黑龙江十五里桥金矿龙江组火山岩地球化学特征及构造背景分析

对十五里桥龙江组岩性组合与地球化学研究结果表明：龙江组火山岩SiO₂为53.56%~73.43%，Al₂O₃为14.90%~18.74%，K₂O为1.76%~4.20%，为高钾钙碱性系列.样品稀土元素标准化配分曲线表现为轻重稀土分馏明显，显示弱的铕负异常或无异常.微量元素标准化配分曲线表现为富集大离子亲石元素（LILE）Rb、K、Sr、Ba，亏损高场强元素（HFSE）Nb、Ta、Ti.样品Rb/Sr比值介于0.04~0.43，Ti/Y比值介于144.23~492.19.在构造环境判别图解上，样品位于火山弧区和大陆弧、后碰撞弧区，表明龙江组是板块俯冲和碰撞造山转换背景下下地壳部分熔融的产物.

GEOCHEMISTRY AND TECTONIC SETTING OF THE VOLCANIC ROCKS OF LONGJIANG FORMATION IN SHIWULIQIAO GOLD DEPOSIT,HEILONGJIANG PROVINCE

Study on the lithological association and geochemistry of Longjiang Formation in Shiwuliqiao gold deposit shows that the contents of SiO₂, Al₂O₃ and K₂O in the volcanic rocks are 53.56%-73.43%, 14.90%-18.74% and 1.76%-4.20% respectively, belonging to high-K calc alkaline series. The REE distribution patterns show distinct fractionation of LREEs and HREEs, with weak negative or no Eu anomaly. The trace elements are characterized by enrichment of LILEs (Rb, K, Sr and Ba), and depletion of HFSEs (Nb, Ta and Ti), with the Rb/Sr ratio of 0.04-0.43 and Ti/Y ratio of 144.23-492.19. The samples fall in the volcanic arc, continental arc and post-collision arc setting zones in the tectonic discrimination diagram, indicating the Longjiang Formation was the product of partial melting of lower crust in the transition of plate subduction and collision orogeny.