东天山东段国宝山晚二叠世—中三叠世花岗质岩石成因与构造意义——年代学和地球化学约束  

Petrogenesis and tectonic significance of Late Permian-Middle Triassic granitoids in Guobaoshan,eastern section of the eastern Tianshan mountains:Constraints from geochronology and geochemistry

作　　者：贺昕宇 方同辉[1] 薄贺天 刘海鹏[1] 张忠义[1] 肖文进[1] HE Xinyu;FANG Tonghui;BO Hetian;LIU Haipeng;ZHANG Zhongyi;XIAO Wenjin(China Non-ferrous Metals Resource Geological Survey,Beijing 100012,China;The Fifth Geological Prospecting Team,Henan Non-ferrous Metals Geological Mineral Resources Bureau,Zhengzhou 450016,Henan,China)

机构地区：[1]有色金属矿产地质调查中心,北京100012 [2]河南省有色金属地质矿产局第五地质大队,河南郑州450016

出　　处：《地质力学学报》2022年第1期126-142,共17页Journal of Geomechanics

基　　金：全国公益性基础地质调查项目(DD20160011)。

摘　　要：东天山—北山地区是中国重要的金属成矿带,对于其晚二叠世—中三叠世构造演化的认识,仍存在较大分歧。东天山东段国宝山地区出露有一系列晚二叠世—中三叠世花岗质岩石,包括花岗闪长岩、二长花岗岩、石英正长岩、正长花岗岩和天河石花岗岩。该系列岩体整体以富硅、富碱为特征,其中花岗闪长岩、二长花岗岩和石英正长岩具有钾质和富镁特征,轻稀土相对重稀土更富集(LREE/HREE=0.86),稀土配分曲线整体右倾,呈弱Eu负异常(δEu=0.40~0.68);而正长花岗岩与天河石花岗岩类似,具钠质和铁质特征,富集Ta、Rb,重稀土元素较轻稀土更富集(LREE/HREE=5.11~17.17),稀土配分曲线呈海鸥式,具明显Eu负异常(δEu=0.03)。花岗闪长岩锆石^(206)Pb/^(238)U表面年龄集中于255~250 Ma,早于天河石花岗岩247~240 Ma的年龄。岩石地球化学特征表明正长花岗岩与天河石花岗岩同属A型花岗岩,形成于板内构造环境;花岗闪长岩、二长花岗岩和石英正长岩属I型花岗岩,形成于后碰撞环境,两个岩石组合属不同的岩浆系列,无成因关系。研究认为东天山东段国宝山地区在255~250 Ma仍处于后碰撞环境,~247 Ma进入板内伸展构造环境。The eastern Tianshan-Beishan area is one of the important metallogenic belts in China,but the Late Permian-Middle Triassic tectonic evolution still remains a controversial issue.The Guobaoshan area is located in the eastern section of the eastern Tianshan mountains.Five kinds of Late Permian-Middle Triassic granitoids are exposed in this area,namely granodiorite,monzonitic granite,quartz syenite,syenogranite and amazonite granite.These granitoids are generally rich in silicon and alkali.Granodiorite,monzonitic granite and quartz syenite are characterized by the enrichment of potassium and magnesium,showing LREE enriched REE patterns(LREE/HREE=0.86)with weakly negative Eu anomaly,while syenogranite,being similar to sodic and ferrous amazonite granite,is characterized by a“sea-gull”REE pattern and significant negative Eu anomaly(δEu=0.03),as well as enrichment of Ta and Rb.The^(206)Pb/^(238)U surface ages of zircons of granodiorite are concentrated in the range of 255~250 Ma,which are earlier than that of amazonite granite.Both syenogranite and amazonite are typical A-type granite and formed in intra-plate environment,but the other granitoids are I-type granite and formed in post-collision tectonic setting.There is no genetic relation between two groups of granitoids and they belong to different magma series.The Guobaoshan area was still in the post-collision tectonic setting during 255~250 Ma,and switched to the intra-plate environment before 247 Ma.

关 键 词：东天山 花岗岩 二叠纪 三叠纪 构造环境 构造岩浆组合 

分 类 号：P588.1[天文地球—岩石学]