鲁山太华群麻粒岩相岩石形成的地球化学限制

鲁山太华群麻粒岩相岩石形成的地球化学限制徐启东，高山，刘庆生（中国地质大学，武汉４３００７４）主题词麻粒岩相岩石，ＬＩＬ元素亏损，下地壳太华群提要河南鲁山太古宙高级区表壳岩中的麻粒岩相岩石及相关的角闪岩相岩石与世界其它地区麻粒岩相岩石相比并没有明显的...

Geochemical Constraints of Granulite Facies Rocks in Taihua Group,Lushan County,Henan Province

A comparison of the Lushan granulite facies rocks and related amphibolitefacies rocks with the granulite facies rocks in other parts of the world showsthat the former rocks are not apparently depleted in LIL elements.The slightRb and U depletion accompanied by no Th depletion suggests that granulitefacies rocks have not been transformed by special fluids or melts,and thatthe slight Rb and U depletion might be attributed to the devolatilizationthat occurred during or bofore amphibolite facies metamorphism.The geoche-mical features,combined with the fact that there exist no CO_2-rich fluidinclusions in the rocks and no positive Eu anomaly in the chondrite-normalized REE patterns of the rocks,have ruled out the possibility that thepermeation of CO_2 fluids and partial melting might have acted as the meta-morphic mechanism of the granulite facies rocks.The trace element dlstribu-tion patterns of the Lushan granulite facies rocks are equivalent to the patt-erns of the average crustal compositions on the southern margin of the NorthChina platform,and this implies that there has been no obvious crust growthin this area since Proterozoic and that the material cycling1 has been mainlyintracrustal recycling.The high heat-producing element contents of the Lushangranulite and amphibolite facies rocks might be one of the factors thathave caused the long heat nonequilibrium in the crust of the area and a series of tectonic activities since Proterozoic.