摘要
华夏古板块与扬子古板块结合带内的广丰、玉山红色碎屑沉积盆地均有橄榄玄粗岩产出,SHRIMP锆石UPb年代学研究表明,橄榄玄粗岩锆石U-Pb年龄为93±1 Ma,属晚白垩世早期的产物。广丰盆地橄榄玄粗岩(^(87)Sr/^(86)Sr)_i值为0.706 191~0.706 352,εNd(t)值为0.27~0.55,(^(206)Pb/^(204)Pb)_i值为18.045~18.080,(^(207)Pb/^(204)Pb)_i值为15.503~15.543,(^(208)Pb/^(204)Pb)_i值为38.240~38.256;玉山盆地橄榄玄粗岩(^(87)Sr/^(86)Sr)_i值为0.705 856~0.706 024,εNd(t)值为1.74~1.93,(^(206)Pb/^(204)Pb)_i值为17.956~18.063,(^(207)Pb/^(204)Pb)_i值为15.456~15.498,(^(208)Pb/^(204)Pb)_i值为38.195~38.232。在(^(87)Sr/^(86)Sr)_i-(^(206)Pb/^(204)Pb)_i、(^(143)Nd/^(144)Nd)_i-(^(206)Pb/^(204)Pb)_i和(^(143)Nd/^(144)Nd)_i-(^(87)Sr/^(86)Sr)i图解中,广丰、玉山盆地橄榄玄粗岩均位于亏损地幔(DMM)和EMⅡ型富集地幔之间,而且(^(87)Sr/^(86)Sr)_i和(^(206)Pb/^(204)Pb)_i呈正相关,(^(143)Nd/^(144)Nd)_i和(^(206)Pb/^(204)Pb)_i呈负相关,指示其源区中可能均有DMM和EMⅡ型地幔的贡献;玉山盆地橄榄玄粗岩更偏向DMM端员,指示其DMM端员所占的比例更高。广丰、玉山盆地橄榄玄粗岩具有EMⅡ型地幔的贡献,说明华夏古板块与扬子古板块结合带的岩石圈地幔与华夏古板块的岩石圈地幔属相同类型,为华夏古板块俯冲于扬子古板块之下提供了新的证据。
Lying at the junction of the Yangtze paleoplate and the Cathaysian paleoplate, Guangfeng and Yushan basins are characterized by red clastic rocks and mafic volcanic rocks. SHRIMP U-Pb dating of zircon shows that shoshonite in Guangfeng and Yushan basins has an age of 93 ＋ 1 Ma, belonging to early Late Cretaceous. （87Sr/86Sr）i values of shoshonite in Guangfeng are 0. 706 191-0. 706 352, ε Nd（t） =0.27～0.55, （206Pb/204Pb）i = 18.045 ～ 18.08, （ 207 Pb/204 Pb ） i = 15.503～ 15.543, and （ 208 Pb/a04 Pb ） i = 38.240 ～38.256, whereas （ 87 Sr/86 Sr） i values of shoshonite in Yushan basin are in the range of 0.705 856～0. 706 024, εNd （t） = 1.74～1.93, （206Pb/204Pb）i = 17.956～ 18.063, （207Pb/204Pb）i = 15. 456～ 15. 498, and （208～b/204Pb）i = 38.195 ～ 38.232. In the （87Sr/86Sr）i-（206Pb/204Pb）i, （143Nd/144Nd）i - （206Pb/204Pb）i and （ 143Nd/144Nd）i - （878r/86Sr）i diagrams,the values fall exclusively between the DMM and EMⅡ positions, （87Sr/86Sr）i and （206Pb/204Pb）i show positive correlation, whereas （143 Nd/144 Nd）i and （206Pb/204 Pb）i show negative correlation, which suggests that the source mantle of the shoshonite rocks probably had both DMM and EMⅡ magma, with a higher proportion of DMM in the Yushan basin.
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
2014年第4期645-656,共12页
Acta Petrologica et Mineralogica
基金
国家自然科学基金项目(41372071)
中国核工业集团总公司项目(中核地计[2008]74号)
