摘要
在滇中易门-罗茨断裂带以西前人划分的昆阳群美党组中发现了大量的中酸性凝灰岩。采用锆石激光剥蚀法(LAICP-MS)对易门县铜厂一带的英安质凝灰岩、石英晶屑凝灰岩进行了年龄测定,获得锆石U-Pb年龄加权平均值为1842±26Ma(MSWD=7.6,n=29)和1860±25Ma(MSWD=2.5,n=11)。2件样品的锆石Th/U值为0.2～1.0,且均具清晰的振荡环带结构,为岩浆成因锆石。该套凝灰岩产于一套厚度超过1000m的火山-细碎屑岩组合中,其下发育厚约800m的黑色板岩-碳酸盐岩组合,表明滇中易门地区存在厚度超过2000m的古元古界。此年龄值与全球性的Columbia超大陆事件一致,所以,在进行Columbia超大陆重建时需要充分考虑扬子陆块的位置及意义。
Medium-acid tuff was extensively found in Meidang Formation of Kunyang Group, which was determined by previous researchers in the west of Yimen-Luoci faults belt. Using the zircon laser denudation method （LA-ICP-MS）, the authors obtained weighted average ages of 1842±26Ma （MSWD=7.6, n=29） and 1860±25Ma （MSWD=2.5, n=11） from dacitic tuff and quartz crystal tuff in Tongchang area, Yimen County, central Yunnan Province. Th/U ratios of zircon, which was ofmagmatic origin and with clear vibration band, were obtained from two samples （0.2-1.0）. The tuff was found from a volcanic-microclastic rock assembly, which is over 1000m in thickness. There is a black slate-carbonate rock assembly, which is about 800m in thickness, under the volcanic-microclastic rock assembly. It is thus inferred that there is a large area of Paleoproterozoic strata, which are over 2000m in thickness in Yimen area of central Yunnan Province. The ages coincide with Columbia Supercontinent, and hence Yangtze block＇ s location and significance ought to be taken into account in the reconstruction process of Columbia Supercontinent.
作者
刘军平
曾文涛
徐云飞
孙柏东
胡绍斌
刘桂春
宋冬虎
吕勃烨
王晓峰
LIU Junping;ZENG Wentao;XU Yunfei;SUN Baidong;HU Shaobin;LIU Guichun;SONG Donghu;LV Boye;WANG Xiaofeng(Yunnan Institute of Geological Survey,Kunming 650216,Yunnan,China;Yunnan Provincial Institute of Environmental Monitoring,Kunming 650216,Yunnan,China;Kunming University of Science and Technology,Kunming 650093,Yunnan,China)
出处
《地质通报》
CAS
CSCD
北大核心
2018年第11期2055-2062,共8页
Geological Bulletin of China
基金
中国地质调查局项目<云南1:5万二街
易门
鸣矣河
上浦贝幅区域地质调查>(编号:DD20160017)和<云南区域地质调查片区总结与服务产品开发>(编号:DD20160345-02)
关键词
古元古界
锆石U-PB年龄
滇中易门地区
Columbia超大陆重建
Paleoproterozoic
zircon U-Pb age
Yimen area of central Yunnan Province
reconstruction process of Columbia Supercontinent
