摘要
本文对赣中贵溪花岗岩进行了锆石U-Pb定年和岩石地球化学分析测试,探讨了其成因类型、源区性质、熔融机制和地球动力学背景。贵溪花岗岩岩性为白云母花岗岩,锆石U-Pb年龄为438±5 Ma。全岩主微量元素测试结果显示,贵溪花岗岩表现为高硅、高钾、贫镁、贫钙和强过铝质的特征。贵溪花岗岩LREE/HREE为7.35~10.4,(La/Yb)N为8.08~15.0,总体表现为轻稀土富集、重稀土亏损、轻重稀土分馏明显的特点,且相对富集Rb、Th、U和K,亏损Sr、Ba、Ta、Nb。相对较高的全岩Nb/Ta、Zr/Hf、K/Rb和Eu/Eu~*值以及较低的TE1,3值,说明贵溪花岗岩并非高分异花岗岩。较低的Zr+Nb+Ce+Y(<200×10^(-6))和Ga/Al值(<2.5)、高的A/CNK值(>1.2)以及富铝矿物白云母的出现和镁铁质暗色矿物的缺失说明贵溪花岗岩在岩石成因类型上应属于S型花岗岩。富集的全岩Nd同位素组成(ε_(Nd)(t)=-11)、高的Rb/Sr比值(>2)、中等的轻稀土饱和温度和锆饱和温度(699℃~794℃)以及贫钛(<0.2%)的特征,说明贵溪花岗岩的源区为古老变沉积岩,其形成于白云母脱水熔融作用。贵溪花岗岩形成于同碰撞环境而非俯冲环境,华南早古生代的构造属性应为陆内造山作用。
In this study,we present the results of zircon U-Pb dating and whole-rock geochemical analysis of the Guixi granite in central Jiangxi Province.We discuss its genetic type,source characteristics,melting mechanism,and geodynamic background.The Guixi granite is classified as muscovite granite,with a zircon U-Pb age of 438±5 Ma.The results of whole-rock major and trace element analysis show that the Guixi granite is characterized by high silica,high potassium,low magnesium,low calcium,and strong peraluminous features.The LREE/HREE ratio of the Guixi granite ranges from 7.35 to 10.4,and their(La/Yb)N ranges from 8.08 to 15.0,indicating enrichment of light rare earth elements,depletion of heavy rare earth elements,and significant fractionation between light and heavy rare earth elements.The granite is relatively enriched in Rb,Th,U and K,while depleted in Sr,Ba,Ta,Nb.The relatively high Nb/Ta,Zr/Hf,K/Rb and Eu/Eu*ratios,as well as the low TE1,3 values,suggest that the Guixi granite is not a highly fractionated granite.The low Zr+Nb+Ce+Y(<200×10^(-6))contents and Ga/Al ratios(<2.5),high A/CNK ratios(>1.2),the presence of aluminum-rich mineral muscovite,and the absence of mafic dark minerals indicate that the Guixi granite belongs to the S-type granite in terms of genetic type.The enriched whole-rock Nd isotope composition(ε_(Nd)(t)=-11),high Rb/Sr ratio(>2),moderate light rare earth element saturation temperatures and zircon saturation temperatures(699℃~794℃),and low titanium contents(<0.2%)suggest that the Guixi granite was derived from ancient metasedimentary rocks and formed through muscovite dehydration melting.The Guixi granite was formed in a collisional environment rather than a subduction environment,indicating an intracontinental orogeny in the Early Paleozoic of South China.
作者
宋振韬
洪文涛
赵子豪
Song Zhentao;Hong Wentao;Zhao Zihao(School of Petroleum Engineering and Environmental Engineering,Yanan University,Yanan,Shaanxi 716000;State Key Laboratory for Mineral Deposits Research,Nanjing University,Nanjing 210023;Nanjing Center of China Geological Survey,Nanjing 210016)
出处
《地质科学》
CAS
CSCD
北大核心
2024年第2期420-436,共17页
Chinese Journal of Geology(Scientia Geologica Sinica)
基金
南京大学内生金属矿床成矿机制研究国家重点实验室开放基金项目(编号:2023-LAMD-K07)资助。
关键词
淡色花岗岩
华南
早古生代
岩石成因
全岩地球化学
Leucogranite
South China
Early Paleozoic
Petrogenesis
Whole-rock geochemistry
