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| Nadingco Formation volcano rocks zircon U-Pb age and geochemical characteristics in Gêrzê county area of northern Tibet area |
| CHU Huili |
| Fujian Institute of Geological Survey, Fuzhou 350013, China |
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Abstract Volcanic rocks of the Nadingco Formation is mainly distributed in the north of the Bangong lake-Nujiang suture zone.It is belong to the volcano rock formation of the Qiangtang-Sanjiang composite plate Duoma stratigraphic division Quegang district formation,and represents the volcanic activity of the south of Qiangtang area in Paleogene。Its main rock type is latite-trachyte.There are 3 dating samples which show the ages of (35.99±0.29) Ma、(37.2±0.65) Ma and (35.23±0.37) Ma.The geochemistry samples exhibit w(SiO2)=58.7%-65.51% which is high, A/NFC=0.046-1.029 which is low,w(MgO)=1.10%-2.95% which is high,∑REE=243.38×10-6-313.48×10-6,and δEu=0.77-0.91. It indicates that the basalt is slightly enriched in light rare earth elements(LREE)and without remarkable Eu depletion. Large ion affinity rock elements such as Rb and Th are high content. High field-strength elements such as Hf and heavy rare earth elements (HREE) are low content.Most samples shows that Ti, Ta and Nb are low content.w(La)/w(Sm) shows stable content.w(Sm)/w(Yb)=4.3-6.7,which is low. According to the features of rock geochemistry,the primitive magma originates from the special crust mantle transitional zone, which is based on the thickened continental crust of the Qinghai Tibet Plateau. Its forming is the initial intraplate continental extensional rift environment near the orogenic belt.
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Received: 07 April 2016
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2016, Vol. 3 
