东南极格罗夫山变质基性岩地球化学特征

Geochemical characteristics of the metabasic volcanic rocks in the Grove Mountains, East Antarctica.

东南极格罗夫山变质基性岩的地球化学研究表明,该区存在两类玄武岩,即洋岛型玄武岩(OIB)和洋中脊型玄武岩(MORB)。OIB型具有大体类似的地球化学性质,它们均富集Ti(TiO2-2.68％)、REE(=202μg/g)、LREE[(La/Yb)N=4.8]、Ti/Y(=343)、Zr/Y(=3.1),具洋岛玄武岩的特征,推测岩浆来源于富集地幔源区(EM)。而MORB型以低Ti(TiO2=1.1％～1.31％),明显低于OIB的P的含量(P2O5=0.1％～0.2％),低REE(47～93μg/g)、LREE/HREE(2.27～2.54)、(La/Yb)N(=1.30～1.62)为特征,具洋中脊玄武岩的特征。MORB和OIB组合的出现说明在泛非期该区可能存在过洋盆。

Based on geochemical signatures of metabasic volcanic rocks, two types of basalt in the Grove Mountains are recognized, namely, oceanic island basalt (OIB) and Mid-oceanic ridge basalt (MORB). Type 1 rocks have similar geochemical characteristics, with high Ti (TiO2=2.68%), REE (=202mug/g), LREE [(La/Yb)(N)=4.8], Ti/Y (=343) and Zr/Ti (=3.1), which are similar to those of OIB, and are considered to be products of magma from enriched mantle sources (EM). Type 2 rocks are characterized by low Ti (TiO2 = 1.1%similar to1.31%), REE (47similar to93mug/g), LREE/HREE (2.27similar to2.54), (La/Yb)(N) (= 1.30similar to1.62) and lower P (P2O5 = 0.1%similar to0.2%) than those of OIB, which are similar to those of MORB. The presence of such rock assemblages suggests the existence of an ocean basin in this region during Pan-African ages.