鲁西徂徕山地区傲来山序列二长花岗岩锆石LA-ICP-MS U-Pb定年及其地质意义

LA-ICP-MS U-Pb Zircon Dating and Geological Significance of Monzonitic Granite in Aolaishan Sequence in Culaishan Area in Western Shandong Province

摘要:

出露于鲁西徂徕山地区的傲来山序列二长花岗岩是鲁西新太古代岩浆作用的重要记录，在野外地质工作的基础上，通过对其进行锆石LAICPMS UPb同位素年代学研究，得到了二长花岗岩的形成时代，并对鲁西地区新太古代的岩浆活动进行了讨论。研究得到，谐和度＞90%的锆石中存在岩浆锆石~2520Ma和继承性岩浆锆石2611Ma~2766Ma两个年龄区间。岩浆锆石的加权平均年龄为(2525±18)Ma，认为这一年龄代表了二长花岗岩的形成年龄。2611Ma~2766Ma继承性岩浆锆石的存在反映了鲁西地区至少经历了2次壳源物质的重熔和加入。

Abstract:

Monzonitic granite in Culaishan area in western Shandong is one of the most important record of Neoarchean magmatism. On the basis of field survey, through study on zircon LA-ICP-MS U-Pb isotopic chronology, the forming time of monzonitic granite has been determined, and Neoarchean magmatism in western Shandongn have been discussed. It is regarded that there are two age ranges in the zircons which harmonic degree is more than 90%, such as ~2520Ma and 2611~2766 Ma which respectively corresponding to magma zircons and inherited magma zircons. Weighted mean age of magma zircons is (2525±18)Ma which represents the forming time of monzonitic granite. The existence of inherited magma zircons with ages between 2611Ma and 2766Ma indicate that western area in Shandong province has experienced at least two remelting and adding.