Age, origin, and thermal evolution of the ultra-fresh ~ 1.9 Ga Winnipegosis Komatiites, Manitoba, Canada
Graphical abstract
Introduction
Komatiites are generally believed to represent high-temperature, large-degree melts of the mantle (Arndt et al., 2008, Nisbet et al., 1993). As such, they have long been used as probes of both the chemical and thermal evolution of the mantle through time (Bickle et al., 1976, Campbell and Griffiths, 2014, Maier et al., 2009). However, the temporal record of mantle temperature and chemistry provided by komatiites is irregular; the vast majority of komatiites erupted during the Archaean (Arndt et al., 2008), with only two occurrences known from the Phanerozoic (Echeverria, 1980, Hanski et al., 2004). Despite comprising almost half of Earth history, only a handful of komatiites and related high MgO igneous rocks have been reported from the Proterozoic Eon, including: Ti-rich komatiites of the Karasjok and Central Lapland Greenstone Belts (Barnes and Often, 1990, Hanski et al., 2001); basaltic komatiites of the Vetreny Belt, (Puchtel et al., 1997); and a number of basaltic komatiites and compositionally similar intrusions from the Circum-Superior Belt (Arndt, 1982, Arndt et al., 1987, Hynes and Francis, 1982, Minifie et al., 2013).
In light of the paucity of Proterozoic komatiites, this paper describes the exceptionally fresh ~ 1.87 Ga Winnipegosis Komatiites from Manitoba, Canada. The minimally altered nature of the Winnipegosis Komatiite sequence provides an excellent opportunity both to study komatiite formation during the Proterozoic, and to compare the chemical and thermal state of Archaean and Proterozoic mantle. We present petrographical and geochemical observations with a view to understanding the mode of formation and thermal evolution of the Winnipegosis Komatiites. We demonstrate that the Winnipegosis lavas are komatiites by any definition, showing spinifex textures and derivation from a liquid with > 18 wt% MgO (Kerr and Arndt, 2001). The Winnipegosis Komatiites show many geochemical similarities to Archaean Al-undepleted komatiites, and formed from a nominally dry, depleted mantle source. Their high liquidus temperatures are ~ 100 °C lower than their hottest Archaean counterparts, but still require thermally anomalous mantle for their formation. We discuss possible modes of formation of the Winnipegosis Komatiites in light of these findings and the regional geological context.
Section snippets
Geological setting
The Winnipegosis Komatiite Belt (WKB; Hulbert et al., 1994) is located in the Superior Boundary Zone, in Manitoba, Canada, adjacent to the subsurface extension of the Thompson Nickel Belt (Fig. 1). The Superior Boundary Zone lies along the northwestern margin of the Archaean Superior Craton, and forms a narrow eastern foreland to the ~ 1.8 Ga Trans-Hudson Orogen (e.g. White et al., 2002). The Trans-Hudson Orogen was formed during the closure of the Manikewan Ocean (Stauffer, 1984), and resulted
Petrography and flow descriptions
Thin sections from approximately 200 samples from a 250 m section of komatiite intersected by borehole RP91-1A (hereafter RP1A), and approximately 70 samples from a 230 m section of komatiite intersected by borehole RP94–12 (hereafter RP12) were investigated petrographically. Previous core logging and petrographical examination of RP1A (Hulbert et al., 1994) identified at least 28 komatiite flows ranging between ~ 3 m and ~ 36 m in thickness, with a median thickness of 6 m. Core logging of RP12 (
Sample selection for geochemistry
A large body of core samples, rock powders, and thin sections, from > 250 samples used during the initial characterisation of the rocks by both Cominco and the Geological Survey of Canada (GSC), was obtained from the GSC archives in Ottawa. We utilised a large database (hereafter the ‘GSC database’) of unpublished geochemical data collected during the 1990s, including whole rock major element data measured by XRF; whole rock Fe2O3:FeO, H2Ot, and CO2 determined by wet chemical methods; and
XRF major and minor elements
Variations of elements measured by XRF are shown in Fig. 4. Some incompatible elements, such as Al2O3 and TiO2, show extremely tight correlations which extrapolate through measured olivine compositions. Others show more scatter and regression lines extend to higher (e.g. CaO) or lower (e.g. Na2O) MgO than Winnipegosis olivine. Samples from borehole RP12 lie along the same regression trends as the RP1A samples, but are generally more scattered.
