Field and geochemical characteristics of the Mesoarchean (∼3075Ma) Ivisaartoq greenstone belt, southern West Greenland: Evidence for seafloor hydrothermal alteration in supra-subduction oceanic crust

Polat, Ali; Appel, Peter; Frei, Robert; Pan, Yuanming; Dilek, Yıldırım; Ordóñez-Calderón, Juan C.; Fryer, Brian J.; Hollis, Julie; Raith, Johann

doi:10.1016/j.gr.2006.02.004

Cited by 104 publications

(38 citation statements)

References 74 publications

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“…Although it is generally accepted that the source of silica in BIF was ambient seawater during most of the Precambrian, when the biological sink for seawater silica was presumably absent (Siever, 1992), the source of silica to the oceans of that time period remains uncertain. Two potential sources, similar to that for iron, have been proposed: submarine hydrothermal fluids (Mortlock et al, 1993;Wang et al, 2009) and the continents (Frei and Polat, 2007;Hamade et al, 2003). Support for the latter proposition has come mainly from the study of Ge/Si ratios in IFs, as hydrothermal fluids and rivers have very different Ge/Si ratios (Froelich et al, 1985;Mortlock et al, 1993).…”

Section: Hydrothermal Pulses Of Si Synchronous With Fe Addition To Sementioning

confidence: 95%

Iron Formations: Their Origins and Implications for Ancient Seawater Chemistry

Bekker

Planavsky

Rasmussen

et al. 2014

Treatise on Geochemistry

152

158

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Section: Hydrothermal Pulses Of Si Synchronous With Fe Addition To Sementioning

confidence: 95%

Iron Formations: Their Origins and Implications for Ancient Seawater Chemistry

Bekker

Planavsky

Rasmussen

et al. 2014

Treatise on Geochemistry

152

158

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“…[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

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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.

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“…Unambiguous indicators of plate underflow-blueschist + low-T eclogite belts and HP-UHP cratonal subduction complexes (Figs. 3 and 5)-date from about 0.75 and 0.53 Ga, respectively (Ernst 1983;Scott et al 1992;Maruyama et al 1996;Kusky et al 2001;Condie 2005;Polat et al 2005Polat et al , 2007Polat et al , 2008Brown 2006Brown , 2008Tsujimori and Ernst 2014). Eclogitic micro-inclusions in diamonds as ancient as ϳ3.0 Ga were reported by Shirey and Richardson (2011), and they have been interpreted by these authors as marking the onset of the Wilson-cycle of plate tectonics.…”

mentioning

confidence: 98%

Plate-tectonic evolution of the Earth: bottom-up and top-down mantle circulation

2016

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Abstract:Intense devolatilization and chemical-density differentiation attended accretion of planetesimals on the primordial Earth. These processes gradually abated after cooling and solidification of an early magma ocean. By 4.3 or 4.2 Ga, water oceans were present, so surface temperatures had fallen far below low-pressure solidi of dry peridotite, basalt, and granite, ϳ1300, ϳ1120, and ϳ950°C, respectively. At less than half their T solidi, rocky materials existed as thin lithospheric slabs in the near-surface Hadean Earth. Stagnant-lid convection may have occurred initially but was at least episodically overwhelmed by subduction because effective, massive heat transfer necessitated vigorous mantle overturn in the early, hot planet. Bottom-up mantle convection, including voluminous plume ascent, efficiently rid the Earth of deep-seated heat. It declined over time as cooling and top-down lithospheric sinking increased. Thickening and both lateral extensional + contractional deformation typified the post-Hadean lithosphere. Stages of geologic evolution included (i) 4.5-4.4 Ga, magma ocean overturn involved ephemeral, surficial rocky platelets; (ii) 4.4-2.7 Ga, formation of oceanic and small continental plates were obliterated by return mantle flow prior to ϳ4.0 Ga; continental material gradually accumulated as largely sub-sea, sialic crust-capped lithospheric collages; (iii) 2.7-1.0 Ga, progressive suturing of old shields + younger orogenic belts led to cratonal plates typified by emerging continental freeboard, increasing sedimentary differentiation, and episodic glaciation during transpolar drift; onset of temporally limited stagnant-lid mantle convection occurred beneath enlarging supercontinents; (iv) 1.0 Ga-present, laminar-flowing asthenospheric cells are now capped by giant, stately moving plates. Near-restriction of komatiitic lavas to the Archean, and appearance of multicycle sediments, ophiolite complexes ± alkaline igneous rocks, and high-pressure-ultrahigh-pressure (HP-UHP) metamorphic belts in progressively younger Proterozoic and Phanerozoic orogens reflect increasing negative buoyancy of cool oceanic lithosphere, but decreasing subductability of enlarging, more buoyant continental plates. Attending supercontinental assembly, density instabilities of thickening oceanic plates began to control overturn of suboceanic mantle as cold, top-down convection. Over time, the scales and dynamics of hot asthenospheric upwelling versus lithospheric foundering + mantle return flow (bottom-up plume-driven ascent versus top-down plate subduction) evolved gradually, reflecting planetary cooling. These evolving plate-tectonic processes have accompanied the Earth's thermal history since ϳ4.4 Ga.Résumé : Un intense dégagement de matières volatiles et une différentiation selon la densité chimique faisait partie de l'accrétion de planétésimaux à la Terre primordiale. Ces processus ont grandement diminué après le refroidissement et la solidification d'un océan primitif de magma. Vers 4,3 ou 4,2 Ga, il existait des océan...

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Field and geochemical characteristics of the Mesoarchean (∼3075Ma) Ivisaartoq greenstone belt, southern West Greenland: Evidence for seafloor hydrothermal alteration in supra-subduction oceanic crust

Cited by 104 publications

References 74 publications

Iron Formations: Their Origins and Implications for Ancient Seawater Chemistry

Iron Formations: Their Origins and Implications for Ancient Seawater Chemistry

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

Plate-tectonic evolution of the Earth: bottom-up and top-down mantle circulation

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