Trace element and isotopic evidence for temporal changes of the mantle sources in the South Shetland Islands, Antarctica
We present Sr–Nd–Pb isotope data from the Paleocene-Eocene volcanic rocks in King George Island, South Shetland Islands, West Antarctica. The initial isotopic ratios of the analyzed samples display limited variations: 143Nd/144Nd, 0.512790 to 0.512905 (εNd, +4.2 to +6.5); 87Sr/86Sr, 0.703342 to 0.70...
| Main Authors: | , , , |
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| Other Authors: | |
| Format: | Text |
| Language: | English |
| Published: |
2007
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| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.473.2068 http://www.terrapub.co.jp/journals/GJ/pdf/4202/42020207.pdf |
| Summary: | We present Sr–Nd–Pb isotope data from the Paleocene-Eocene volcanic rocks in King George Island, South Shetland Islands, West Antarctica. The initial isotopic ratios of the analyzed samples display limited variations: 143Nd/144Nd, 0.512790 to 0.512905 (εNd, +4.2 to +6.5); 87Sr/86Sr, 0.703342 to 0.703877 (εSr, –15.6 to –8.0); 206Pb/204Pb, 18.48 to 18.64; 207Pb/ 204Pb, 15.50 to 15.64; 208Pb/204Pb, 37.99 to 38.41. We interpret these data in combination with previously published trace and isotope data for Meso–Cenozoic volcanic rocks in the South Shetland Islands to gain a better understanding of the geochemical evolution of the mantle source region. The studied rocks are from four volcanic islands and range in age from 143 to 44 Ma. They have high abundances of large ion lithophile elements and light rare earth elements relative to high field strength elements, consistent with products of subduction related magmatism. The systematic inter-island variations are recognized from a comprehensive examination of the trace elements and isotopic compositions. The degree of enrich-ment of Sr–Nd–Pb isotopic compositions decreases towards younger samples, while the ratios of fluid-mobile elements/ HFSE (Sr/Yb, Pb/Yb and U/Yb) gradually increase. The previous studies on these volcanic rocks concluded that the compositional variations of the South Shetland Islands volcanic suites were mainly controlled by two component mixing between altered MORB and Pacific sediments. However, we here propose that the compositional trends observed in the volcanic rocks of the South Shetland Islands can be created from the addition of a relatively constant subduction compo-nent to temporally varying heterogeneous mantle sources. The higher radiogenic Pb and Sr isotopes and lower 143Nd/ |
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