Impacts answer to many phenomenon on Earth?

A significant factor, where are the major elements e.g. Mg, Fe, Si, Al, Ca, P, Ni that make up the asteroid or comet after the impact, has been ignored since the proposal of the impact events. In a striking contrast, there are many remaining unanswered or poorly answered questions regarding the formation and nature of banded iron formation (BIF), iron stone, phosphorite, bedded manganese ore, dolomite and carbonaceous black shales. The appearance of Lake Superior type banded ion formation associated with dolomite, quartzite, and black shale, the deposition of manganese ore and the occurrence of large phosphate repository during the Plaeoproterozoic; the onset of BIF with phosphate deposition and sedimentary manganese deposits and cap dolomite during the Neoproterozoic; the penecontemporary formation of oolitic iron stone taking place of the BIF, bedded manganese deposit, phosphorite, dolomite, and black shale during the Phanerozoic, which suggest a genetic link among them from the perspective of chemical elements. Actually, during hypervelocity impact cratering events, the main part of the asteroid or comet and target material are vaporizing, which forms a mushroom cloud of vapor in the atmosphere.　The previous study shows that the calcite, magnetite, clay minerals and organic compounds condense from a solar gas at 10−4 atm with temperature less than 400 K, which provides an analog for the generation of the chemical sedimentary ore deposits. This also supported by table isotopes fractionation at small sacle (grain size, cm scale), all stable isotopes fractionation e.g. (Cr, Fe, S, Si, O,C) and mass-independent fractionation of sulphur isotopes following the rule of isotope fractionation during impacts: the earlier the condensed material, the more enriched in lighter isotopes. Thus, the impact of the asteroid or comet provides not only the elements source of chemical sedimentary ore deposits and the mechanism for their formation. The enrichment in iridium in BIFs and their associated impact spherule units are the other evidence to demonstrate that BIFs are the products of impacts. Impacts produce black shale, banded iron formation, limestone and dolomite. Based on the coeval sub-continental lithosphere mantle (SCLM) formation, juvenile crust generation, banded iron formations, mantle plumes and black shale, it seems that impacts maybe the driving force for Earth.

Impacts and Earth: Mass dependent isotope fractionation during impacts induced the Archaean mass-independent fractionation of sulphur: Evidence against Great Oxidation Event

Impacts and Earth: Mass dependent isotope fractionation during impacts induced the Archaean mass-independent fractionation of sulphur: Evidence against Great Oxidation Event

Mass dependent isotope fractionation during impacts induced the Archaean mass-independent fractionation of sulphur: Evidence against Great Oxidation Event(All rights reserved)

 A prevailing hypothesis, low-oxygen level of the Archaean atmosphere,

relies strongly on the presence of strong mass-independent fractionation

(MIF) of the sulfur isotopes in sulfide- and sulfate-bearing minerals older

than 2.4 billion years1,2,3,4. Actually, there is “a broad overlap between

MIF signals observed within Archaean sedimentary sequences and

periods of enhanced asteroid impacts represented by impact ejecta/fallout

units” (Fig. 1)5. Impact processes (vaporization and condensation) are

sufficient to explain the MIF signals following the principle: the earlier

the condensed material, the more enriched in lighter isotopes6. The nature

of the MIF of the sulfur isotopes is that the fractionation of isotope is still

mass dependent during impacts, which means the measured nonzero

⊿33S values of Archean sulfide- and sulfate-bearing minerals indicate

that their different condensation sequences. Thus, it is clear that the

signals are the markers of impact rather than O2 poor atmosphere.

Furthermore, the lack of MIF-S in several Archaean units before 2.4

billion years also supports this idea7,8.

 
References:

1 Farquhar, J., Bao, H. M. & Thiemens, M. Atmospheric influence of Earth's earliest sulfur cycle. Science 289, 756-758 (2000).

2 Farquhar, J. et al. Isotopic evidence for Mesoarchaean anoxia and changing atmospheric sulphur chemistry. Nature 449, 706-U705, doi:10.1038/nature06202 (2007).

3 Farquhar, J. & Wing, B. A. Multiple sulfur isotopes and the evolution of the atmosphere. Earth Planet. Sci. Lett. 213, 1-13, doi:10.1016/s0012-821x(03)00296-6 (2003).

4 Kaufman, A. J. et al. Late Archean biospheric oxygenation and atmospheric evolution. Science 317, 1900-1903, doi:10.1126/science.1138700 (2007).

5 Glikson, A. Archaean asteroid impacts, banded iron formations and MIF-S anomalies: A discussion. Icarus 207, 39-44, doi:10.1016/j.icarus.2009.11.024.

6 Huang, H. Isotope fractionation during impacts. Available from Nature Precedings

(2010).

7 Bao, H. M., Rumble, D. & Lowe, D. R. The five stable isotope compositions of Fig Tree barites: Implications on sulfur cycle in ca. 3.2 Ga oceans. Geochimica et Cosmochimica Acta 71, 4868-4879, doi:10.1016/j.gca.2007.05.032 (2007).

8 Ohmoto, H., Watanabe, Y., Ikemi, H., Poulson, S. R. & Taylor, B. E. Sulphur isotope evidence for an oxic Archaean atmosphere. Nature 442, 908-911, doi:10.1038/nature05044 (2006).

Impacts and Earth: Isotope fractionation during impacts (All rights reserved)

Impacts and Earth: Isotope fractionation during impacts (All rights reserved)

Impact induced VMS and MVT ore deposit

Impact induced Cu-Ni-PGE ore deposit

Impact induced balck shale, banded iron formation, limestone and dolomite

This idea will be updated soon.

Isotope fractionation during impacts (All rights reserved)

Evaporation–condensation, a significant process, happened during impact events (Melosh 1989). Of special interest, this process can lead to significant isotope fractionations. The nature of the isotope fractionations is the energy for the bonds formed by the light isotope is less than bonds involving the heavy isotope (Hoefs 2009). During evaporation, the solid or liquid is enriched in the heavy isotopes relative to the gas (Fig.1A Richter and Dauphas 2009). During condensation, the solid or liquid is enriched in the light isotopes (Fig.1B Richter 2004). Earlier condensed material is enriched in lighter isotope whereas samples with the heavier isotope (especially positive values) could be the later condensed material or the residue of vaporization. This idea is being ubdated, all the references will be added soon.