Geochemical Characteristicts of Pillow Lavas in Ophiolite and It''s Overlying Rock Sequence in the Laohushan Area from Jingtai County, Gansu Province
甘肃景泰县老虎山地区蛇绿岩及其上覆岩系中枕状熔岩的地球化学特征

The Early Paleozoic ocean crust of the Laohushan area consists of two parts of rocks: the lower part composed of ophiolite and the overlying rock sequence on the ophiolite, which is included in sediment rocks and extrusive mafic and andesitic rocks. The overlying rock sequence belongs to off axis magma series but not to ophiolite member. The pillow lava from the ophiolite has the characteristics of N MORB, and those from the overlying rock sequence are similar to E MORB by geochemistry. The former is from the magma chamber below the spreading ridge. The latter is supposed to be from the magma chamber out of the spreading ridge and also the products of middle high degree partial melting of asthenospheric mantle, but maybe with adding of a few materials from lower mantle.