江西金溪熊家山钼矿床加里东期与燕山期花岗岩对比及其对成矿作用的启示  

A comparison study between Caledonian and Yanshanian granites from Xiongjiashan molybdenum deposit in Jinxi County,Jiangxi Province,and its implications to metallogenesis

作　　者：邱检生[1] 杨泽黎 邢光福[2] 余明刚[2] 赵姣龙[1] 王睿强 

机构地区：[1]南京大学地球科学与工程学院,南京210023 [2]中国地质调查局南京地质矿产研究所,南京210016

出　　处：《岩石学报》2015年第3期656-674,共19页Acta Petrologica Sinica

基　　金：高等学校博士学科点专项科研基金(20120091130003);国家重点基础研究发展计划“973”项目(2012CB416702);中国地质调查局科研项目(12120113065200)联合资助

摘　　要：加里东期和燕山期花岗岩是华南分布最广的二期花岗岩,以往的研究较少关注它们之间的成因联系及各自对成矿的贡献。江西金溪熊家山Mo矿床同时发育有加里东期和燕山期花岗岩,本文对该区二期花岗岩进行了锆石U-Pb年龄及元素与Sr-Nd-Hf同位素组成的系统测定,据此揭示了二者地质地球化学特征的差别,并探讨了它们之间的成因联系及其对成矿的可能制约关系。锆石LA-ICP-MS U-Pb定年表明,区内加里东期和燕山期岩体的成岩年龄分别为～440Ma和～155Ma。化学组成上,二期花岗岩均具有亚碱、过铝、贫铁的特征,但加里东期花岗岩更富铝,而燕山期花岗岩总体更富碱。二期花岗岩均富Cs、Rb、Th、Pb和轻稀土,贫Ba、Sr、P、Ti、Nb、Ta,但燕山期花岗岩Nb、Ta、Th含量更高,并具有偏高的Rb/Sr和Rb/Ba比值、偏低的K/Rb比值和LREE/HREE比值,以及更显著的铕负异常,指示其演化程度更高。Sr-Nd-Hf同位素组成指示加里东期花岗岩主要起源于早中元古代基底地壳物质的部分熔融,幔源或初生地壳组分未显著参与成岩过程。燕山期花岗岩具有与加里东期花岗岩类似的Sr-Nd-Hf同位素组成,且在燕山期花岗岩中存在较多的加里东期岩浆继承锆石。综合分析表明,燕山期花岗岩并非完全起源于加里东期花岗岩的重熔,后者仅是作为燕山期花岗岩源岩的组成部分参与成岩。区内钼成矿主要受燕山期岩浆事件制约,燕山期花岗质岩浆的隐爆对成矿具有重要的控制作用。加里东期花岗岩对成矿的影响主要体现在两方面,其一是通过直接参与燕山期花岗质岩浆的形成为成矿提供部分物源,另一方面是该期岩浆活动促进了陆壳的成熟和成矿元素的富集从而间接制约成矿。The Caledonian and Yanshanian granites are the most widely distributed granites in South China. Previous study show less concern on the genetic link between the two stage granites and their respective contributions to mineralization. Both the Caledonian and the Yanshanian granites are spatially coexisted within the Xiongjiashan molybdenum deposit in Jinxi,Jiangxi Province. This paper presents comprehensive petrological,geochronological,major and trace element,and Sr-Nd-Hf isotopic data for both the Caledonian and the Yanshanian granites developed in this deposit,aiming to systematically unravel the geological and geochemical differences between them,and to probe their genetic link and possible metallogenic relationships. Zircon LA-ICP-MS U-Pb dating results show that the ages of the Caledonian and the Yanshanian granites are ～ 440 Ma and ～ 155 Ma,respectively. Chemically,the both stage granites show subalkaline,peraluminous and Fe-poor signatures,and are enriched in Cs,Rb,Th,Pb,and LREE,depleted in Ba,Sr,P,Ti,Nb,Ta. However,the Caledonian granites are more enriched in aluminum,while the Yanshanian granites are more enriched in alkaline,and have higher concentrations of Nb,Ta,Th. The Yanshanian granites also show higher Rb / Sr and Rb / Ba,lower K / Rb and LREE / HREE ratios relative to the Caledonian granites,and exhibit more distinct negative europium anomalies,implying they have suffered a higher degree of differentiation. Sr-Nd-Hf isotopic compositions indicate that the Caledonian granites were originated mainly from partial melting of Paleo- to Mesoproterozoic basement crustal rocks,and mantle-derived or juvenile crustal materials were less involved in petrogenesis. The Yanshanian granites have similar Sr-Nd-Hf isotopic compositions to that of the Caledonian granites,and contain more inherited magmatic zircons with Caledonian ages. Integrated geological and geochemical data suggest that the Yanshanian granites were not generated completely from remelting of the Caledonian granites,rather the latter were s

关 键 词：加里东期 燕山期 花岗岩 成矿作用 江西金溪 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]