摘要
对伊春地区南部中寒武世细中粒二长花岗岩进行LA-ICP-MS锆石U-Pb定年,岩石年龄为(504.1±5.4)Ma,是中寒武世岩浆活动的产物。岩石地球化学特征显示该岩石具富碱、富钾的特征,高K_2O/Na_2O,低TFe O,属钾玄至高钾钙碱性系列。岩石总体上相对富集大离子亲石元素,亏损高场强元素,A/CNK>1.1,为强过铝质,显示出S型花岗岩的特征。R1-R2图解上大部分样品集中在同碰撞区和造山晚期花岗岩区;Rb-Hf-Ta图解上样品落在同碰撞-碰撞后构造花岗岩区;在Nb-Y图解上样品落在火山弧-同碰撞花岗岩区;在Rb-(Y+Nb)图解上,样品落在同碰撞花岗岩区。该地区中寒武世细中粒二长花岗岩揭示了岩石形成于板块碰撞作用,表明伊春地区在中寒武世存在碰撞造山事件。在该时期佳木斯与松嫩—张广才岭板块已经拼合,并形成具有壳源特征的同碰撞花岗岩。
LA-ICP-MS zircon U-Pb age of 504.1 ＋ 5.4Ma was obtained for the fine-medium grained monzogranite from southern Yichun, which suggests the monzogranite formed in Middle Cambrian. Geochemical data for the monzogranite reveal K2O ＋ Na2O contents of 7.41% - 8.70% , K2O/Na2O ratios of 1.80% - 2.28% , and low TFeO abundances, indicating it belongs to shoshonite to high K calc-alkaline series. While A/CNK 〉 1.1 suggests peraluminous feature of S-type granite. Trace element geochemistry of the monzogranite also shows LILE enrich- ment and HFSE depletion. Most of the samples are concentrated on syn-collision and late orogenic tectonic set- tings in R1-R2 diagram, fall into syn-collision and post-collision settings in Rb- Hf -Ta diagram, plot into areas of volcanic arc and syn-collision in Nb-Y diagram, and cluster in syn-collision setting in Rb- （ Y ＋ Nb） diagram. Based on above-stated petrological and geochemical data it is inferred that the monzogranite of Yichun might be derived from a syn-collision setting, the Jiamusi and Songnen massifs amalgamated together in Middle Cambrian, and the amalaganmtion may be responsible for the crustal derived syn-collisional granites.
出处
《中国地质调查》
2015年第6期26-33,共8页
Geological Survey of China
基金
黑龙江省资源补偿项目"黑龙江省朱拉比拉河
东风经营所幅1:5万区域地质矿产调查(编号:HLJKD2008-10)"项目资助
