新疆博格达地区发现类似稀土四分组效应的辉绿岩

摘要

This paper focuses on the diabase which is exposed at Xialaoba area of northern Bogeda.The diabase is rich in aluminum and highly evolved (with high FM and FL values), which is due to subsequent alteration or a mixed origin of crustal and mantle materials.The Y/Ho, Zr/Hf and Nb/Ta ratios of the diabase are different from those of chondrites.It is firstly reported that the diabase displays obvious tetrad effect on the chondrite-nomalized REE pattern,as evidenced by high TE1,3 and TE1,3,4 (>1.1).This tetrad effect is ascribed to high-degree evolution of parent magma,contamination of high-aluminum crust and influence of later volatiles and fluids.%通过对博格达东部下涝坝地区的辉绿岩进行研究，发现该区辉绿岩具富铝、高演化（FM和FL值都较高）、经过壳幔混合或改造（高烧失量）、Y/Ho、Zr/Hf和Nb/Ta的比值显示出非球粒陨石的特点。首次在该区发现了辉绿岩的稀土元素具四分组效应，通过对辉绿岩稀土四分组效应的程度进行量化，发现本区的辉绿岩稀土元素具明显的“MM”型四分组效应，且TE1、3TE1、3、4均大于1.1，表明稀土元素“M”型效应非常明显。认为该地区辉绿岩稀土元素的“MM”型四分组效应是由于辉绿岩的高演化、受到高铝质的地壳改造，及后期挥发分和流体的改造等因素造成。