Zircon U-Pb dating and Hf isotopic composition for quartz diorite and monzonitic granite from Tengchong-Lianghe block and its geological implications
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    Abstract:

    The Tengcong-Lianghe granitoids are the eastward extending of Gangdese Batholith , and diorite,quartz diorite and granite have close relationship in spatio-temporal. Zircon LA-ICP-MS U-Pb dating for quartz diorite and monzonitic granite yield crystallization ages 127.10±0.96Ma and 123.8±2.5 Ma,respectively. Geochemical data indicate that these granitoids belong to calc-alkaline to high-k calc-alkaline series with poored in K and lowed in P2O5. In addition, the diorite and quartz diorite belong to meataluminous, and the granite belongs to meataluminous to weak pera luminous. The SiO2-Mg# diagram indicates than the diorite and quartz diorite originated from the partial melting of lithosphere mantal following crustal assimilation and fractional crystallization(AFC), the granite originated from the partial melting of crustal following mantal assimilation and fractional crystallization(AFC) .Both diorite and granite are LREE-rich,HREE-depletion, weak Eu passtive to medium Eu negative anomaly.And both of them have higher LILE concentrations, lower HFSE abundance ,showing characteristics of arc magma. Zircons from quartz diorite yield εHf(t)values of -7.61 to -3.80. Combined with available εHf(t)values from coeval diorite ang granite at same area , the quartz diorite derived from the full mixing depleted mantal melt and ancient crustal melt. We propose the early cretaceous granitoids were most likely generated in a setting associated with sourthward subbuction of the Bangong-Nujing ocean floor, where mantal wedge-derived magmas have provided the heat and material for the anatexis of ancient crust of the Tengchong-Lianghe Block.

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LI Zaihui, LIN Shiliang, CONG Feng, ZOU Guangfu, XIE Tao.2012. Zircon U-Pb dating and Hf isotopic composition for quartz diorite and monzonitic granite from Tengchong-Lianghe block and its geological implications[J]. Acta Geologica Sinica,86(7):1047-1062

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History
  • Received:October 29,2011
  • Revised:February 23,2012
  • Adopted:February 23,2012
  • Online: July 10,2012
  • Published: