Paragneiss
(cummingtonite and garnet lithologies)
.
The oldest rock on Earth !
4.280Ga (+0.053/-0.081)Ga
Download the full thesis :
The
Geology of Nuvvuagittuq Greenstone Belt and its Implications for the
Early Earth’s Evolution
Cummingtonite-rich and Garnet-rich
lithologies
of "faux-amphibolite"
For Sale
<>
(The purple/red plots are garnets)
Abstarct :
The Nuvvuagittuq
greenstone belt is an Eoarchean/Hadean succession preserved along the eastern coast
of Hudson Bay in the Northeastern Superior Province, Quebec, Canada. It is
essentially composed of three major lithological units: 1) mafic
cummingtonite-amphibolite, known as the
“faux-amphibolite”, which is the dominan
lithology of the belt, 2) ultramafic and mafic sills that intrude the
fauxamphibolite,
and 3) chemical sedimentar rocks comprising a banded iron formation (BIF) and a
silica-formation. The faux-amphibolite has a basaltic to
andesitic composition. It is composed of variable proportions of cummingtonite + biotite + quartz, ± plagioclase ± garnet ± anthophyllite ± cordierite and ranges from cummingtonite amphibolite to garnet-biotite schist. Some rocks from the Nuvvuagittuq greenstone belt have lower 142Nd/144Nd ratios than the terrestrial standard (142Nd = -0.07 to -0.15). The 142Nd/144Nd ratios for the faux-amphibolitecorrelate positively with their Sm/Nd ratios and produce a 146Sm-142Nd isochron with an age of 4280 (+53 –81) million years. The 4.28 Ga faux-amphibolite is intruded by highly deformed gabbro sills yielding a 147Sm-143Nd isochron with a slope corresponding to an age of 4023 ± 110 Ma. The Nuvvuagittuq greenstone belt also comprises 3.8 Ga felsic bands and is surrounded by 3.66 Ga tonalite interpreted to have been produced by the melting of the older mafic fauxamphibolite.
andesitic composition. It is composed of variable proportions of cummingtonite + biotite + quartz, ± plagioclase ± garnet ± anthophyllite ± cordierite and ranges from cummingtonite amphibolite to garnet-biotite schist. Some rocks from the Nuvvuagittuq greenstone belt have lower 142Nd/144Nd ratios than the terrestrial standard (142Nd = -0.07 to -0.15). The 142Nd/144Nd ratios for the faux-amphibolitecorrelate positively with their Sm/Nd ratios and produce a 146Sm-142Nd isochron with an age of 4280 (+53 –81) million years. The 4.28 Ga faux-amphibolite is intruded by highly deformed gabbro sills yielding a 147Sm-143Nd isochron with a slope corresponding to an age of 4023 ± 110 Ma. The Nuvvuagittuq greenstone belt also comprises 3.8 Ga felsic bands and is surrounded by 3.66 Ga tonalite interpreted to have been produced by the melting of the older mafic fauxamphibolite.
Cummingtonite-rich and Garnet-rich
lithologies
of "faux-amphibolite"
For Sale
<>
(The purple/red plots are garnets)
| 3.60g Slice : 43$ SOLD | 5.85g Slice : 64$ SOLD | 5.35g Slice : 70$ SOLD |
| 7.41g Slice : 88$ SOLD | 6.75g Slice : 81$ SOLD | 3.72g Slice : 45$ SOLD |
| 6.77g Slice : 81$ HOLD | 3.13g Slice : 37$ SOLD | 6.20g Slice : 74$ SOLD |
| 4.59g Slice : 55$ SOLD | 5.60g Slice : 67$ SOLD | 5.71g Slice : 68$ SOLD |
| 6.96g Slice : 84$ SOLD | 3.90g Slice : 47$ SOLD | 6.43g Slice : 77$ SOLD |
| 2.75g Slice : 33$ SOLD | 6.35g Slice : 76$ SOLD | 1.33g Slice : 16$ SOLD |
| 4.55g Slice : 54$ SOLD |
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