Genesis and Geochemical Characteristics of the Kalamaili Potassic Basalt in the
详细信息
- 责任者：Yang Gaoxue (Key Laboratory of Western China’s Mineral Resources and Geological Engineering ; Ministry of Education ; Xi’an 710054 ; China) ; Li Yongjun
- 刊名：Acta Petrologica Sinica
- 出版年：2010
- 卷期：26(8)
- 关键词：玄武岩 ; basalts ; 岩石地球化学 ; lithogeochemistry ; 构造环境 ; tectonic setting ; 新疆 ; Xinjiang
- 页码：p.2345-2356
- 图表：7 illus., 1 table, 72 refs.
- 分类号：0801
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
///Kalamaili potassic basaltic rocks occur within the Lower Carboniferous Batamayineishan Formation,NE margin of the Junggar Basin. The potassic basaltic rocks mainly composed of trachybasalt and basalic trachyandesite,have moderate SiO2 ( 46. 29% ～ 51. 56% ) values,relatively high alkali ( K2O + Na2O = 5. 39% ～ 6. 96% ) ,TiO2 ( 0. 94% ～ 1. 21% ) contents and K2O/Na2O ratios ( K2O/Na2O = 0. 5 ～ 1. 4) ,displaying characteristics of shoshonitic basalts series. Through researching petrogeochemistry, showing the rocks enriched in LILE ( such as K,Rb and Sr) and LREE ( ( La/Yb) N = 4. 39 ～ 6. 25) ,possess positive Eu anomalies ( δEu=1.3 ～1.7) ,relatively depleted in HFSE ( such as Zr,Hf) ,with strong negative Ta,Nb and Ti“TNT”anomalies,high Ba/ Nb and Ba/Ta ratios ( 38 ～ 93, 574 ～ 1 470 respectively) ,indicating typical island-arc characteristics,and Nd-Sr isotopes show a depleted mantle source. The ratios of incompatible element ( Nb/La) N and Ba/La ( 0. 33 ～ 0. 41,11. 07 ～ 18. 82 respectively) ,and high Nb ( 4. 45 × 10 -6 ～ 7. 76 × 10 -6 ) contents,suggesting that the potassic basaltic rocks were derived from a metasomatized, phlogopite- and/or amphibole-bearing mantle source. Through hierachical set of discrimination diagrams of tectonic settings for Kalamaili potassic basalt, indicating Batamayineishan Formation shoshonitic basalts formed in the post-collisional arc-type surroundings. Due to intracontinental adjustment in the post-collisional period,lithosphere extended and thinned,with the process, the mantle wedge ( phlogopite and/or potassic amphibole-spinel facies lherzolite) metasomatized by fluid in earlier stage melted partially