佳木斯地块中部晚三叠世埃达克岩年代学、地球化学特征及其地质意义  

Geochronology and Geochemistry of Late Triassic Adakite in the Central Jiamusi Block,China and Their Geological Significance

作　　者：赵强 汤静如[1] 杨恒毅 张学琳 罗林菊 ZHAO Qiang;TANG Jing-ru;YANG Heng-yi;ZHANG Xue-lin;LUO Lin-ju(College of Earth Sciences,Guilin University of Technology,Guilin 541006,Guangxi,China;School of Resources and Environmental Engineering,Hefei University of Technology,Hefei 230009,Anhui,China)

机构地区：[1]桂林理工大学地球科学学院,广西桂林541006 [2]合肥工业大学资源与环境工程学院,安徽合肥230009

出　　处：《地球科学与环境学报》2023年第2期240-255,共16页Journal of Earth Sciences and Environment

基　　金：黑龙江省财政拨款项目(HLJKD2015-28);国家自然科学基金项目(41662009)。

摘　　要：大八浪岩体位于佳木斯地块中部的桦南隆起区,岩性为中细粒黑云母花岗闪长岩,其侵入到晚二叠世白云母二长花岗岩中。岩石LA-ICP-MS锆石U-Pb年龄为(234±1)Ma,属于晚三叠世早期。大八浪岩体具有较高的SiO 2含量(质量分数,下同)(62.04%~64.30%)、Al 2O 3含量(15.68%~16.95%)、Sr/Y值(23.38~36.15)、(La/Yb)N值(18.57~33.04),较低的MgO含量(0.91%~1.20%)和中等Mg#值(34.03~37.27),以及低Yb含量((1.18~1.52)×10^(-6),平均值为1.30×10^(-6))、Y含量((15.43~20.50)×10^(-6),平均值为16.94×10^(-6)),同时Na 2O/K 2O值为0.77~1.06,平均值为0.94,显示与C型埃达克岩相似的地球化学特征。结合佳木斯地块东缘二叠世处在活动大陆边缘弧环境以及佳木斯地块晚三叠世周缘增生杂岩的分布特点,认为大八浪岩体可能是晚三叠世在古太平洋板块向佳木斯地块下部俯冲,造成佳木斯地块不断缩短加厚,其下地壳发生部分熔融的产物。The Dabalang pluton,located in Huanan uplift area of the central Jiamusi block,is lithologically medium-to-fine-grained biotite granodiorites,which intrude into Late Permian muscovite monzogranites.LA-ICP-MS zircon U-Pb age is(234±1)Ma,the biotite granodiorites are in early Late Triassic.The Dabalang pluton has high SiO 2 content(62.04%-64.30%),Al 2O 3 content(15.68%-16.95%),Sr/Y ratio(23.38-36.15)and(La/Yb)N ratio(18.57-33.04),containing low MgO content(0.91%-1.20%),moderate Mg#value(34.03-37.27),as well as low Yb content((1.18-1.52)×10^(-6)with an average of 1.30×10^(-6))and Y content((15.43-20.50)×10^(-6)with an average of 16.94×10^(-6)),Na 2O/K 2O is 0.77-1.06 with an average of 0.94.The above geochemical characteristics are similar to the C-type adakites.Considering the active continental margin arc setting of Permian in the eastern margin of Jiamusi block and the distribution characteristics of Late Triassic peripheral accretionary complexes,it is found that the Dabalang pluton may be a product of partial melting of crust below Jiamusi block,which is continuously shortened and thickened due to the subduction of Paleo-Pacific plate towards the lower part of Jiamusi block in Late Triassic.

关 键 词：埃达克岩 地球化学 晚三叠世 锆石U-PB年龄 花岗岩 佳木斯地块 

分 类 号：P597[天文地球—地球化学]