摘要
赣北发育的超大型W多金属矿床与晚中生代花岗岩密切相关。这些岩体和相伴的矿床侵入于新元古代双桥山群和新元古代九岭花岗闪长岩中,而且被认为与双桥山群变质沉积岩具有成因联系。对双桥山群沉积岩的地球化学研究显示,这些沉积岩具有大的成分变化,但都具有低的Na_(2)O、MgO、CaO和高的Al_(2)O_(3)含量;SiO_(2)/Al_(2)O_(3)比值指示其具有中等的成熟度,而较高的CIA值指示其源区经历了较强的风化作用。双桥山群沉积岩相对贫Ba、Sr、Sn、Nb、Cr和Ni,而富集Li、Be、Cs、Rb和W等元素;稀土总量较高,尤其是重稀土。主量元素和微量元素特征都表明双桥山群沉积岩的物源区含有更多基性—中性火成岩物质而缺少古老的再循环物质。Li、Nb、Be、Rb、Sn等稀有金属元素与岩石的CIA值呈现很好的正相关关系,表明黏土矿物的增加有利于稀有金属元素的富集。本次研究利用Geops软件对岩石进行了部分熔融模拟。模拟结果显示由双桥山群变质沉积岩很难直接熔融出大湖塘中生代花岗岩的原始岩浆,而双桥山群变质沉积岩和变质玄武岩8:2比例的混合源区可熔融出与大湖塘花岗岩相似的岩浆。这种有基性火山岩参与的部分熔融模式既可以解释赣北W矿往往伴生Cu-Mo成矿的特征,也可以解释这些中生代花岗岩中锆石的低氧同位素的特征。
The giant Dahutang tungsten polymetallic deposits in northern Jiangxi are closely related to the late Mesozoic Yanshanian granites.These granites,with related deposits,intrude the Neoproterozoic Shuangqiaoshan Group sedimentary rocks and the Neoproterozoic Jiuling granodiorite,and are believed to have a close genetic link to these sedimentary rocks.The meta-sedimentary rocks of the Shuangqiaoshan Group display large composition variations with low Na_(2)O,MgO,CaO and high Al_(2)O_(3).Their SiO_(2)/Al_(2)O_(3)ratios indicate medium maturity,and high CIA values suggest strong chemical weathering occurring in the source area of these sedimentary rocks.The sedimentary rocks of the Shuangqiaoshan Group are relatively depleted in Ba,Sr,Sn,Nb,Cr and Ni,and enriched in Li,Be,Cs,Rb and W.These sedimentary rocks also have high rare earth elements(REE).The characteristics of major and trace elements suggest that the source area of sedimentary rocks of the Shuangqiaoshan Group contains more mafic to intermediate igneous rocks and less old recycled materials.Rare metal elements,such as Li,Nb,Be and Sn,show a good positive correlation with the CIA values of rocks,indicating that the increase of clay minerals is conducive to the enrichment of rare metal elements in sedimentary rocks.In this study,the GeoPS software is used to model the partial melting of the rocks.The modelling results show that it is difficult to directly produce melts with compositions similar to the primitive magma of the late Mesozoic Dahutang granites from the meta-sedimentary rocks of the Shuangqiaoshan Group,whereas magma similar to the Dahutang granite can be produced from the mixture of the meta-sedimentary rocks and meta-basalts in the Shuangqiaoshan Group with an 8:2 ratio.This partial melting model with the participation of mafic volcanic rocks can explain not only the characteristics of the Cu-Mo mineralization often associated with the W deposits in the northern Jiangxi,but also the low oxygen isotope compositions of zircons in the Dahutang granite.
作者
刘冰琪
于津海
蒋威
蔡元峰
LIU Bingqi;YU Jinhai;JIANG Wei;CAI Yuanfeng(School of Earth Science and Engineering,Nanjing University,Nanjing,Jiangsu 210023,China)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2023年第2期433-447,共15页
Acta Geologica Sinica
基金
国家自然科学基金重大计划“战略性关键金属超常富集成矿动力学”的重点项目(编号91962221)资助成果。
关键词
赣北W矿
双桥山群
地球化学
部分熔融模拟
tungsten deposits in northern Jiangxi
Shuangqiaoshan Group
geochemistry
partial melting modelling
