@phdthesis{Mailer2009,
  author    = {Mailer, Tina},
  title     = {Neon, Helium and Argon isotope systematics of the Hawaiian hotspot},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-39633},
  school      = {Universit{\"a}t Potsdam},
  year      = {2009},
  abstract  = {This study presents noble gas compositions (He, Ne, Ar, Kr, and Xe) of lavas from several Hawaiian volcanoes. Lavas from the Hawaii Scientific Drilling Project (HSDP) core, surface samples from Mauna Kea, Mauna Loa, Kilauea, Hualalai, Kohala and Haleakala as well as lavas from a deep well on the summit of Kilauea were investigated. Noble gases, especially helium, are used as tracers for mantle reservoirs, based on the assumption that high 3He/4He ratios (>8 RA) represent material from the deep and supposedly less degassed mantle, whereas lower ratios (~ 8 RA) are thought to represent the upper mantle. Shield stage Mauna Kea, Kohala and Kilauea lavas yielded MORB-like to moderately high 3He/4He ratios, while 3He/4He ratios in post-shield stage Haleakala lavas are MORB-like. Few samples show 20Ne/22Ne and 21Ne/22Ne ratios different from the atmospheric values, however, Mauna Kea and Kilauea lavas with excess in mantle Ne agree well with the Loihi-Kilauea line in a neon three-isotope plot, whereas one Kohala sample plots on the MORB correlation line. The values in the 4He/40Ar* (40Ar* denotes radiogenic Ar) versus 4He diagram imply open system fractionation of He from Ar, with a deficiency in 4He. Calculated 4He/40Ar*, 3He/22Nes (22NeS denotes solar Ne) and 4He/21Ne ratios for the sample suite are lower than the respective production and primordial ratios, supporting the observation of a fractionation of He from the heavier noble gases, with a depletion of He with respect to Ne and Ar. The depletion of He is interpreted to be partly due to solubility controlled gas loss during magma ascent. However, the preferential He loss suggests that He is more incompatible than Ne and Ar during magmatic processes. In a binary mixing model, the isotopic He and Ne pattern are best explained by a mixture of a MORB-like end-member with a plume like or primordial end-member with a fractionation in 3He/22Ne, represented by a curve parameter r of 15 (r=(³He/²²Ne)MORB/(³He/²²Ne)PLUME or PRIMORDIAL). Whether the high 3He/4He ratios in Hawaiian lavas are indicative of a primitive component within the Hawaiian plume or are rather a product of the crystal-melt- partitioning behavior during partial melting remains to be resolved.},
  language  = {en}
}
@article{KahmenSachseArndtetal.2011,
  author    = {Kahmen, Ansgar and Sachse, Dirk and Arndt, Stefan K. and Tu, Kevin P. and Farrington, Heraldo and Vitousek, Peter M. and Dawson, Todd E.},
  title     = {Cellulose delta O-18 is an index of leaf-to-air vapor pressure difference (VPD) in tropical plants},
  series = {Proceedings of the National Academy of Sciences of the United States of America},
  volume    = {108},
  journal   = {Proceedings of the National Academy of Sciences of the United States of America},
  number    = {5},
  publisher = {National Acad. of Sciences},
  address   = {Washington},
  issn      = {0027-8424},
  doi       = {10.1073/pnas.1018906108},
  pages     = {1981 -- 1986},
  year      = {2011},
  abstract  = {Cellulose in plants contains oxygen that derives in most cases from precipitation. Because the stable oxygen isotope composition, delta O-18, of precipitation is associated with environmental conditions, cellulose delta O-18 should be as well. However, plant physiological models using delta O-18 suggest that cellulose delta O-18 is influenced by a complex mix of both climatic and physiological drivers. This influence complicates the interpretation of cellulose delta O-18 values in a paleo-context. Here, we combined empirical data analyses with mechanistic model simulations to i) quantify the impacts that the primary climatic drivers humidity (e(a)) and air temperature (T-air) have on cellulose delta O-18 values in different tropical ecosystems and ii) determine which environmental signal is dominating cellulose delta O-18 values. Our results revealed that e(a) and T-air equally influence cellulose delta O-18 values and that distinguishing which of these factors dominates the delta O-18 values of cellulose cannot be accomplished in the absence of additional environmental information. However, the individual impacts of e(a) and T-air on the delta O-18 values of cellulose can be integrated into a single index of plant-experienced atmospheric vapor demand: the leaf-to-air vapor pressure difference (VPD). We found a robust relationship between VPD and cellulose delta O-18 values in both empirical and modeled data in all ecosystems that we investigated. Our analysis revealed therefore that delta O-18 values in plant cellulose can be used as a proxy for VPD in tropical ecosystems. As VPD is an essential variable that determines the biogeochemical dynamics of ecosystems, our study has applications in ecological-, climate-, or forensic-sciences.},
  language  = {en}
}