Remnants of arc-related Mesoarchaean oceanic crust in the Tartoq Group of SW Greenland

Szilas, Kristoffer; Hinsberg, Vincent J. van; Kisters, Alex; Hoffmann, J. Elis; Windley, Brian F.; Kokfelt, Thomas F.; Scherstén, Anders; Frei, Robert; Rosing, Minik T.; Münker, Carsten

doi:10.1016/j.gr.2011.11.006

Cited by 53 publications

(43 citation statements)

References 75 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is evident by the higher TiO 2 contents of Akia terrane supracrustal rocks for any given MgO, in combination with flat to slightly enriched incompatible trace element patterns. A closer resemblance for the basaltic range of the Akia supracrustal rocks is observed when comparing them with Mesoarchaean tholeiitic basalts of the Tartoq Group in SW Greenland [105,109]. The Al 2 O 3 /TiO 2 ratios of the Fiskefjord region peridotites are intermediate between the Tartoq and Isua serpentinites.…”

Section: Petrogenesis Of the Fiskefjord Region Peridotitesmentioning

confidence: 67%

Peridotite enclaves hosted by Mesoarchaean TTG-suite orthogneisses in the Fiskefjord region of southern West Greenland

Szilas

Kelemen

Bernstein³

2015

GeoResJ

Self Cite

View full text Add to dashboard Cite

a b s t r a c tThis study presents bulk-rock major, trace, and platinum-group element data, as well as mineral chemistry for peridotites which form large enclaves (up to 500 Â 1000 m) within Mesoarchaean orthogneisses of the Akia terrane in the Fiskefjord region, southern West Greenland. The largest peridotite body, known as Seqi, contains highly fosteritic olivine with a median Mg# of 92.6 and hosts extensive layers of chromitite, which can be traced for tens of metres with thicknesses of up to 30 cm. Thinner (<100 m thick), but extensive (up to 2000 m long) peridotite sheets are associated with coarse norite and orthopyroxenite with distinct cumulate textures in the Amikoq complex, located a few tens of kilometres south of Seqi. Intercalated amphibolites of tholeiitic basaltic composition show complementary geochemical evolution to the peridotites, consistent with igneous crystal fractionation trends. The U-shaped trace element patterns of the peridotites may either reflect the parental melt composition from which these olivine-rich rocks were derived, or alternatively this feature may be the result of melt-rock interaction. Overall, we interpret the Fiskefjord region peridotites to have formed as ultramafic cumulates derived from Archaean high-Mg, low Ca/Al magmas, although their geodynamic setting remains to be established.

show abstract

Section: Petrogenesis Of the Fiskefjord Region Peridotitesmentioning

confidence: 67%

Peridotite enclaves hosted by Mesoarchaean TTG-suite orthogneisses in the Fiskefjord region of southern West Greenland

Szilas

Kelemen

Bernstein³

2015

GeoResJ

Self Cite

View full text Add to dashboard Cite

show abstract

“…The full data compilation can be obtained upon request from the author. [37] It was found that the most effectively way to classify the metavolcanic rocks in distinct petrogenetic suites of tholeiitic and calc-alkaline affinity was to use their La/Sm ratio, which distinguishes a bimodal population within the data set as seen in Figure 2 above. The main argument for the robustness of this bimodal distribution is the fact that it occurs even on an outcrop scale, and that both geochemical suites display primary volcanic features, such as pillow structures and volcaniclastic features [23,26,27,35,36].…”

Section: Methodsmentioning

confidence: 99%

A Geochemical Overview of Mid-Archaean Metavolcanic Rocks from Southwest Greenland

