黑龙江张广才岭一面坡晚三叠世花岗岩地球化学特征和LA-ICP-MS锆石U-Pb年龄

耿雯; 秦江锋; 李永飞; 赖绍聪

黑龙江张广才岭一面坡晚三叠世花岗岩地球化学特征和LA-ICP-MS锆石U-Pb年龄

Geochemistry and LA-ICP-MS zircon U-Pb age of the Late Triassic granite from Yimianpo area, Zhangguangcai Mountain, Heilongjiang Province

摘要

摘要: 对张广才岭南部一面坡花岗岩的地质学、岩石学、地球化学及锆石U-Pb年龄研究表明，岩石富硅富铝，属于过铝质岩石（A/CNK=1.04~1.07），全碱（K2O+Na2O）含量为8.24%~8.85%，K2O/Na2O值为1.58~1.68，属于高钾钙碱性系列I型花岗岩。岩石富集LREE、Rb、Th、U、K，相对亏损Nb、Ta、P、Ti，具有明显的Eu负异常，LA-ICP-MS锆石206Pb/238U年龄加权平均值为211Ma±4Ma（MSWD=1.4, 2σ），代表了花岗岩的结晶年龄。岩石具有相对亏损的锆石Hf同位素组成（εHf(t)=+1.75～ +13.81），TDM2为367~1136Ma。结合区域构造环境分析，认为一面坡晚三叠世花岗岩属于I型花岗岩，可能形成于后碰撞伸展构造环境，是岩石圈伸展阶段新增生下地壳物质发生部分熔融的产物。

Abstract: This paper has reported the field geology, petrography, major and trace elements, zircon U-Pb age and Lu-Hf isotopic data for the granite from Yimianpo area, Zhangguangcai Mountain. The granite is high in SiO2 and Al2O3. A/CNK=1.04~1.07, (K2O+Na2O)=8.24%~8.85%，and K2O/Na2O=1.58~1.68, belonging to peraluminous and I-type high-K calc-alkaline series. The granite is enriched in LREE, Rb, Th, U, K and depleted in Nb, Ta, P, Ti with significant negative Eu anomalies. It has 206Pb/238U weighted mean age of 211Ma±4Ma (MSWD=1.4, 2σ), which represents the crystallization age of the granite. Zircon Hf isotope composition is εHf(t)=+1.75～+13.81, TDM2=367~1136Ma. Therefore, the I-type granite in the study area might have been formed in a typical post-collsional tectonic setting and resulted from partial melting of juvenile basaltic lower crust in an extensional setting.

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