广东河台金矿区印支期花岗岩与混合岩成因联系及大地构造意义  

The petrogenetic links of Indosinian granitoid and migmatite in the Hetai goldfield, Guangdong Province of South China and the tectonic implication

作　　者：焦骞骞 贺昌坤 董有浦 许德如 陈根文[3] 陈诚[1] 师爽 高亦文 JIAO QianQian;HE ChangKun;DONG YouPu;XU DeRu;CHEN GenWen;CHEN Cheng;SHI Shuang;GAO YiWen(Faculty of Land Renource Engineering,Kunming University of Science and Technology,Kunming 650093,China;State Key Laboratory for Nuclear Renources and Environment,East China University of Technology,Nanchang 330013,China;CAS Key Laboratory of Mineralogy and Metallogeny,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China;The 5th Brigade of Guangdong Geological Bureau,Zhaoqing 526600,China)

机构地区：[1]昆明理工大学国土资源工程学院,昆明650093 [2]东华理工大学核资源与环境国家重点实验室,南昌330013 [3]中国科学院广州地球化学研究所,中国科学院矿物学与成矿学重点实验室,广州510640 [4]广东省地质局第五地质大队,肇庆526600

出　　处：《岩石学报》2020年第3期893-912,共20页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41902086);国家重点研发计划项目(2016YFC0600401);昆明理工大学地质资源与地质工程省级一流学科建设项目(1407839305)联合资助。

摘　　要：广东省河台金矿区位于两广交界的云开地区,矿区内印支期花岗岩、混合岩和韧性剪切带并存,是研究花岗岩与混合岩岩石成因关系的良好场所。通过LA-ICP-MS锆石U-Pb定年获得矿区内云楼岗花岗闪长岩的年龄为253±1.6Ma,云开群混合岩年龄为240.3±5.1Ma,在分析误差范围内前者形成时间比后者早了约10Myr。云楼岗花岗闪长岩与云开群混合岩具有某些类似的地球化学特征:过铝质;高的K2O含量、Fe2O3/MgO比值以及Rb、Pb、LREE含量和初始(87^Sr/86^Sr)(ISr)比值;εNd(t)为负值;具有低的10000Ga/Al值;亏损Ba、Nb、Sr、P和Ti;SiO2与TiO2、Fe2O3^T、CaO、Nb都具有负相关关系;这些特征表明它们可能都是壳源的。另外,两者中的黑云母都是再平衡的原生黑云母,表明成岩后两种岩石又在近乎相同的温压条件下遭受了改造。然而,云楼岗花岗闪长岩与云开群混合岩、变质沉积岩之间的稀土特征和Sr-Nd同位素又有所差异。前者Nd模式年龄为1821~1692Ma,明显晚于后两者(2264~1783 Ma、2170~1910Ma);另外,岩体的Rb/Sr比值为1.4~1.8,明显低于混合岩的2.7~9.2。所以,云楼岗花岗闪长岩可能来自下地壳深熔作用,并混入有少量年轻地幔成分而形成的混合岩浆,而云开群混合岩只是变质沉积岩的原地熔融产物。因此,云楼岗花岗闪长体与邻近云开群混合岩不是同源的,前者也不是后者的最终产物。云楼岗岩体和云开群混合岩的形成时间可能分别代表了华南板块和印支板块碰撞高峰期和终了期。The Hetai goldfield of Guangdong Province is located at the Yunkai area,the junction of Guangdong and Guangxi provinces of South China.The goldfield is a favorable place for the study of the petrogenesis links of migmatite and granitoid,because of the coexistence of Indosinian plutons,migmatites and ductile shear zones.A new LA-ICP-MS U-Pb zircon age of the Yunlougang granodiorite pluton and Yunkai migmatite is 253±1.6Ma and 240.3±5.1Ma,indicating the time of magmatism is ca.10Myr earlier than the migmatization within analytical errors.The Yunlougang pluton and Yunkai migmatite share some geochemical characteristics,for example,they are both peraluminous,both have high K2O,Rb,Pb,LREE contents,Fe2O3/MgO and(87^Sr/86^Sr)i ratios,negativeεNd(t)values,low 10,000Ga/Al ratios,the depletion of Ba,Nb,Sr,P and Ti,and the negative correlation between SiO2 and TiO2,Fe2O3^T,CaO,Nb,suggesting they are likely from the crust remelting.Moreover,the biotite in them are all re-equilibrated primary biotite,indicting they were likely modified at almost the same P-T conditions after their diagenesis.However,the REE and Sr-Nd isotopes are distinction between the Yunlougang pluton and the Yunkai Group migmatite and meta-sedimentary.The Yunlougang pluton has Nd model ages(1821~1692 Ma)younger than the Yunkai Group migmatite(2264~1788 Ma)and meta-sedimentaty(2170~1910 Ma),and smaller Rb/Sr ratio(1.4~1.8)than that of the migmatite(2.7~9.2),indicating the pluton is likely derived from a hybrid magma of anatectic lower crust with small juvenile externally(mantle)magm.,the migmatite simply from the in-situ re-melting of Yunkai Group meta-sedimentary.Therefore,the Yunlougang pluton is not congenetic with the migmatite nearby,not the final product of Yunkai Group migmatization.The age of Yunlougang pluton and Yunkai Group migmatite are likely represent the peak and terminal time of the collision between South China Block and Indochina Block.

关 键 词：云楼岗花岗闪长岩 云开群混合岩 印支期 云开地区 

分 类 号：P588.122[天文地球—岩石学] P597.3[天文地球—地质学]