右江褶皱带东南缘西大明山矿集区燕山期长英质岩浆锆石SHRIMP原位氧同位素组成与地质意义  

Oxygen isotopic compositions and geological significance of zircons from the Yanshanian felsic intrusions in the Xidamingshan cluster,southeastern margin of the Youjiang fold belt,South China: In situ SHRIMP analysis

作　　者：肖昌浩 申玉科[1] 刘欢[3] 韦昌山[1] 乐兴文 傅斌 XIAO ChangHao;SHEN YuKe;LIU Huan;WEI ChangShan;LE XingWen;FU Bin(Laboratory of Dynamic Digenesis and Metallogenesis, Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China;School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China;4.Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;Geological team No. 4 of Guangxi Zhnang Autonomic Region, Nanning 530031, China;Research School of Earth Sciences, Australian National University, Canberra 2601, Australian)

机构地区：[1]中国地质科学院地质力学研究所动力成岩成矿实验室,北京100081 [2]中国地质大学地球科学与资源学院,北京100083 [3]中国地质科学院矿产资源研究所,北京100037 [4]广西壮族自治区第四地质队,南宁530031 [5]澳大利亚国立大学地球科学学院

出　　处：《岩石学报》2018年第5期1441-1452,共12页Acta Petrologica Sinica

基　　金：国家重点基础研究发展规划(2015CB452606);国家自然科学基金项目(41702095);中国地质调查局项目(DD20160053);广西找矿突破战略行动方案项目(桂国土资函﹝2017﹞350号)联合资助

摘　　要：右江褶皱带晚白垩世岩浆岩的物质来源和成因机制及其相关的大规模Sn-W多金属成矿作用是目前研究的热点和前沿问题之一。本文在已获得锆石U-Pb年龄及Hf同位素基础上,对广西西大明山地区酸性岩浆进行了锆石SHRIMP氧同位素研究。石英斑岩δ^(18)O_(Zrn)值为5.31‰~9.31‰(平均值为7.61±2.17‰)、绢英岩化黑云母花岗岩δ^(18)O_(Zrn)值为7.11‰~9.79‰(平均值为8.36±1.33‰)、细粒黑云母花岗岩δ^(18)O_(Zrn)值为5.06‰~9.27‰(平均值为7.73±2.23‰)、中粒黑云母花岗岩δ^(18)O_(Zrn)值为5.06‰~9.27‰(平均值为7.73±2.23‰)二长花岗岩δ^(18)O_(Zrn)值为5.48‰~10.99‰(平均值为7.55±2.77‰)。测试结果显示广西西大明山地区酸性岩浆锆石氧同位素普遍具有双峰式分布特征且Hf-O同位素组成构成负相关性,暗示地壳组份和富集地幔两端元混合的特征。Hf-O同位素特征指示酸性岩浆岩源主要来自古老的地壳,并混有部分幔源物质。地幔物质的存在暗示了同时期来自地幔的物质不仅参与右江褶皱带晚白垩世岩浆作用的形成,可能为的地壳部分熔融,花岗岩岩浆的形成提供了热能。西大明山地区酸性岩浆具有高δ^(18)O_(Zrn)值和低ε_(Hf)(t)值且低Ce(Ⅳ)/Ce(Ⅲ)比值(即低氧逸度),显示出有利于形成大型以Pb-Zn为主的矽卡岩型矿床特征。本文研究结果表明,锆石O-Hf同位素综合研究能限定幔源岩浆参与花岗岩形成中的作用能帮助更加准确的限定岩浆源区。同时锆石氧同位素可以作为成矿规律研究的有效途径之一。The source and petrogenesis of the Late Cretaceous magmatism and associated Sn-W mineralization in the South China are yet well documented. This paper reports the oxygen isotope compositions of previously analyzed zircons from the Yanshanian felsic intrusions in the Xidamingshan cluster,along the southeastern margin of the Youjiang fold belt,Guangxi,South China. Zircon（ Zrn）δ^18 O for quartz porphyry ranges from 5. 31‰ to 9. 31‰,VSMOW,averaging at 7. 61 ± 2. 17‰. δ^18 OZrn for beresitization biotite granite,fine biotite granite and medium biotite granite range from 7. 11‰ to 9. 79‰（ average = 8. 36 ± 1. 33‰）,from 5. 06‰ to9. 27‰（ average = 7. 73 ± 2. 23‰） and from 6. 27‰ to 9. 77‰（ average = 8. 04 ± 1. 75‰）,respectively. Monzonitic granite records a wide range in δ^18 OZrn（5. 48‰ - 10. 99‰） with average of 7. 55 ± 2. 77‰. The majorities are greater than the＂mantle-like＂values（δ^18 O： 5. 3 ± 0. 6‰,2σ）. Except beresitization biotite granite,five samples have bimodal or multi-modal distribution characteristics and Hf-O plots of zircons have a negative correlation,indicating a crust-mantle interaction. Hf-O isotopic compositions suggest that the source of the magma was mainly derived from partial melting of crustal material with input of mantle-derived components. The mantlederived melts imply that these melts not only provided necessary heat energy for crust partial melting,but also put got involved in the generation of granitic melts. Low oxygen fugacity as indicated by low Ce（ Ⅳ）/Ce（ Ⅲ） ratios may be responsible for formation of large Pb-Zn-dominated skarn deposits. Our current research illustrates that combination of zircon Hf-O isotope could more accurately trace the source of magma through distinguish juvenile components and parental magmas derived from reworking of pre-existing crustal material. And zircon O isotope is one of the most efficient techniques to study the metallogenetic regularity.

关 键 词：锆石氧同位素 SHRIMP 罗维钨锌矿床 右江褶皱带 

分 类 号：P588.121[天文地球—岩石学] P597.2[天文地球—地质学]