Geochemistry of basalts at DSDP Hole 83-504B@en

The major element geochemistry of basalts recovered from Leg 83, Hole 504B, shows the typical features of midocean ridge basalts (MORB). The range of variation in their composition, together with the behavior of compatible trace elements (Co, Ni, Cr), indicate the well-known relative abundance of minerals that crystallize from these basaltic liquids: plagioclase, olivine, pyroxene, and spinel in decreasing abundance. The hygromagmaphile (or LILE or incompatible) elements are extremely depleted in light rare earths. Nevertheless, some units show flat and enriched REE patterns. These patterns, together with the values of the La/Ta ratio, are interpreted in terms of local mantle heterogeneity.大洋钻探第83航次504B孔所获玄武岩的主量元素地球化学特征，具有洋中脊玄武岩（mid-ocean ridge basalts, MORB）的典型特征。该类玄武岩的成分变化范围，连同相容微量元素（钴（Co）、镍（Ni）、铬（Cr））的地球化学行为，共同揭示了这类玄武质熔体结晶析出的矿物相对丰度规律：斜长石、橄榄石、辉石与尖晶石的丰度依次递减。亲岩浆元素（hygromagmaphile，又称大离子亲石元素（LILE）或不相容元素）在轻稀土组分中呈现极度亏损状态；不过，部分地层单元展现出平坦型且富集型的稀土元素（rare earth elements, REE）配分模式。上述稀土配分模式与镧/钽（La/Ta）比值数据，均可通过区域地幔不均一性得到合理解释。