Valentine Township Carbonatite

The only known concentration of carbonatite complexes in North America is in northern Ontario and western Quebec, in a petrographic province named the Ontario Carbonatite Province (Fig.1). This petrographic province has some 50 known carbonatite complexes over an area of 1.3 million km2. Almost all of the carbonatite bodies occur along recognizable major tectonic features. Due to their circular shape and distinct magnetic Expression most of these complexes were discovered during regional aeromagnetic surveys in the mid- 1960s. Many of the complexes are poorly exposed or unexposed in this glaciated and heavily drift covered terrane and chances are that some, lacking a strong magnetic signature and a circular shape, have escaped detection to date.

According to their ages, the carbonatite bodies belong to four age groups: 1,700, 1,100, 570, and 120 m.y groups. Complexes of the two younger age groups occur only in the southeaster part of the carbonatite province along the Ottawa graben, whereas the two older groups, the 1,100 and 1,700 m.y., are situated along the Kapuskasing High and the Albany Forks and Carb structures (Fig.1).

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Fig.1: Fig.1: The Ontario Carbonatite Province showing location of carbonatite complexes (blue circles), gravity (dotted red zones), and magnetic highs (black dashed lines) and major structures (Red lines). Sea and lakes in light blue. Modified from Erdosh, G. (1979)



The apparent structural control of most of the carbonatite bodies is a noteworthy feature of the Ontario Carbonatite Province, the most pronounced structural controls are:

1) The Ottawa graben along which at least nine carbonatite complexes, from Oka to Iron Island, are aligned and, although the graben was originally not postulated that far, the Township 107 and Seabrook complexes are also on a straight line in the extension of the graben, extending a distance of at least 750 km.
2) The Kapuskasing High, a gravity and magnetic high along a rift zone running southwesterly for atleast 400 km from near James Bay to a point where it apparently dies out before reaching the Ottawa graben. Nine complexes from Argor to Seabrook are known along this high whereas two more, the Cargill and Firesand complexes appear to be on a subsidiary branch subparallel to the Kapuskasing High.
3) A structure, named the Albany Forks structure, is relatively short, perhaps 200 km long, but nine complexes ave known along or near it (from Poplar to Nagagami complexes), all buried under deep Paleozoic cover.
4) A possible structure, named the Carb structure, though not as obvious as the previous three, but strongly suggested by alignment of several alkalic complexes. On this possible structure are Carb at the north end, Big Beaver House and Schryburt in the middle, and Prairie with two alkalic ultramafic intrusives (Killala and Port Coldwell, clustered at the Lake Superior end).

It seems apparent that the principal carbonatite magmatism occurred during two distinct periods in the Superior geologic province, first around 1,700 m.y., then a second period, probably mainly along the same structural zones, at 1,000 to 1,100 m.y. Two younger episodesa re suggesteda long the Ottawa graben at about 570 and 120 m.y. During these younger episodes the remainder of the Superior province did not experience rejuvenation of carbonatite magmatism. This geographical distribution of carbonarite ages strongly suggests an early migration of carbonatite magmatism, an idea originally proposed by Gittinse t al. (1967), or, conversely a relarive westerly movement of the continent over a deep source of carbonatite magma generation.

Another remarkable fact is that the great majority of carbonatite complexes are found associated with gravity highs as well as with the axes of magnetic highs, thus strengthening the suspicion that mosts tructural controls are major rift zones of continental scale and significance.

The Valentine Township Carbonatite Complex
The Valentine Township Carbonatite Complex is located in the northern portion of the Kapuskasing Subprovince of the Superior Province of the Canadian Shield. The intrusion was likely emplaced into one of the many northeast-trending zones that characterize this subprovince. The carbonatite does not outcrop at surface but lies buried beneath a minimum of 120 m of overburden and Paleozoic rocks. The age of the complex is unknown but it is assumed to be Late Precambrian and coeval with most alkalic rock - carbonatite events within the Kapuskasing Sub province.
Due to deep burial any structure internal or external to the complex is uncertain. The complex has been emplaced into the northern portion of the Kapuskasing Subprovince of the Superior Province which is characterized by northeasttrending faulting. The complex is likely oval to dike-like in plan view and was likely emplaced into one of these fault zones. The long axis of the body probably trends northeast parallel to the regional structure.

Sample doned by Anton Chakhmouradian (University of Manitoba)

Bibliography



• Erdosh, G. (1979). The Ontario carbonatite province and its phosphate potential. Economic Geology, 74(2), 331-338. • Sage, R. P. (1988). Geology of Carbonatite - Alkalic Rock Complexes in Ontario: Valentine Township Carbonatite Complex, District of Cochrane; Ontario Geological Survey, Study 39, 37p.

