八达岭花岗杂岩的组成、地球化学特征及其意义
A granitoid complex from Badaling area, North China: composition, geochemicalcharacteristics and its implications
-
摘要: 北京地区八达岭花岗杂岩是燕山期岩浆侵入活动的典型代表,按照地球化学特征及成因,本文将其分为3类第1类由辉长-闪长岩组成,富Fe、Ti和P,Th/Ta比值近似等于1(0.7~1.2),ISr和εNd(t)值低(分别为0.705和-8~-11),产于板内环境,推测是大陆岩石圈地幔部分熔融形成的,可能代表了燕山期时底侵到加厚陆壳底部的玄武质岩浆.第2类为八达岭花岗杂岩的主体,由石英闪长岩-花岗闪长岩-二长花岗岩组成,其地球化学特征为SiO2>57%,K2O>2.7%,Na2O/K2O=0.9~1.7,Al2O3在16%~14%之间,LREE富集,(La/Yb)N=25~41,HREE亏损(Yb<1.32μg/g),无或有弱的负铕异常(Eu/Eu*=1.0~0.9),富Sr(354~1191μg/g),贫Y(<16μg/g),Sr/Y比值高(45~156).上述地球化学特征除了K2O含量偏高和Al2Os含量偏低外,大体类似于埃达克质岩石的性质,表明岩浆的源区很深,与石榴石处于平衡,暗示其来源于燕山期华北加厚的陆壳底部,可能是下地壳中基性麻粒岩部分熔融形成的.第3类由碱长花岗岩和石英二长岩组成,Na2O+K2O>9%,贫Sr、Ba,富Rb,LREE富集,有明显的负铕异常(Eu/Eu*=0.4~0.5),属于A型花岗岩,是由于第2类埃达克质岩石形成之后,引起了岩石圈拆沉,造成地幔上涌至减薄陆壳的底部,引起壳幔过渡带物质部分熔融的结果.该区燕山期岩浆活动与古太平洋板块的消减作用无关,是板内伸展事件的产物.
-
Key words:
- Granitoid /
- Adakite-like rocks /
- Geochemistry /
- Genesis /
- Badaling area. /
-
[1] [1]Atherton M P, Petford N. 1993. Generation of sodium-rich magmas from newly underplated basaltic crust. Nature,362:144-146
[2] [2]Bai Z M, Xu S Z, Ge S W. 1991. The Badaling Granitoids. Beijing:Geol. Publ. House,1-169 (in Chinese)
[3] [3]Bao Y G, Bai Z M, Ge S W. 1995. Volcanic Geology and Volcanic Rocks in Beijing Areaduring Yanshanian Period. Beijing: Geol.Publ. House, 1-164. (in Chinese)
[4] [4]Defant M J, Drummond M S. 1993. Mount St. Helens: Potential example of the partialmelting of the subducted Lithosphere in a volcanic arc. Geology, 21:547-550
[5] [5]Defant M J & Drummond M S. 1990. Derivation of some modern arc magmas by meltingof young subduction Lithosphere. Nature,662-665
[6] [6]Deng J F, Liu H X, Zhao H L. 1996. Yanshanian igneous rocks and orogeny model inYanshan-Liaoning area. Geoscience, 10:137-148. (in Chinese with English abstract)
[7] [7]Deng J F, Zhao G C, Zhao H L. 2000. Yanshanian igneous petrotectonic assemblage andorogenic-deep process in east China. Geological Review, 46: 41- 48. (in Chinese withEnglish abstract)
[8] [8]Drummond M S, Defant M J. 1990. A model for trondhjemitetonalite-dacite genesis andcrustal growth via slab melting:Archean to modern comparisons. J. Geophys. Res. , 95(B13):21503-21521
[9] [9]Kay S M, Ramos V A, Marques M. 1993. Evidence in Cerro Pampa Volcanic Rocks forSlab-Melting Prior to Ridge-Trench Collision in Southern South American. J. Geol. , 101:703-714
[10] [10]Liu F S and Shi Z L. 1995. Characteristics and genesis of unitsuperunits aboutmember of Laiyuan-Badaling batholith, Hebei Province. Geoscience 9: 409-418. (in Chinesewith English abstract)
[11] [11]Martin H. 1999. Adakitic magmas: modern analogues of Archean granitoids. Lithos,46:411-429
[12] [12]Martin H. 1986. Effect of steeper Archean geothermal gradient on geochemistry ofsubduction-zone magmas. Geology, 14: 753-756
[13] [13]Peacock S M, Rushmer T, Thompson A B. 1994. Partial melting of subducted oceaniccrust. Earth Planet. Sci. Lett., 121: 227-244
[14] [14]Rapp R P, Watson E B, Miller C F. 1991. Partial melting of amphibolite/eclogiteand the origin of Archaean trondhjemites and tonalites. Precamb. Res., 51:1-25
[15] [15]Rudnick R L, Fountain D M. 1995. Nature and composition of the continental crust:a 1ower crust perspective. Res. Geophys. ,33:267-309
[16] [16]XuBL, YanGH, XuZB, HeZP, ZhaoH. 1999. Geochemistry and genetic implication ofthree series of Yanshanian granite in northern Hebei Province. Acta Petrologica Sinica,15: 208-216. (in Chinese with English abstract)
[17] [17]Yu JH, Fu H Q, Zhang FL, GuanM S. 1994. The plutonism of Beijing area. Beijing:Geological Publishing House. (in Chinese with English abstract)
[18] [18]Zhang Q, Wang Y and Wang Y L. 2001. Preliminary study on the components of thelower crust in the eastern China Plateau during Yanshanian Period: Constraints on Sr andNd isotopic compositions of adakite-like rocks. Acta Petrologica Sinica, 17(4) :505-513(in Chinese with English abstract)
[19] [19]白志民,许淑贞,葛世伟.1991.八达岭花岗杂岩.北京:地质出版社,1-172
[20] [20]鲍亦冈,白志民,葛世伟.1995.北京燕山期火山地质及火山岩.北京:地质出版社,164
[21] [21]邓晋福,刘厚祥,赵海玲.1996.燕辽地区燕山期火成岩与造山模型.现代地质,10:137-148
[22] [22]邓晋福,赵国春,赵海玲.2000.中国东部中生代火成岩构造组合与造山-深部过程.地质论评,46:41-48
[23] [23]刘凤山,石准立.1995.河北涞源-八达岭岩基段单元-超单元特征及其成因.现代地质,9:409-418
[24] [24]许保良,阎国翰,徐振邦,何中甫,赵晖.1999.冀北燕山期三个系列花岗质岩石的地球化学特征及其成因意义.岩石学报,15:208-216
[25] [25]郁建华,付会芹,张凤兰,管梅生.1994.北京地区岩浆深成作用.北京:地质出版社
[26] [26]张旗,王焰,王元龙.2001.燕山期中国东部高原下地壳组成初探:埃达克质岩Sr、Nd同位素制约.岩石学报,17(4):505-513
计量
- 文章访问数: 7246
- PDF下载数: 4920
- 施引文献: 0