西秦岭党川地区泥盆纪花岗岩类地质地球化学特征及构造意义  

Geologic and Geochemical Features of Devonian Granites in Dangchuan area,Western Qinling,and Its Tectonic Significance

作　　者：温志亮[1] 徐学义[1] 赵仁夫[1] 王锋[2] 胡伟 

机构地区：[1]中国地质调查局西安地质矿产研究所,西安710054 [2]长安大学地球科学与资源学院,西安710054 [3]陕西凤县恒洲矿业有限责任公司,陕西宝鸡721700

出　　处：《地质论评》2008年第6期827-836,共10页Geological Review

基　　金：国家科技支撑项目(编号2006BAB01A11)的成果

摘　　要：党川地区位于祁连—北秦岭造山带结合部位,该地区分布有不同时期的花岗岩类,泥盆纪花岗岩类由党川岩体、火炎山岩体2个岩体组成。党川岩体岩石化学以富集SiO2(SiO2=72.29%～73.40%)、K2O(K2O?Na2O=0.86～2.01)、Al2O3(A?CNK=1.05～1.20)为主要特征;火炎山岩体岩石总体SiO2较低(平均69.70%),但K2O(K2O?Na2O=1.14～1.88)、Fe2O3+FeO?MgO较高。岩体的共同特征是岩石属钾玄质系列,表现为过铝质岩石(A?CNK大于1.0)的特征;微量元素相对富集Ba、Zr、Rb、Sm、Ta及Rb、Ba、Th、Nb等元素;稀土元素丰度总体较高,以富集轻稀土元素,发育明显的铕负异常和铕亏损,δEu值较低(δEu=0.36～0.61)为主要特征;岩石锶初始比n(87Sr)/n(86Sr)i大于0.7070,氧同位素δ18OSMOW较高(δ18OSMOW=+8.89‰～+11.08‰),岩体物质来源为上地壳,属浅源的壳源型花岗岩类,具S型花岗岩的特征,其形成与后造山阶段的大陆抬升作用有关。Dangchuan, Located in the junction area of Qilian and North Qinlin Orogenic Belts, has different granites occurring at different time. And these which are formed in Devonian are composed of Dangchuan intrusion and Huoyanshan intrusion. Based on the major and trace element, Sr--Nd isotope data, Dangchuan intrusion exhibit significantly higher SiO2 （SiO2 =72.29%-73.40%）, K2O（K2O/ Na2O =0.86-2.01） and Al2O3 （A/CNK = 1.05 - 1.20）, whereas, Huoyanshan intrusion shows conspicuous lowerSiO2 （with an average of 69.70% ）, higher K20 （K2 O/Na2O =1.14 - 1.88）, Fe2O3 ＋ FeO and MgO. Both the two intrusions belong to Shoshonitic Series with the features of perluminous rock （A/CNK 1.0）, relatively higher Ba, Zr, Rb, Srn, Ta, Th, Nb, ∑ REE and ∑ LREE values, obvious Eu negative anomaly, Low δEu （ δEu = 0.36 -0. 61）; higher ratios of [n（87Sr）/n（86Sr）]i （〉7.070） and high δ18OSMOW（δ18OSMOW= ＋8. 89‰＋11. 08‰） contents, indicate the two intrusions are derived from partial melting of upper-crust material, showing the characteristics of S-Type granites, and are regarded as crust- derived granites. We suggest that the petrogenesis of the granites may be a result of continental uplift during the period of post-orogenics.

关 键 词：花岗岩类 地球化学 构造环境 泥盆纪 党川 西秦岭 

分 类 号：P588.121[天文地球—岩石学]