一个造山后的辉长岩──河南新县王母观岩体的地球化学特征  

GEOCHEMISTRY AND TECTONIC SIGNIFICANCE OF POST-TECTONIC GABBRO FROM WANGMUGUAN OF XINXIAN COUNTY, HENAN PROVINCE

作　　者：张旗[1] 马文璞[1] 金唯俊 李秀云[1] 

机构地区：[1]中国科学院地质研究所,中国地质大学

出　　处：《地球化学》1995年第4期341-350,共10页Geochimica

基　　金：国家自然科学基金

摘　　要：河南新县王母观辉长岩（２６１Ｍａ）侵位在定远组（３９１Ｍａ）中。岩体贫Ｋ、Ｚｒ、Ｙ、Ｔａ、Ｔｈ、Ｈｆ，ＬＲＥＥ略亏损，具明显的Ｅｕ正异常，εＮｄ（ｔ）较低（＋３－－１．９），εＳｒ（ｔ）低（－５－－８），δ（１８）Ｏ在地幔范围内（＋５．６‰－＋６．４‰）。Ｎｄ－Ｓｒ同位素关系暗示岩体源于大陆下略亏损的地幔源区，推测为亏损地幔端元（ＤＭＭ）与第一类富集地幔端元（ＥＭＩ）混合的产物。矿物、微量元素和同位素资料表明，岩体是在拉张环境下形成的，产于造山后阶段，其成因可能与岩石圈的拆沉作用（ｄｅｌａｍｉｎａｔｉｏｎ）有关。The Wangmuguan gabbro (WMGG)(261Ma) which emplaced into the Dingyuan Formation (391Ma) is composed of olivine gabbro with middle values of Fo (73-74)and An (65-75). The relationship between olivine, clinopyroxene and plagioclase indicates that the WMGG was not derived from island arc setting, and its origin is not related to subduction. The WMGG is geochemically poor in K, Rb, Zr, Ta,Th, Hf, and slightly depleted in LREE, but with positive Eu anomaly. It has low values of εNd (+3.0--1.9) and εSr(-5--8), implying that the source may have been a slightly depleted mantle, and its formation may have been related to the mixing of the depleted mantle member (DMM) and the enriched mantle I (EM I). The value of δ18O (+5.8-+6.4) falls into the mantle field.The WMGG might be a post-tectonic magma suite member. One possible explanation for this is that its origin is related to delamination after continental collision.

关 键 词：辉长岩 地球化学 岩浆活动 岩体 造山带 

分 类 号：P588.124[天文地球—岩石学]