摘要
本文对新疆东准噶尔阿尕什敖包二长花岗岩进行了锆石U-Pb年代学,锆石Hf同位素和岩石地球化学研究。研究结果表明,阿尕什敖包二长花岗岩的LA-ICP-MS锆石U-Pb定年结果为372.1±1.5Ma,MSWD=0.22,为晚泥盆世。其全岩的SiO2含量为70.7%~71.7%,K2O含量(3.93%~4.33%)和K2O/Na2O(1.00~1.17)相对较高,属于高钾钙碱性系列。该花岗岩的A/CNK值在1.01~1.04之间,具有低的10000×Ga/Al值(1.81~1.90),显示出I-型花岗岩的特征。它们显示出轻稀土元素(LREEs)和大离子亲石元素(LILEs)的富集,Nb、Ta和Ti等高场强元素(HFSEs)亏损,暗示其可能受俯冲带消减组分的影响。这些二长花岗岩具有高的、正的εHf(t)值(11.2~15.2)和年轻的Hf二阶段模式年龄(TDM2=408~779Ma),加上其较高的Zr/Nb(7.46~8.24)和Th/Ce(0.16~0.55),表明它们可能来源于年轻下地壳的部分熔融。阿尕什敖包南高钾钙碱性I-型花岗岩具有较低的Ta(1.60×10-6~1.79×10-6)和Yb(1.41×10-6~1.67×10-6)含量,Rb-Y+Nb和Yb-Ta图解中落入VAG系列,表明形成于岛弧环境。因此,结合区域构造,沉积等相关证据,我们提出东准噶尔地区在晚泥盆世为俯冲相关的岛弧环境。而晚泥盆世的洋脊俯冲及其板片窗的形成在东准噶尔同时期各种特殊岩石组合产生过程中扮演着重要作用。
In this article, zircon U-Pb dating, Hf isotope and geochemistry of the Agashiaobao monzogranite in the eastern Junggar, Xinjiang were carried out. LA-ICP-MS zircon U-Pb dating for monzogranite yields a late Devonian age of 372.1±1.5 Ma(MSWD=0.22). Geochemical analysis shows that the monzogranite is characterized by high contents of SiO2(70.7%~71.7%) and K2O(3.93~4.33%), K2O/Na2O of 1.00~1.17 with the A/CNK of 1.01~1.04 and low 10000 Ga/Al(1.81~1.90), sugguesting that they belong to high-K calc-alkaline I-type granite. The monzogranite displays enrichment of LREEs and LILEs(i.e. Baand Sr) and depletion of HFSEs(such as Nb, Ta and Ti), indicating that it may be influenced by subducted material. High εHf(t)(11.2~15.2) and young Hf two-stage model age(388~554 Ma), as well as high Zr/Nb ratio of 7.46~8.24 and high Th/Ce ratios of 0.16~0.55, suggest that it may derive from partial melting of juvenile lower crust. The high-K calc-alkaline I-type granite has low contents of Ta(1.60×10-6~1.79×10-6) and Y(1.41×10-6~1.67×10-6). Rb-(Y+Nb) and Yb-Ta classification diagrams show that the monzogranite falls in the VAG area, indicating that it formed in an island-arc enviroment. Therefore, combined with regional tectonic and sedmentary evidence, this study concludes that the East Jungger area was in an island-arc setting related to subduction in late Devonian. Late Devonian ocean-ridge subduction and slab window formation played an important role in the formation of various rock assemblages in eastern Junggar at the same period.
作者
徐志华
尹继元
陈文
李大鹏
孙敬博
喻顺
杜秋怡
吴春燕
XU Zhihua;YIN Jiyuan;CHEN Wen;LI Dapeng;SUN Jingbo;YU Shun;DU Qiuyi;WU Chunyan(Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing-,100037;School of Earth Sciences and Resources,China University of Geosciences,Beijing,100083;Shannxi Yanchang Petroleum(Group)Crop.Ltd.,Xi'an,710075)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2019年第11期2797-2812,共16页
Acta Geologica Sinica
基金
国家重点研发计划项目（2017YFC0601301）
自然资源部深地动力学重点实验室自主研究课题（编号J1901-5）
中国地质调查项目（DD20190001,DD20190004）
中国地质科学院地质研究所基本科研业务费项目（J1902）
国家自然科学基金项目（编号41473053,41573045,41611530698
41873060,41830216）
同位素地球化学国家重点实验室开放基金（中国科学院广州地球化学研究所SKLIG-KF-16-10）
IGCP662资助成果
