摘要
与东南亚锡矿带的形成紧密相关的晚白垩世—古新世花岗岩带广泛发育于缅甸地区,然而有关花岗岩形成的动力学背景及时-空规律尚未形成统一认识。本文对缅甸甘宝矿区花岗岩进行了锆石U-Pb定年、岩石学和地球化学的综合研究。研究表明甘宝矿区岩体由黑云母二长花岗岩构成,两件样品的锆石LA-ICP-MS U-Pb年龄分别为(64.0±0.69)Ma(n=25,MSWD=1.9)和(65.7±1.5)Ma(n=19,MSWD=3.8),表明岩浆侵位形成于晚白垩至古新世早期。代表性岩石样品具有高SiO_(2)(74.5%~77.2%)、高碱性元素(w(Na_(2)O+K_(2)O)=7.05%~8.48%),为过铝质(A/CNK>1.11)和高钾钙碱性属S型花岗岩。岩石具“平坦型”REE配分模式和强烈负铕异常(Eu/Eu^(*)=0.14~0.19),微量元素原始地幔标准化图显示富集的大离子亲石元素(Rb、Th、U、K和Pb)和亏损的高场强元素(Nb、Ta、Zr、Hf和Ti)。高的初始^(87)Sr/^(86)Sr比值(0.7322~0.7446)和负的εNd(t)值(–7.51~–6.95)以及TDM2年龄(1.55~1.51 Ga)表明,岩浆的初始熔体起源于中元古界陆壳基底的部分熔融,并经历了高程度分异结晶作用。甘宝矿区花岗岩体是属缅甸晚白垩世—古新世花岗岩带(90~60 Ma)的一部分,均形成于板块俯冲引起的弧后伸展环境,花岗岩体与钨成矿是新特提斯洋壳东向俯冲期间的岩浆-成岩-成矿事件的具体表现。
The Late Cretaceous to Paleogene granite belt,closely associated with the formation of the Southeast Asian tin belt,is extensively developed in the Myanmar region.However,there is still no unified understanding of the dynamic background and spatiotemporal patterns of granite formation.This study presents a comprehensive investigation of the granite in the Kanbauk mining area of Myanmar through zircon U-Pb dating,petrology,and geochemistry.The research reveals that the Kanbauk granite is predominantly composed of biotite monzogranite,with zircon LA-ICP-MS U-Pb ages of(64.0±0.69)Ma(n=25,MSWD=1.9)and(65.7±1.5)Ma(n=19,MSWD=3.8)for two samples,indicating magmatic emplacement during the Late Cretaceous to early Paleogene.Representative rock samples exhibit high SiO_(2)(74.5%–77.2%)and negativeεNd(t)values(–7.51 to–6.95)with TDM2 ages(1.55-1.51 Ga)suggest that the magma's initial melt originated from partial melting of the Middle Jurassic continental crust and underwent significant fractional crystallization.The granite bodies in the mining area are part of the Late Cretaceous to Paleogene granite belt(90-60 Ma)in Myanmar,and they formed in an arc-trench extensional setting induced by plate subduction.The granite from the Kanbauk mining area,along with tungsten mineralization,represents specific manifestations of magmatic-metamorphic-mineralization events during the eastward subduction of the Neo-Tethyan oceanic crust.
作者
朱德勇
谢志鹏
李文昌
陈爱兵
江小均
张如成
李志鹏
董紫奥
ZHU Deyong;XIE Zhipeng;LI Wenchang;CHEN Aibing;JIANG Xiaojun;ZHANG Rucheng;LI Zhipeng;DONG Ziao(Faculty of Land Resources Engineering,Kunming University of Science and Technology,Kunming,Yunnan 650093;Tengchong Hengyi Mineral Products Economic and Trade Co.,LTD.,Baoshan,Yunnan 679100)
出处
《地球学报》
CAS
CSCD
北大核心
2024年第4期591-608,共18页
Acta Geoscientica Sinica
基金
云南省科技计划项目(编号:202202AG050006)
云南省科技基础研究计划项目(编号:202201AT070077)联合资助。
