Continental Mantle Xenoliths beneath Wangqing, Jilin Province, Northeastern China
Spinel Iherzolite, dunite, wehrlite, and clinopyroxenite xenoliths in the Pleistocene alkaline basalts from Wangqing, Jilin Province, northeastern China were examined to provide chemical and mineralogical data of the continental mantle beneath northeastern China. Spinel Iherzolite seems to represent chemical composition of the continental upper mantle beneath northeastern China, and no distinctive chemical difference can be recognized between oceanic and continental mantle. The recorded temperature in the spinel Iherzolites ranges from approximately 1100℃ to lower than 800℃. The investigated spinel Iherzolites should represent the continental mantle materials of variable depths beneath northeastern China. In contrast, the dunite and clinopyroxenite retain rather low equilibrium temperature: it ranges from 850℃ to 750℃. The geothermal gradient beneath northeastern China is similar to that beneath the oceanic region. Although their host alkaline basalts are highly enriched in K_2O, the Na_2O contents of them are not so considerable. Neither significant chemical discrepancy nor essential inconsistency of geothermal gradient has been emphasized between the continental mantle material investigated in this paper and oceanic mantle material reported elsewhere. It should be significant, however, to point out that the studied mantle Iherzolites are highly magnesian and depleted compared with the Hawaiian Iherzolites.
- 東北アジア研究 = Northeast Asian studies
東北アジア研究 = Northeast Asian studies 3 233-247, 1999-03-31