The Mandaleke ophiolite belongs to the late Paleozoic ophiolite belt i n South Tianshan Mountains and is composed of serpentinized peridotites, basalts and radiolarian cherts. The chromite or Cr-spinel occurs in the serpentinized p eridotites as a ubiquitous accessory mineral, some of which has the podiform tex ture. Petrographic observation and electron microprobe analysis indicate that th e Cr-spinel grains display obvious composition zoning, suggesting the path of su ch thermal events as crystallization, upwelling and alteration. The core of the Cr-spinel crystal represents the provenance where the mineral crystallized. The authors thus chose cores of the Cr-spinel to trace the nature of the mantle and the whole crystals to deduce the thermal events that the host rocks have experie nced. On the basis of olivine_spinel geothermometry, the crystallized temperatur e of the anhedral core is estimated to be from 1359℃ to 1394℃, 1379℃ on average. Similarly, according to the Cr-spinel geobarometer, the mantle pressur e i s estimated to be from 2.76 GPa to 3.00 GPa, 2.87 GPa on average, while the oxygen fugacity relative to FMQ buffer is FMQ-1.50～ FMQ-2.92 log units, FMQ-2.14 log units on average. Furthermore, the degree of partial melting of the man tle is estimated to be from 16.7% to 18.0%, 17.3% on average, in the light of its relationship with Cr#. These parameters provide some clues of the physi cochemical conditions: these peridotites were derived from garnet lherzolites lo cated in the asthenosphere of the upper mantle, and the incompatible element-dep leted mantle might have resulted from previous partial melting. The tectono-disc rimination diagrams imply that the Mandaleke ophiolite was formed in a fore-arc setting. The compo sitional zoning suggests that the peridotites have undergone a thermal path of d ecreasing temperature and increasing oxygen fugacity. It can be inferred that the mantle peridotites experienced the process from a high temperature and high pr essure mantle (lower oxygen fugacity) stage to a thrusting slice stage to reach the crustal surface, where they were subjected to regional metamorphism (higher oxygen fugacity).