Photo
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Phlogopite (brown), calcite, apatite (high relief, colorless) and magnetite (black) crystals in a carbonatite from Valentine Township Complex. PPL image, 1x (Field of view = 9mm)
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Phlogopite (high birefringence), calcite, apatite (I order gray) and magnetite crystals in a carbonatite from Valentine Township Complex. XPL image, 1x (Field of view = 9mm)
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Phlogopite (brown), calcite, apatite (high relief, colorless) and magnetite (black) crystals in a carbonatite from Valentine Township Complex. PPL image, 1x (Field of view = 9mm)
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Phlogopite (high birefringence), calcite, apatite (I order gray) and magnetite crystals in a carbonatite from Valentine Township Complex. XPL image, 1x (Field of view = 9mm)
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Phlogopite (brown), calcite, apatite (high relief, colorless) and magnetite (black) crystals in a carbonatite from Valentine Township Complex. PPL image, 1x (Field of view = 9mm)
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Phlogopite (high birefringence), calcite, apatite (I order gray) and magnetite crystals in a carbonatite from Valentine Township Complex. XPL image, 1x (Field of view = 9mm)
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Phlogopite (brown), calcite, apatite (high relief, colorless) and magnetite (black) crystals in a carbonatite from Valentine Township Complex. PPL image, 1x (Field of view = 9mm)
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Phlogopite (high birefringence), calcite, apatite (I order gray) and magnetite crystals in a carbonatite from Valentine Township Complex. XPL image, 1x (Field of view = 9mm)
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Phlogopite (brown), calcite, apatite (high relief, colorless) and magnetite (black) crystals in a carbonatite from Valentine Township Complex. PPL image, 1x (Field of view = 9mm)
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Phlogopite (high birefringence), calcite, apatite (I order gray) and magnetite crystals in a carbonatite from Valentine Township Complex. XPL image, 1x (Field of view = 9mm)
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Phlogopite (brown), calcite, apatite (high relief, colorless) and magnetite (black) crystals in a carbonatite from Valentine Township Complex. PPL image, 1x (Field of view = 9mm)
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Phlogopite (high birefringence), calcite, apatite (I order gray) and magnetite crystals in a carbonatite from Valentine Township Complex. XPL image, 1x (Field of view = 9mm)
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Calcite and apatite (I order gray) crystals in a carbonatite from Valentine Township Complex. XPL image, 2x (Field of view = 7mm)
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Calcite and apatite (I order gray) crystals in a carbonatite from Valentine Township Complex. XPL image, 2x (Field of view = 7mm)
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Phlogopite (brown), calcite, apatite (high relief, colorless) and tremolite (fibrous pale green) crystals in a carbonatite from Valentine Township Complex. PPL image, 2x (Field of view = 7mm)
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Phlogopite (high birefringence), calcite, apatite (I order gray) and tremolite (high birefringence) crystals in a carbonatite from Valentine Township Complex. XPL image, 2x (Field of view = 7mm)
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Phlogopite (brown), calcite, apatite (high relief, colorless) and tremolite (fibrous pale green) crystals in a carbonatite from Valentine Township Complex. PPL image, 2x (Field of view = 7mm)
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Phlogopite (high birefringence), calcite, apatite (I order gray) and tremolite (high birefringence) crystals in a carbonatite from Valentine Township Complex. XPL image, 2x (Field of view = 7mm)
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Phlogopite (high birefringence), calcite, apatite (high relief, colorless) and tremolite (fibrous pale green) crystals in a carbonatite from Valentine Township Complex. PPL image, 2x (Field of view = 7mm)
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Phlogopite (high birefringence), calcite, apatite (I order gray) and tremolite (high birefringence) crystals in a carbonatite from Valentine Township Complex. XPL image, 2x (Field of view = 7mm)
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Phlogopite (brown), calcite, apatite (high relief, colorless) and tremolite (fibrous pale green) crystals in a carbonatite from Valentine Township Complex. PPL image, 2x (Field of view = 7mm)
valentine(47).jpg

