赣南横市辉长岩的成因及其地质意义:年代学、地球化学和Sr-Nd-Pb-Hf同位素证据  

Petrogenesis and implications of the Hengshi gabbros in south Jiangxi Province:Evidence from geochronology,geochemistry and Sr-Nd-Pb-Hf isotopes

作　　者：贾小辉[1,2] 王晓地[1,2] 杨文强[1] 周岱[1,2] JIA XiaoHui;WANG XiaoDi;YANG WenQiang;ZHOU Dai(China Geologieal Surey,Wuhan Cener of Geological Survey,Wuhan 430223,China;Reerch Ccner for Perogeneis and Minaisation of Ganioid Rals,Wuhan Conier of Cologial Survey,Wahan 43023,Chin)

机构地区：[1]中国地质调查局武汉地质地质调查中心,武汉430223 [2]中国地质调查局花岗岩成岩成矿地质研究中心,武汉430223

出　　处：《岩石学报》2021年第5期1405-1418,共14页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41302046);中国地质调查局地质调查项目(DD20190047、DD20190374)联合资助。

摘　　要：华南早古生代基性岩浆岩出露少而小,对其岩石成因的研究仍存在较大争议,较大地制约了对华南早古生代造山作用的深入理解。横市辉长岩位于赣南地区,有数个小的侵入体组成,SHRIMP锆石U-Pb定年结果显示其形成时代为423.3±4.9Ma。辉长岩具有均一的硅含量(Si O_2=49.14%~52.05%),相对高的镁含量(Mg O=7.16%~9.43%)和Mg^#值(60.7~67.3)。稀土总量(∑REE)为80.6×10^(-6)~131.5×10^(-6),无-弱的铕正异常(δ_(Eu)=0.97~1.21)。Sr-Nd-Pb-Hf同位素组成为:ISr=0.7048~0.7060,ε_(Nd)(423Ma)=-3.11~-1.97;(^(206)Pb/^(204)Pb)_i=17.73~18.03,(^(207)Pb/^(204)Pb)_i=15.57~15.59,(^(208)Pb/^(204)Pb)i=37.80~38.19;ε_(Hf)(t)=-3.71~+1.55。元素及同位素组成表明,横市辉长岩可能源自类似于EMⅠ和EMⅡ混合的富集地幔源区的部分熔融。大规模的岩石圈拆沉作用可能是形成华南早古生代基性岩石的动力学机制。The outcrop area of Early Paleozoic basic rocks and the individual plutons were very small,and the research on them was relatively weak,especially on their petrogenesis,which restricted the deep understanding of Early Paleozoic orogeny in South China.The Hengshi gabbros were located in southern Jiangxi Province.SHRIMP U-Pb dating from gabbros showed that they were formed at423.3±4.9 Ma.Gabbros had uniform silicon contents(Si O_(2)=49.14%~52.05%),high magnesium contents(Mg O=7.16%~9.43%)and Mg#value(60.7~67.3).The∑REE values were 80.6×10^(-6)~131.5×10^(-6),with no-weak positive anomaly of Eu(δEu=0.97~1.21).The Sr-Nd-Pb-Hf isotopic compositions of gabbros were ISr=0.7048~0.7060,εNd(423 Ma)=-3.11~-1.97;(^(206)Pb/^(204)Pb)i=17.73~18.03,(^(207)Pb/^(204)Pb)i=15.57~15.59,(208 Pb/^(204)Pb)i=37.80~38.19;εHf(t)=-3.71~+1.55.The elemental and isotopic compositions suggested that the Hengshi gabbros originated from partial melting of a rich mantle source similar to the mixture of EMⅠand EMⅡ.Large-scale lithospheric delamination was a potential the dynamic mechanism for the formation of the Early Paleozoic basic rocks in South China.

关 键 词：华南 早古生代 基性岩 地球化学特征 岩石圈拆沉 

分 类 号：P588.124[天文地球—岩石学] P597.3[天文地球—地质学]