caa a22 4500 477064205 CHVBK 20180405111408.0 cr unu---uuuuu 170330e19960901xx s 000 0 eng 10.1007/BF02369012 doi (NATIONALLICENCE)springer-10.1007/BF02369012 Thorium and uranium isotopes in a manganese nodule from the Peru basin determined by alpha spectrometry and thermal ionization mass spectrometry (TIMS): Are manganese supply and growth related to climate? [Elektronische Daten] [A. Bollhöfer, A. Eisenhauer, N. Frank, D. Pech, A. Mangini] Thorium- and uranium isotopes were measured in a diagenetic manganese nodule from the Peru basin applying alpha- and thermal ionization mass spectrometry (TIMS). Alpha-counting of 62 samples was carried out with a depth resolution of 0.4 mm to gain a high-resolution230Thexcess profile. In addition, 17 samples were measured with TIMS to obtain precise isotope concentrations and isotope ratios. We got values of 0.06-0.59 ppb (230Th), 0.43-1.40 ppm (232Th), 0.09-0.49 ppb (234U) and 1.66-8.24 ppm (238U). The uranium activity ratio in the uppermost samples (1-6 mm) and in two further sections in the nodule at 12.5±1.0 mm and 27.3-33.5 mm comes close to the present ocean water value of 1.144±0.004. In two other sections of the nodule, this ratio is significantly higher, probably reflecting incorporation of diagenetic uranium. The upper 25 mm section of the Mn nodule shows a relatively smooth exponential decrease in the230Thexcess concentration (TIMS). The slope of the best fit yields a growth rate of 110 mm/Ma up to 24.5 mm depth. The section from 25 to 30.3 mm depth shows constant230Thexcess concentrations probably due to growth rates even faster than those in the top section of the nodule. From 33 to 50 mm depth, the growth rate is approximately 60 mm/Ma. Two layers in the nodule with distinct laminations (11-15 and 28-33 mm depth) probably formed during the transition from isotopic stage 8 to 7 and in stage 5e, respectively. The Mn/Fe ratio shows higher values during interglacials 5 and 7, and lower ones during glacials 4 and 6. A comparison of our data with data from adjacent sediment cores suggests (a) a variable supply of hydrothermal Mn to sediments and Mn nodules of the Peru basin or (b) suboxic conditions at the water sediment interface during periods with lower Mn/Fe ratios. Springer-Verlag, 1996 Manganese nodules nationallicence Thorium dating nationallicence Uranium isotopes nationallicence Peru basin nationallicence TIMS nationallicence Bollhöfer A. Heidelberger Akademie der Wissenschaften, c/o Institut für Umweltphysik, INF 366, D-69120, Heidelberg, Germany aut Eisenhauer A. Heidelberger Akademie der Wissenschaften, c/o Institut für Umweltphysik, INF 366, D-69120, Heidelberg, Germany aut Frank N. Heidelberger Akademie der Wissenschaften, c/o Institut für Umweltphysik, INF 366, D-69120, Heidelberg, Germany aut Pech D. Heidelberger Akademie der Wissenschaften, c/o Institut für Umweltphysik, INF 366, D-69120, Heidelberg, Germany aut Mangini A. Heidelberger Akademie der Wissenschaften, c/o Institut für Umweltphysik, INF 366, D-69120, Heidelberg, Germany aut Geologische Rundschau Springer-Verlag 85/3(1996-09-01), 577-585 0016-7835 85:3<577 1996 85 531 https://doi.org/10.1007/BF02369012 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF02369012 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Bollhöfer A. Heidelberger Akademie der Wissenschaften, c/o Institut für Umweltphysik, INF 366, D-69120, Heidelberg, Germany aut NATIONALLICENCE 700 1- Eisenhauer A. Heidelberger Akademie der Wissenschaften, c/o Institut für Umweltphysik, INF 366, D-69120, Heidelberg, Germany aut NATIONALLICENCE 700 1- Frank N. Heidelberger Akademie der Wissenschaften, c/o Institut für Umweltphysik, INF 366, D-69120, Heidelberg, Germany aut NATIONALLICENCE 700 1- Pech D. Heidelberger Akademie der Wissenschaften, c/o Institut für Umweltphysik, INF 366, D-69120, Heidelberg, Germany aut NATIONALLICENCE 700 1- Mangini A. Heidelberger Akademie der Wissenschaften, c/o Institut für Umweltphysik, INF 366, D-69120, Heidelberg, Germany aut NATIONALLICENCE 773 0- Geologische Rundschau Springer-Verlag 85/3(1996-09-01), 577-585 0016-7835 85:3<577 1996 85 531 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer