赣南晚侏罗世九龙脑钨锡铅锌矿集区不同成矿类型花岗岩年龄、地球化学特征对比及其地质意义

Zircon SHRIMP U-Pb Dating,Geochemistry,Sr-Nd Isotopic Analysis of the Late Jurassic Granitoids in the Jiulongnao W-Sn-Pb-Zn Ore-Concentrated Areas in Jiangxi Province and Their Geological Significance

九龙脑花岗岩体位于南岭东部,它周围分布着众多钨、锡和铅锌矿床(点)。本文选择岩体北侧淘锡坑石英脉型钨矿、东侧宝山矽卡岩型铅锌矿底部的隐伏花岗岩,对比九龙脑岩体开展了成岩年代学、地球化学、Sr-Nd同位素研究。上述岩体的SHRIMP锆石U-Pb年龄分别是158.7±3.9Ma、157.7±2.7Ma、154.9±2.2Ma,形成年龄在误差范围内一致,为晚侏罗世产物。SiO2含量较高(69.67%~76.99%),Al2O3=12.41%~14.32%,A/CNK=1.00~1.37,属于准铝-弱过铝质高钾钙碱性花岗岩类,宝山矿区隐伏花岗岩的TiO2、CaO、TFe2O3、FeO、LOI含量相对偏高。九龙脑花岗岩、淘锡坑隐伏花岗岩和宝山隐伏花岗岩的εNd(t)值分别为-10.5^-9.1,-10.6^-10.2,-9.4^-8.6,t2DM值分别为1.84~1.63Ga、1.78~1.74Ga、1.61~1.54Ga,低于华夏地块大部分地区基底岩石(2.2~1.8Ga)和华南典型S型花岗岩(1.8Ga)的Nd模式年龄。三个岩体均为古-中元古代地壳物质熔融的产物,九龙脑岩体兼具淘锡坑和宝山隐伏花岗岩的两种特征,宝山花岗岩在成岩过程中基性组分参与的程度更高。幔源物质的加入可能与中生代地壳拉张减薄作用有关,而地幔物质的上涌对华南地区一些重要金属矿床的形成起了重要作用。

The Jiulongnao granitic intrusion is located in southern Jiangxi Province of the East Nanling area,with a number of W,Sn,Zn and Pb prospects around it.This contribution selected hidden granites from the Taoxikeng quartz vein-type tungsten deposit in the north and the skarn-type Pb-Zn deposit in the east to conduct comparison study of diagenesis chronology,geochemistry,Sr-Nd isotopic compositions.Zircon SHRIMP U-Pb dating yields an age of 158.7±3.9Ma for the Taoxikeng granite,157.7±2.7Ma for the Baoshan granite,154.9±2.2Ma for the Jiulongnao granite,indicating that the Yingqian pluton is the Late-Jurassic magmatic intrusions.The SiO2 contents of 69.67% ~ 76.99%,Al2O3 content of 12.41% ~ 14.32%,and A/CNK of 1.00 ~ 1.37 indicate that all of the rocks fall into meta-to weak peraluminous and high-K calc-alkaline category.TiO2,CaO,TFe2O3,FeO,LOI contents of the Baoshan granitoids are higher than those of other granitoids.Analysis of the whole rock trace elements of the Baoshan granite demonstrate shows LREE enrichment,weak Eu anomalies,and obvious fractionation between LREE and HREE.The REE of the Jiulongnao granite have ＂tetrad effect＂.The εNd（t） and t2DM values of the Jiulongnao,Taoxikeng and Baoshan granites are from-10.5 ^-9.1,-10.6 ^-10.2 to-9.4 ^-8.6 and from 1.84Ga ~ 1.63Ga,1.78Ga ~ 1.74Ga to 1.61Ga ~ 1.54Ga respectively,which are below those of the basement（2.2~ 1.8Ga） in Cathaysian Block and those of typical S-type granites（1.8Ga） in South China.These data indicate that three intrusions were result of partial melting of paleo-Proterozoic crustal materials,interacted with mantle-derived magmas.The Late-Jurassic magmatism formed in a continental crustal extension and thinning setting,which is a favorable event to interaction with crustal and mantle.