云南威信地区玄武岩的地质地球化学特征及其意义  

Geological,geochemical characteristics and its significance of basalts in Weixin area,Yunnan

作　　者：秦亚 杨启军[1,2] 吕勇 潘明[3] 山克强[3] QIN Ya;YANG Qi-jun;LV Yong;PAN Ming;SHAN Ke-qiang(Engineering Research Center of the Ministry of Education for Exploration of non-ferrous and Precious Metal deposits,Guilin University of Technology,Guilin,Guangxi,541004;Key laboratory for exploration of concealed metal minerals in Guangxi,Guilin university of technology,Guilin,Guangxi,541004;Institute of Karst Geology,Chinese Academy of Geological Sciences,Guilin 541004,China)

机构地区：[1]桂林理工大学有色及贵金属隐伏矿床勘查教育部工程研究中心,广西桂林541004 [2]桂林理工大学广西隐伏金属矿产勘查重点实验室,广西桂林541004 [3]中国地质科学院岩溶地质研究所,广西桂林541004

出　　处：《桂林理工大学学报》2018年第4期625-639,共15页Journal of Guilin University of Technology

基　　金：广西自然科学基金项目(2017GXNSFBA198166; 2018GXNSFAA281248);广西科技计划项目(桂科AD16450001);中国地质科学院岩溶地质研究所区调项目研究专题(YR-JJHT-2014-492);有色及贵金属隐伏矿床勘查教育部工程研究中心项目(2018GCZX004);广西高校科研项目(KY2015YB127)

摘　　要：为研究云贵川交界部位的峨眉山玄武岩的地质地球化学特征,对云南威信地区玄武岩开展野外地质、岩相学、岩石地球化学和年代学研究。威信地区玄武岩呈孤立点状、片状和狭窄条带状分布,主要为气孔-杏仁玄武岩和致密块状玄武岩。5件样品的LA-ICP-MS锆石U-Pb测年结果表明,该区玄武岩形成于257. 4±1. 8 Ma,并含大量捕获锆石。22件样品分析结果表明,本区玄武岩具有高铁镁(MgO2. 09%～5. 64%,Fe OT11. 37%～14. 72%)、低钾钠(K_2O 0. 29%～1. 99%,Na_2O 2. 06%～4. 45%)的主量元素特征,为钠质(Na_2O/K_2O 1. 79～10. 90)、亚碱性系列拉斑玄武岩(σ43除3粒特高值外,平均为1. 90),为典型的高钛玄武岩(Ti O24. 18%～4. 86%; Ti/Y 618. 83～670. 70)。具有右陡倾的稀土配分模式(ΣREE 249. 37×10-6～277. 83×10-6;ΣLREE/ΣHREE 6. 64～8. 62),负铕异常不明显(δEu 0. 91～1. 02);不相容元素比值(Zr/Nb 7. 47～9. 28,La/Nb 1. 02～1. 16,Ba/Nb 3. 16～19. 00,Ba/Th 18. 24～124. 94,Th/La 0. 13～0. 17,Th/Nb 0. 14～0. 17,Ba/La 3. 10～17. 00,Rb/Nb 0. 05～1. 00)显示威信地区玄武岩为经历了地壳物质混染的大陆玄武岩。野外产状、地球化学特征和构造环境判别图解均显示威信地区玄武岩形成于大陆板内构造环境,属于峨眉山玄武岩东岩区的一部分。In order to research the geological and geochemical characteristics of Emeishan basalts at the junction of Yunnan-Guizhou-Sichuan.Field geology,lithology,geochemistry and chronology research on basalts are carried out in Weixin,Yunnan province.The basalts in Weixin area distributed in spots,flake and narrow strip.The main rock types are stomatal-almond basalt and dense block basalts.The results of the LA-ICP-MS zircon U-Pb dating of 5 samples showed that the basalts in the Weixin area were formed in 257.4±1.8 Ma and contained a large amount of capture zircon.The analysis of 22 samples shows that the basalt in Weixin area has the major elements characteristics of high Fe(FeO T=11.37%-14.72%),Mg(MgO=2.09%-5.64%)and low K(K 2O=0.29%-1.99%),Na(Na 2O=2.06%-4.45%).They are sodium(N 2O/K 2O=1.79-10.90),subalkaline series of tholeiite basalt(the mean ofσ43 is 1.90 except for three extra-high grains)and are typical high Ti basalt(TiO 2=4.18%-4.86%,Ti/Y=618.83-670.70).It has the right steep rare earth distribution mode(ΣREE=249.37×10-6-277.83×10-6,ΣLREE/ΣHREE 6.64-8.62),and the negative europium anomaly is not obvious(δEu=0.91-1.02).The ratio of incompatible elements(Zr/Nb=7.47-9.28,La/Nb=1.02-1.16,Ba/Nb=3.16-19.00,Ba/Th=18.24-124.94,Th/La=0.13-0.17,Th/Nb=0.14-0.17,Ba/La=3.10-17.00,Rb/Nb=0.05-1.00)indicates that the basalts in Weixin area with the mixing of crustal materials are continental basalts.Field occurrence,geochemical characteristics and structural environment discriminant diagrams all show that the basalt in Weixin area was formed in continental plate tectonic environment and belonged to the east rock area of Emeishan basalt.

关 键 词：峨眉山玄武岩 岩石地球化学特征 LA-ICP-MS定年 板内玄武岩 威信地区 

分 类 号：P588.145[天文地球—岩石学]