Paleoarchean bedrock lithologies across the Makhonjwa Mountains of South Africa and Swaziland linked to geochemical, magnetic and tectonic data reveal early plate tectonic genes flanking subduction margins

Wit, Maarten de; Furnes, Harald; MacLennan, S. A.; Doucouré, Moctar; Schoene, Blair; Weckmann, U.; Martinez, Uma; Bowring, Sam

doi:10.1016/j.gsf.2017.10.005

Cited by 47 publications

(10 citation statements)

References 218 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A possible causal mechanism for the conductor C3 may thus be associated with elevated lower-crustal temperatures >700 °C due to high-concentrations of radiogenic heat sources in the upper crust 25 – 27 , coupled with the presence of hydrated minerals as a results of fluid and magma migration from the lower most crust and upper mantle to the brittle-ductile zone 28 . Similar electrically conductive lithospheric structures were revealed in layered intrusive complexes of the Slave 29 and Kaapvaal Cratons 30 and for a world-class gold deposit in the Barberton Greenstone Belt 31 .…”

Section: Discussionsupporting

confidence: 57%

The crustal geophysical signature of a world-class magmatic mineral system

Heinson

Didana

Soeffky

et al. 2018

Sci Rep

View full text Add to dashboard Cite

World-class magmatic mineral systems are characterised by fluid/melt originating in the deep crust and mantle. However, processes that entrain and focus fluids from a deep-source region to a kilometre-scale deposit through the crust are unclear. A magnetotelluric (MT) and reflection seismic program across the margin of the Gawler Craton, Australia yield a distinct signature for a 1590 Ma event associated with emplacement of iron-oxide copper gold uranium (IOCG-U) deposits. Two- and three-dimensional MT modelling images a 50 km wide lower-crustal region of resistivity <10 Ωm along an accreted Proterozoic belt. The least resistive (~1 Ωm) part terminates at the brittle-ductile transition at ~15 km, directly beneath a rifted sedimentary basin. Above the brittle-ductile transition, three narrow low-resistivity zones (~100 Ωm) branch to the surface. The least resistive zone is remarkably aligned with the world-class IOCG-U Olympic Dam deposit and the other two with significant known IOCG-U mineral occurrences. These zones are spatially correlated with narrow regions of low seismic reflectivity in the upper crust, and the deeper lower-crust conductor is almost seismically transparent. We argue this whole-of-crust imaging encapsulates deep mineral system and maps pathways of metalliferous fluids from crust and mantle sources to emplacement at discrete locations.

show abstract

Section: Discussionsupporting

confidence: 57%

The crustal geophysical signature of a world-class magmatic mineral system

Heinson

Didana

Soeffky

et al. 2018

Sci Rep

View full text Add to dashboard Cite

show abstract

“…Ga in the Pilbara Craton (Western Australia) and southern India, and during the Neoarchean in the Superior Province of North America and the North China Craton (Calvert et al, 1995;Cawood et al, 2006;de Wit et al, 2018;Friend and Nutman, 2005;Kusky et al, 2016;Santosh et al, 2015;Smithies et al, 2007;Van Kranendonk et al, 2015b). On a global scale, statistical analysis of the chemical composition of continental igneous rocks with ages spanning 3.8 Ga to the present day reveals patterns consistent with secular cooling of the mantle since the late Archaean (Keller and Schoene, 2012).…”

Section: Introductionmentioning

confidence: 92%

Secular change in TTG compositions: Implications for the evolution of Archaean geodynamics

Johnson

Kirkland

Gardiner

et al. 2019

Earth and Planetary Science Letters

110

View full text Add to dashboard Cite

It is estimated that around three quarters of Earth's first generation continental crust had been produced by the end of the Archaean Eon, 2.5 billion years ago. This ancient continental crust is mostly composed of variably deformed and metamorphosed magmatic rocks of the tonalitetrondhjemite-granodiorite (TTG) suite that formed by partial melting of hydrated mafic rocks. However, the geodynamic regime under which TTG magmas formed is a matter of ongoing debate. Using a filtered global geochemical dataset of 563 samples with ages ranging from the Eoarchaean to Neoarchaean (4.0-2.5 Ga), we interrogate the bulk rock major oxide and trace element composition of TTGs to assess evidence for secular change. Despite a high degree of scatter in the data, the concentrations or ratios of several key major oxides and trace elements show statistically significant trends that indicate maxima, minima and/or transitions in the interval 3.3-3.0 Ga. Importantly, a change point analysis of K 2 O/Na 2 O, Sr/Y and La N /Yb N demonstrates a statistically significant (>99% confidence) change during this 300 Ma period. These shifts may be linked to a fundamental change in geodynamic regime around the peak in upper mantle temperatures from one dominated by non-uniformitarian, deformable stagnant lid processes to another dominated by the emergence of global mobile lid or plate tectonic processes by the end of the Archaean. A notable change is also evident at 2.8-2.7 Ga, which coincides with a major jump in the rate of survival of metamorphic rocks with contrasting thermal gradients, which may relate to the emergence of more potassic continental arc magmas and an increased preservation potential during collisional orogenesis. In many cases, the chemical composition of TTGs shows an increasing spread through the Archaean, reflecting the irreversible differentiation of the lithosphere.