Szilas

2018

Geosciences

Self Cite

View full text Add to dashboard Cite

Abstract:The present contribution reviews bulk-rock geochemical data for mid-Archaean (ca. 3075-2840 Ma) metavolcanic rocks from the North Atlantic Craton of southwest Greenland. The data set includes the most recent high quality major and trace element geochemical analyses for ten different supracrustal/greenstone belts in the region. When distilling the data set to only include the least altered metavolcanic rocks, by filtering out obviously altered samples, mafic/ultramafic cumulate rocks, late-stage intrusive sheets (dolerites) and migmatites, the remaining data (N = 427) reveal two fundamentally distinct geochemical suites. The contrasting trends that emerge from the filtered geochemical data set, which best represents the melt compositions for these mid-Archaean metavolcanic rocks are: (1) tholeiitic (mainly basaltic) versus (2) calc-alkaline (mainly andesitic). These two rock suites are effectively separated by their La/Sm ratios (below or above three, respectively). It is demonstrated by geochemical modelling that the two contrasting suites cannot be related by either fractional crystallization or crustal assimilation processes, despite occurring within the same metavolcanic sequences. The tholeiitic basaltic rocks were directly mantle-derived, whereas the petrogenesis of the calc-alkaline andesitic rocks involve a significant (>50%) felsic component. The felsic contribution in the calc-alkaline suite could either represent slab-melt metasomatism of their mantle source, mafic-felsic magma mixing, or very large degrees of partial melting of mafic lower crust. At face value, the occurrence of andesites, and the negative Nb-Ta-Ti-anomalies of both suites, is consistent with a subduction zone setting for the origin of these metavolcanic rocks. However, the latter geochemical feature is inherent to processes involving crustal partial melts, and therefore independent lines of evidence are needed to substantiate the hypothesis that plate tectonic processes were already operating by the mid-Archaean.

show abstract

“…Bulk rock compositions of these samples were determined by flux-digestion ICP-MS on powdered samples. Full details of the analysis method as well as the complete data set are available in [6,8,11]. Bulk compositions for samples used in the present study are also listed in Supplementary Table S1.…”

Section: Methodsmentioning

confidence: 99%

“…Modified after [2]. The rocks exposed in the Tartoq belt are predominantly tholeiitic meta-basalts of back-or forearc affinity [6]. Metamorphism and deformation have largely overprinted original textures and unit relationships, although gabbroic and pillow textures, as well as dyke and sill relationships can locally be observed.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Pressure–Temperature History of the >3 Ga Tartoq Greenstone Belt in Southwest Greenland and Its Implications for Archaean Tectonics

et al. 2018

Self Cite

View full text Add to dashboard Cite

The Tartoq greenstone belt of southwest Greenland represents a well-preserved section through >3 Ga old oceanic crust and has the potential to provide important constraints on the composition and geodynamics of the Archaean crust. Based on a detailed structural examination, it has been proposed that the belt records an early style of horizontal convergent plate tectonics where elevated temperatures, compared to the modern-day, led to repeated aborted subduction and tonalite-trondhjemite-granodiorite (TTG) type melt formation. This interpretation hinges on pressure-temperature (P-T) constraints for the belt, for which only preliminary estimates are currently available. Here, we present a detailed study of the pressure-temperature conditions and metamorphic histories for rocks from all fragments of the Tartoq belt using pseudosection modelling and geothermobarometry. We show that peak conditions are predominantly amphibolite facies, but range from 450 to 800 • C at up to 7.5 kbar; reaching anatexis with formation of TTG-type partial melts in the Bikuben segment. Emplacement of the Tartoq segments into the host TTG gneisses took place at approximately 3 Ga at 450-500 • C and 4 kbar as constrained from actinolite-chlorite-epidote-titanite-quartz parageneses, and was followed by extensive hydrothermal retrogression related to formation of shear zone-hosted gold mineralisation. Tourmaline thermometry and retrograde assemblages in mafic and ultramafic lithologies constrain this event to 380 ± 50 • C at a pressure below 1 kbar. Our results show that the convergent tectonics recorded by the Tartoq belt took place at a P-T gradient markedly shallower than that of modern-day subduction, resulting in a hot, weak and buoyant slab unable to generate and transfer 'slab pull', nor sustain a single continuous downgoing slab. The Tartoq belt suggests that convergence was instead accomplished by under-stacking of slabs from repeated aborted subduction. The shallow P-T path combined with thermal relaxation following subduction stalling subsequently resulted in partial melting and formation of TTG melts.

show abstract

Remnants of arc-related Mesoarchaean oceanic crust in the Tartoq Group of SW Greenland

Cited by 53 publications

References 75 publications

Peridotite enclaves hosted by Mesoarchaean TTG-suite orthogneisses in the Fiskefjord region of southern West Greenland

Peridotite enclaves hosted by Mesoarchaean TTG-suite orthogneisses in the Fiskefjord region of southern West Greenland

A Geochemical Overview of Mid-Archaean Metavolcanic Rocks from Southwest Greenland

Pressure–Temperature History of the >3 Ga Tartoq Greenstone Belt in Southwest Greenland and Its Implications for Archaean Tectonics

Contact Info

Product

Resources

About