摘要
对青海省格尔木窑洞山地区四道沟侵入岩进行岩石学、岩石化学、微量元素的分析及研究,主要岩石类型有二长花岗岩、二云母二长花岗岩和白云母花岗岩等,SiO_2含量为65. 65%~77. 32%,K_2O、Na_2O分别含量为2.78%~7.73%和1.26%~5.78%,显示钙碱性系列特征,σ=0.61~2.07,Al_2O_3>CaO+K_2O+Na_2O,A,CNK=1. 09~2.48,为中高钾过铝质岩石。LREE/REE=3. 30~6.24,δEu=0.37~0. 56,均小于1,具明显的负铕异常。K、Rb、Ba、Th、Ce富集,其中Ba具负异常特征,Ta、Zr亏损,具碰撞花岗岩特征。由上述特征表明,窑洞山地区的晚奥陶世花岗岩具壳源花岗岩(S型)特征,是非典型碰撞型花岗岩,形成于岛弧或陆缘弧部位。同时在四道沟西侧的二云母二长花岗岩中获得(471±2)Ma LA-ICP-MS锆石U-Pb年龄,为东昆仑地区古生代多级构造—岩浆演化提供了精确的地质时代证据。
The analysis and study of petrology, petrochemistry and trace elements of the Sidao gou in Yaodongshan area of Golmud City, Qinghai Province, the main rock types are monzonite granites, Biotite-Mus monzonite granites and muscovite granites, the rocks have the following chemical composition:siO_2= 65. 65%~77. 32%,K_2O and Na_2O are different between 2. 78% ~7. 73 %and 1. 26% ~5. 78 %, This indicates the granite rocks with the character of calcium alkalescence siries. σ = 0. 61 ~2.07,Al_2O_3>CaO+ K_2O+Na_2O,A/CNK = 1. 09 ~ 2. 48, They are medium-high potassium aluminum rocks. LREE/REE = 3. 30 ~ 6. 24,△Eu = 0. 37~ 0. 56, all less than 1, indicate Eu pronounced Obviously negative abnormalty. K, Rb, Ba, Th, Ce are abundant, of which Ba has negative abnormalty, Ta, Zr are loss-making, with collision granite characteristics. From the above characteristics, it is shown that the late Ordovician granites in the Yaodongshan area are Crustal granite(S-type granite), Atypical Syn-Collision granite,formed in island arcs or continental margin arcs. At the same time, We took a sample of the Biotite-Mus monzonite granites in the Yaodongshan area to analys U-Pb age. The LA-ICP-MS U-Pb age analyses show that the granite ages of late Ordovician are(471±2)Ma, the zircon trace elements age provide accurately Geological Age on the Paleozoic multi-stage tectonic-magmatic events of the Eastern Kunlun area.
引文
曹建辉,袁万明,郝娜娜,冯云磊,等.2015.东昆仑沟里地区花岗岩年代学、岩石地球化学及其地球动力学意义[J].地质科技情报,43(4):42-51.
陈加杰,付乐兵,魏俊浩,田宁,等.2016.东昆仑沟里地区晚奥陶世花岗闪长岩地球化学特征及其对原特提斯洋演化的制约[J].地球科学,41(11):1683-1882.
陈能松,孙敏,王勤燕,张克信,等.2008.东昆仑造山带中的锆石U-Pb定年与构造演化启示[J].地球科学,38(6):1991,657-666.
古凤宝,吴向农,姜常义.1996.东昆仑华力西-印支期花岗岩组合及构造环境[J].青海地质,18-36.
郝娜娜,袁万明,张爱奎,曹建辉,等.2014.东昆仑祁漫塔格晚志留世-早泥盆世花岗岩:年代学、地球化学及形成环境[J].地质论评,60(1):201-215.
何成,王力圆,田立明,徐净.2018.东昆仑哈拉森地区花岗岩类岩石成因及地质意义[J].地球科学,41(11):1207-1220.
李善平,马海州,沈存祥,魏海成.2008.青藏高原北羌塘盆地结扎乡一带二叠系尕笛考组火山岩的特征及构造环境[J].西北地质,41(2):31-48.
陆露,张延林,吴珍汉,胡道功.2013.东昆仑早古生代花岗岩锆石U-Pb年龄及其地质意义[J].地球学报,34(4):447-454.
莫宣学,罗照华,邓晋福,喻学惠,等.2007.东昆仑造山带花岗岩及地壳生长[J].高校地质学报,13(3):403-414.
姚文光,贾群子,张汉文,等.2002.青海督冷沟铜钴矿床地质特征及成因[J].矿床地质,21(增刊):523-526.