江西相山酸性火山——侵入杂岩精确年代学与演化序列研究  

Zircon geochronology and evolution sequence of the acidic volcano-intrusive complex from Xiangshan, Jiangxi Province

作　　者：郭福生[1] 杨庆坤[1,2] 谢财富[1] 孟祥金[3] 周万蓬[1] 姜勇彪[1] 张树明[1] 吴志春[1] 

机构地区：[1]东华理工大学地球科学学院,南昌330013 [2]中国地质大学(北京),北京100083 [3]中国地质科学院地质研究所,北京100037

出　　处：《地质科学》2015年第3期684-707,共24页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：中国地质调查局三维地质调查试点项目（编号：1212011220248）、国家自然科学基金项目（编号：41040019,41072077）、江西省领军人才计划项目和东华理工大学校长基金项目（编号：DHXK201403）资助.

摘　　要：相山火山盆地主体岩石为一套由熔结凝灰岩、流纹英安岩、流纹英安斑岩、碎斑熔岩、粗斑花岗斑岩及似斑状花岗岩组成的酸性火山一侵入杂岩体，构成了两个完整的喷发-溢流（侵出）-侵入的岩浆活动亚旋回。本文在野外地质调查的基础上，采用SIMS、LA—ICP—MS技术对主要岩类进行了高精度的锆石u—Pb年代学研究，并建立了火山-侵入杂岩体的演化序列。结果表明，打鼓顶组熔结凝灰岩代表了相山火山一侵入活动的最早期产物，其锆石U—Pb年龄为140．7±2．7Ma、140．1±1．8Ma和138．2±1．6Ma，第一亚旋回主体流纹英安岩的锆石U-Pb年龄135．0±1．8Ma。鹅湖岭组熔结凝灰岩代表了火山一侵入活动的第二亚旋回的开始，其U-Pb年龄为135．6±1．2Ma，第二亚旋回主体碎斑熔岩的锆石U—Pb年龄133．6±1．3Ma，沙洲单元的粗斑花岗斑岩和似斑状花岗岩属于该亚旋回最晚期的侵入岩，其锆石U-Pb年龄代表了相山火山-侵入活动的结束时间（分别为133．4±1．2Ma和133．9±1．1Ma）。相山早白垩世火山一侵入活动延续时间较短，整体上呈现一个连续的过程，初始时间在141Ma附近，结束时间在132Ma左右。概言之，第一亚旋回（141—135Ma）以形成熔结凝灰岩、流纹英安岩和流纹英安斑岩为主，第二亚旋回（135—132Ma）以熔结凝灰岩、碎斑熔岩、粗斑花岗斑岩和似斑状花岗岩为主。岩石地球化学和野外地质特征也与两个亚旋回火山一侵入岩浆活动相吻合。The host rocks of Xiangshan volcanic basin are volcanic-intrusive complex, involves the welded tuff, rhyolite dacite, rhyolite dacite porphyry, porphyroclastic lava, macrophyric granite porphyry and porphyritic granite, constitutes two complete magmatism sub cycle of eruption-overflow （intrusive）-intrusive. The authors use SIMS, LA-ICP-MS technology to analyze the zircon U-Pb geochronology on the main rocks and discuss the origin and evolution characteristics of Xiangshan complex. The results show that, ignimbrite of Daguding Formation represents the early outcome of Xiangshan volcanic intrusive activities, the zircon U-Pb age is 140.7±2.7 Ma, 140. 1±1.8 and 138.2±1.6 Ma, U-Pb zircon age of rhyodacite is 135± 1.8 Ma. Ignimbrite of Ehuling Formation represents the second begining of the volcanic intrusive activities and the U-Pb age is 135.6± 1.2 Ma. Zircon U-Pb age of porphyroclastic pava is 133.6±1.3 Ma. Macrophyric granite porphyry and porphyritic granite are the youngest rocks and the zircon U-Pb age（ 133.4±1.2 Ma and 133.9±1.1 Ma, respectively）represents the end of the volcanic intrusive activity. From the Early Cretaceous, the duration of the Early Cretaceous volcanic intrusive activity is short, showing a continuous process, with the beginning is about 141 Ma and the end is about 132 Ma. The Xiangshan volcanic intrusive activity takes on two sub cycles. In the first sub cycle（ 141- 135 Ma）, the magmatites involve welded tuff, rhyolite dacite and rhyodacite porphyry, while the second sub cycles （135- 132 Ma） involve ignimbrite, porphyroclastic lava, macrophyric granite porphyry and porphyritic granite. Rock geochemical and geological features are inconsistent with the evolution sequence.

关 键 词：锆石U-PB年代学 演化序列 火山-侵入杂岩体 相山 

分 类 号：P597.3[天文地球—地球化学]