河南信阳地区龟山岩组新元古代变质玄武岩的地球化学特征、Sr-Nd同位素组成及地质意义

对信阳地区商丹断裂带南侧龟山岩组新元古代变质玄武岩进行了岩石学、地球化学及Sr-Nd同位素研究，分析结果显示该套玄武岩为亚碱性拉斑玄武系列，分为低Ti及高Ti两种类型：低Ti型较富Mg，不相容元素富集程度及稀土分馏程度较低，具有E-MORB的微量元素地球化学特征，Sr-Nd同位素组成相对富集，可能来自地幔柱引发的岩石圈地幔的部分熔融，并受到一定程度的地壳混染；高Ti型较富Fe，强烈富集不相容元素，具有OIB的地球化学特征，Sr-Nd同位素组成较为亏损，可能来自地幔柱的部分熔融，并较少受到地壳物质的影响。综合构造判别显示该套玄武岩可能为地幔柱伸展背景下的岩浆活动产物，可能为区域上沿商丹断裂带分布的中—新元古代局部伸展背景岩浆活动产物的组成部分。

Geochemical characteristics,Sr-Nd Isotopic compositions and geological implications of metamorphic basalts from the Guishan complex in the Xinyang area,Henan Province.

In this report, we present the geochemical characteristics and Sr-Nd isotopic compositions of Neoproterozoic metamorphic basalts from the Guishan complex in the Xinyang area, south of the Shang-Dan Fault. All basalt samples analyzed belonged to the sub-alkaline tholeiitic basaltic series and could be classified into high-Ti and low-Ti types. The low-Ti type basalts had higher Mg content, low degrees of LREE/HREE fractionation and enrichment of incompatible elements, and relatively enriched Sr-Nd isotopes, showing E-MORB characteristics. The high-Ti type basalts had higher Fe content, high degrees of LREE/HREE fractionation and enrichment of incompatible elements, and relatively depleted Sr-Nd isotopes—compatible with OIB features. The low-Ti type basalts might result from the partial melting of lithospheric mantle caused by a mantle plume, with some crustal contamination. The high-Ti type basalts, on the other hand, might be generated from the partial melting of a mantle plume with minor crustal influence. The geochemical discriminant diagrams of tectonic setting show that the metamorphic basalts erupted in the extensional mantle-plume environment, possibly as part of the Meso-Neoproterozoic magmatic activities in the extensional environment of the Shang-Dan Fault.