【摘要】 报道了东昆仑群力地区正长花岗岩体的锆石U-Pb年龄和岩石地球化学特征,并对岩石成因及其构造意义进行了讨论。锆石LA-ICP-MS U-Pb定年结果表明群力正长花岗岩体的形成时代为376.2Ma（MSWD=0.25）,属晚泥盆世。岩石地球化学成分显示其属于高钾钙碱性、准铝质-弱过铝质系列花岗岩。岩体富硅（SiO₂=74.61%～77.85%）、富碱（Na₂O+K₂O=7.03%～7.94%）、高铁镁比（FeO^T/MgO=11.39～36.93）、贫钙（CaO=0.50%～1.01%）、贫镁（MgO=0.06%～0.20%）;稀土配分模式表现为"海鸥型"分布特点,具有强烈的负铕异常（δEu=0.08～0.09）;高镓含量(Ga=22.86×10^-6～27.06×10^-6),富集高场强元素组合(Zr+Ce+Nb+Y=720×10^-6～891×10^-6)、亏损Ba、Sr、P、Nb、Ta、Ti等;同时岩体具有高的锆石饱和温度（991℃～1 201℃）。综合岩石地球化学特征表明群力正长花岗岩体属于A型花岗岩中的A₂型花岗岩,结合区域研究成果,认为群力正长花岗岩形成于始特提斯洋闭合后的伸展构造背景。这一结果将始特提斯洋闭合后的伸展作用时限从中泥盆世延长到晚泥盆世。更多还原

【Abstract】 New zircon U-Pb dating is undertaken and geochemical characteristics,petrogenesis and tectonic significance are discussed in this study for Qunli syenogranite from the eastern Kunlun. LA-ICP-MS zircon U-Pb dating suggests that the age of Qunli syenogranite is 376.2 Ma（ MSWD = 0. 25）,belonging to Late Devonian.The petrogeochemical composition shows that it belongs to high potassium calc-alkaline,quasi-aluminous-weak peraluminous granite. The syenogranite is characterized by high SiO₂（ 74. 61% ～ 77. 85%）,high alkali（ Na₂ O +K₂ O = 7. 03% ～ 7. 94%）,high FeOT/MgO（ FeOT/MgO = 11.39～36.93）,low CaO（0.50%～1.01%） and MgO(0.06%～0.20% contents. Moreover,the syenogranite is characterized by a "sea-gull"REE pattern and strong negative Eu anomaly（ δEu = 0. 08 ～ 0. 09）,high gallium content( Ga = 22. 86 × 10^-6～27.06×10^-6),enrichment of high field strength element combination( Zr + Ce + Nb + Y = 720 × 10^-6～891×10^-6),and strong depletion of Ba,Sr,P,Nb,Ta and Ti. Meanwhile the rock mass has high zircon saturation temperature（ 991℃～ 1 201℃）. Comprehensive petrogeochemistry characteristics indicate that Qunli syenogranite belongs to A₂ type granite. Integrating regional research results,it is suggested that Qunli syenogranite was formed in the extensional tectonic setting after the closure of the Proto-Tethys Ocean. This result extends the extensional limit after the closure of the Proto-Tethys Ocean from the Middle Devonian to Late Devonian.更多还原