陆缘弧岩浆寂静期花岗质岩浆成因:以青藏高原东南缘腾冲地块晚白垩世花岗岩为例  

Origin of granitic magma within continental margin arc magmatic lull:Constraints by the Late Cretaceous granites in Tengchong Block,SE Tibet

作　　者：赵少伟 方肖雨 文泰 赖绍聪[2] 裴先治[1] 李佐臣[1] ZHAO ShaoWei;FANG XiaoYu;WEN Tai;LAI ShaoCong;PEI XianZhi;LI ZuoChen(School of Earth Science and Resources,Chang an University,Xi'an 710054,China;Department of Geology,State Key Laboratory of Continental Dynamics,Northwest University,Xi'an 710069,China)

机构地区：[1]长安大学地球科学与资源学院,西安710054 [2]大陆动力学国家重点实验室,西北大学地质学系,西安710069

出　　处：《岩石学报》2025年第1期91-111,共21页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(42272052、41902046);中央高校基本科研业务费专项资金项目(300102273102);陕西高校青年创新团队项目联合资助.

摘　　要：陆缘弧岩浆活动常具有幕式特征,展现出弧岩浆爆发和寂静交替的现象。虽然对其律动特征广泛研究,但目前对于岩浆寂静期的岩浆成因机制了解较少。本文通过对比新特提斯洋俯冲相关的陆缘弧岩浆分布特征,以新特提斯洋俯冲过程中陆源弧岩浆寂静期的腾冲地块晚白垩世花岗质岩石为研究对象,探讨其形成过程,为寂静期岩浆的成因动力学机制提供重要约束。腾冲地块户撒地区二长花岗岩锆石U-Pb年龄为73Ma,形成于新特提斯洋俯冲陆缘弧晚白垩世(85~65Ma)的岩浆寂静期,为准铝质-弱过铝质和钙碱质花岗岩,具有富集的Nd-Hf同位素,其源岩为高黎贡山群正变质片麻岩。通过区域对比,晚白垩世(85~65Ma)新特提斯洋低角度俯冲相关的陆源弧应为挤压环境,腾冲地块同期花岗岩类应形成于加厚地壳背景下。通过与爆发期(55~50Ma)岩石组合、地化特征、锆饱和温度和斜长石环带特征的对比,本文认为腾冲地块晚白垩世花岗岩类是加厚地壳长期热积累诱发的下地壳片麻岩部分熔融的结果。因此,在幔源岩浆低通量的陆缘弧寂静期,通过加厚地壳长期热积累可以在陆缘弧局部形成长英质岩浆。Magmatism in continental margin arc is generally episodic,and alternatively appears with magmatic flare-up and lull.Although numerous researches are related to arc tempos,there is little understanding for the genetic mechanism of magmatism during a lull.According to the distribution characteristics of magmatic rocks in the Neo-Tethyan continental margin arc,this study selected the Late Cretaceous granitic rocks in Tengchong Block to further constrain their petrogenesis and dynamics process during lulls.The monzogranite ages in Husa area of Tengchong Block are 73Ma,formed within the Late Cretaceous magmatic lull(85~65Ma)at the continental margin arc related to Neo-Tethyan subduction.They are metaluminous to weakly peraluminous and calc-alkaline,with enriched Nd-Hf isotopic characteristics.These signatures reveal their sources are orthometamorphic gneisses in the Gaoligongshan Group.In addition,the continental margin arc related to the flat subduction of Neo-Tethyan slab should be compressional state during Late Cretaceous(ca.85~65Ma).Comparing Late Cretaceous magmatic rock assemblages,geochemical signatures,Zr saturated temperature and zoning in plagioclase with these in Early Eocene rocks during magmatic flare-up(ca.55~50Ma),the granitic rocks during a magmatic lull formed at a thicken crust and partial melting of gneisses induced by a long-time thermal accumulation.Therefore,the continental margin arc could form granitic magma by a long-time thermal accumulation within a thicken crust during a magmatic lull with the low mantle-derived magma flux at a local region.

关 键 词：岩浆寂静期 腾冲地块 晚白垩世 花岗岩 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]