2 released by decarbonation reactions in previously formed talc-carbonate and carbonate-silica alteration zones.The only primary igneous phase identified in this study was chromite, which occurs as scattered relict cores within large altered grains. These are relatively common in metaserpentinites, but also occur in metaperidotites and even in carbonate-skarn-quartz rocks. Even though Mg, Fe 2+ , and Zn abundances in these relict chromites may have been somewhat modified, absolute concentrations and ratios of Cr and Al appear to be essentially unmodified. The lobate to amoeboid morphology and observed Cr# range (0.41-0.67) of the best-preserved grains are more consistent with residual depleted lherzolite to harzburgite textures than a cumulate origin. However, during regional metamorphism, most mantle chromites were either pervasively altered to ferrian chromites and Cr-magnetites or (where CO 2 and S fugacities were high, such as within smaller ultramafic bod...

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“…2.06 Ga Siilinjärvi and 2.09-2.05 Ga Väystäjä bimodal volcanic complexes show crustally contaminated (Archean) and non-contaminated plume-derived magma types, and these units correlate well with each other. The occurrence of 2.1-2.05 Ga volcanic complexes in Tohmajärvi (Nykänen et al, 1994), Siilinjärvi (Lukkarinen, 2008), Kiiminki (Honkamo, 1989), Väystäjä and the Otanmäki alkaline granites (Kontinen et al, 2013) represent the "soft points" of a 'zigzag' rift pattern (100-150 km displacement, Fig. 1 inset) above small-scale convection cells (Gac & Geoffroy, 2009), which formed during continent breakup (Lahtinen et al, 2015c).…”

Section: Tectonic Implications and Correlationsmentioning

confidence: 99%

Geochemical and U-Pb and Sm-Nd isotopic constraints on the evolution of the Paleoproterozoic Ylitornio nappe complex, northern Fennoscandia

Lahtinen¹,

Huhma²,

Lauri³

et al. 2019

Bull Geol Soc Finland

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The Ylitornio area in northern Finland is a typical example of a poorly outcropping, multiply deformed, complex Precambrian terrain. U-Pb, Sm-Nd and geochemical data from metavolcanic, metasedimentary and plutonic rocks combined with structural data define the lithodemic units and tectonostratigraphy of the area. The Mellajoki, Martimo, Hosiojoki, Kierovaara and Uusivirka suites form the Ylitornio nappe complex. Although main thrust stacking had occurred between 1.92-1.89 Ga, later reverse faulting probably continued until 1.78 Ga. The Väystäjä bimodal volcanic rocks (2.09-2.05 Ga) from the Martimo suite are plume-related EMORB-OIB rocks formed during a continent breakup. The Kaskimaa greywacke of the Martimo suite is inferred to represent sedimentation in a deepening rift basin in the continental margin. The coeval Hosiojoki felsic rocks with A-type affinity and the Kierovaara suite granites (2.00-1.98 Ga) represent dry melting of a dominantly 2.1-2.05 Ga contaminated mafic underplate, and hydrous melting of both the mafic underplate and a refractory lower crust of Archean age, respectively. The older rocks of the Uusivirka suite are early-collisional (1.92-1.91 Ga) and derived from poorly mixed local sources, whereas younger psammite-pelite associations (Ristivuoma) are syn-collisional (1.91-1.89 Ga) and derive from multiply recycled and thoroughly mixed sources. These rocks were deformed during continued collision with the development of foreland fold-and thrust belt.

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Transitional (2.1 Ga) Fe-tholeiitic-tholeiitic magmatism in the Fennoscandian Shield signifying lithospheric thinning during Palaeoproterozoic extensional tectonics

Cited by 34 publications

References 44 publications

Three Palaeoproterozoic basins—Yerrida, Bryah and Padbury—Capricorn Orogen, Western Australia

Three Palaeoproterozoic basins—Yerrida, Bryah and Padbury—Capricorn Orogen, Western Australia

Metamorphism and Chromite in Serpentinized and Carbonate-Silica-Altered Peridotites of the Paleoproterozoic Outokumpu-Jormua Ophiolite Belt, eastern Finland

Geochemical and U-Pb and Sm-Nd isotopic constraints on the evolution of the Paleoproterozoic Ylitornio nappe complex, northern Fennoscandia

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