东秦岭俯冲消减古洋壳的地球化学鉴定

高长林; 秦德余; 吉让寿; 殷勇

doi:10.11781/sysydz199002135

东秦岭俯冲消减古洋壳的地球化学鉴定

doi: 10.11781/sysydz199002135

地质矿产部石油地质中心实验室无锡

计量
- 文章访问数: 576
- HTML全文浏览量: 60
- PDF下载量: 382
- 被引次数: 0
出版历程
- 刊出日期: 1990-04-25

A GEOCHEMICAL DETERMINATION OF THE SUBDUCTION OCEAN CRUST IN EAST QINLING MOUNTAINS

Central Laboratory of Petroleum Geology, MGMR

摘要

摘要: 本文据笔者所提出的鉴定俯冲消减古洋壳的地质地球化学方法,证实了东秦岭商南松树沟地区存在有俯冲消减的古洋壳的残余。蛇绿岩套和对火山岩带的存在是鉴定俯冲消减古洋壳的主要可靠证据。松树沟蛇绿岩套中,超基性岩为纯橄榄岩和斜辉辉橄岩,具亏损地幔岩的稀土元素地球化学特征,其中的(变)基性岩为大洋拉斑玄武岩,SiO₂含量值小于52%,TiO₂含量值大于0.80%,TiO₂/SiO₂值高,Q值高,K值低,∑REE低,∑Ce/∑Y值低,不富集轻稀土,与大洋玄武岩相类似。而与蛇绿岩套紧邻的丹凤群火山岩为钙碱性岛弧型岩石,其TiO₂/SiO₂值低,Q值低,K值高,∑REE高,∑Ce/∑Y值高,富轻稀土,与岛弧型火山岩相似,据上述资料及常量元素对应分析结果,表明丹凤群火山岩形成于岛弧环境,松树沟地区的(变)火山岩形成于大洋环境。

Abstract: The relic of subduction palaeooceanic crust is recognized in Song Shugou area of Shangnan in the eastern Qinling with the geochemical methods proposed by the authors. The existence of ophiolite suite and volcanic rock zone is the reliable evidence for the determination of subduction palaeooceanic crust. Ultrabasic rocks, which are pure olivinfels and orthorhomic pyroxene in Song Shugou ophiolite suite, are geochemically characterized by rare earth elements of loss mantle rocks. The basic (metamorphic) lava mixed in the ophiolite suite is practically a oceanic tholeiites and they have some characteristics such as less SiO₂ (52%), high TiO₂ (0.80%), high ratios of TiO₂ /SiO₂, high Q value, low K value, low REE value, low ratios of ΣCe/ΣY and poor in light rare earth elements, these and tholeiites are resemble to oceanic basalts. The volcanic rocks of Danfeng group adjacent to the ophiolite suite are calc-alkali island arc-typed rocks with low ratio of TiO₂/SiO₂, low Q value, and high values of K, ΣREE, and ΣCe/ΣY, enriched with light rare earthelements, which are similar to the volcanic rocks of island arc type. Based on the data mentioned above and the results of correlation analysis of common elements, the authors suggested that the volcanic rocks of Danfeng group were formed in island arc environment, while the volcanic rocks in Song Shugou area were formed in oceanic environment.

HTML全文

参考文献(15)

[1]	Miyashiro, A.,1975. Classification, Characteristics and Origin of ophioites,The Jur.of Geol.83 P.249.
[2]	Pearce. J.A.,Cann J.R.,1971, Ophiolite origin investigated by discriminant analysicusing Ti. Zr and Y. Earth Planet. Sci. Lett.,12, P.339.
[3]	Pearce. J.A.,Cann J.R.,1973, Tectonic setting of basic volcanic rocks determined using trace element analyses, Earth Planet.Sci.Lett.,Yol. is, P.290.
[4]	Pearce. J.A.et al.,1975, The TiOx-KxO-PxOs diagram; A method of discriminating betweenocean and non-oceanic basalts. Earth Planet.Sci.Lett.24, P.419.
[5]	Yasuyukimiyake. 1985 MORB-like tholeiites formed within the Miocene forearc basin Southwest Japan, Lithos, 18, P.23-34.
[6]	张旗、张魁武、李达周,1987,论造山带中超镁铁岩的成对分布,岩石矿物学杂志,22卷2期.
[7]	万渝生,1987,论构造地球化学图解的局限性,岩石犷物学杂志,7卷4期,318-324页.
[8]	於崇文,1986,地球化学的理论体系与方法论,地球科学,11卷4期,331-340页.
[9]	James B. G.,1981, Orogenic andesites and Plate tectonics, Springer-Verlag.
[10]	张秋生、朱永正,1984.东秦岭古生代蛇绿岩套,长春地质学院学报,3期.
[11]	赵伦山、张本仁等编著,地球化学,地质出版社,155页.
[12]	Ringwood. A.E.,1975. Composition of Petrology of the earth's mantle, McGraw-Hill.
[13]	王希斌、鲍佩声,1985,西藏蛇绿岩中纯橄榄岩及其地质意义,中国地质科学院地质研究所所刊,12号.
[14]	安三元、王培荣,1985.陕西商南秦岭群闪岩系的原岩恢复与多期变质作用,中国区域地质,13辑,地质出版社.
[15]	高长林、王振元,1985,内蒙白乃庙古岛弧型火山岩的地球化学特征,勘查地:味物理勘查地球化学文集,张本仁主编,第二集,地质出版社.