show abstract

“…2c), and from those generated in mid-ocean ridges to those created in suprasubduction settings (Furnes et al, 2014;Kusky et al, 2011). Based on new models of ophiolite structure, some of the bestdocumented Archean ophiolites include portions of the 2.5 Ga Shangyin-Zunhua Belt of North China (Kusky and Li, 2010;Kusky et al, 2001), the 3.3 Ga Barberton Belt (de Wit et al, 2018), and the 3.8 Ga Isua Belt (Fig. 4).…”

Section: Geological Evidence For the Operation Of Plate Tectonics In mentioning

confidence: 99%

“…In Barberton, seven major thrust sheets each with distinctive tectonic histories have been delineated (de Wit et al, 2018;de Wit, 2004), each resembling parts of different types of ophiolites formed in modern oceanic backarc-like settings. New field, geochemical and geochronological data (Grosch and Slama, 2017) indicate that the primitive Kromberg massive and pillowed mafic lavas, gabbros, and ultramafic cumulate sequence and overlying cherts are a fragment of an Archean ophiolite, and were not (Kersting, 1995); Mariana (Plank et al, 2000); Japan (Wakita, 2012); Nankai (Shipoard Scientific Party, 2000); Ballantrae (Sawaki et al, 2010); Lleyn (Maruyama et al, 2010);…”

Section: Geological Evidence For the Operation Of Plate Tectonics In mentioning

confidence: 99%

Geological Evidence for the Operation of Plate Tectonics throughout the Archean: Records from Archean Paleo-Plate Boundaries

2018

View full text Add to dashboard Cite

Plate tectonics describes the horizontal motion of rigid lithospheric plates away from midoceanic ridges and parallel to transforms, towards deep-sea trenches, where the oceanic lithosphere is subducted into the mantle. This process is the surface expression of modern-day heat loss from Earth. One of the biggest questions in Geosciences today is "when did plate tectonics begin on Earth" with a wide range of theories based on an equally diverse set of constraints from geology, geochemistry, numerical modeling, or pure speculation. In this contribution, we turn the coin over and ask "when was the last appearance in the geological record for which there is proof that plate tectonics did not operate on the planet as it does today". We apply the laws of uniformitarianism to the rock record to ask how far back in time is the geologic record consistent with presently-operating kinematics of plate motion, before which some other mechanisms of planetary heat loss may have been in operation. Some have suggested that evidence shows that there was no plate tectonics before 800 Ma ago, others sometime before 1.8-2.7 Ga, or before 2.7 Ga. Still others recognize evidence for plate tectonics as early as 3.0 Ga, 3.3-3.5 Ga, the age of the oldest rocks, or in the Hadean before 4.3 Ga. A key undiscussed question is: why is there such a diversity of opinion about the age at which plate tectonics can be shown to not have operated, and what criteria are the different research groups using to define plate tectonics, and to recognize evidence of plate tectonics in very old rocks? Here, we present and evaluate data from the rock record, constrained by relevant geochemical-isotopic data, and conclude that the evidence shows indubitably that plate tectonics has been operating at least since the formation of the oldest rocks, albeit with some differences in processes, compositions, and products in earlier times of higher heat generation and mantle temperature, weaker oceanic lithosphere, hotter subduction zones caused by more slab-melt generation, and under different biological and atmospheric conditions.

show abstract

Paleoarchean bedrock lithologies across the Makhonjwa Mountains of South Africa and Swaziland linked to geochemical, magnetic and tectonic data reveal early plate tectonic genes flanking subduction margins

Cited by 47 publications

References 218 publications

The crustal geophysical signature of a world-class magmatic mineral system

The crustal geophysical signature of a world-class magmatic mineral system

Secular change in TTG compositions: Implications for the evolution of Archaean geodynamics

Geological Evidence for the Operation of Plate Tectonics throughout the Archean: Records from Archean Paleo-Plate Boundaries

Contact Info

Product

Resources

About