安徽大别山硬玉石英岩地球化学特征及其地质意义
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摘要
硬玉石英岩是大别山超高压变质带的重要成员。硬玉石英岩主量元素平均含量为SiO_2 72.73%、Al_2O_311.77%、MgO1.61%、Fe_2O_3 5.00%、Na_2O 5.45%、K_2O 0.22%、TiO_2 0.59%,具有明显的富硅、富铁、富钠的特征;特征微量元素平均含量Th 10.12×10~(-6)、U 1.94×10~(-6)、Hf 10.91×10~(-6)、Sc 7.68×10~(-6)、Zr 437.05×10~(-6)、Nb 15.81×10~(-6)、Y 45.36×10~(-6)、Ba 141.88×10~(-6)、Sr 30.07×10~(-6);Th/U为5.18、Th/Sc为1.56、La/Sc 9.50;∑REE平均含量223.07×10~(-6),(La/Yb)N 7.01,δEu=0.61,Eu负异常明显,轻稀土富集。原岩恢复结果为富钠的杂砂岩,原岩可能形成于古元古代扬子大陆板块的活动大陆边缘,在中生代三叠纪与华北板块碰撞过程中经受了超高压变质作用。
Jadeite quartzite is an important member of the ultrahigh pressure metamorphic belt of the Dabie Mountain. The average contents of main elements in jadeite quartzite are 72.73% for SiO_2, 11.77% Al_2O_3, 1.61%MgO, 5.00% Fe_2O_3, 5.45% Na_2 O, 0.22% K_2 O and 0.59% TiO_2, showing remarkable Si-Fe-Na-rich features.Average contents of characteristic trace elements are 10.12 x10~(-6) for Th, 1.94 x10~(-6) U, 10.91 x10~(-6) Hf, 7.68 x10~(-6) Sc, 437.05 x10~(-6) Zr, 15.81 x10~(-6) Nb, 45.36 x10~(-6) Y, 141.88 x10~(-6) Ba, 30.07 x10~(-6) Sr; 5.18 Th/U, 1.56 Th/Sc, 9.50 La/Sc;the average content of ΣREE is 223.07 x10~(-6),(La/Yb)N 7.01, Eu=0.61, distinct negative anomaly of Eu. Protolith reconstruction result is sodium-rich graywacke, which possibly formed in the Paleoproterozoic active continental margin of the Yangtze continental plate, and suffered ultra-high pressure metamorphism during the process of collision with North China Plate in Mesozoic Triassic.
Jadeite quartzite is an important member of the ultrahigh pressure metamorphic belt of the Dabie Mountain. The average contents of main elements in jadeite quartzite are 72.73% for SiO_2, 11.77% Al_2O_3, 1.61%MgO, 5.00% Fe_2O_3, 5.45% Na_2 O, 0.22% K_2 O and 0.59% TiO_2, showing remarkable Si-Fe-Na-rich features.Average contents of characteristic trace elements are 10.12 x10~(-6) for Th, 1.94 x10~(-6) U, 10.91 x10~(-6) Hf, 7.68 x10~(-6) Sc, 437.05 x10~(-6) Zr, 15.81 x10~(-6) Nb, 45.36 x10~(-6) Y, 141.88 x10~(-6) Ba, 30.07 x10~(-6) Sr; 5.18 Th/U, 1.56 Th/Sc, 9.50 La/Sc;the average content of ΣREE is 223.07 x10~(-6),(La/Yb)N 7.01, Eu=0.61, distinct negative anomaly of Eu. Protolith reconstruction result is sodium-rich graywacke, which possibly formed in the Paleoproterozoic active continental margin of the Yangtze continental plate, and suffered ultra-high pressure metamorphism during the process of collision with North China Plate in Mesozoic Triassic.
引文
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[11]Bhatia M R.Plate Tectonics and Geochemical Composition of Sandstones:A Reply[J].Journal of Geology,1983,91(6):611~627.
[2]Shutong X,Wen S,Yican L,et al.Diamond from the dabie shan metamorphic rocks and its implication for tectonic setting[J].Science,1992,256(5053):80~82.
[3]Liu Y C,Gu X F,Rolfo F,et al.Ultrahigh-pressure metamorphism and multistage exhumation of eclogite of the Luotian dome,North Dabie Complex Zone(central China):Evidence from mineral inclusions and decompression t e x t u r e s[J].J o u r n a l o f A s i a n E a r t h S c i e n c e s,2 0 11,42(4):607~617.
[4]郑永飞.超高压变质与大陆碰撞研究进展:以大别-苏鲁造山带为例[J].科学通报,2008,53(18):2129~2152.
[5]吴维平,徐树桐,江来利,刘贻灿,苏文.中国东部大别山超高压变质杂岩中的石英硬玉岩带[J].岩石学报,1998(01):61~65+69~71.
[6]翟明国,从柏林,赵中岩,等.大别山榴辉岩带的高压硬玉石英岩块体及其地质意义[J].科学通报,1992,37(11):1013~1015.
[7]刘晓春,关雅先.大别山高压变质杂岩中的硬玉[J].矿物学报,1993(4):341~345.
[8]Su Wen,Xu Shutong,Jiang Laili,et al.Coesite from quartz-jadeitite in the Dabie Mountains,Eastern China[J].Mineralogical Magazine,1996,60(4):659~662.
[9]Wang X,Liou J G,Mao H K.Coesite-bearing eclogite from the Dabie Mountains in central China[J].Geology,1989,17(1989):1085~1088.
[10]柴广路,李双应.北淮阳东段佛子岭群变质岩地球化学特征及其地质意义[J].地学前缘,2016,23(4):29~45.
[11]Bhatia M R.Plate Tectonics and Geochemical Composition of Sandstones:A Reply[J].Journal of Geology,1983,91(6):611~627.