地质通报Issue(1)：43-54,12.
太行山南段洪山岩体中粗面斑岩地球化学特征及LA-ICP-MS锆石U-Pb定年
摘要
Abstract
Based on detailed field investigation, the authors studied the petrology, geochemistry and geochronology of trachyte por⁃phyry in Hongshan intrusion. The SiO2 and Al2O3 of the rock range from 63.57% to 67.85% and 16.75% to 18.77%, 65.19% and 18.21%on average respectively. Rittmann index (σ) ranges 5.6~8.2, the K2O/Na2O ratio ranges 1.00~1.74, with an average of 1.24. A/CNK varies from 1.00 to 1.06. These data suggest that it belongs to alkaline syenite rock. The REE content is between 33.75×10-6 and 144.30×10-6, with (La/Yb)N ratios of 9.18~33.28 andδEu of 0.99~1.16. The intrusion is remarkably characterized by enriched LREE and depleted HREE. The chondrite-normalized REE patterns show weak positive Eu anomaly. In the primitive mantle nor⁃malized trace element spider diagrams, the samples show strong enrichment of LILEs and relative depletion of HFSEs. In addition, tra⁃chyte porphyry's LA-ICP-MS zircon U-Pb dating indicates that the trachyte porphyry were emplaced at ca.128.6±1.0Ma. The zir⁃conεHf(t) values (-16.0~-11.4) yielded zircon Hf crustal modal ages of 1258~1432Ma. Based on the data obtained, the authors hold that Hongshan volcanic rocks originated from partial melting of an EMI-type mantle source, contaminated by LCC. Trachyte por⁃phyry formed in the same time as the Hongshan intrusion in the Mesozoic Cretaceous. Magmatic activities took place in the transfor⁃mation period of the collision environment, causing the partial melting of the mantle and producing the trachyte porphyry. This might have been one of the important ways of lithospheric mantle thinning.关键词
太行山南段/粗面斑岩/地球化学/锆石U-Pb年龄/Hf同位素/构造意义Key words
southern Taihang Mountains/trachyte porphyry/geochemistry/zircon U-Pb dating/zircon Hf isotope/tectonic signifi-cance分类
天文与地球科学引用本文复制引用
刘昕曜,董国臣,李玉成,权瑞..太行山南段洪山岩体中粗面斑岩地球化学特征及LA-ICP-MS锆石U-Pb定年[J].地质通报,2016,(1):43-54,12.基金项目
国家自然科学基金项目(批准号90914002)、长江学者和创新团队发展计划项目（编号IRT1083）和河北省国土厅科研项目 （批准号90914002）
