粤东鸿沟山金矿区流纹斑岩锆石SHRIMP U-Pb定年、Lu-Hf同位素组成及其地质意义

摘要

鸿沟山矿区位于华南粤东莲花山钨矿床的中部,是近年来通过地质矿产调查新发现具有找寻金矿潜力的矿床之一.本文以与鸿沟山金等多金属矿化关系密切的流纹斑岩为研究对象,开展了锆石SHRIMP U-Pb定年、流纹斑岩和矿石岩石地球化学、锆石Lu-Hf同位素组成特征研究.获得流纹斑岩锆石206Pb/238U加权平均年龄为169.1±1.5Ma,说明岩体形成于中侏罗世.在微量元素特征方面,流纹斑岩都表现为相对亏损大离子亲石元素Ba、Sr和高强场元素Nb、P、Zr、Hf,富集大离子亲石元素Rb,高强场元素U、Ce、Sm和轻稀土元素La、Nd,流纹斑岩与矿石稀土元素特征基本相似,Eu具中等负异常,但随着矿化强度的增强稀土元素更加富集.流纹斑岩εHf(t)(-15.0～2.2)分布范围宽,二阶段模式年龄TDM2主要变化范围为0.82～0.93 Ga,表明成岩物质主要来源于新元古代古老地壳变质泥岩和变质砂岩部分熔融,并有幔源物质的加入.因此,围绕着该时间段的流纹斑岩岩体,对于找寻W、Cu、Pb、Zn、Bi、Au、稀土、稀有和稀散元素矿产具有重要意义.%High precision geochronological data of gold related rock mass are less in the eastern Guangdong Province.And studying the rhyolitic porphyry related to gold—polymetallic mineralization will be very important for understanding the evolution of volcanic rocks and the relationship between volcanic rocks and gold mineralization.The Honggoushan rhyolitic porphyry is closely related to gold—polymetallic mineralization,which is in the central part of Lianhuashan tungsten deposit,eastern Guangdong Province,South China.It is a newly discovered gold deposit in recent years that having gold prospecting potential.On the basis of field geological investigation,we choose the typical rhyolitic porphyry and mineralization of samples in order to detailed study on the Honggoushan ore block.Zircon U-Pb age analysis for rhyolitic porphyry weighted average 206Pb/238U age was 169.1 ± 1.5Ma.Trace element characteristics show that the porphyritic granite depleted in Ba,Sr,HF elements Nb,P,Zr,Hf,and enriched in Rb,HF elements U,Ce,Sm and La,Nd.Rhyolitic porphyry has similar rare earth elements characteristics with ore with Eu moderate negative anomaly.However,with the increase of mineralization intensity,REE is more enriched.The eHf(t) values of rhyolitic porphyry constraint widely(-15.0～2.2).Moreover,the ages of second stage is between 1.946Ga and 2.788Ga.Rhyolitic porphyry formed in the middle Jurassic,materials sources mostly derived from the partial metling of Paleoproterozoic,and Neoarchean crustal metamorphic shale and sandstone with the input of mantle-derived magma.Therefore,it is a great significance to focus the research on the mid-Jurassic rhyolite porphyry for the discovery of W,Cu,Pb,Zn,Bi,Au,rare earth,rare and dispersed elements of mineral resources.