摘要
通过LA-ICP-MS测得辽宁赛马地区浅肉红色霞霓正长岩中的锆石U-Pb年龄为225.8±1.9 Ma,赛马碱性杂岩的侵位时代为晚三叠世。地球化学分析表明,霞霓正长岩SiO_(2)含量为55.87%~60.88%,Na_(2)O为0.41%~5.32%,Al_(2)O_(3)为17.81%~19.53%,K_(2)O为9.46%~11.91%,MgO为0.46%~1.36%,里特曼指数为7.54~17.01;稀土元素总量较高,高于300×10^(-6),强烈富集轻稀土元素,(La/Yb)N值大于10,个别达到100以上;亏损Nb、Ta、P等高场强元素,富集Rb、Th等大离子亲石元素,总体表现出富碱性岩石特征。锆石ε_(Hf)(t)值为-13.37~-9.30,对应的两阶段Hf模式年龄T_(DM2)为2102~1855 Ma。通过岩石成因分析和构造环境判别,赛马碱性杂岩可能形成于由俯冲挤压向陆内伸展、拉张转换的动力背景下的下地壳(或上地幔)部分熔融。赛马碱性杂岩侵位时代(225.8±1.9 Ma)可能代表了华北克拉通北缘岩石圈开始伸展减薄的时间,也是郯庐断裂形成的时间。
The light-red aegirine nepheline syenite in Liaoning Saima area has a LA-ICP-MS U-Pb age of 225.8±1.9 Ma,and the emplacement age of the Saima alkaline complex is the Late Triassic.Aegirine nepheline syenite shows SiO_(2) of 55.87%~60.88%,Na_(2)O of 0.41%~5.32%,Al_(2)O_(3) of 17.81%~19.53%,K_(2)O of 9.46%~11.91%,MgO of 0.46%~1.36%,σ43 of 7.54~17.01.The total amount of rare earth elements is higher than 300×10^(−6),and it is strongly enriched with light rare earth elements.Depletion of high field strength elements such as Nb,Ta,P,and enrichment of large ion lithophilic elements such as Rb,Th,shows the characteristics of alkaline rich rocks.The zirconε_(Hf)(t)value is−13.37~−9.30,the corresponding two-stage Hf model age T_(DM2) is 2102~1855 Ma.The Saima alkaline complex may be formed by the partial melting of the lower crust(or upper mantle)under the dynamic background of subductionsqueezing to inland extension and extension conversion.The age of emplacement(225.8±1.9 Ma)may represent the time when the lithosphere began to stretch and thin on the northern margin of the North China Craton,and also the time when the Tanlu fault was formed.
作者
杨凤超
宋运红
胥嘉
顾玉超
杨宏智
YANG Fengchao;SONG Yunhong;XU Jia;GU Yuchao;YANG Hongzhi(Shenyang Center,China Geological Survey,Shenyang 110034,Liaoning,China)
出处
《地质通报》
CAS
CSCD
北大核心
2024年第1期76-85,共10页
Geological Bulletin of China
基金
中国地质调查局项目《东北地区铜金稀有金属战略性矿产资源调查》(编号:DD20230028)和《辽宁甜水幅(K51E019015)、草河口幅(K51E019016)深部矿产地质调查》(编号:DD20190156-1)。
