Oxygen isotopic compositions and trace element contents of minerals from 9 peridotite xenoliths hosted by Cenozoic basalts\ in Nushan, SE China have been obtained by laser fluorination method and LA-ICP-MS respectively. Some samples dont show oxygen isotope equilibrium between pyroxene and olivine with the lowest Delta(Cpx)(18)O ( = delta(18)O(Cpx)-delta(18)O(OI)) of -0.5 parts per thousand. Clinopyroxenes from the amphibole-bearing xenoliths are enriched in LILE (Sr, Th, LREE) and depleted in HFSE (Nb, Zr, Ti). Oxygen isotope data suggest that the Nushan upper mantle experienced metasomatism by oceanic fluids from the subducted plate. Based on the negative correlation between Delta(Cpx-01)(18)O and formation depth of Nushan xenoliths, we propose an "ascending + buffering" model for mantle metasomatism in Nushan. The degree of oxygen isotopic disequilibrium is not related with LILE enrichment and HFSE depletion, suggesting at least two metasomatic events happened in the Nushan mantle, one was responsible to LILE enrichment/HFSE depletion and another to oxygen isotopic disequilibrium.
Oxygen isotope and trace element compositions of peridotite xenolitlis from Nushan volcano, SE China and implications for mantle metasomatism / Yu, Hm; Xia, Qk; Dallai, L; Chazot, G. - In: ACTA PETROLOGICA SINICA. - ISSN 1000-0569. - 21:3(2005), pp. 829-838.
Oxygen isotope and trace element compositions of peridotite xenolitlis from Nushan volcano, SE China and implications for mantle metasomatism
Dallai L;
2005
Abstract
Oxygen isotopic compositions and trace element contents of minerals from 9 peridotite xenoliths hosted by Cenozoic basalts\ in Nushan, SE China have been obtained by laser fluorination method and LA-ICP-MS respectively. Some samples dont show oxygen isotope equilibrium between pyroxene and olivine with the lowest Delta(Cpx)(18)O ( = delta(18)O(Cpx)-delta(18)O(OI)) of -0.5 parts per thousand. Clinopyroxenes from the amphibole-bearing xenoliths are enriched in LILE (Sr, Th, LREE) and depleted in HFSE (Nb, Zr, Ti). Oxygen isotope data suggest that the Nushan upper mantle experienced metasomatism by oceanic fluids from the subducted plate. Based on the negative correlation between Delta(Cpx-01)(18)O and formation depth of Nushan xenoliths, we propose an "ascending + buffering" model for mantle metasomatism in Nushan. The degree of oxygen isotopic disequilibrium is not related with LILE enrichment and HFSE depletion, suggesting at least two metasomatic events happened in the Nushan mantle, one was responsible to LILE enrichment/HFSE depletion and another to oxygen isotopic disequilibrium.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
