山东郭城牧牛山二长花岗岩的岩石成因:地球化学和锆石U—Pb年代学制约

山东胶莱盆地东北缘郭城牧牛山二长花岗岩的锆石LA--ICP--MS U--Pb年代学及岩石地球化学特征表明,牧牛山花岗岩为古元古代(2 138±15 Ma)岩浆侵入产物,是一套钾玄岩系列岩石,A/CNK为1.07~1.13。稀土配分曲线表现为右倾模式,轻稀土和重稀土分异明显,Eu/Eu*值为0.59~0.71。蛛网图表明明显富集大离子亲石元素(Rb、K),相对亏损高场强元素(Th、U、Nb、Ta、Ti、P)。岩石10 000 Ga/Al值(2.73~2.85),为A型花岗岩。岩石的Mg~#值为12~28,Nd/Th值为1.62~1.96,Rb/Sr值为4.70~9.71,显示壳源特征。综合分析认为,古元古代胶辽地块向西俯冲引发幔源岩浆底侵,导致地壳物质部分熔融形成牧牛山花岗岩。

Condition of geochemistry and zircon U- Pb geochronology for monzonitic granite in Muniushan，Guocheng，Shandong

LA- ICP-MS zircon U-Pb dating and geochemical study of the Muniushan monzonitic granite in Guocheng area，the northeast fringe of Jiaolai Basin，show that Muniushan granite is the Paleoproterozoic (2 138 ± 15Ma) magmatic intrusion product，which is a series of shoshonite rocks，with A / CNK from 1. 07 to 1. 13．ＲEE curve shows right leaning mode，and the differentiation between LＲEE and HＲEE is significant． Eu/Eu * val- ues are from 0. 59 to 0. 71． The spider diagram shows significant enrichment in LILE (Ｒb， K)， and relative deple- tion in high field strength elements (Th，U，Nb，Ta，Ti，P)． The value of 10 000 Ga / Al of rocks is 2. 73 ～ 2. 85，showing the A- type granites． Mg# ranging from 12 to 28，Nd/Th ranging from 1. 62 to 1. 96，Ｒb/Sr ranging from 4. 70 to 9. 71，all display the character of shell source． Comprehensive analysis indicates that westward sub- duction by Paleoproterozoic Jiaoliao Lot initiate mantle magma intrusion，which results in partial melting of crustal material to form Muniushan granite．