摘要
为了解晚古生代西伯利亚板块南缘增生造山过程中的岩浆活动特征，对东乌旗巴彦都兰二长花岗岩岩相学、锆石U-Pb年代学、锆石Hf同位素和岩石地球化学进行了研究，并讨论了岩石成因和构造环境。锆石LA-ICP-MSU-Pb定年结果为（277．2±0．7）Ma，以正的锆石εHf（t）（6．8～14．1）为特征，具有年轻的锆石地壳模式年龄（fbM）（865~655Ma），属于早二叠世晚期岩浆活动产物。二长花岗岩以高钾[w（K）：3．63％～4．95％，K2O／Na2O=0．91～1．47]、富碱[甜（K2O＋Na2O）=7．5%~9．16％]、准铝质-弱过铝质（A／CNK=0．96～1．15）为特征；稀土元素，总量较低（38．82×10-6～193．20×10-6），（La／Yb）。为3．91～23．08，轻、重稀土元素分异较明显，呈弱负铕异常（dEu为0．34～1．17）；富集部分大离子亲石元素（LREE、Rb、K等）；Zr弱负异常、Hf弱正异常，亏损Sr、Nb、Ta、P、Ti，显示后造山花岗岩特征。综合分析表明，巴彦都兰二长花岗岩形成于伸展的构造环境中，是贺根山洋盆闭合后的后造山阶段产物，为865~655Ma前洋壳俯）十形成的先成地壳部分熔融而成。
In order to learn the characteristics of magma activity along the southern plate of Siberianlate during Late Palaeozoic Eta. , petrography, U-Pb chronology of the zircon, zircon Hf-isotopeand geochemis- try of the Bayandulan monzonitic granite are studied to constrain the genesis and tectonic setting of the rock in Dong Ujimqin Qi, Inner Mongolia. Zircon U-Pb dating obtained by LA-ICP-MS analyses from the monzonitic granite is （277.2±0.7）Ma, suggesting period of Early Permian. The eHf （t） values and the ite, are 6.8-14.1 and 865-655 Ma respectively. that it is the production of magmatic activities in later crust model ages （tDMc） of Bayandulan monzonitic gran- The Bayandulan monzonitic granite is enriched in K（K =3.63%-4.95%,K20/Na20=0.91-1.47） and alkali （K2Oq-Na20=7.52%-9.16%）, suggesting the feature of metaluminous to weak peraluminous （A/CNK = 0. 96- 1. 15）. It is apparently different in LREE and HREE, with most rocks having weakly negative Eu anomalies （δEu=0. 34-1.17）. The rock is depleted in rare earth elements （δREE=38.82;K10^ 6-193.32×10 -6^）, andSr, Nb, Ta, P, Tienriched in partial LILE （LREE, Rb, K and so on） with weakly negative Zr anomaly and weakly positive Hf anom- aly, showing characteristics of post-orogenic granites. The monzonitic granite produced in extent environ- ment, and was the product of post-orogenic evolution after closing of the Hegenshan Ocean. And the for- mation of the rock is partial melting of juvenile continental crust resulted from subducted oceanic crust ex- ised during 865-655 Ma.
出处
《地质科技情报》
CSCD
北大核心
2015年第4期6-14,共9页
Geological Science and Technology Information
基金
中国地质调查局中国地质调查项目"内蒙古1:5万奥尤特等六幅区调"(1212011220446)
