中秦岭南部耀岭河群稀土元素特征及其构造环境分析

THE CHARACTERISTICS OF REE AND TECTONIC SETTING ANALYSIS ON YIAOLINGHE GROUP IN THE SOUTH OF MIDDLE QINLING

根据大量稀土元素样品分析，耀岭河群ＲＥＥ的总体特征为“液体型”的右倾分布模式，稀土分馏不明显向稀土分馏明显演化。（Ｃｅ／Ｙｂ）＿Ｎ比值由玄武岩向中酸性岩逐渐增加，反映部分熔融程度的减少和分离结晶作用的加强；（Ｌａ／Ｓｍ）＿Ｎ比值由基性向酸性岩逐渐增高，反映了裂谷早期扩张较快，后期暗示着挤压环境；从Ｅｕ／Ｓｍ比值逐渐降低；δＭＥｕ由上异常转向负异常，表明分异程度的增强。从（Ｌａ／Ｙｂ）＿Ｎ比值判别本区相当于Ｅ－ＭＯＲＢ富集型源区，其构造环境属大陆活动边缘裂谷发展的弧后洋盆。

Based on analysing a large of REE samples,the overall Characteristics of REE of YiaolingheGroup is right trending distributing model as“liquid type”with REE fractionation evalution fromabvious to unabvious. The value of(Ce /Yb)_N ratio increase gradually from basalt to intermediateacid rock reflecting that decrease of partial molting degree and strengthen of fractional crystalliza-tion;the value of(La/Sm)_N ratio increase gradually from basic to acid rock reflecting spreadingfaster during the early stage of rift event and compressive setting during later stage; the value ofEu/Sm ratio decrease gradually and δEu turn from postive anomaly to negative showing thestrengthen of differentiation degree. Distinguishing from the value of(La/Yb)_N ratio,the study-ing area is equal to source area of E-MORB rich type. ts tectonic setting belongs to back-arcocean basin from rift developed in continental active margin.