鲁西太古代徂徠山杂岩体花岗质岩石成因探讨

鲁西太古代徂徕山杂岩体主要由片麻状花岗岩和钾长花岗岩构成,此外尚发育少量小规模的中粗粒、细粒闪长岩。本文着重讨论花岗质岩石的成因。徂徕山杂岩体岩石地球化学研究表明,片麻状花岗岩为深源(下地壳)花岗质岩浆侵位结晶的产物;钾长花岗岩是片麻状花岗岩在区域变质作用过程中部分熔融形成的,两者具有密切的成因联系。

THE GENESIS OF ARCHEAN CULAISHAN GRANITIC COMPLEX IN WEST SHANDONG

The Archean Culaishan granitic complex, surrounded by Taishan Group of amphibolite-facies metamorphic rocks and Quaternary sediments in West Shandong province, is mainly composed of gneissic granites and massive K-feldspar granites.The complex is formed through two related processes. By the studying on the lithcchemistry and geochemistry, the gneissic granites are the crvstalization products of the typhonic granitic magma and the K-feldspar granites are formed through the partial-melting of the gneissic granites during the regional metamorphism.The gneissic granite which it's magma intruded into Taishan Group at 2668Ma befor the regional metamorphism is characterized by it's blastogranitic structure. The essential minerals are plagioclase (An = 25-30), quartz, biotite. The accessory minerals are apatite, sphene, epidote, magnetite, allanite and zircon, the contents of which could be more than 5%. The REE patterns are HREE depletional type with no Eu anomaly, that might be the results of the partial-melting of hornblende, garnetriching mafic layer at lower crust. The composition of the granite in A-C-F diagram is plotted in "I" type granite area .The K-feldspar granite is the production in the anatexis process of the gnissic granite which is mainly composed of microcline, albite and quartz and characterized by granitic texture. The REE pattern is varied with the different contents of total REE and Eu anomaly. The genesis significance of quartz and feldspar, and the felsic lecosomes in the partial-melting process are discussed in the paper.