Origin of carbonaceous matter, fullerenes, and elemental sulfur in rocks of the Whitewater Group, Sudbury impact structure, Ontario, Canada

Abstract

New carbon determinations of 20 rocks confirm that both the breccias of the BlackMember of the Onaping Formation and the mudstones of the Onwatin Formation of the Whitewater Group in the 1.8-Ga Sudbury impact structure contain appreciable amounts of carbonaceous matter. The origin of the carbon has been a long-standing enigma. Carbon-bearing target rocks, either carbonaceous mudstones or carbonate target rocks are not its source, and neither is CO 2 from the atmosphere of the impact area, or carbon from the impacting projectile itself. Fumarolic activity is also ruled out. New isotopic δ 13 C results of carbon from 17 Black Member breccias, and 1 each from a Gray Member breccia and an Onwatin Formation range from -35.22 to -26.26‰. Together with Raman spectra of carbon from 11 of these samples, they lead to the conclusion that the Black Member carbon is biogenic. This unit cannot have formed as an "instant clastic sediment," but must have accumulated over several millions of years while prolific prokaryotic activity (archaea and bacteria) occurred. Isotopic δ 13 C and Raman results of carbon from an anthraxolite confirm that this carbon is derived from the Onwatin Formation. A search for fullerenes C60 and C70 by high-performance liquid chromatography (HPLC) in 17 rocks from the Black Member of the Onaping Formation, 1 rock from the Gray Member of the Onaping Formation, and by mass spectrometry of 3 breccias from the Black Member failed to find any fullerenes. Elemental sulfur in the breccias from the Gray and Black Members of the Onaping Formation and in one sample of the Onwatin Formation is due to weathering of pyrrhotite. The isotopic composition of the elemental sulfur as well as that of the sulfide-S contains a mass-independent fractionation component whose origin is not understood.

Terrestrial and Extraterrestrial Fullerenes

“…[126] Other investigators have failed to find fullerenes in their samples of the same formation. [127] Table 2 T2 lists the results of all searches for fullerenes in rocks from the Sudbury structure. Clearly some samples contained fullerenes whilst others did not.…”

“…Raman spectra show that the carbon is highly disordered. [127] Various theories about the origin of this carbon exist, but extensive 13 C= 12 C measurements have now conclusively demonstrated that the Black Member carbon is isotopically the same as carbon from the Onwatin and Chelmsford Formations, hence is biogenic. The carbon proper is not from the impactor, but postdates the formation of the crater.…”

“…The carbon proper is not from the impactor, but postdates the formation of the crater. [127] Algal remains, formed within the crater's lake, were later graphitized by low-grade greenschist facies metamorphism. Hence the C 60 molecules were not formed during the impact event from some carbon-bearing matter of the impactor or from the very sparse local target sources of carbonates and carbonaceous matter, but were already contained within the impactor prior to its collision with Earth, or were formed much later.…”

“…[129] It has also been argued that the rock fragments and glasses of the Black Member were actually stream-carried from outside the central depression into the central depression where redeposition occurred under euxinic aquatic conditions. [127,130] When did the first rains come after the impact? Did they cool the surface sufficiently to allow preservation of fullerenes?…”

“…It has been suggested here that every one these was derived from algal remains via metamorphic carbonization. For the carbon in the Black Member of the Onaping Formation that has been proven [127] but investigators of shungite are divided on the biogenic origin of its carbon. [106] The discoverers of fullerenes in the Czech bitumens claim a biogenic origin for these also.…”