Spinels are widely present in peridotite and pyroxenite xenoliths within Cenozoic alkali basalts of eastern China, with their abundance typically ranging from 1% to 10%. They are small (0.1—1mm) and irregular crystals, sometimes forming graphic intergrowths with py-roxene or olivine. Spinels from deep-seated xenoliths of Cenozoic basalts in eastern China belong to picotite and hercynite. Spinels from kimberlites, their mantle xenoliths and diamonds are dominated by aluminochromite, followed in order by ferrochromite, with rare picotite. Compared with those from pyroxenite xenoliths, spinels from peridotite xenoliths in Xenozoic basalts of eastern China are higher in Cr2O3, Cr/(Cr+Al), Cr/(Cr+Al),Cr/(Cr+Al+Fe3+),Cr2O3/(Cr2O3+ Al2O3+MgO+TFeO) amd MgCr2O4+FeCr2O4-mol,but lower in Al2O3. The reasons are as follows: chromium is a compatible element, but aluminium is an incompatible element; peridotites in basalts belong to the residual upper mantle after the removal of basaltic melts derived from partial melting of the upper mantle, and to mantle-derived xenoliths, thus causing their spinels to be rich in Cr and poor in Al. Pyroxenites in basalts are crystallization products of basaltic magma in the upper mantle, with their spinels poor in Cr and rich in Al. Studies reveal that Cr2O3content, Cr/(Cr+Al), Cr/(Cr+Al+Fe3+),Cr2O3/(Cr2O3+ Al2O3+MgO+TFeO),MgCr2O4and FeCr2O4of spinels from deep-seated xenoliths in basalts are notably low relative to those of macrocrystalline spinels from kimberlites, their mantle-de-rived xenoliths and diamonds, suggesting that the formation pressure of spinels in xenoliths of basalts is lower than that of spinels in kimberlites, their xenoliths, and diamonds.