1. College of Earth Science��Jilin University��Changchun 130061��China; 2. Geology and Mineral Exploration Institute��Qinghai Provincial Bureau of Nonferrous Metal and Geological Exploration��Xining 810007��China; 3. Qiqihar Institute of Mineral ��esources Exploration��Qiqihar 161006��Heilongjiang China

The paper discusses the pyroxene diorite which is closely related to ore- forming bodies in Galinge deposit�� Geochemical characteristics show that the pyroxene diorite in Galinge belongs to calc- alkaline and metalu- minous series�� The trace element is enriched in more mobile incompatible elements (e�� g�� Th��U) and L��EE�� relatively depleted in high field strength elements (e�� g�� Nb��Ta��Ti and P)��and exhibits weak negative Eu a- nomalies (δEu =0. 924 ��0. 962)�� The zircon ε Hf (t) values ��3. 79 �� ��1. 70��all yield relatively ancient model ages (T DM2 )��ranging from 1 223 to 1 339 Ma�� Zircon LA - - ICP - - MS U - - Pb dating for the pyroxene diorite yields age of Galinge is 228 ±2 Ma (MSWD = 0. 32)��indicating the Late Triassic�� Combined with previous research a- bout the regional geological background��we propose that anemaqen oceanic crust was already subducted and break- off during a period of change in the tectonic setting of the EKO from compression to extension��and it in- duced the upwelling of deep asthenosphere and the addition of mantle- derived material��providing enhanced heat and triggering the partial melting of overlying ancient lower crust��eventually forming the Galinge pyroxene diorite��