Characterization of contaminant phases in Foraminifera carbonates by electron microprobe mapping

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doi: 10.1029/2008GC002018
Author(s): Pena, L. D.; Cacho, I.; Calvo, E.; Pelejero, C.; Eggins, S.; Sadekov, A.
Author Affiliation(s): Primary:
University of Barcelona, Department of Stratigraphy, Paleontology and Marine Geosciences, Barcelona, Spain
Institut de Ciències del Mar, Spain
Australian National University, Australia
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 9(7). Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English. 26 refs.; illus., incl. 1 table
Summary: The advent of new microanalytical techniques such as electron microprobe mapping (EMP) and laser ablation microsamplers coupled to mass spectrometers (LA-ICP-MS) provides a new array of possibilities to explore in great detail the trace elements distribution in foraminiferal carbonates. Here we apply these techniques to characterize diagenetic phases present in foraminiferal shells from Ocean Drilling Program Site 1240 in the Panama Basin, a region characterized by the presence of manganese-rich minerals in the sediments. The combined application of these techniques allows us to characterize the elemental and spatial distribution on the surface and across the foraminiferal shells. Results illustrate the presence of at least two different Mn-rich contaminant phases in the foraminiferal carbonates: Mn-rich carbonates and ferromanganese oxides. Elemental maps also highlight the relevance of the foraminifera shell texture and porosity in the distribution and formation of these contaminant phases. In the case of Neogloboquadrina dutertrei, Mn phases form a continuous thin layer in the inner part of the chambers, whereas for Globigerinoides ruber, Mn phases have a rather patchy distribution and are usually found within the pores. Significant high magnesium concentrations are always associated with these Mn-rich phases. These new findings support the need of removing these Mn-rich contaminant phases in order to measure accurately the Mg/Ca ratios in the foraminifera shell and therefore obtain reliable Mg/Ca paleotemperature reconstructions.
Year of Publication: 2008
Research Program: ODP Ocean Drilling Program
Key Words: 06 Petrology, Sedimentary; Alkaline earth metals; Calcium; Carbonates; Carboniferous; East Pacific; Electron probe data; Equatorial Pacific; Foraminifera; Globigerinacea; Globigerinidae; Globigerinoides; Globigerinoides ruber; ICP mass spectra; Invertebrata; Laser ablation; Laser methods; Leg 202; Magnesium; Marine sediments; Mass spectra; Metals; Microfossils; Neogloboquadrina; Neogloboquadrina dutertrei; ODP Site 1240; Ocean Drilling Program; Pacific Ocean; Paleotemperature; Paleozoic; Panama Basin; Protista; Rotaliina; Sea-surface temperature; Sediments; Spectra
Coordinates: N000100 N000100 W0822800 W0822800
Record ID: 2009060161
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