摘要
出露于浙江省东南部的大爽岩体为黑云母二长花岗岩,LA-ICP-MS锆石U-Pb年代学研究表明该岩体形成于227±2Ma,属印支晚期岩浆作用的产物。地球化学分析显示该岩石低Na2O、富K2O,A/CNK=1.26~1.49(大于1.1),为强过铝质、钾玄质系列花岗岩;岩石稀土总量较高,富Sr(Sr=874.6×10-6~1158×10-6),贫Yb(Yb=3.00×10-6~3.92×10-6),富轻稀土而亏损重稀土,具轻微的负铕异常(δEu=0.68~0.70);相对富集Rb、Th等大离子亲石元素,而亏损Nb、Ta等高场强元素;Sr-Nd同位素分析表明岩石具有较高的初始锶比值(I Sr=0.710718~0.711008)和较低εNd(t)值(εNd(t)=-10.9^-11.1),上述地球化学特征指示该岩体岩浆源区为古老的地壳物质。综合分析认为大爽岩体是古老地壳部分减压熔融的产物,受控于印支造山后的伸展应力作用。
The Dashuang pluton in the southeast of Zhejiang Province is composed of biotite monzonitic granite. The LA-ICPMS zircon dating is 227 ＋ 2Ma, which indicates that the pluton was formed during the Late Indosinian period. Most of granite samples exhibit lower Na20, but higher K20 and A/CNK values ranging from 1.26 to 1.49 （ 〉 1.1 ） . These results indicate strongly peraluminous and shoshonitic granite features, with enriched content of Sr but depleted content of Yb （ Sr = 874. 6 x 10 -6 - 1158 x 10 -6, Yb = 3.00 x 10 -6 - 3.92 x 10 -6 ）. The content of rare earth elements is relatively higher, showing enriched in LREE and display weakly to moderately negative eupopium anomalies （ 8Eu = 0. 63 ） in the chondrite- normalized REE distribution patterns. Large-ion lithophile elements Rb and Th are relatively enrichment while high field strength elements Nb, Ta are relatively depleted. The characteristics of Sr-Nd isotopic show high ages of Isr（ = 0. 710718 - 0. 711008 ） and low value of 6Nd （t） （ = -- 10. 9 - -- 11. 1 ） The geochemistry and Sr-Nd isotopic characteristics suggest that the Dashuang granitic pluton was derived from the ancient crust sources of partial decompression melting which under the post-orogenic （Indosinian） extensional tectonic setting.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2013年第9期3131-3141,共11页
Acta Petrologica Sinica
基金
浙江省国土资源厅项目([省资]2010001)资助