Phlogopite (high birefringence), calcite, apatite (I order gray) and tremolite (high birefringence) crystals in a carbonatite from Valentine Township Complex. XPL image, 2x (Field of view = 7mm)
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Phlogopite (brown), calcite, apatite (high relief, colorless) and magnetite crystals in a carbonatite from Valentine Township Complex. PPL image, 2x (Field of view = 7mm)
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Phlogopite (high birefringence), calcite, apatite (high relief, colorless) and magnetite crystals in a carbonatite from Valentine Township Complex. XPL image, 2x (Field of view = 7mm)
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Phlogopite (brown), calcite, apatite (high relief, colorless) and magnetite crystals in a carbonatite from Valentine Township Complex. PPL image, 2x (Field of view = 7mm)
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Phlogopite (brown), calcite, apatite (high relief, colorless) and tremolite (fibrous pale green) crystals in a carbonatite from Valentine Township Complex. PPL image, 2x (Field of view = 7mm)
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Phlogopite (high birefringence), calcite, apatite (I order gray) and tremolite (high birefringence) crystals in a carbonatite from Valentine Township Complex. XPL image, 2x (Field of view = 7mm)
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Phlogopite (brown) and calcite crystals in a carbonatite from Valentine Township Complex. PPL image, 2x (Field of view = 7mm)
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Phlogopite (brown), calcite, apatite (high relief, colorless) and tremolite (fibrous pale green) crystals in a carbonatite from Valentine Township Complex. PPL image, 2x (Field of view = 7mm)
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Phlogopite (high birefringence), calcite, apatite (I order gray) and tremolite (high birefringence) crystals in a carbonatite from Valentine Township Complex. XPL image, 2x (Field of view = 7mm)
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Phlogopite (brown), calcite, apatite (high relief, colorless) and tremolite (fibrous pale green) crystals in a carbonatite from Valentine Township Complex. PPL image, 2x (Field of view = 7mm)
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Phlogopite (high birefringence), calcite, apatite (I order gray) and tremolite (high birefringence) crystals in a carbonatite from Valentine Township Complex. XPL image, 2x (Field of view = 7mm)
valentine(7).jpg

Phlogopite (brown), calcite, apatite (high relief, colorless) and tremolite (fibrous pale green) crystals in a carbonatite from Valentine Township Complex. PPL image, 2x (Field of view = 7mm)
valentine(8).jpg

Phlogopite (high birefringence), calcite, apatite (I order gray) and tremolite (high birefringence) crystals in a carbonatite from Valentine Township Complex. XPL image, 2x (Field of view = 7mm)
valentine(43).jpg

Phlogopite (brown), calcite, apatite (high relief, colorless) and tremolite (fibrous pale green) crystals in a carbonatite from Valentine Township Complex. PPL image, 2x (Field of view = 7mm)
valentine(44).jpg

Phlogopite (high birefringence), calcite, apatite (I order gray) and tremolite (high birefringence) crystals in a carbonatite from Valentine Township Complex. XPL image, 2x (Field of view = 7mm)
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Tremolite (fibrous pale green), fhlogopite, calcite and apatite (high relief, colorless) crystals in a carbonatite from Valentine Township Complex. PPL image, 10x (Field of view = 2mm)
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Tremolite (high birefringence), fhlogopite, calcite and apatite (I order gray) crystals in a carbonatite from Valentine Township Complex. XPL image, 10x (Field of view = 2mm)
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Tremolite (fibrous pale green), fhlogopite, calcite and apatite (high relief, colorless) crystals in a carbonatite from Valentine Township Complex. PPL image, 10x (Field of view = 2mm)
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Tremolite (high birefringence), phlogopite, calcite and apatite (I order gray) crystals in a carbonatite from Valentine Township Complex. XPL image, 10x (Field of view = 2mm)
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Tremolite (fibrous pale green), plogopite, calcite and apatite (high relief, colorless) crystals in a carbonatite from Valentine Township Complex. PPL image, 10x (Field of view = 2mm)
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Tremolite (high birefringence), phlogopite, calcite and apatite (I order gray) crystals in a carbonatite from Valentine Township Complex. XPL image, 10x (Field of view = 2mm)
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Plogopite, calcite and apatite (high relief, colorless) crystals in a carbonatite from Valentine Township Complex. PPL image, 10x (Field of view = 2mm)
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Plogopite, calcite and apatite (high relief, colorless) crystals in a carbonatite from Valentine Township Complex. PPL image, 10x (Field of view = 2mm)
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Plogopite, calcite and apatite (high relief, colorless) crystals in a carbonatite from Valentine Township Complex. PPL image, 10x (Field of view = 2mm)
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Calcite crystals in a carbonatite from Valentine Township Complex. XPL image, 10x (Field of view = 2mm)
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Calcite crystals and apatite crystal (with calcite inclusions) in a carbonatite from Valentine Township Complex. XPL image, 10x (Field of view = 2mm)
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Calcite crystals and apatite crystal (with calcite inclusions) in a carbonatite from Valentine Township Complex. XPL image, 20x (Field of view = 1mm)