Post-collisional Adakitic Porphyries in Tibet:Geochemical and Sr-Nd-Pb Isotopic Constraints on Partial Melting of Oceanic Lithosphere and Crust-Mantle Interaction
  • 【DOI】

    10.3321/j.issn:1000-9515.2003.02.007

  • 【摘要】

    The distribution of Neogene felsic porphyries intruding in earlier granitic batholiths was mainly controlled by north-south-tending rifting zones and normal faults. The main rock types of the felsic p... 展开>>The distribution of Neogene felsic porphyries intruding in earlier granitic batholiths was mainly controlled by north-south-tending rifting zones and normal faults. The main rock types of the felsic porphyries include granodiorite-porphyry, monzonitic granite-porphyry and quartz monzonitic porphyry. The porphyries are characterized by high SiO2 (≥64.26%) and Al2O3 (>15% at 70% SiO2), low Y and HREE (Yb) contents, strong enrichment of LILE and LERR, especially K and Sr. Geochemical features of the porphyries show distinct adakitic magma affinity. Nd, Sr and Pb isotopic compositions of the porphyries form a linear alignment from MORB to EM2, suggesting a mixing of the MORB reservoir with the metasomatized mantle reservoir. Considering also the geochemical characteristics of the porphyries and the sequence of observable structural-thermal-magmatic events at Gangdise, it is thought that the Neogene porphyries were formed by partial melting of dead subducted oceanic crust in a post-collision setting. K-enrichment in the porphyries is attributed to the interaction of slab-derived melts, i.e., adakites, with the metasomatized mantle during the ascent. There might be a delamination of residual eclogites or amphibole eclogites before the eruption of potassic lava on the Tibetan plateau since 13 Ma. 收起<<

  • 【作者】

  • 【作者单位】

    Shijiazhuang College of Economy/Institute of Mineral Resources/Hebei Bureau of Land and Resources

  • 【刊期】

    地质学报(英文版) SCI 2003年2期

  • 【关键词】

    adakite  crust-mantle interaction  post-collisional magmatism  Tibet 

  • 【基金项目】

    国家高技术研究发展计划(863计划)