摘要
洼兴Mo多金属矿床位于小兴安岭-张广才岭成矿带中段,是区域内新发现、正在勘探的斑岩型矿床。矿区内发育多期岩浆活动,锆石U-Pb定年结果表明,二长花岗岩(MG)、花岗闪长岩(GD)和黑云母二长花岗岩(BMG)的侵位年龄分别为177±1.9 Ma~174±1.2 Ma、170±1.9 Ma~169±2.1 Ma和172±1.5 Ma~172±1.4 Ma。三类花岗岩均以富硅(64.41%~77.77%)、富集大离子亲石元素、亏损P(P2O5=0.02%~0.21%)和Nb、Ta等高场强元素为特征。其铝饱和指数(A/CNK)在0.99~1.21之间,为准铝-弱过铝质、高钾钙碱性Ⅰ型花岗岩。全岩Nb/Ta值(7~13)与地壳可类比,三类花岗岩锆石εHf(t)值为3.9~18.8,表明其可能主要来源于新生地壳的部分熔融,暗色微粒包体(MMEs)的广泛发育暗示可能有一定的地幔物质加入。综合区域构造演化史,认为研究区花岗岩可能形成于佳木斯和松嫩地块碰撞晚期-碰撞后的构造背景。矿区花岗闪长岩和黑云母二长花岗岩分别与Cu-W、Mo-W矿化具有较好的空间耦合关系,且二者的侵位年龄与辉钼矿Re-Os加权平均年龄(169.0±2.2 Ma;MSWD=0.042)在误差范围内一致,暗示二者可能为成矿岩体,而二长花岗岩则为成矿前贫矿岩体。结合锆石U-Pb年代学、Hf同位素特征和岩相学特征综合分析认为,黑云母二长花岗岩与花岗闪长岩可能为同期岩浆不同演化程度的产物,更高的演化程度可能有利于岩浆中Mo的富集。矿区成矿期花岗岩(La/Yb)_(N)值较成矿前花岗岩显著降低,表明该地区在此期间发生了挤压-伸展的构造转换,此种转换可能有利于大规模岩浆-流体的累积和集中释放,从而有利于Mo矿化的形成。
The Waxing Mo polymetallic deposit is a newly discovered porphyry type deposit in the Lesser Xing'an Range-Zhangguangcailing metallogenic belt.There are several periods of magmatic activity in the mine area.Zircon U-Pb dating results show that the emplacement ages of monzonite granite,granodiorite and biotite monzonite are 177±1.9 Ma~174±1.2 Ma,170±1.9 Ma~169±2.1 Ma,and 172±1.5 Ma~172±1.4 Ma,respectively.The three types of granites are all characterized by high SiO_(2)(64.41%~77.77%)contents,and are enriched in large ion lithophile elements,depleted P_(2)O_5(0.02%~0.21%)and high field strength elements such as Nb and Ta.The A/CNK[molecular Al_(2)O_(3)/(CaO+Na_(2)O+K_(2)O)values are between 0.99 and 1.21],suggesting they belong to high-K calc-alkaline metaluminous-slight peraluminous type Ⅰ granite.The whole rock Nb/Ta ratio(7~13)is comparable to that of the crust.ZirconεHf(t)values range from 3.9 to 18.8,indicative of juvenile crustal origin.A number of mafic microgranular enclaves(MMEs)are observed in these granitoids,suggesting that mantle-drived magma was involved in the source region.Combined with the regional tectonic evolution history,we believe that the granite in the Waxing ore field was formed in the late collision-post-collisional setting.We found that granodiorite and biotite monzonitic granite have good spatial relationship with Cu-W and Mo-W mineralization,respectively,and their emplacement ages are correlated with the weighted average age of molybdenite Re-Os(169.0±2.2 Ma;MSWD=0.042).These support the granodiorite and biotite monzonitic granite are syn-mineral intrusion,while the monzonite is pre-mineral pluton.Combined with zircon U-Pb chronology and Hf isotope characteristics,the biotite monzonite granite and granodiorite may be the products of different magmatic evolution degrees at the same time,and higher evolution degrees may be conducive to Mo enrichment in magmas.Ratios of granite(La/Yb)_(N) decrease abruptly from pre-mineral to syn-mineral intrusions,probably indicating a transition from compression to extension,which may be conducive to Mo formation.
作者
易陈龙
史冬岩
张兴春
蓝江波
王洪超
荣学谦
邓聚庭
汪殿钟
杨宗永
朱经经
YI Chen-long;SHI Dong-yan;ZHANG Xing-chun;LAN Jiang-bo;WANG Hong-chao;RONG Xue-qian;DENG Ju-ting;WANG Dian-zhong;YANG Zong-yong;ZHU Jing-jing(State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,China;College of Earth and Planetary Science,University of Chinese Academy of Sciences,Bejing 100049,China;Heilongjiang Mining Group Corporation Ltd.,Harbin 150036,China;The Fifth Geological Prospecting Institute of Heilongjiang Province,Harbin 150036,China)
出处
《岩石矿物学杂志》
北大核心
2025年第1期87-112,共26页
Acta Petrologica et Mineralogica
基金
国家自然科学基金项目(42222206)
中国科学院王宽诚教育基金项目(GJTD-2020-13)
BR计划青年项目。
关键词
Ⅰ型花岗岩
全岩地球化学
年代学
壳幔混合
构造背景转换
Mo矿床
Ⅰ-granite
whole rock geochemistry
chronology
crust-mantle mixing
tectonic transformation
molybdenum deposit
