西秦岭吴家山群地层时代及物源特征:来自碎屑锆石U-Pb年龄证据  

Stratigraphic Ages and Provenance Characteristics of Wujiashan Group in West Qinling,China:Evidences from Detrital Zircon U-Pb Age

作　　者：丁振举[1] 文成雄[1,2] 国阿千 牛广德[1,4] 王增祥 刘志宇 DING Zhenju;WEN Chengxiong;GUO Aqian;NIU Guangde;WANG Zengxiang;LIU Zhiyu(Faculty of Earth Resources,China University of Geosciences,Wuhan 430074,Hubei,China;Hunan Institute of Geological Survey,Changsha 410116,Hunan,China;Yunnan Institute of Geological Survey,Kunming 650216,Yunnan,China;Gansu Nonferrous Geological Survey Institute,Lanzhou 730000,Gansu,China;Cores and Samples Center of Land and Resources,China Geological Survey,Sanhe 065201,Hebei,China)

机构地区：[1]中国地质大学(武汉)资源学院,湖北武汉430074 [2]湖南省地质调查院,湖南长沙410116 [3]云南省地质调查院,云南昆明650216 [4]甘肃省有色地质调查院,甘肃兰州730000 [5]中国地质调查局国土资源实物地质资料中心,河北三河065201

出　　处：《地球科学与环境学报》2018年第2期111-132,共22页Journal of Earth Sciences and Environment

基　　金：国土资源公益性行业科研专项项目(201211008);全国危机矿山接替资源找矿专项项目(20089939)

摘　　要：对西秦岭吴家山群4件样品碎屑锆石进行LA-ICP-MS U-Pb定年研究,限定地层沉积时代并示踪沉积物源。锆石U-Pb年龄介于(399±3)^(2 858±43)Ma,主要集中分布在0.40~0.50、0.70~1.05Ga两个年龄段,少量分布在1.10~1.40、1.45~1.85、2.35~2.65Ga等年龄区间。其中两粒锆石的最小年龄为399 Ma和401 Ma,限定了吴家山群地层沉积的最大年龄约为400Ma,由此推断沉积地层形成于早—中泥盆世。吴家山群碎屑锆石U-Pb年龄谱与北秦岭地体、华北地块、南秦岭地体、华南(扬子)地块岩浆活动U-Pb年龄对比结果表明:0.40~0.50Ga锆石碎屑源区应主要为北秦岭地体;0.70~1.05Ga锆石主体应来自北秦岭地体,有少量南秦岭地体或扬子地块物质的加入;1.10~1.85Ga锆石应来自北秦岭地体;而2.35~2.65Ga锆石来自南秦岭地体或扬子地块,也可能来自华北地块。总体来看,吴家山群源区主要为北秦岭地体,少量来自南秦岭地体或扬子地块。结合吴家山群地层时代及陆源物质源区的示踪结果,秦岭早古生代洋盆在西秦岭地区闭合时间应不晚于泥盆纪。LA-ICP-MS detrital zircon U-Pb ages of 4 samples from Wujiashan Group in West Qinling,China were used to establish the maximum depositional age and trace the provenance.The detrital zircon U-Pb ages are(399±3)-(2 858±43)Ma with two main ranges of 0.40-0.50 Ga and 0.70-1.05 Ga,and with a small amount ranges of 1.10-1.40,1.45-1.85 and 2.35-2.65 Ga,respectively.The U-Pb ages of two youngest detrial zircons are 399 Ma and 401 Ma,and place the maximum deposition age of Wujiashan Group at^400 Ma;therefore,Wujiashan Group belongs to Lower-Middle Devonian.On the basis of the comparison of U-Pb age spectra of Wujishan Group with the magmatism recorded by zircon U-Pb ages from North Qinling terrane,North China Block,South Qinling terrane,and South China Block(Yangtze Block),the results show that the detrital sources of 0.40-0.50 Ga zircons originate from North Qinling terrane,and those of 0.70-1.05 Ga mainly from North Qinling terrane with minor contribution from South Qinling terrane or Yangtze Block;the detrital zircons of 1.10-1.85 Ga come from North Qinling terrane,and those of 2.35-2.65 Ga from South Qinling terrane,Yangtze Block or North China Block.In general,Wujiashan Group is mainly of a provenance of North Qinling terrane,with a small proportion from South Qinling terrane or Yangtze Block.The stratigraphic ages and provenance of Wujiashan Group likely indicate that the closure time of Qinling Palaeozoic ocean in West Qinling is not later than Devonian.

关 键 词：地层时代 物源 锆石U-Pb年龄 泥盆纪 北秦岭地体 南秦岭地体 吴家山群 西秦岭 

分 类 号：P597[天文地球—地球化学]