The elements SiO2, FeO, and MnO show less
Olivine control and screening for the effects of alteration
Strong correlations between MgO and many incompatible elements that intersect olivine compositions are indicative of olivine control; consistent with the petrographical observation that olivine was the dominant crystallising mineral. A regression of Cr2O3 against MgO for the RP1A samples intersects a mixing line between average olivine and chromite compositions at 1.1 ± 0.1% chromite (95% confidence interval), suggesting the spread of data can be explained by the addition/subtraction of a mixture
Winnipegosis Komatiite Belt as part of the Circum-Superior Belt
The new 1870.3 ± 7.1 Ma age of the Winnipegosis Komatiite Belt is identical, within uncertainty, to the youngest mafic and ultramafic bodies previously dated in the Circum-Superior Belt, both in the adjacent Thompson Nickel Belt and more than 2000 km away in the New Quebec Orogen (Heaman et al., 2009). The Winnipegosis Komatiites also share many petrological features with other igneous rocks of the CSB: mafic/ultramafic rocks are abundant; magmatic olivine with Mg# ≥ 0.92, indicative of high
Conclusions
The Winnipegosis Komatiites formed at 1870.3 ± 7.1 Ma as part of the Circum-Superior Belt LIP. They occur as both massive and differentiated flows containing olivine spinifex layers. Their parental melt contained ~ 24 wt% MgO, which, along with the presence of spinifex layers and a median MgO of 22.4 wt% over > 250 m thickness of flows, confirms that these lavas are Proterozoic komatiites.
The parental melts crystallised only olivine from 1501 °C to approximately 1424 °C, and then a mixture of olivine +
Acknowledgements
Pedro Waterton performed this work under the tenure of an NSERC Vanier Scholarship at the University of Alberta. Analytical work was funded by the Canada Excellence Research Chairs Program and the Geological Survey of Canada. We thank Stan Mertzman and Karen Mertzman for the XRF analyses, and Thomas Stachel and Gerhard Brey for supplying and discussing olivine standards. Constructive discussions with Yannick Bussweiler, Richard Stern, Tom Chacko, Mark Hamilton, Richard Ernst and Larry Heaman
References (92)
How deep do common basaltic magmas form and differentiate?
Journal of Geophysical Research
(1992)Tectonic evolution of the Manitoba-Saskatchewan segment of the Paleoproterozoic Trans-Hudson Orogen, Canada
Canadian Journal of Earth Sciences
(2005)Kisseynew metasedimentary gneiss belt, Trans-Hudson orogen (Canada): back-arc origin and collisional inversion
Geology
(1995)Proterozoic spinifex-textured basalts of Gilmour Island, Hudson Bay
- et al.
Komatiites
Geology
(1980) - et al.
Fractionation of REEs by olivine and the origin of Kambalda komatiites, Western Australia
Geochimica et Cosmochimica Acta
(1992) Geochemistry, petrogenesis and tectonic environment of Circum- Superior Belt basalts, Canada. Geological Society Special Publications No. 33
- et al.
Komatiite
(2008) U–Pb zircon ages from the Lynn Lake and Rusty Lake metavolcanic belts, Manitoba: two ages of Proterozoic magmatism
Canadian Journal of Earth Sciences
(1987)- et al.
High pressure experimental calibration of the olivine-orthopyroxene-spinel oxygen geobarometer: implications for the oxidation state of the upper mantle
Contributions to Mineralogy and Petrology
(1991)
The Circum-Superior Belt: a Proterozoic plate margin?
Chromite in Komatiites, 1. Magmatic controls on crystallization and composition
Journal of Petrology
Ti-rich komatiites from northern Norway
Contributions to Mineralogy and Petrology
Oxidation state of iron in komatiitic melt inclusions indicates hot Archaean mantle
Nature
Archean greenstone belts are not oceanic crust
The Journal of Geology
Mantle composition derived from the chemistry of ultramafic lavas
Nature
CAMIRO Project 97E-02, Thompson Nickel Belt: Final Report March 2002, Revised and Updated 2003
Implications of mantle plume structure for the evolution of flood basalts
Earth and Planetary Science Letters
Did the formation of DPrime; cause the Archaean-Proterozoic transition?
