德兴地区新元古代镁铁-超镁铁岩的地球化学特征及其地质意义

GEOCHEMISTRY AND GEOLOGICAL IMPLICATIONS OF MAFIC-ULTRAMAFIC ROCKS AS OLD AS ～838 Ma IN THE DEXING AREA,NE JIANGXI

镁铁-超镁铁质岩的成岩过程、原始岩浆的成分特征及岩浆源区性质的判别对探讨大地构造演化的动力学过程具有重要意义。对赣东北德兴地区年龄约838 Ma的镁铁-超镁铁岩的主、微量元素、REE和Sm-Nd同位素进行了分析研究,认为它们多属亚碱性系列,地球化学特征既有共性,又有明显的差异性。它们都一致具有较高的εNd(t)值;但有些样品具有明显的“弧玄武岩”的地球化学特征,有些则显示板内拉张的信息等。作者据此探讨了赣东北地区新元古代镁铁质岩的成因、岩浆演化过程和构造背景。

Mafic-ultramafic rocks dated at - 838 Ma in the Dexing area, NE Jiangxi belong to sub-alkaline series. On the one hand, they have some similar geochemical characteristics such as high εnd（ t）values. However, different samples show distinctive differences in certain other features. Some samples display characteristics of arc volcanic rocks, while others of within-plate basalts and tectonic discrimination. According to the analyses of major dements, trace elements, REE and SmNd isotopic data, this paper gives some implications for petrogenesis, the geochemical properties of original magma, magma evolution, and the tectonic environment of these mafic-ultramafic rocks.