Distribution and evolution of carbon and nitrogen in Earth

In this paper we discuss the distribution, geochemical cycle, and evolution of CO 2 and N 2 in Earth's degassed mantle, and atmosphere plus continental crust. We estimate the present distribution of CO 2 and N 2 in Earth's degassed mantle based on amounts of He and Ar in the degassed mantle and observed outgassing ratios of CO2/He and N2/Ar at mid-ocean ridges. Estimated CO 2 in present degassed mantle is (1.8_ +9) x 1022 mol, representing (72 + 10)% of total degassable CO2, an amount far higher than fractions previously inferred for noble gases. This strongly suggests that most CO 2 has been recycled from Earth's surface into the degassed mantle through subduction, which is consistent with many recent discussions. For N2, the estimated amount in the present mantle is ~ 2.5 × 1019 mol, representing ~ 12% of total degassable N 2. Recycling of N 2 back to the mantle is also inferred, but on a much smaller scale. A simple model for the outgassing and recycling of CO 2 and N 2 in Earth is presented. Outgassing is assumed to be via melt-vapor partitioning of volatiles. Recycling back into the mantle via subduction is assumed to be proportional to the mass of the volatile component in the crust. This simple model is consistent with all currently available constraints. Difficulties arise from the dependence of the recycling constant on time. Hence, no single evolution history can be obtained for CO 2 based on the available data. Model results tentatively point to a higher CO 2 content on Earth's surface in the Archean and Proterozoic than at present. Important future constraints may come from records in sedimentary rocks, improved understanding of carbonate production, and better modeling of the recycling process.

[1]  F. Pineau,et al.  The volatiles record of a “popping” rock from the Mid-Atlantic Ridge at 14°N: chemical and isotopic composition of gas trapped in the vesicles , 1991 .

[2]  B. Marty.  Neon and xenon isotopes in MORB: implications for the earth-atmosphere evolution , 1989 .

[3]  J. Dymond,et al.  The closed-system approximation for evolution of argon and helium in the mantle, crust and atmosphere , 1985 .

[4]  P. Sarda,et al.  Mid-ocean ridge popping rocks: implications for degassing at ridge crests , 1990 .

[5]  E. F. Osborn,et al.  The Solubility of Water and Effects of Oxygen Fugacity and Water Content on Crystallization in Mafic Magmas , 1964 .

[6]  M. Lyle,et al.  Age of oceanic plates at subduction and volatile recycling , 1984 .

[7]  G. Wasserburg,et al.  The role of plumes in mantle helium fluxes: Earth and Planetary Science Letters , 1990 .

[8]  A. Jambon,et al.  Major volatiles from a North Atlantic MORB glass and calibration to He: A size fraction analysis , 1987 .

[9]  T. Bernatowicz,et al.  Nuclear components in the atmosphere , 1978 .

[10]  P. Agrinier,et al.  Volatiles and Stable Isotopes in Recycling , 1989 .

[11]  A. Jambon,et al.  Solubility of He, Ne, Ar, Kr and Xe in a basalt melt in the range 1250–1600°C. Geochemical implications , 1986 .

[12]  Youxue Zhang,et al.  Noble gas constraints on the evolution of the Earth's atmosphere , 1989 .

[13]  B. Marty,et al.  Helium isotopes and CO2 in volcanic gases of Japan , 1989 .

[14]  Y. Bottinga,et al.  MORB degassing : bubble growth and ascent , 1990 .

[15]  S. H. Richardson,et al.  Noble gases in basalt glasses from a Mid-Atlantic Ridge topographic high at 14°N: geodynamic consequences , 1989 .

[16]  I. Tolstikhin,et al.  Geodynamics, magmatism, and degassing of the Earth , 1990 .

[17]  B. Wilkinson,et al.  Sedimentary carbonate record of calcium-magnesium cycling , 1989 .

[18]  J. Hunt.  Distribution of Carbon in Crust of Earth: GEOLOGICAL NOTES , 1972 .

[19]  S. Taylor,et al.  The continental crust: Its composition and evolution , 1985 .

[20]  Claude J. Allègre,et al.  Carbon geodynamic cycle , 1982, Nature.

[21]  E. Stolper,et al.  Experimental determination of the solubility of carbon dioxide in molten basalt at low pressure , 1988 .

[22]  S. Taylor.  The continental crust , 1985 .

[23]  J. Veizer.  Trace elements and isotopes in sedimentary carbonates , 1983 .

[24]  T. Staudacher,et al.  Neon isotopes in submarine basalts , 1988 .

[25]  J. P. Riley,et al.  Chemical and mineralogical studies of deep-sea sediments , 1961 .

[26]  M. Kurz,et al.  Constraints on evolution of Earth's mantle from rare gas systematics , 1983, Nature.

[27]  J. Lupton.  TERRESTRIAL INERT GASES: Isotope Tracer Studies and Clues to Primordial Components in the Mantle , 1983 .

[28]  Bernard Marty,et al.  C3He in volatile fluxes from the solid Earth: implications for carbon geodynamics , 1987 .

[29]  C. Langmuir,et al.  Global correlations of ocean ridge basalt chemistry with axial depth and crustal thickness , 1987 .

[30]  D. H. Zenger.  Dolomite Abundance and Stratigraphic Age: Constraints on Rates and Mechanisms of Phanerozoic Dolostone Formation: DISCUSSION , 1989 .

[31]  B. Mysen,et al.  The solubility of carbon monoxide in silicate melts at high pressures and its effect on silicate phase relations. [in terrestrial and other planetary interiors , 1979 .

[32]  G. Lux.  The behavior of noble gases in silicate liquids: Solution, diffusion, bubbles and surface effects, with applications to natural samples , 1987 .

[33]  N. Grevesse,et al.  Abundances of the elements: Meteoritic and solar , 1989 .

[34]  T. Staudacher,et al.  Rare gas systematics: formation of the atmosphere, evolution and structure of the Earth's mantle , 1987 .

[35]  P. Thurston,et al.  Geochemistry of Precambrian carbonates: II. Archean greenstone belts and Archean sea water. , 1989, Geochimica et cosmochimica acta.

[36]  Brian M. Smith,et al.  Cretaceous ocean crust at DSDP Sites 417 and 418: Carbon uptake from weathering versus loss by magmatic outgassing , 1989 .

[37]  R. Clayton,et al.  Geochemistry of Precambrian carbonates: 3-shelf seas and non-marine environments of the Archean , 1990 .

[38]  T. Staudacher,et al.  40Ar36Ar in MORB glasses: constraints on atmosphere and mantle evolution , 1985 .

[39]  R. Hervig,et al.  The pressure and temperature dependence of carbon dioxide solubility in tholeiitic basalt melts , 1991 .

[40]  W. Hay,et al.  Mass/age distribution and composition of sediments on the ocean floor and the global rate of sediment subduction , 1988 .

[41]  D. Sibley,et al.  Chemical Mass Balance of the Earth's Crust: The Calcium Dilemma (?) and the Role of Pelagic Sediments , 1976, Science.

[42]  F. Pineau,et al.  Carbon and nitrogen isotopes in the mantle , 1986 .

[43]  M. Gaffey,et al.  The Chemical Evolution of the Atmosphere and Oceans , 1984 .

[44]  E. Ito.  Chemical Cycles in the Evolution of the Earth , 1989 .

[45]  H. D. Holland.  The chemistry of the atmosphere and oceans , 1978 .

[46]  F. Fanale.  A case for catastrophic early degassing of the earth. , 1971 .