Abstract:Cebojiyi area, belonging to southern middle Bangong Co Nujiang River metallogenic belt, is located at the northeast of Xainza county about 40km. There are produced with nickel sulfide minerals in the ultrabasic rocks of this deposit, also with chromium and cobalt mineralization been found. It plays an important role in resource potential evaluation and mineral exploration for Cebojiyi, even the whole Bangong Co Nujiang River metallogenic belt that researching the geochemical characteristics and origin of the ultrabasic rocks in this area. The rocks containing nickel are mainly ultrabasic rocks such as harzburgite, most of which were strongly serpentinized. Nickel minerals are mainly alloy minerals such as inconel alloy, iron nickel alloy, sulfide minerals such as millerite, iron millerite and heazlewoodite, silicate minerals such as nickel containing olivine, nickel containing serpentine and so on. The Mg# values of Cebojiyi harzburgite are in the range of 8703~8825, with an average of 8782, close to the Mg#(89~91) of metaperidotite in ophiolite. The m/f values are in the range of 671~751, with an average of 722, suggesting the harzburgite are magnesia. And the Cebojiyi harzburgite are alkaline series. In the rocks, large ion lithophile elements such as U, Th, Pb and high field strength elements such as Ta, P are enriched, while the elements such as Ba, K, Sr and Nb, Ti are poor, which roughly comply with the characteristics of island arc magmas. The total REE of the rocks are very low, and the ∑REE values are in the range of 039×10-6~137×10-6, with an average of 094×10-6. It is obvious of light and heavy REE fractionation, with LREE/HREE ranging from 507 to 604 and (La/Yb)N from 298 to 608. The rocks have a weak positive Eu anomaly(δEu=115~154, with an average of 142) and no obvious Ce anomaly(δCe=093~115, with an average of 104). The 206Pb/204Pb values are 18428~18554(average is 18476), 207Pb/204Pb are 15498~15614(average is 15575), and 208Pb/204Pb are 37712~38730(average is 38386). While the 87Rb/86Sr values are 08686~38985(average is 21145),87Sr/86Sr are 0709148~0711524(average is 0710257), 147Sm/144Nd are 01090~01237(average is 01178), and 143Nd/144Nd are 0512028~0512112(average is 0512075). The results show that the tectonic environment of Cebojiyi harzburgite are island arc environment, and the magma are from the subduction zone mixed with upper crust and mantle, simultaneously, the magma source are spinel amphibole lherzolite enriched mantle source region. The average nickel content of harzburgite in Cebojiyi deposit is 20173 × 10-6, while it is 24292 × 10-6 in Cebojiyi serpentinized harzburgite. If the nickel mineral were sulfide minerals, then the content have been reached the cut off grade both in Cebojiyi harzburgite and serpentinized harzburgite. At the same time, the nickel content of iron ore in Cebojiyi deposit has been reached the cut off grade, with an average of 63231×10-6. What’s more, the cobalt content of iron ore in Cebojiyi deposit has been reached the cut off grade, with an average of 6326×10-6. And the chromium content of iron ore in Darucuo deposit has been reached the cut off grade, with an average of 526794×10-6. So attention should be paid that the nickel, cobalt and chromium prospecting work in the ultrabasic rocks associated with ophiolite, especially the iron ore in ultrabasic rocks in Bangong Co Nujiang River metallogenic belt.