Geochemistry and Zircon U-Pb Geochronology of the Luotuobozi Pluton in the Haduohe Area in the Northern the Greater Hinggan Mountains
详细信息
- 责任者：Gao Yuan (College of Earth Science ; Jilin University ; Changchun 130061 ; China) ; Zheng Changqing
- 刊名：Acta Geologica Sinica
- 出版年：2013
- 卷期：87(9)
- 关键词：正长花岗岩 ; syenogranite ; 花岗闪长岩 ; granodiorites ; 二长花岗岩 ; monzogranite ; 大兴安岭 ; Greater Hinggan Mountains
- 页码：p.1293-1310
- 图表：11 illus., 4 tables, 62 refs.
- 分类号：0801
- issnNo：ISSN0001-5717
- isbnNo：CN11-1951/P
摘要
The Luotuobozi pluton,located in southeast of Haduohe area in Daxing’anling,with its geotectonical position in the east of Xingmeng Orogenic belt,is composed of syenogranite,granodiorite（with dioritic enclaves）,monzonite.Zircons are characterized by euhedral shape,typical oscillatory zoning and high Th/ U ratios,indicating magmatic origin.LA-ICP-MS zircon U-Pb dating indicates that the weighted average ages of zircons from the Luotuobozi pluton are 127±1 Ma for yenogranite,126±1 Ma for granodiorite,131±1 Ma for dioritic enclaves,and 130±1 Ma monzonite;all are concentrating in Early Cretaceous.Except diorite enclave,the rock is weak peraluminous belonging to high potassium calc-alkaline series,characterized by high Si（SiO2 =71.11%76.89%）,high Alkali（Na2O+K2O=8.04%9.17%）,high aluminum（Al2O3 =12.9%14.99%）and low titanium（TiO2 =0.08%0.22%）,with A/CNK value 0.971.10.The rock experiences a highly fractionated and evolving stage,which is reflected by DI（86.1 97.46）and SI（0.15.59）,negative and positive Eu anomalies（δEu=0.262.51）,LREE enrichment（LREE/HREE=6.3532.16）and HREE depletion（La/Yb）N =6.3532.16).The rock are also enriched in Th,U,Hf,Zr,La,Rb and depleted in Ti,Ta,Nb.TFeO/MgO ratios are relatively low（= 2.376.41）,Zr+Nb+Ce+Y=106.48×10-6162.74×10-6,both of which are lower than the lowlimit values of the A-type granites.Zircon saturation temperatures are also lower than the low-limit values of the A-type granites,ranging from 723.43to 760.48℃.Combined with petrography,rock geochemical characteristics,chronology and regional geological feature,the Luotuobozi pluton belongs to highly fractionated high-potassium calc-alkaline I-type granites,and the formation of this pluton likely caused by the extensional continental lithosphere thinning in northeast China after the subduction of the Pacific plate in Mesozoic.
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