Physics
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufm.v33a1173b&link_type=abstract
American Geophysical Union, Fall Meeting 2007, abstract #V33A-1173
Physics
1025 Composition Of The Mantle, 1027 Composition Of The Planets, 1040 Radiogenic Isotope Geochemistry, 1115 Radioisotope Geochronology
Scientific paper
New high-precision Nd isotope measurements have shown that the present-day 142Nd/144Nd for average chondrites is approximately 20 ppm lower than that for the terrestrial standard and all recent mantle- derived samples measured to date. One explanation for these differences is that an enriched 'missing' reservoir with lower 142Nd/144Nd resides in the mantle to balance the bulk Earth to chondritic. Data from Archean Greenland rocks show anomalies in 142Nd/144Nd of up to 40 ppm higher than the proposed average for chondrites. This difference between the Archean Greenland rocks and present-day mantle-derived samples has been interpreted to result from remixing of an early-formed enriched reservoir into the convecting mantle during the Archean. If so, the implication from this is that remixing of the enriched reservoir largely shut down some time in the past such that it must at present reside in a region in the mantle that infrequently participates dynamically and leading to volcanism at the surface. Several studies have suggested that the missing reservoir may be present just above the core-mantle boundary (CMB). Depending on the size of this reservoir it could potentially make up all of D" or exist as distinct domains within it. If such a reservoir does exist, then mantle-derived samples from plume systems that are thought to come from the CMB may be the best opportunity to identify this component using high-precision Nd isotope measurements. To test this, picrites from Hawaii with coupled enrichments in 186Os-187Os that has been proposed to be a signature of core-mantle interaction were measured on the JSC Triton for high-precision 142Nd/144Nd. For comparison, picrites from Hawaii and Iceland that do not show coupled enrichments in 186Os-187Os were measured. We have established an external precision for 142Nd/144Nd of ±3.6 ppm (2σ) during the analytical campaign. The Iceland (n=5) and Hawaiian data (n=9) have ɛ142Nd ranging from -0.01±0.03 to +0.03±0.03 (2σ) and there is no resolvable difference between samples with Os isotope enrichments versus those without. The average ɛ142Nd of +0.011±0.034 (2σ) for all of the samples (n=14) is not resolvable from the Ames and La Jolla standards with ɛ142Nd of 0.000±0.036 (n=16, 2σ). These data confirm recent measurements on lavas for the absence of an ancient enriched 142Nd isotopic signature in plume systems likely derived from D" and indicates that such a reservoir, if existing, must now reside in areas of the deep mantle that plumes do not sample.
Brandon Alan D.
Debaille Vinciane
Norman Douglas M.
No associations
LandOfFree
High-Precision Nd isotopes in Picrites from Hawaii and Iceland - No Evidence for an Early- Formed Enriched Reservoir does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with High-Precision Nd isotopes in Picrites from Hawaii and Iceland - No Evidence for an Early- Formed Enriched Reservoir, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High-Precision Nd isotopes in Picrites from Hawaii and Iceland - No Evidence for an Early- Formed Enriched Reservoir will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1408970