西北地质Issue(4)：37-49,13.
青藏高原北羌塘祖尔肯乌拉山地区查保马组陆相火山岩地球化学特征及锆石 U-Pb 测年
The Geochemical Characteristics and Zircon U-Pb Dating of the Miocene Continental Volcanic Rocks from Chabaoma Formation in the Mt. Jurhen Ul Area of North Qiangtang,Qinghai-Tibetan Plateau
摘要
Abstract
In the Chabaoma Formation of Mt. Jurhen Ul area,the main rock types of continental volcanic rockare latite and andesite,which were formed in Neogene-Miocene epoch. The geo-chemical characteristics indicate that the contents of SiO2 (main element)range from 42.45% to 62.60%,and most of them are 58.08%-62.60%,which is relatively higher than the ones of FeO,MgO,K2 O,TiO2 and P2 O5 ,suggesting these rocks belong to the ones of mantle-derived magmatic rock series. The values of σ(Litman index)are 2.87-3.41,with an average of 3.1 9, showing these rocks have the characteristics of calc-alkaline rock series. The total alkali (Na2 O+K2 O)contents of these volcanic rocks are high,the contents of Na2 O-2 are less than the ones of K2 O,and the ratios of K2 O/Na2 O are 1.12-1.43,suggesting theses rocks belong to shoshonite-series.For the trace elements,the strong incompatible elements (such as Rb,Ba,Th,U and K) showstrong enrichment,but the weakly incompatible elements (Ta,Nb,La,Ce,P,Zr,Hf and Sm)show weak enrichment,while the transition elements (Ti,Y and Yb)are weakly less,and the compatible element (Lu)is strong loss.The strong enrichment of incompatible elements re-veal that these volcanic rocks were soured from the enriched mantle (EM II). The distribution model of REE is right abligue in the orientation,with significant REE fractionation and weak negative Eu anomalies,suggesting that the crustal material had mixed into the magma during the upwelling process,which lead to the occurring of assimilation and hybridization. The analysis show that,these rocks formed in an intraplate setting. The ICP-MS zircon U-Pb dating reveals that the crystallization ages of these volcanic rocks are 20±1Ma,belonging to the Miocene Epoch of Neogene Period.关键词
祖尔肯乌拉山/中新世/查保马组/火山岩/锆石 U-Pb 测年Key words
Mt. Jurhen Ul/Miocene/Chabaoma Formation/volcanic rocks/zircon U-Pb dating分类
天文与地球科学引用本文复制引用
王钊飞,曹波,陈炳锦..青藏高原北羌塘祖尔肯乌拉山地区查保马组陆相火山岩地球化学特征及锆石 U-Pb 测年[J].西北地质,2015,(4):37-49,13.基金项目
中国地质调查局项目“青海沱沱河地区1∶5万 I46E013003、I46E013004、I46E014003、I46E014004四幅区域地质调查”(1212011221010) （1212011221010）
