摘要
本文对庐枞盆地砖桥地区科学深钻ZK01中的粗安岩、正长岩和黑云母二长岩进行了LA-MC-ICP MS锆石U-Pb定年,年龄分别是131.29±0.85Ma,130.95±0.56Ma,130.88±0.41Ma。全岩主、微量元素分析结果表明ZK01中的火成岩富钾(K2O平均为3.7%)、富碱(K2O+Na2O平均为8.4%),富集强不相容元素和轻稀土元素,亏损高场强元素和重稀土元素,均属于准铝质-过铝质岩石。在SiO2-K2O图解中,绝大多数样品点落在含钾较高的钾玄岩区域中,火山岩和侵入岩均属于橄榄玄粗岩系。岩浆演化过程中有矿物的分离结晶作用。粗安岩、正长岩和黑云母二长岩的锆石εHf(t)值分别为-12.9^-7.6,-10.1^-6.5,-11.1^-3.4。推测ZK01中的岩浆岩主要来源于俯冲板片流体交代形成的富集地幔,稍有陆壳物质的混染,岩浆形成于岩石圈拉张伸展的构造背景之下。
LA-MC-ICP MS zircon U-Pb datings yield the ages of 131.29 ± 0. 85Ma, 130. 95 ±0. 56Ma, 130. 88 ± 0. 41Ma for trachyandesite, syenite and biotite monzonite from scientific deep drilling ZK01 in Zhuanqiao, Lujiang-Zongyang volcanic basin. Major and trace elements suggest, belonging to metaluminous-peraluminous series, these igneous rocks in ZK01 are characterized by high content of potassium （ K20 averaged at 3.7% ）, rich alkali （ K20 ＋ Na20 averaged at 8.4% ） and LREEs but depleted strong incompatible elements. Most samples plot in the field of shoshonite in Si02-K20 diagram, indicating the volcanic and intrusive reeks are shoshonite series. Mineral fractional crystallization occured during the evolution of magma, cHf （t） values of trachyandesite, syenite and biotite monzonite are - 12. 9～ -7. 6, - 10. 1～ -6. 5 and - 11.1～ -3.4, respectively. It has been inferred that igneous rocks in ZK01 derived from enriched mantle produced by fluid metasomatism of subduction slab, less contaminated by continental material, and magma formed in the tectonic setting of lithosphere tension.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2014年第4期995-1016,共22页
Acta Petrologica Sinica
基金
国家"深部探测技术与实验研究"专项课题(SinoProbe-03-06)
"十二五"国家科技支撑计划(2011BAB04B03)联合资助
