湘东北栗山铅锌铜矿床二长花岗岩岩石成因及其氧逸度对成矿的指示意义  

Petrogenesis of Monzogranites in Lishan Pb-Zn-Cu Deposit,Northeastern Hunan Province and Mineralization Significance of Oxygen Fugacity

作　　者：于得水[1,2] 许德如 王智琳 陈根文 赵朝霞[1,2] 黄沁怡 YU Deshui;XU Deru;WANG Zhilin;CHEN Genwen;ZHAO Zhaoxia;HUANG Qinyi(CAS Key Laboratory of Mineralogy and Metallogeny,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,Guangdong,China;University of Chinese Academy of Sciences,Beijing 100049,China;State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,Jiangxi,China;MOE Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring,School of Geosciences and Info-Physics,Central South University,Changsha 410083,Hunan,China)

机构地区：[1]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,广东广州510640 [2]中国科学院大学,北京100049 [3]东华理工大学,核资源与环境国家重点实验室,江西南昌330013 [4]中南大学地球科学与信息物理学院,有色金属成矿预测与地质环境监测教育部重点实验室,湖南长沙410083

出　　处：《大地构造与成矿学》2023年第3期580-597,共18页Geotectonica et Metallogenia

基　　金：国家自然科学基金重点项目(41930428);国家重点研发计划“深地资源勘查开采”重点专项(2016YFC0600401)联合资助。

摘　　要：栗山铅锌铜矿床位于江南造山带多金属成矿带中段,是湘东北地区近几年发现的一大型矿床。本文对矿区内的黑云母二长花岗岩和二云母二长花岗岩进行了岩石地球化学、Sr-Nd同位素和黑云母矿物成分研究。岩石地球化学特征显示,两种二长花岗岩均属于高钾钙碱性系列。其中,黑云母二长花岗岩属于正常S型花岗岩,富集Rb、Th、K大离子亲石元素,亏损Ba、Nb、Ta、Sr、P、Ti高场强元素,有弱的Eu负异常,源区岩石为变质杂砂岩;二云母二长花岗岩属于分异的S型花岗岩,富集Rb、Th、U、K大离子亲石元素,亏损Ba、Nb、Sr、P、Ti高场强元素,Eu负异常大于前者,源区岩石为变泥质岩和少量变质杂砂岩。黑云母二长花岗岩的(^(87)Sr/^(86)Sr)i值在0.7143~0.7159之间,ε_(Nd)(t)值介于-9.4~-8.5,两阶段模式年龄tDM2变化范围为1631~1703 Ma;二云母二长花岗岩的(^(87)Sr/^(86)Sr)i值在0.7156~0.7231之间,ε_(Nd)(t)值介于-11.2~-9.5之间,两阶段模式年龄tDM2变化范围为1696~1834 Ma。矿区内的两种岩体可能由新元古代冷家溪群岩石部分熔融形成的岩浆分异演化而成。黑云母矿物成分特征显示,两种岩体的黑云母均为铁质黑云母。然而,黑云母二长花岗岩中的黑云母结晶温度为651~695℃,氧逸度(ƒo_(2))为-18.9~-16.9;二云母二长花岗岩中的黑云母结晶温度为515~659℃,氧逸度(ƒo_(2))为-23.8~-16.0。两种岩性的氧逸度总体较低,暗示其铜成矿潜力有限。Located in the central segment of the Jiangnan Orogen polymetallic metallogenic belt,the Lishan Pb-Zn-Cu deposit is a large deposit discovered in recent years.The biotite monzogranite and two-mica monzogranite are characterized by high-K calc-alkaline series.The biotite monzogranite is enriched in LILE of Rb,Th and K,and depleted in HFSE of Ba,Nb,Ta,Sr,P and Ti,with weak negative Eu anomaly,and belongs to normal S-type granite with a source rock of metagraywacke;whereas the two-mica monzogranite is enriched in LILE of Rb,Th,U and K,and depleted in HFSE of Ba,Nb,Sr,P and Ti,with significant negative Eu anomaly(greater than that of the biotite monzogranite),and belongs to fractionated S-type granite with source rocks of metapelite and minor metagreywacke.The biotite monzogranite has(^(87)Sr/^(86)Sr)i values of 0.7143 to 0.7159 andε_(Nd)(t)values of-9.4 to-8.5 with two-stage model ages of 1631 Ma to 1703 Ma;the two-mica monzogranite has(^(87)Sr/^(86)Sr)i values of 0.7156 to 0.7231 andε_(Nd)(t)values of-11.2 to-9.5 with two-stage model ages of 1696 Ma to 1834 Ma.These monzogranites were likely derived from partial melting of the Neoproterozoic Lengjiaxi Group metasedimentary rocks and experienced fractional crystallization.The biotites in both the biotite monzogranite and two mica monzogranite are ferrobiotites,however,have different crystallization temperatures and oxygen fugacities,i.e.,the biotite in the biotite monzogranite has crystallization temperatures of 651℃to 695℃,and the oxygen fugacity(ƒo_(2))of-18.9 to-16.9,whereas the biotite in the two-mica monzogranite has crystallization temperatures of 515℃to 659℃,and the oxygen fugacity(ƒo_(2))of-23.8 to-16.0.The low oxygen fugacity of the two intrusions may be responsible for their limited Cu metallogenic capacity.

关 键 词：栗山铅锌铜矿床 地球化学 SR-ND同位素 黑云母 氧逸度 湘东北地区 

分 类 号：P581[天文地球—岩石学] P612[天文地球—地质学]