Earth and Planetary Science Letters
Rb, Sr, Y, Zr and Nb in some ocean floor basaltic rocks
Earth and Planetary Science Letters
Aluminum-in-olivine thermometry of primitive basalts: evidence of an anomalously hot mantle source for large igneous provinces
Chemical Geology
Paleoproterozoic crustal evolution and tectonic process: insights from the Lithoprobe program in the Trans Hudson Orogen, Canada
The Palaeoproterozoic Trans-Hudson Orogen: a prototype of modern accretionary processes
Experimental determination of X-ray intensities
Evolution of the Snow Lake portion of the Palaeoproterozoic Flin Flon and Kisseynew belts, Trans-Hudson Orogen, Manitoba, Canada
Precambrian Research
Plates, Plumes and Mantle Convection
Recycled dehydrated lithosphere observed in plume-influenced mid-ocean-ridge basalt
Nature
A general equation for estimating Fe3 + concentrations in ferromagnesian silicates and oxides from microprobe analyses, using stoichiometric criteria
Mineralogical Magazine
Tertiary or Mesozoic komatiites from Gorgona Island, Colombia: field relations and geochemistry
Contributions to Mineralogy and Petrology
Large igneous provinces (LIPs), giant dyke swarms, and mantle plumes: significance for breakup events within Canada and adjacent regions from 2.5 Ga to the present
Canadian Journal of Earth Sciences
Chrome-spinel in progressive metamorphism - preliminary analysis
Geochimica et Cosmochimica Acta
Melting of refractory mantle at 1.5, 2 and 2.5 GPa under anhydrous and H2O-undersaturated conditions: implications for the petrogenesis of high-Ca Boninites and the influence of subduction components on mantle melting
Journal of Petrology
Contrasted liquid lines of descent revealed by olivine-hosted melt inclusions and the external magma
Journal of Petrology
The Baffin Bay lavas and the value of picrites as analogues of primary magmas
Contributions to Mineralogy and Petrology
The mean composition of ocean ridge basalts
Geochemistry, Geophysics, Geosystems
The Palaeoproterozoic Komatiite–Picrite association of Finnish Lapland
Journal of Petrology
Origin of the Permian–Triassic komatiites, northwestern Vietnam
Contributions to Mineralogy and Petrology
Timing and geochemistry of 1.88 Ga Molson Igneous events, Manitoba: insights into the formation of a craton-scale magmatic and metallogenic province
Precambrian Research
PRIMELT3 MEGA.XLSM software for primary magma calculation: peridotite primary magma MgO contents from the liquidus to the solidus
Geochemistry, Geophysics, Geosystems
Plume-associated ultramafic magmas of Phanerozoic age
Journal of Petrology
Thermal history of the earth and its petrological expression
Earth and Planetary Science Letters
Chemical differentiation of the earth: the relationship between mantle, continental crust, and oceanic crust
Earth and Planetary Science Letters
Paleoproterozoic arc magmatism imposed on an older backarc basin: implications for the tectonic evolution of the Trans-Hudson orogen, Canada
GSA Bulletin
The Winnipegosis komatiite belt, central Manitoba
U–Pb zircon and Re–Os isotope geochronology of mineralized ultramafic intrusions and associated nickel ores from the Thompson Nickel Belt, Manitoba, Canada
Economic Geology
A transect of the early Proterozoic Cape Smith foldbelt, New Quebec
Tectonophysics
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2021, Geochimica et Cosmochimica ActaCitation Excerpt :Melting extents can also be estimated using moderately compatible elements; as Winnipegosis komatiites are both HREE and LREE depleted, we estimate melting extents from Gd concentrations. A Gd concentration of 1.50 ppm for sample RP1A-87, which has a composition close to the estimated parental melt (Waterton et al., 2017), is 2.9 times higher than PUM (Hofmann, 1988) and 3.8 times higher than depleted mantle (Salters and Stracke, 2004). Assuming Gd was exhausted in the source, this corresponds to batch melt fractions of ~34% for a PUM-like source and ~26% for a depleted mantle source.
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2019, Chemical GeologyCitation Excerpt :Different calibrations exist for low-pressure magmatic olivine in equilibrium with spinel (Coogan et al., 2014; Wan et al., 2008) and for olivine in garnet peridotites (Bussweiler et al., 2017; De Hoog et al., 2010). Recent studies have applied Al-in-olivine thermometry to picrites (Trela et al., 2017) and komatiites (Waterton et al., 2017), mineral inclusions in diamonds (Korolev et al., 2018), and to the mantle olivine cargo in lamproites (e.g., Jaques and Foley, 2018; Shaikh et al., 2019) and kimberlites (Lawley et al., 2018). Moreover, the minor and trace element composition of magmatic olivine can be used as an indicator for different petrogenetic processes, including fingerprinting different magma sources (Howarth and Harris, 2017; Sobolev et al., 2005; Weiss et al., 2016; Zhang et al., 2016) or tracing its metasomatic history (e.g., Ammannati et al., 2016).
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