武夷山中段建宁地区淡色花岗岩形成时代、地球化学特征及地质意义  

Geochronological and Geochemical Constraints of Leucogranites in Jianning Area,Central Wuyishan,and Their Geological Implications

作　　者：卢运可 辛宇佳 李建华 王金铭[1,2] LU Yunke;XIN Yujia;LI Jianhua;WANG Jinming(Key Laboratory of Paleomagnetism and Tectonic Reconstruction,Ministry of Natural Resources,Beijing 100081;Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081)

机构地区：[1]自然资源部古地磁与古构造重建重点实验室,北京100081 [2]中国地质科学院地质力学研究所,北京100081

出　　处：《地球学报》2024年第6期926-940,I0001-I0005,共20页Acta Geoscientica Sinica

基　　金：国家自然科学基金项目(编号:42102274);自然资源部古地磁与古构造重建重点实验室开放课题(编号:KLPTR-09)。

摘　　要：淡色花岗岩是了解造山过程中地壳物质部分熔融行为的重要岩石探针,对于揭示造山演化过程中变质和岩浆作用之间的联系具有十分重要的意义。本文对武夷山中段建宁地区淡色花岗岩开展了系统的岩石学、锆石U-Pb年代学及地球化学研究。结果表明,建宁淡色花岗岩形成于~440 Ma,并记录了晚期410~405 Ma深熔事件。淡色花岗岩属强过铝质岩石,且富含800~700 Ma年龄继承锆石,表明其源岩为新元古代麻源群变质沉积岩。建宁淡色花岗岩具高SiO_(2)、K_(2)O,贫MgO、FeOt、CaO、Na_(2)O,富集LREE和LILEs,亏损HREE和HFSEs,高Rb/Sr比值等特征,暗示其源岩可能发生了黑云母参与的含水或脱水熔融反应。综合本文结果和华南早古生代沉积、变质、岩浆等多方面地质记录可知,建宁地区淡色花岗岩形成于同造山地壳加厚背景下,而晚期410~405 Ma的深熔事件可能与后造山伸展减薄有关。Our study shows the combined petrological,geochemical,and geochronological analysis of the Jianning leucogranites in Central Wuyishan.MC-LA-ICPMS zircon U-Pb dating data show the formation of Jianning leucogranites at~440 Ma with a late-stage anatectic event occurring at 410–405 Ma.These leucogranites are strongly peraluminous and contain inherited zircons with ages clustering at 800–700 Ma,suggesting that the Neoproterozoic meta-sedimentary rocks of the Mayuan Group are their source rocks.They exhibit high SiO_(2) and K_(2)O,low MgO,FeOt,CaO,and Na_(2)O,enrichment in LREE and LILEs,depletion in HREE and HFSEs,and high Rb/Sr ratios,suggesting their generation by biotite fluid-fluxed or dehydration melting reactions.Integrating our results and other Early Paleozoic orogenic sedimentary,metamorphic,and magmatic records of South China,we inferred that the Jianning leucogranites were formed during the syn-orogenic crustal thickening phase,and the 410~405 Ma anatectic event may be related to the post-orogenic crustal thinning.

关 键 词：武夷山 早志留世—早泥盆世 淡色花岗岩 地壳加厚 伸展减薄 MC-LA-ICPMS锆石U-Pb 

分 类 号：P588.121[天文地球—岩石学]