摘要
埃达克岩(Adakite)的特殊性及其科学和现实意义广泛地吸引着地球科学工作者。位于青藏高原东北缘的祁连山早古生代造山带是新中国地学界认识板块构造的摇篮。本文研究了北祁连造山带中段毛藏寺地区侵入岩的岩石学和地球化学特征,结果表明:毛藏寺地区加里东期中酸性侵入岩具有较高的SiO_2、Al_2O_3、Na_2O含量及Na_2O/K_2O值,MgO较低;LREE强富集,HREE明显亏损,L/H比值>15;岩石Th、Sr、Ba具显著的正异常,Sr含量一般在507×10^(-6)以上,具有高Sr/Y、La/Yb比值和较高的Cr、Ni含量;岩石σ值一般为1.45～2.76,A/CNK值为0.83～1.15,多数<1.0,主体属于钙碱性岩系列,偏铝质花岗岩类。岩石化学特征指向埃达克岩。在(La/Yb)_N-Yb_N和Sr/Y-Y判别图上,样品落入埃达克岩范围;在SiO_2-Mg~#图解上,岩体处在"板片来源的埃达克岩"区域,表明毛藏寺地区侵入岩属于"O"型埃达克岩,岩浆起源于俯冲洋壳的部分熔融。毛藏寺"O"型埃达克岩的识别表明,在早古生代中期,北祁连中段经历了洋壳俯冲、岛弧发育和壳幔共同作用的构造演化过程,为祁连山造山带的板块构造演化历史提供了新资料,为祁连山地区寻找和勘查与埃达克岩相关的矿产资源提供了一个可能的方向。
The specificity and its scientific and practical significance of Adakite deeply attracted scientists on Earth. The Qilian Early Paleozoic orogenic belt,which located in the northeastern margin of Qinghai-Tibet Plateau,is cradle of Chinese scientists to study the plate tectonics. By contrast,the characteristics of intrusive rocks in Lianhuashan of the north Qilian orogenic belt were studied. The results is：intermediate-acid intrusive rocks of Caledonian in Lianhuashan have high SiO/, Al2O3, Na2O content, Na2O/K2O ratio is high, while MgO is lower, LREE enrichment strong, HREE apparent loss, the majority of L/H ratio〉 15 ; Th, Sr, Ba is an obvious positive anomalies, of which Sr content is more than 507 × 10-6, Sr/Y, La/Yb （21.39 - 41.72 ） ratio is high and the Cr,Ni. values of the rock are 1.45 -2.76,A/CNK were 0.83 × 1.15, the majority 〈 1.0, the main rocks are calc-alkaline granitoids series aluminum side. Rock eigenvalue are pointing to Adakite. In the（La/Yb） N-YbN and Sr/Y-Y discriminant diagram, samples fall into the scope of the Adakite. In the SiO2-Mg# diagram, the rock fall ＂slab origin Adakite＂ region,content of the rock, also in line with the ＂ 0＂ type Adakite characteristics. These show that Adakite of Lianhuashan region originated in the subduction of the partial melting of oceanic crust, which is ＂O＂ type Adakite. The geodynamic background is the subduction of the north Qilian oceanic crust to the north China plate during Early Paleozoic. Discovery of the ＂O＂ type Adakite in the region confirms previous understanding of Qilian orogenic belt and its tectonic evolution, and puts forward new ideas of mineral resources exploration in the region.
出处
《地质科学》
CAS
CSCD
北大核心
2012年第2期347-359,共13页
Chinese Journal of Geology(Scientia Geologica Sinica)
基金
甘肃省基金项目(编号:Y1.02)资助
